Vibrations in the drive line? *FIXED*
11-20-2011, 10:44 PM
#1
Rennlist Member
Thread Starter
Vibrations in the drive line? *FIXED*
1988 Auto,
Trying to sort out the vibration I have, at a steady speed, say 60mph I have this vibration, feels like its in the drive line, when I change down from drive to 3rd the vibrations become stronger and at a higher frequency.
I think I'm right in thinking that rules out any problems with the wheels, tyres, wheel bearings and driveshafts as these are still revolving at the same speed?
Thinking that it was the Torque tube, earlier this year I removed it and fitted a set of Constantine's Super Bearings but that didn't solve the vibration.
When stationary in park and holding the revs at 3k you can feel there's something amiss
Yesterday I disconnected the driveshaft at the flexplate and started the engine, no load on the engine of course but it seemed smooth enough so I guess its in the trans/TC, could it be the converter bearings causing the vibration or could it be an internal fault inside the TC itself and not the bearings, I've not got any experience in this area.
Any thoughts appreciated.
Trying to sort out the vibration I have, at a steady speed, say 60mph I have this vibration, feels like its in the drive line, when I change down from drive to 3rd the vibrations become stronger and at a higher frequency.
I think I'm right in thinking that rules out any problems with the wheels, tyres, wheel bearings and driveshafts as these are still revolving at the same speed?
Thinking that it was the Torque tube, earlier this year I removed it and fitted a set of Constantine's Super Bearings but that didn't solve the vibration.
When stationary in park and holding the revs at 3k you can feel there's something amiss
Yesterday I disconnected the driveshaft at the flexplate and started the engine, no load on the engine of course but it seemed smooth enough so I guess its in the trans/TC, could it be the converter bearings causing the vibration or could it be an internal fault inside the TC itself and not the bearings, I've not got any experience in this area.
Any thoughts appreciated.
Last edited by Whitesands; 12-12-2011 at 01:30 PM.
11-21-2011, 12:34 AM
#2
Team Owner
check the motor mounts and the trans mounts,
the engine oil pan should be flush with the front cross member,
and the trans should have about an inch of clearance between the cross member and the bottom of the trans
the engine oil pan should be flush with the front cross member,
and the trans should have about an inch of clearance between the cross member and the bottom of the trans
11-21-2011, 01:00 AM
#3
Rennlist Member
1. Have you checked the crank end float? It should be around 0.2mm
2. The torque converter bearings are susceptible to premature wear
3. I presume you have checked for tension on the flex plate and that you have painted with some white paint the area around the clamp/shaft so that you have a visual cue if there is any slippage taking place. My late S4 used to vibrate at exactly 3050 rpm if when the clamp slipped to a position of 3mm pre-load.
Indeed on the basis you have been dealing with Constantine I assume you fitted one of the recognised flexplate clamp solutions.
Regards
Fred
2. The torque converter bearings are susceptible to premature wear
3. I presume you have checked for tension on the flex plate and that you have painted with some white paint the area around the clamp/shaft so that you have a visual cue if there is any slippage taking place. My late S4 used to vibrate at exactly 3050 rpm if when the clamp slipped to a position of 3mm pre-load.
Indeed on the basis you have been dealing with Constantine I assume you fitted one of the recognised flexplate clamp solutions.
Regards
Fred
11-21-2011, 01:27 AM
#4
Drifting
He is saying the vibration is absent under no load, & only exists above 3000 rpm when the car is stationary (almost no load), but appears at 2200 or 2600 rpm when car is moving, under load, in either 3rd and 4th gears.
Bad torque converter bearings are usually associated with bearing whine.
What have you done to rule out any load related vibration, such as a bad torque converter, fuel injection malfunction, or ignition malfunction?
Bad torque converter bearings are usually associated with bearing whine.
What have you done to rule out any load related vibration, such as a bad torque converter, fuel injection malfunction, or ignition malfunction?
11-21-2011, 03:08 AM
#5
Team Owner
if you put different bearings into the TT then there is a possibility that the TT damper was left out. Porsche has a document that explains the use of the damper in the TT,
it is used for dampening a vibration from 2200 to 3500 RPM in the automatic TT
And possibly in the 5 speed version,
I dont fully recall all of the parameters of the TSB
it is used for dampening a vibration from 2200 to 3500 RPM in the automatic TT
And possibly in the 5 speed version,
I dont fully recall all of the parameters of the TSB
11-21-2011, 06:56 AM
#6
Former Vendor
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Hi Ivan,
As long as you followed our directions and placed the three Super Bearings in the TT as directed, the TT can be discounted as a source of your problems.
As for the vibration dampener, three (3) Super Bearings have been engineered to replace the weight of that problem proned part, so it should not be placed back in. There are many rebuilt TTs using our Super Bearings and no one is reporting of vibrations after the rebuild.
We would concentrate on the TC and transmission since disconnecting the TT from the equation did not produce the same vibrations in your tests. There was a post about vibration problems from a failed TC a few years ago that was found by an independent shop. The transmission fluid level should also be checked to ensure the correct amount of fluid exists. Bad TC bearings would also sound awful if they are the bad enough to cause vibrations.
Another possibility is the engine could be missing under load as Borland mentions above. We would slowly raise the RPMs as you sit in the car and carefully feel for any difference in vibrations as you do so.
Call if you want to knock around some ideas, 772-713-1289.
HTH,
As long as you followed our directions and placed the three Super Bearings in the TT as directed, the TT can be discounted as a source of your problems.
As for the vibration dampener, three (3) Super Bearings have been engineered to replace the weight of that problem proned part, so it should not be placed back in. There are many rebuilt TTs using our Super Bearings and no one is reporting of vibrations after the rebuild.
We would concentrate on the TC and transmission since disconnecting the TT from the equation did not produce the same vibrations in your tests. There was a post about vibration problems from a failed TC a few years ago that was found by an independent shop. The transmission fluid level should also be checked to ensure the correct amount of fluid exists. Bad TC bearings would also sound awful if they are the bad enough to cause vibrations.
Another possibility is the engine could be missing under load as Borland mentions above. We would slowly raise the RPMs as you sit in the car and carefully feel for any difference in vibrations as you do so.
Call if you want to knock around some ideas, 772-713-1289.
HTH,
11-21-2011, 08:23 PM
#7
Rennlist Member
Thread Starter
Thanks all,
Mrmerlin,
MM's fairly new, left out the damper as not needed with the Super Bearings but the transmission is sitting very close to the cross member so will get some new mountings.
FredR,
End float well within spec, flexplate ok, only 300 miles since TT refurb.
borland,
No bearing whine, engine pulls good and the vibration doesn't seem/feel to becoming from the front also just fitted a new set of plugs, old ones were all uniform in color
Constantine,
Followed your instructions to the letter, Will do the rev test on Wednesday and report back. When I did the TT the new bearings did remove some vibrations, but obviously I had more than one.
Mrmerlin,
MM's fairly new, left out the damper as not needed with the Super Bearings but the transmission is sitting very close to the cross member so will get some new mountings.
FredR,
End float well within spec, flexplate ok, only 300 miles since TT refurb.
borland,
No bearing whine, engine pulls good and the vibration doesn't seem/feel to becoming from the front also just fitted a new set of plugs, old ones were all uniform in color
Constantine,
Followed your instructions to the letter, Will do the rev test on Wednesday and report back. When I did the TT the new bearings did remove some vibrations, but obviously I had more than one.
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11-22-2011, 11:09 PM
#9
Rennlist Member
Much interest on this topic.
I have a 87 with similar issues but very much around 3k rpm which became very prominent after the flex plate release and intake/ignition system refresh.
MMs and gbox mounts are stock. Issue is only under load.
I have a 87 with similar issues but very much around 3k rpm which became very prominent after the flex plate release and intake/ignition system refresh.
MMs and gbox mounts are stock. Issue is only under load.
11-23-2011, 12:47 AM
#10
Rennlist Member
Which motor mounts are we using. I put the volvo's in and trans mounts within a 30 day time period. I have noticed a change in my 3,000 rpm vibe. It is not as noticable now. I will be doing the TT as soon as trans hoist arrives.
I did have to go back under and pry the exhaust shields away from MM's which also helped. I know my TT bearings need replacement as the front one was in the bell housing at one point. I pushed it back in 10" and retained it with 3 screws. I did not retain it from going back which I believe has happened now.
Has anyone with this vibration noticed that it is not present at certain times?
I have become very **** about this as to where I am alway's running it up to 3,000 to make sure it is still there before I shut it down.
I had a oil change while down at sharktoberfest and they used Mobile 1. I dumped it as soon as I returned to Wash. and went back to Kendall 20-50 and it seems to help.
So, my 3,000 vibe is at least 80% cured but not giving up until 100%.
When relieving the flex plate do not pry either way on flywheel when tightning the pinch bolt, I find it best to leave it relaxed.
Thomas
I did have to go back under and pry the exhaust shields away from MM's which also helped. I know my TT bearings need replacement as the front one was in the bell housing at one point. I pushed it back in 10" and retained it with 3 screws. I did not retain it from going back which I believe has happened now.
Has anyone with this vibration noticed that it is not present at certain times?
I have become very **** about this as to where I am alway's running it up to 3,000 to make sure it is still there before I shut it down.
I had a oil change while down at sharktoberfest and they used Mobile 1. I dumped it as soon as I returned to Wash. and went back to Kendall 20-50 and it seems to help.
So, my 3,000 vibe is at least 80% cured but not giving up until 100%.
When relieving the flex plate do not pry either way on flywheel when tightning the pinch bolt, I find it best to leave it relaxed.
Thomas
11-23-2011, 09:13 AM
#12
Rennlist Member
I have yet to prove but my theory is that good intentions result in highlighting vibration issues.
With an untouched drivetrain theres an amount of pressure in the system which we know pushes the crankshaft into the thrust bearing which in turn fails causing the engine block to fail.....goodbye engine.
We fix the issue by releasing the clamp on the front flex plate, adding the Pklamp and/or the super clamp and super bearings. All good but.......
My theory is the drivetrain when released allows everything that was held in good relation to each other to move and upset the equilibriun balance. The flex plates spring back to a neutral position and the TT brgs move in the tube all resulting in magnifying the engine vibes.
With OEM motor mounts and transmission rubber the vibes are further transmitted.
Appreciate comments, thx.
With an untouched drivetrain theres an amount of pressure in the system which we know pushes the crankshaft into the thrust bearing which in turn fails causing the engine block to fail.....goodbye engine.
We fix the issue by releasing the clamp on the front flex plate, adding the Pklamp and/or the super clamp and super bearings. All good but.......
My theory is the drivetrain when released allows everything that was held in good relation to each other to move and upset the equilibriun balance. The flex plates spring back to a neutral position and the TT brgs move in the tube all resulting in magnifying the engine vibes.
With OEM motor mounts and transmission rubber the vibes are further transmitted.
Appreciate comments, thx.
11-23-2011, 09:42 AM
#13
Former Vendor
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Hi Malcolm,
When the automatic driveline was first designed the front flexplate clamp was assisted in holding the drive shaft with a circlip, bearing and washers placed at the front of the drive shaft to set a prescribed distance between the flexplate and flywheel that is explained in the 928 WSMs.
Later and for unstated reasons, Porsche stopped using the circlip, bearing and washers at the front of the drive shaft. However they did not change the front flexplate clamp which was not initially designed to work by itself to hold the drive shaft firmly enough to not let it move within it. This then sets up forward pressure and thrust bearing failure (TBF) of the engine can result. This pressure can also cause premature wear of the TT and TC bearings causing them to be noisy.
Tension in the driveline due to the drive shaft pullout is a very bad thing to have. The driveline should have zero pressure on it.
The original bearing units are aging and they are now moving around in the TT which causes vibrations by not supporting the drive shaft at the correct points to stop the long metal rod from vibrating. The original bearing units are moving around since there outer rubber surfaces have shrunk, not because the driveline tension has been relieved.
However driveline vibrations can also be caused for other reasons, all which have already been mentioned in this thread. It is an expensive and time consuming hunt for the sources of these driveline vibrations.
HTH,
When the automatic driveline was first designed the front flexplate clamp was assisted in holding the drive shaft with a circlip, bearing and washers placed at the front of the drive shaft to set a prescribed distance between the flexplate and flywheel that is explained in the 928 WSMs.
Later and for unstated reasons, Porsche stopped using the circlip, bearing and washers at the front of the drive shaft. However they did not change the front flexplate clamp which was not initially designed to work by itself to hold the drive shaft firmly enough to not let it move within it. This then sets up forward pressure and thrust bearing failure (TBF) of the engine can result. This pressure can also cause premature wear of the TT and TC bearings causing them to be noisy.
Tension in the driveline due to the drive shaft pullout is a very bad thing to have. The driveline should have zero pressure on it.
The original bearing units are aging and they are now moving around in the TT which causes vibrations by not supporting the drive shaft at the correct points to stop the long metal rod from vibrating. The original bearing units are moving around since there outer rubber surfaces have shrunk, not because the driveline tension has been relieved.
However driveline vibrations can also be caused for other reasons, all which have already been mentioned in this thread. It is an expensive and time consuming hunt for the sources of these driveline vibrations.
HTH,
11-23-2011, 11:42 AM
#14
Rennlist Member
Thanks constantine.
Amazing the change in design of the driveline......probably never know the full reasoning.
What I do understand is the pressure on the driveline does build over time unless preventative action is taken with components such as you offer. For those with stock systems tshooting the vibrations is from the MMs, through the TT, TC and gearbox mpounts and everything in between.
A donting task indeed.
Amazing the change in design of the driveline......probably never know the full reasoning.
What I do understand is the pressure on the driveline does build over time unless preventative action is taken with components such as you offer. For those with stock systems tshooting the vibrations is from the MMs, through the TT, TC and gearbox mpounts and everything in between.
A donting task indeed.
11-24-2011, 12:54 AM
#15
Just to add to Constantine's comments about the different TT arrangements, the WSM for the earlier circlip-equipped shafts calls for at-rest rearward thrust of 0.5mm (as I recall, may be 0.3mm?? Was a few months ago when I did this job). This is achieved by the use of shims at the front of the shaft, forward of the flex plate. The more shims the shorter the effective length of the shaft and the greater the rearward thrust once all bolted up. In effect, with the whole circlip-equipped assembly in place and the flex plate at rest as far forward as possible there would therefore be 0.5mm clearance between the front of the flex plate and the rear of the flywheel surface before these two are bolted together. This of course goes to zero when the flex plate bolts are tightened to the flywheel, thus inducing the 0.5mm of WSM-required rearward thrust.
Fitting an earlier circlip-equipped 25mm diameter shaft in lieu of the later non-circlip 28mm shaft is relatively simple and cheap, if the shaft is out anyway for the purposes of replacing the bearings.
Fitting an earlier circlip-equipped 25mm diameter shaft in lieu of the later non-circlip 28mm shaft is relatively simple and cheap, if the shaft is out anyway for the purposes of replacing the bearings.