high rate of crankshaft thrust bearing failure.
02-24-2002, 11:32 PM
#1
Three Wheelin'
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high rate of crankshaft thrust bearing failure.
I’ve been hearing 928 engines, with automatic transmissions; have a high rate of crankshaft thrust bearing failure. There is a condition known, in the transmission industry, as torque converter ballooning. The torque converter physically increases its size and exerts an outward pressure. Over revving the engine and excessive torque converter pressure are contributing factors.
The torque converter has two main functions. It acts as a fluid coupling connecting the engine power, through transmission fluid, to the transmissions planetary gear set. It also multiplies the torque of the engine and transmits this torque to the rear driving wheels, propelling the car at a torque multiplication of 2:1 in a Porsche.
The transmission oil pump charges (pressurizes) the torque converter with transmission fluid, when the engine is running. As the TC spins, at engine speed, there are forces in the torque converter exerting pressure on the crankshaft thrust bearing through the torque tube drive shaft.
These pressures are:
1. Rotary fluid flow generated by the rotating fluid.
2. Vortex fluid flow also generated by the rotating fluid in the torque converter.
These forces create a centrifugal force in the torque converter, which push on the torque tube drive shaft in turn pushing the crankshaft forward cutting off lubrication to the thrust bearing.
Excessive torque converter pressures can multiply centrifugal forces. The main causes of excessive pressures are:
1. Restriction in the cooling circuit.
2. A plugged transmission cooler in the radiator.
3. A crimped cooler line. (Torque converter fluid is the feed oil that goes to the radiator to be cooled.)
4. Highline pressure (working pressure).
5. A bad modulator.
6. A stuck pressure regulator valve.
7. A disconnected vacuum line to the modulator.
These can all cause excessive torque converter pressure. The engine rebuilding association blames the torque converter for thrust bearing failure in most cars. The transmission industry claims the failure is due to a flaw in the crankshaft design. Both agree that modifying the thrust bearing or the crankshaft can be beneficial in some engines.
If you remove your engine or transmission make absolutely sure that you adjust the pinch clamps on the torque tube drive shaft (according to the workshop manuals). Mercedes Benz issued a tech bulletin on torque converter ballooning. They want you to lay down the torque converter on its primary pump flange (hub) and measure from the work surface to the top of the flywheel mounting ears. If it’s more then 121.5mm, the torque converter has ballooned and needs to be replaced. Everyone knows, and if you don’t know, 98% of the internal components of our transmissions are Mercedes Benz parts. Porsche made the cases for both the 3 and 4 speed.
If you’re rebuilding your engine, have the crankshaft or thrust bearing modified for an increase in lubrication. If your one of those who disconnected the vacuum modulators vacuum line, you should reconnect it. If you want a firmer shift install a shift kit or adjust the modulator by one turn only.
Steve C
The Great White
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
The torque converter has two main functions. It acts as a fluid coupling connecting the engine power, through transmission fluid, to the transmissions planetary gear set. It also multiplies the torque of the engine and transmits this torque to the rear driving wheels, propelling the car at a torque multiplication of 2:1 in a Porsche.
The transmission oil pump charges (pressurizes) the torque converter with transmission fluid, when the engine is running. As the TC spins, at engine speed, there are forces in the torque converter exerting pressure on the crankshaft thrust bearing through the torque tube drive shaft.
These pressures are:
1. Rotary fluid flow generated by the rotating fluid.
2. Vortex fluid flow also generated by the rotating fluid in the torque converter.
These forces create a centrifugal force in the torque converter, which push on the torque tube drive shaft in turn pushing the crankshaft forward cutting off lubrication to the thrust bearing.
Excessive torque converter pressures can multiply centrifugal forces. The main causes of excessive pressures are:
1. Restriction in the cooling circuit.
2. A plugged transmission cooler in the radiator.
3. A crimped cooler line. (Torque converter fluid is the feed oil that goes to the radiator to be cooled.)
4. Highline pressure (working pressure).
5. A bad modulator.
6. A stuck pressure regulator valve.
7. A disconnected vacuum line to the modulator.
These can all cause excessive torque converter pressure. The engine rebuilding association blames the torque converter for thrust bearing failure in most cars. The transmission industry claims the failure is due to a flaw in the crankshaft design. Both agree that modifying the thrust bearing or the crankshaft can be beneficial in some engines.
If you remove your engine or transmission make absolutely sure that you adjust the pinch clamps on the torque tube drive shaft (according to the workshop manuals). Mercedes Benz issued a tech bulletin on torque converter ballooning. They want you to lay down the torque converter on its primary pump flange (hub) and measure from the work surface to the top of the flywheel mounting ears. If it’s more then 121.5mm, the torque converter has ballooned and needs to be replaced. Everyone knows, and if you don’t know, 98% of the internal components of our transmissions are Mercedes Benz parts. Porsche made the cases for both the 3 and 4 speed.
If you’re rebuilding your engine, have the crankshaft or thrust bearing modified for an increase in lubrication. If your one of those who disconnected the vacuum modulators vacuum line, you should reconnect it. If you want a firmer shift install a shift kit or adjust the modulator by one turn only.
Steve C
The Great White
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
02-25-2002, 12:10 AM
#2
Rennlist Member
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Capt'n Earl has done a great deal of very good work in this area on the 928. Here are some earlier posts from him on this subject.
Wally
This is an update to the use of Loctite on the driveshaft/thrustplate hub on
automatic cars to reduce hub migration that pushes on the crankshaft and may
cause engine crankshaft thrust bearing failure.
On test car "D" we did the Loctite procedure but, we did NOT let the Loctite
cure for 24 hours due to geographic constraints. After 600 spirited miles the
hub has not migrated. I would still recommend the 24 hour cure if at all
possible.
I have attached my previous Emails with procedure for your information.
Earl Gillstrom '88 5Speed
I have some possible good news for automatic owners that are worried about
crankshaft thrust bearing failure. One (now two) of the cars that I have been
monitoring for drive shaft movement in the front hub of the thrust plate has
stopped moving. We did an experiment on Gary Knox's '88 automatic (car "C" in
my previous email) that seems to have stopped the movement of the shaft. Here
is what we did:
Removed the pinch (clamp) bolt in the front driveshaft hub. This relieved the
thrust plate tension and allowed the shaft to attain the proper position.
Poured Loctite 290 (penetrating formula) into the three slots in the hub. The
intent was to Loctite the shaft to the hub without disassembly. Disassembly
requires removal of the torque tube. You should "prime" parts before
assembly, but it is pretty time consuming to R&R the TT.
Installed a new bolt P/N 931.421.240.00. using Loctite 242 before assembly,
torqued to 65 ft.lb. Porsche had recommended to Fred Rourke's mechanics,
replacing the bolt and tightening to 110% of recommended torque. The standard
torque is 59 ft.lb. The Loctite was our idea. I doubt that the Loctite on the
bolt was necessary, but it can't hurt.
Let the car sit for 24 hours. Loctite says that a full cure takes 24 hours.
The car now has about 2000 miles on it since we did this, including two days
of drivers education with NO hub movement. You can say that this is not a
long term test, which is true. But we checked this car previously and found
that the hub had moved .016 in about 2,000 miles and one DE. The first check
we did, there was .105" movement (40,000 miles). So it is very encouraging.
This is not an expensive procedure. About $6.00 for the bolt and $6.00 for
the Loctite. It takes about an hour or two depending on experience. Check the
crankshaft end play while you are in there.
We painted the shaft splines white where they enter the clamping hub. After
reassembly we could look through the hole in the bottom of the bell housing
cover and see the painted splines. We think that we can do a quick spot check
for shaft movement without any disassembly at every oil change by looking in
the hole. Maybe a small diameter fiber optic light would make the job easier
but the white paint helps a lot.
I have included my first email on this, as well as the procedure. Car "D" was
done on 11/11 using Loctite on the splines and was added to the original
email. Unfortunately we used red paint, so it may be harder to check hub
movement without disassembly.
Here is the first email sent on 9-24-00.
I have been assisting 3 friends with automatic transmissions in trying to
determine if crankshaft thrust bearing wear is excessive on their cars. For
simplicity, I have named the cars A,B and C. Here are the findings. "Hub
movement" means: with a dial indicator on the center of the thrust plate hub,
loosen the hub clamping screw and record movement of the hub. This shows the
preload on the crankshaft. Presumably, no preload is desirable.
Car Year Mileage Hub movement CS End play
"A" '89 85K .120" .040" .009"
"B" '89 114K .100" .002"
"C" '88 44K .105" .016 .007"
"D" '89 58K .134" .005" (added 12-05-00)
We also checked the difference in preload caused by a cold car and a hot car
using car "C". After making the initial check and finding .105" hub movement,
we tightened the hub clamping bolt with no preload. The car was then driven
~2000 miles including one DE. We then checked the car cold and found .016"
preload. Hub migration? We reclamped the hub and drove the car ~30 miles and
rechecked the preload hot and found .003" preload. It appears that the
shaft/torque tube do not change enough in length from cold to hot to affect
the preload. Or was the .003" change caused by migration? Car A was also
rechecked after 2,000 miles and the hub moved .040".
It also appears that the hub does migrate forward enough to put significant
pressure on the thrust bearing, although the wear on cars A and C seems
acceptable.
To try to stop migration on car "C", we used Loctite 290 penetrating formula
on the hub splines and 242 on the threads of the clamping bolt, although the
bolt does not appear to loosen. We will check periodically to see if this
stops migration.
( the results are above)
On cars "A and "B" we used 271 on the threads. All bolts were replaced and
torqued to 110% as per advise from Porsche.
One thing that we don't understand is: why does car "B" only have .002"
crankshaft end play? On car "A"and "C" the crankshaft "clunks" back and forth
when we pry them. Car "B" does not appear to move, but the dial indicator
shows .002" movement. The specification is .00236" (.06mm) minimum. It is
hard to believe that a car with over 114,000 miles has less than the minimum
axial play. (Update: 12-05-00 an oil analysis showed no problems.)
Is this a symptom of the dreaded thrust bearing failure? Is there another way
to check for thrust bearing failure without tearing the engine down?
Earl Gillstrom '88 5 speed (.007 CS end play) 99,000 miles
Here is the procedure:
Drop the exhaust at the manifolds.
Remove the bell housing bottom cover.
Install a dial indicator on the rear side of the forward Drive Shaft Hub.
Loosen The hub clamping screw and watch for hub movement.
On the three automatics that I have done this on, the hub moved back between
.100"and .120". This preload puts pressure on the rear face of the crankshaft
thrust bearing. If the hub does not move more than a few thousandths of an
inch when you loosen the pinch bolt then all is OK. (Update 12-05 -00,
Car""D" had .134" movement.)
After the pinch bolt is loose then put the dial indicator on the flywheel,
(not the flexplate). Pry the flywheel back and forth to check the crankshaft
end play. The spec for later engines is .0024" to .0076". Wear limit is .016".
If your end play is more than .016", then you are experiencing "Thrust
Bearing Failure".
If you are installing a TT, clean the shaft and hub splines with Loctite
primer before assembly. Tighten the forward hub pinch bolt last.
Pour Loctite 290 (penetrating formula) into the three slots in the hub. It
doesn't matter if hot or cold or the position of the crankshaft.
Install a new bolt P/N 931.421.240.00. using Loctite 242 before assembly,
torque to 65 ft.lb. The standard torque is 59 ft.lb. I doubt that the Loctite
on the bolt is necessary, but it can't hurt.
Paint the shaft splines white where it enters the hub for future verification.
Reassemble cover and exhaust.
Let the car sit for 24 hours. Loctite says that a full cure takes 24 hours.
Look through the hole in the bottom of the bell housing every oil change to
check for hub migration.
The pinch bolt is 10 mm with an 8 mm "Allen" head. Hardness is 12.9.
Part number is 931,421,240,00.
I will try to assemble a list of results if you try this experiment. Let me
know how you make out.
Earl Gillstrom '88 5 speed
Hope that this helps someone.
Wally
This is an update to the use of Loctite on the driveshaft/thrustplate hub on
automatic cars to reduce hub migration that pushes on the crankshaft and may
cause engine crankshaft thrust bearing failure.
On test car "D" we did the Loctite procedure but, we did NOT let the Loctite
cure for 24 hours due to geographic constraints. After 600 spirited miles the
hub has not migrated. I would still recommend the 24 hour cure if at all
possible.
I have attached my previous Emails with procedure for your information.
Earl Gillstrom '88 5Speed
I have some possible good news for automatic owners that are worried about
crankshaft thrust bearing failure. One (now two) of the cars that I have been
monitoring for drive shaft movement in the front hub of the thrust plate has
stopped moving. We did an experiment on Gary Knox's '88 automatic (car "C" in
my previous email) that seems to have stopped the movement of the shaft. Here
is what we did:
Removed the pinch (clamp) bolt in the front driveshaft hub. This relieved the
thrust plate tension and allowed the shaft to attain the proper position.
Poured Loctite 290 (penetrating formula) into the three slots in the hub. The
intent was to Loctite the shaft to the hub without disassembly. Disassembly
requires removal of the torque tube. You should "prime" parts before
assembly, but it is pretty time consuming to R&R the TT.
Installed a new bolt P/N 931.421.240.00. using Loctite 242 before assembly,
torqued to 65 ft.lb. Porsche had recommended to Fred Rourke's mechanics,
replacing the bolt and tightening to 110% of recommended torque. The standard
torque is 59 ft.lb. The Loctite was our idea. I doubt that the Loctite on the
bolt was necessary, but it can't hurt.
Let the car sit for 24 hours. Loctite says that a full cure takes 24 hours.
The car now has about 2000 miles on it since we did this, including two days
of drivers education with NO hub movement. You can say that this is not a
long term test, which is true. But we checked this car previously and found
that the hub had moved .016 in about 2,000 miles and one DE. The first check
we did, there was .105" movement (40,000 miles). So it is very encouraging.
This is not an expensive procedure. About $6.00 for the bolt and $6.00 for
the Loctite. It takes about an hour or two depending on experience. Check the
crankshaft end play while you are in there.
We painted the shaft splines white where they enter the clamping hub. After
reassembly we could look through the hole in the bottom of the bell housing
cover and see the painted splines. We think that we can do a quick spot check
for shaft movement without any disassembly at every oil change by looking in
the hole. Maybe a small diameter fiber optic light would make the job easier
but the white paint helps a lot.
I have included my first email on this, as well as the procedure. Car "D" was
done on 11/11 using Loctite on the splines and was added to the original
email. Unfortunately we used red paint, so it may be harder to check hub
movement without disassembly.
Here is the first email sent on 9-24-00.
I have been assisting 3 friends with automatic transmissions in trying to
determine if crankshaft thrust bearing wear is excessive on their cars. For
simplicity, I have named the cars A,B and C. Here are the findings. "Hub
movement" means: with a dial indicator on the center of the thrust plate hub,
loosen the hub clamping screw and record movement of the hub. This shows the
preload on the crankshaft. Presumably, no preload is desirable.
Car Year Mileage Hub movement CS End play
"A" '89 85K .120" .040" .009"
"B" '89 114K .100" .002"
"C" '88 44K .105" .016 .007"
"D" '89 58K .134" .005" (added 12-05-00)
We also checked the difference in preload caused by a cold car and a hot car
using car "C". After making the initial check and finding .105" hub movement,
we tightened the hub clamping bolt with no preload. The car was then driven
~2000 miles including one DE. We then checked the car cold and found .016"
preload. Hub migration? We reclamped the hub and drove the car ~30 miles and
rechecked the preload hot and found .003" preload. It appears that the
shaft/torque tube do not change enough in length from cold to hot to affect
the preload. Or was the .003" change caused by migration? Car A was also
rechecked after 2,000 miles and the hub moved .040".
It also appears that the hub does migrate forward enough to put significant
pressure on the thrust bearing, although the wear on cars A and C seems
acceptable.
To try to stop migration on car "C", we used Loctite 290 penetrating formula
on the hub splines and 242 on the threads of the clamping bolt, although the
bolt does not appear to loosen. We will check periodically to see if this
stops migration.
( the results are above)
On cars "A and "B" we used 271 on the threads. All bolts were replaced and
torqued to 110% as per advise from Porsche.
One thing that we don't understand is: why does car "B" only have .002"
crankshaft end play? On car "A"and "C" the crankshaft "clunks" back and forth
when we pry them. Car "B" does not appear to move, but the dial indicator
shows .002" movement. The specification is .00236" (.06mm) minimum. It is
hard to believe that a car with over 114,000 miles has less than the minimum
axial play. (Update: 12-05-00 an oil analysis showed no problems.)
Is this a symptom of the dreaded thrust bearing failure? Is there another way
to check for thrust bearing failure without tearing the engine down?
Earl Gillstrom '88 5 speed (.007 CS end play) 99,000 miles
Here is the procedure:
Drop the exhaust at the manifolds.
Remove the bell housing bottom cover.
Install a dial indicator on the rear side of the forward Drive Shaft Hub.
Loosen The hub clamping screw and watch for hub movement.
On the three automatics that I have done this on, the hub moved back between
.100"and .120". This preload puts pressure on the rear face of the crankshaft
thrust bearing. If the hub does not move more than a few thousandths of an
inch when you loosen the pinch bolt then all is OK. (Update 12-05 -00,
Car""D" had .134" movement.)
After the pinch bolt is loose then put the dial indicator on the flywheel,
(not the flexplate). Pry the flywheel back and forth to check the crankshaft
end play. The spec for later engines is .0024" to .0076". Wear limit is .016".
If your end play is more than .016", then you are experiencing "Thrust
Bearing Failure".
If you are installing a TT, clean the shaft and hub splines with Loctite
primer before assembly. Tighten the forward hub pinch bolt last.
Pour Loctite 290 (penetrating formula) into the three slots in the hub. It
doesn't matter if hot or cold or the position of the crankshaft.
Install a new bolt P/N 931.421.240.00. using Loctite 242 before assembly,
torque to 65 ft.lb. The standard torque is 59 ft.lb. I doubt that the Loctite
on the bolt is necessary, but it can't hurt.
Paint the shaft splines white where it enters the hub for future verification.
Reassemble cover and exhaust.
Let the car sit for 24 hours. Loctite says that a full cure takes 24 hours.
Look through the hole in the bottom of the bell housing every oil change to
check for hub migration.
The pinch bolt is 10 mm with an 8 mm "Allen" head. Hardness is 12.9.
Part number is 931,421,240,00.
I will try to assemble a list of results if you try this experiment. Let me
know how you make out.
Earl Gillstrom '88 5 speed
Hope that this helps someone.
02-25-2002, 12:41 AM
#3
Thanks Wally,
I don't know if the post was directed at the Kennywood Blvd. Timing and Racing Assoc., Midland Tx. Division but, I should know better.
I spend a lot of time in second (3spd) between 3200 & 4700rpm to keep on the Cam.
I suspect that the migration/balloning may also be influenced by HEAT expansion either self-propagating or due to one of 'THE 7' mentioned by Earl.
Has anyone ever put a sHARk on one of those speed/brake rollers and done a scaled temp/cooler line pressure and heat rise chart under load?
In any case the information provided will give me something else to do under the car when I go thru the brakes and suspension.
Keep em'rolling
John S. & Pattycakes <img src="graemlins/c.gif" border="0" alt="[ouch]" />
I don't know if the post was directed at the Kennywood Blvd. Timing and Racing Assoc., Midland Tx. Division but, I should know better.
I spend a lot of time in second (3spd) between 3200 & 4700rpm to keep on the Cam.
I suspect that the migration/balloning may also be influenced by HEAT expansion either self-propagating or due to one of 'THE 7' mentioned by Earl.
Has anyone ever put a sHARk on one of those speed/brake rollers and done a scaled temp/cooler line pressure and heat rise chart under load?
In any case the information provided will give me something else to do under the car when I go thru the brakes and suspension.
Keep em'rolling
John S. & Pattycakes <img src="graemlins/c.gif" border="0" alt="[ouch]" />
02-25-2002, 01:55 AM
#5
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Steve:
I posted <a href="http://members3.boardhost.com/928s4vr/msg/16803.html" target="_blank">a question for you on the 928S4VR message board</a>
I posted <a href="http://members3.boardhost.com/928s4vr/msg/16803.html" target="_blank">a question for you on the 928S4VR message board</a>
03-03-2002, 05:03 PM
#6
Three Wheelin'
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Snow,
I don’t know, I suspect the 4speed, an extra gear places more load on the crank <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
May be Wally knows, I have more information on this subject. Hopefully it will save someone lots of $$$$
Porsche has a Torque converter drive plate bulletin # 3250 1985 thru 1987,
Check the rivets for looseness if loose replace with nuts and bolts, center punch and drill out the rivets, install bolts, head facing the central tube, nuts, and washer facing torque converter, use loctite. Torque to 23 ft lbs.
8 Bolts N010 240 7, 8 Nuts N011 008 8, 8Washers N011 525 19
Central tube installation bulletin dated 1992 # 9203
after the central tube is bolted to the forward housing; first tighten the six-drive plate attaching bolts to 23-28 ft lbs. Then tighten the clamping screw (new one) to 54-62 ft lbs. Following this procedure will ensure necessary running clearance for the crankshaft thrust bearing.
Steve C
The Great White
<img src="graemlins/yltype.gif" border="0" alt="[typing]" /> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
I don’t know, I suspect the 4speed, an extra gear places more load on the crank <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
May be Wally knows, I have more information on this subject. Hopefully it will save someone lots of $$$$
Porsche has a Torque converter drive plate bulletin # 3250 1985 thru 1987,
Check the rivets for looseness if loose replace with nuts and bolts, center punch and drill out the rivets, install bolts, head facing the central tube, nuts, and washer facing torque converter, use loctite. Torque to 23 ft lbs.
8 Bolts N010 240 7, 8 Nuts N011 008 8, 8Washers N011 525 19
Central tube installation bulletin dated 1992 # 9203
after the central tube is bolted to the forward housing; first tighten the six-drive plate attaching bolts to 23-28 ft lbs. Then tighten the clamping screw (new one) to 54-62 ft lbs. Following this procedure will ensure necessary running clearance for the crankshaft thrust bearing.
Steve C
The Great White
<img src="graemlins/yltype.gif" border="0" alt="[typing]" /> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
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11-15-2022, 09:29 AM
#8
Last time I did it, including installing a Ritech clamp...about 2 hours taking my time and triple checking everything along the way, certainly not more than 3. Could be done a lot faster if not installing the clamp and/or in a hurry. It's very easy to check. I can typically have the exhaust disconnected and bell housing cover off in 10 to 20 minutes from the moment I put hands on them.
Last edited by Bulvot; 11-15-2022 at 09:31 AM.
11-15-2022, 09:33 AM
#9
Racer
Last time I did it, including installing a Ritech clamp...about 2 hours taking my time and triple checking everything along the way, certainly not more than 3. Could be done a lot faster if not installing the clamp and/or in a hurry. It's very easy to check. I can typically have the exhaust disconnected and bell housing cover off in 10 to 20 minutes from the moment put hands on them.
11-15-2022, 09:40 AM
#11
BTW - removing the exhaust manifolds with the engine still in the car is not trivial. The passenger side isn't too bad, other than needing small hands and the right combinations of extensions and wobble adapters. You'll need to remove the cross brace supports on both sides. On the driver's side, you also need to disconnect the steering linkage from the steering rack (easiest to do by first removing the steering rack cover plate and letting the steering rack hang). It's a pain, but doable. And THAT process can take a full day for someone to figure out all of the right things to remove and angles to slide things out at. I've done it. And I would do it again if I needed to replace an exhaust manifold. But, it's nowhere near as trivial as removing the six bolts that hold the exhaust pipes to the manifold flanges. Which you would have to do anyway in order to remove the exhaust manifolds. So, at that point, it would be completely pointless to remove the exhaust manifolds. And getting the manifolds out of the car while still attached to the rest of the exhaust seems...impossible. Unless you also remove the cross brace, while supporting the engine from above. Or...just unbolt the exhaust pipes from the manifolds in a few minutes and move one with the rest of the job.
Sounds to me like they were trying to either get a lot more money out of you just because they could...or they really didn't want to do the work and were trying to dissuade you from having them do it.
Sounds to me like they were trying to either get a lot more money out of you just because they could...or they really didn't want to do the work and were trying to dissuade you from having them do it.
Last edited by Bulvot; 11-15-2022 at 09:42 AM.
The following 2 users liked this post by Bulvot:
Bertrand Daoust (11-15-2022),
SecaBlue (11-15-2022)
11-15-2022, 09:48 AM
#12
Racer
BTW - removing the exhaust manifolds with the engine still in the car is not trivial. The passenger side isn't too bad, other than needing small hands and the right combinations of extensions and wobble adapters. You'll need to remove the cross brace supports on both sides. On the driver's side, you also need to disconnect the steering linkage from the steering rack (easiest to do by first removing the steering rack cover plate and letting the steering rack hang). It's a pain, but doable. And THAT process can take a full day for someone to figure out all of the right things to remove and angles to slide things out at. I've done it. And I would do it again if I needed to replace an exhaust manifold. But, it's nowhere near as trivial as removing the six bolts that hold the exhaust pipes to the manifold flanges. Which you would have to do anyway in order to remove the exhaust manifolds. So, at that point, it would be completely pointless to remove the exhaust manifolds. And getting the manifolds out of the car while still attached to the rest of the exhaust seems...impossible. Unless you also remove the cross brace, while supporting the engine from above. Or...just unbolt the exhaust pipes from the manifolds in a few minutes and move one with the rest of the job.
Sounds to me like they were trying to either get a lot more money out of you just because they could...or they really didn't want to do the work and were trying to dissuade you from having them do it.
Sounds to me like they were trying to either get a lot more money out of you just because they could...or they really didn't want to do the work and were trying to dissuade you from having them do it.
11-15-2022, 11:43 AM
#13
Rennlist Member
Whenever this is done, replace the two of the 6 bolts at the rear of the cover with shorter bolts. That way, the cover can be removed in the future without removing the exhaust (I hope I'm correct - been 15+ years since I did that!).
Last edited by Gary Knox; 11-15-2022 at 03:10 PM.
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Bertrand Daoust (11-15-2022)
11-15-2022, 12:12 PM
#14
Rennlist Member
@Gary Knox is correct. You can also (sacrilege!) just omit those 2 bolts. The lower bellhousing cover is not particularly heavy, nor is it subject to any particular stress so the 4 other bolts should be more than enough to hold it in place securely.
Now what I will add to the original question is that, when I was at Camp 928 a couple of years ago I was able to see crank end play being measured on @SteveG 's GTS and there was no need to remove the headers from the engine. However, I don't know what the situation was with the 2 infamous bolts on the lower BH, though I suspect they had been changed/addressed sometime in the past because it sure seemed like it was really just a question of removing the lower cover to get access to the flex plate for measurement.
Good luck!
Now what I will add to the original question is that, when I was at Camp 928 a couple of years ago I was able to see crank end play being measured on @SteveG 's GTS and there was no need to remove the headers from the engine. However, I don't know what the situation was with the 2 infamous bolts on the lower BH, though I suspect they had been changed/addressed sometime in the past because it sure seemed like it was really just a question of removing the lower cover to get access to the flex plate for measurement.
Good luck!
The following 4 users liked this post by Zirconocene:
11-15-2022, 01:16 PM
#15
Racer
@Gary Knox is correct. You can also (sacrilege!) just omit those 2 bolts. The lower bellhousing cover is not particularly heavy, nor is it subject to any particular stress so the 4 other bolts should be more than enough to hold it in place securely.
Now what I will add to the original question is that, when I was at Camp 928 a couple of years ago I was able to see crank end play being measured on @SteveG 's GTS and there was no need to remove the headers from the engine. However, I don't know what the situation was with the 2 infamous bolts on the lower BH, though I suspect they had been changed/addressed sometime in the past because it sure seemed like it was really just a question of removing the lower cover to get access to the flex plate for measurement.
Good luck!
Now what I will add to the original question is that, when I was at Camp 928 a couple of years ago I was able to see crank end play being measured on @SteveG 's GTS and there was no need to remove the headers from the engine. However, I don't know what the situation was with the 2 infamous bolts on the lower BH, though I suspect they had been changed/addressed sometime in the past because it sure seemed like it was really just a question of removing the lower cover to get access to the flex plate for measurement.
Good luck!