Just finished my 1st flex plate / crank end play check
03-09-2014 | 05:17 PM
#17
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From: Oman
I agree 100% with you. The difference between the front and the rear clamp is that the rear one if done up correctly does not seem to slip but the front one, even when tightened correctly, can and way too often will slip and we all know what that entails!
Captain Slow,
There is nothing "normal" about the front clamp slipping 2mm. That this typically happens is the warning that something horrible may happen. Leave it like this at your peril. If you think taking it easy is the answer just remember that max torque is at 3k rpm! Heaven forbid, if TBF happens the first you will know about it is when it is too late.
Do something about it and do it now before it is too late. I have been driving around with my flex plate splines [not the bolt] bonded with Loctite 260 for some 13 years. Not the most elegant solution, that goes to Constantine's clamp, but Loctite 260 [or 270] is the cheapest method.
I also wonder how often folks calibrate their torque wrenches!
Regards
Fred
03-09-2014 | 05:34 PM
#18
Under the Lift
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From: Buckeye, AZ
My PKlamp experience linked below. It has held essentially perfectly. I used to accumulate 2-3 mm of preload in a short time before installing the PKlamp. The PKlamp has held with one exception where it moved a fraction of a mm. I had installed the clamp without any cleaning of the splines. Anyway, I stopped checking it a couple of years ago. I'll check it again soon.
https://rennlist.com/forums/928-foru...xperience.html
The rear clamp tightness is critical, as others mention. Movement is restricted due to the rear position being fixed by a slot cut in the TT shaft into which the bolt fits. If the bolt is loose, the shaft slot and bolt gall each other and the rear splines are damaged if not worse. So, making sure that is properly tightened is first on the list.
https://rennlist.com/forums/928-foru...xperience.html
Despite 264K miles over nearly 25 years, my crank endplay has never changed (0.008" or 0.20mm, in the middle of the factory "new" range). Before the PKlamp it survived 10 years without any release of preload, but preload only accumulated to a little over 2 mm. I started releasing the front clamp and removing the preload 2-3 times a year after I bought the car in 1999. It would accumulate to 2.X mm pretty quickly but never more and with no endplay change. So, I started calling 2-3mm of preload "normal", although others dislike that naming. Something more than that seemed to be required to wear the thrust bearing, but that is conjecture just based on my experience. I have seen some 928s with over 10mm of preload. Why and how exactly, I don't know, but those were in extreme danger of wearing, frying and seizing the thrust bearing. Anyway, with the rear pinch bolt properly torqued and the PKlamp installed, preload accumulation from movement of the shaft through the clamp has become a non-issue for me.
My crank endplay.
https://rennlist.com/forums/928-foru...pictorial.html
https://rennlist.com/forums/928-foru...xperience.html
The rear clamp tightness is critical, as others mention. Movement is restricted due to the rear position being fixed by a slot cut in the TT shaft into which the bolt fits. If the bolt is loose, the shaft slot and bolt gall each other and the rear splines are damaged if not worse. So, making sure that is properly tightened is first on the list.
https://rennlist.com/forums/928-foru...xperience.html
Despite 264K miles over nearly 25 years, my crank endplay has never changed (0.008" or 0.20mm, in the middle of the factory "new" range). Before the PKlamp it survived 10 years without any release of preload, but preload only accumulated to a little over 2 mm. I started releasing the front clamp and removing the preload 2-3 times a year after I bought the car in 1999. It would accumulate to 2.X mm pretty quickly but never more and with no endplay change. So, I started calling 2-3mm of preload "normal", although others dislike that naming. Something more than that seemed to be required to wear the thrust bearing, but that is conjecture just based on my experience. I have seen some 928s with over 10mm of preload. Why and how exactly, I don't know, but those were in extreme danger of wearing, frying and seizing the thrust bearing. Anyway, with the rear pinch bolt properly torqued and the PKlamp installed, preload accumulation from movement of the shaft through the clamp has become a non-issue for me.
My crank endplay.
https://rennlist.com/forums/928-foru...pictorial.html
03-09-2014 | 09:35 PM
#20
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Drifting
Joined: May 2010
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From: Northern Virginia
I didn't leave the plate with 2mm of deflection. I released it. Torqued the bolt to 66 lb-ft. Actually, I did it twice...again after quadruple checking the end play with dial gauge I picked up at Harbor Freight this morning (pics to come). After repeating the measurement with the dial gauge four times, each time getting the same 0.178 mm, I once again torqued the bolt. I didn't use blue Loctite on the threads of the bolt this time because next month (after moving to a new home) I'll be going in again to check the rear clamp and may have to loosen everything and slide the driveshaft to the rear.
One thing is certain...get the dial gauge. So easy to use and so precise and accurate. Wish I had something else to measure
I DO have plans to buy a PKlamp. Constantine's clamp is the ultimate solution, but it is something I'd do when it's time to drop the TT and transmission for other repairs. This weekend my goal was simple - determine if the crank end-play was within spec BEFORE spending more money on the car, including before ordering a PKlamp.
When I said I would take it easy, I was referring to driving it gently after releasing the clamp, prying the flywheel to aft stop, and torquing the bolt - because I'd read that even following the re-torque, the clamp will inevitably migrate. I never got past about 2200 rpm this afternoon. No hard acceleration. I'm just curious to see if any deflection returns even when baby-ing it.
My 15-year-old Snap-On torque wrench has a fresh recalibration certificate from Snap-On...and it sleeps in a very nice case.
I'm pretty happy with the results...0.178 mm, very low end play.
One thing is certain...get the dial gauge. So easy to use and so precise and accurate. Wish I had something else to measure
I DO have plans to buy a PKlamp. Constantine's clamp is the ultimate solution, but it is something I'd do when it's time to drop the TT and transmission for other repairs. This weekend my goal was simple - determine if the crank end-play was within spec BEFORE spending more money on the car, including before ordering a PKlamp.
When I said I would take it easy, I was referring to driving it gently after releasing the clamp, prying the flywheel to aft stop, and torquing the bolt - because I'd read that even following the re-torque, the clamp will inevitably migrate. I never got past about 2200 rpm this afternoon. No hard acceleration. I'm just curious to see if any deflection returns even when baby-ing it.
My 15-year-old Snap-On torque wrench has a fresh recalibration certificate from Snap-On...and it sleeps in a very nice case.
I'm pretty happy with the results...0.178 mm, very low end play.
Last edited by Captain_Slow; 03-10-2014 at 07:51 AM.
03-10-2014 | 12:37 AM
#21
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Drifting
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From: Northern Virginia
Some pictures of the gauge reading and where I took the measurements on the flywheel.
Close up of reading just barely past the 0.007 inch (0.178 mm) mark.
Is this where the access to the rear flex plate bolt is hiding? I think I see the rounded edge of a rubber plug.
Close up of reading just barely past the 0.007 inch (0.178 mm) mark.
Is this where the access to the rear flex plate bolt is hiding? I think I see the rounded edge of a rubber plug.
Last edited by Captain_Slow; 03-10-2014 at 07:57 AM.
03-10-2014 | 06:50 AM
#23
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From: Brisbane, Australia.
03-10-2014 | 08:55 AM
#25
Drifting
Joined: Nov 2005
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From: Sydney Australia
The rear T Tube coupling is the one that ( becomes loose ) for want of a better expression , far more often than the front one , be it manual trans or Auto trans ( full stop ), have been dealing with it for Decades on the 928 series
The rear coupling inhex bolt has to be checked / tightened on a very regular basis( bolt stretch ) & is the main cause for the engine flexplate deflection ( auto trans) with its quite weak designed hollow & split ( in three places) input shaft to the trans , be it auto or manual , this is the only true mechanical stuff up Porsche did with these cars , for some strange reason the front coupling ( auto ) does loosen ( bolt streatch ) but no where as much , not sure why & quite frankly do not care why , and yes a lot of it ( bolt stretch ) is very much related to hard acceleration events from the standing start , so we have seen customers who are do accelerate a bit too quickly from the standing start & its these cars that really suffer the rear coupling in hex bolt stretch much more as compared to the front coupling
If it had a two bolt coupling ( like the 928 3 speed auto & all 944 series in manual trans ) with two solid male splined shafts comming together and the splined female sliding sleeve with 2 X inhex bolts, then the issue would be far far less
The complete fix would be what Porsche finally settled on with the 968 ( last of the 944 series) they had ( again two solid splined male shafts comming together ) but this time with a splined sliding sleeve with 4 inhex bolts ,( 2 inhex bolts at each end of the very strong sliding sleeve) this is the complete fix as this never moves / loosens
However saying all the above , the 928 manual trans ( all) and 4 speed auto ( all ) rear coupling with its near "under engineered for a V8 " hollow and split in 3 places trans input shaft can be managed ,checked / new bolt/s tightened & or reset ( position ) on a regular basis & then all is well
The engine thrustbearing can only wear / become damaged with the use of low oil film strength engine oils , because over the decades we only see worn out engine thrust bearings , be it on 928 / 944 series when they have been on a low viscosity engine oil that was way too low on ZDDP , be we never see the same wear when they have been on a 20w-50 & some 15w-50 oils that have good levels of ZDDP
Use it for what its worth , either way , make no difference to me , because I will never be accused of not warning people of what we have experienced over the decades
The rear coupling inhex bolt has to be checked / tightened on a very regular basis( bolt stretch ) & is the main cause for the engine flexplate deflection ( auto trans) with its quite weak designed hollow & split ( in three places) input shaft to the trans , be it auto or manual , this is the only true mechanical stuff up Porsche did with these cars , for some strange reason the front coupling ( auto ) does loosen ( bolt streatch ) but no where as much , not sure why & quite frankly do not care why , and yes a lot of it ( bolt stretch ) is very much related to hard acceleration events from the standing start , so we have seen customers who are do accelerate a bit too quickly from the standing start & its these cars that really suffer the rear coupling in hex bolt stretch much more as compared to the front coupling
If it had a two bolt coupling ( like the 928 3 speed auto & all 944 series in manual trans ) with two solid male splined shafts comming together and the splined female sliding sleeve with 2 X inhex bolts, then the issue would be far far less
The complete fix would be what Porsche finally settled on with the 968 ( last of the 944 series) they had ( again two solid splined male shafts comming together ) but this time with a splined sliding sleeve with 4 inhex bolts ,( 2 inhex bolts at each end of the very strong sliding sleeve) this is the complete fix as this never moves / loosens
However saying all the above , the 928 manual trans ( all) and 4 speed auto ( all ) rear coupling with its near "under engineered for a V8 " hollow and split in 3 places trans input shaft can be managed ,checked / new bolt/s tightened & or reset ( position ) on a regular basis & then all is well
The engine thrustbearing can only wear / become damaged with the use of low oil film strength engine oils , because over the decades we only see worn out engine thrust bearings , be it on 928 / 944 series when they have been on a low viscosity engine oil that was way too low on ZDDP , be we never see the same wear when they have been on a 20w-50 & some 15w-50 oils that have good levels of ZDDP
Use it for what its worth , either way , make no difference to me , because I will never be accused of not warning people of what we have experienced over the decades
03-10-2014 | 09:46 AM
#26
Drifting
Joined: Dec 2012
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From: Pennsyltucky
There is no replacement for experience. Thanks for this post JET951
The rear T Tube coupling is the one that ( becomes loose ) for want of a better expression , far more often than the front one , be it manual trans or Auto trans ( full stop ), have been dealing with it for Decades on the 928 series
The rear coupling inhex bolt has to be checked / tightened on a very regular basis( bolt stretch ) & is the main cause for the engine flexplate deflection ( auto trans) with its quite weak designed hollow & split ( in three places) input shaft to the trans , be it auto or manual , this is the only true mechanical stuff up Porsche did with these cars , for some strange reason the front coupling ( auto ) does loosen ( bolt streatch ) but no where as much , not sure why & quite frankly do not care why , and yes a lot of it ( bolt stretch ) is very much related to hard acceleration events from the standing start , so we have seen customers who are do accelerate a bit too quickly from the standing start & its these cars that really suffer the rear coupling in hex bolt stretch much more as compared to the front coupling
If it had a two bolt coupling ( like the 928 3 speed auto & all 944 series in manual trans ) with two solid male splined shafts comming together and the splined female sliding sleeve with 2 X inhex bolts, then the issue would be far far less
The complete fix would be what Porsche finally settled on with the 968 ( last of the 944 series) they had ( again two solid splined male shafts comming together ) but this time with a splined sliding sleeve with 4 inhex bolts ,( 2 inhex bolts at each end of the very strong sliding sleeve) this is the complete fix as this never moves / loosens
However saying all the above , the 928 manual trans ( all) and 4 speed auto ( all ) rear coupling with its near "under engineered for a V8 " hollow and split in 3 places trans input shaft can be managed ,checked / new bolt/s tightened & or reset ( position ) on a regular basis & then all is well
The engine thrustbearing can only wear / become damaged with the use of low oil film strength engine oils , because over the decades we only see worn out engine thrust bearings , be it on 928 / 944 series when they have been on a low viscosity engine oil that was way too low on ZDDP , be we never see the same wear when they have been on a 20w-50 & some 15w-50 oils that have good levels of ZDDP
Use it for what its worth , either way , make no difference to me , because I will never be accused of not warning people of what we have experienced over the decades
The rear coupling inhex bolt has to be checked / tightened on a very regular basis( bolt stretch ) & is the main cause for the engine flexplate deflection ( auto trans) with its quite weak designed hollow & split ( in three places) input shaft to the trans , be it auto or manual , this is the only true mechanical stuff up Porsche did with these cars , for some strange reason the front coupling ( auto ) does loosen ( bolt streatch ) but no where as much , not sure why & quite frankly do not care why , and yes a lot of it ( bolt stretch ) is very much related to hard acceleration events from the standing start , so we have seen customers who are do accelerate a bit too quickly from the standing start & its these cars that really suffer the rear coupling in hex bolt stretch much more as compared to the front coupling
If it had a two bolt coupling ( like the 928 3 speed auto & all 944 series in manual trans ) with two solid male splined shafts comming together and the splined female sliding sleeve with 2 X inhex bolts, then the issue would be far far less
The complete fix would be what Porsche finally settled on with the 968 ( last of the 944 series) they had ( again two solid splined male shafts comming together ) but this time with a splined sliding sleeve with 4 inhex bolts ,( 2 inhex bolts at each end of the very strong sliding sleeve) this is the complete fix as this never moves / loosens
However saying all the above , the 928 manual trans ( all) and 4 speed auto ( all ) rear coupling with its near "under engineered for a V8 " hollow and split in 3 places trans input shaft can be managed ,checked / new bolt/s tightened & or reset ( position ) on a regular basis & then all is well
The engine thrustbearing can only wear / become damaged with the use of low oil film strength engine oils , because over the decades we only see worn out engine thrust bearings , be it on 928 / 944 series when they have been on a low viscosity engine oil that was way too low on ZDDP , be we never see the same wear when they have been on a 20w-50 & some 15w-50 oils that have good levels of ZDDP
Use it for what its worth , either way , make no difference to me , because I will never be accused of not warning people of what we have experienced over the decades
03-10-2014 | 11:22 AM
#27
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From: Brisbane, Australia.
All your reasoning is correct.
... ...
Forget all the hyper-engineered "Unobtanium 19-axis supa-hydraulic moon-landing standard" clamp bolt stuff.
... ...
Remove the rear heat shields and look through the 'hole' thru which U can see the clamp bolt. Remove the bolt.
You'll find it worn and shiny in the centre, and maybe even slightly bent.
My challenge to all the flexplate experts: show us the rear pinch bolts you removed at the same time you released the flex on your front flexplates.
We're waiting ....
UpFixedDerPorsche
'89 S4 Auto
Last edited by UpFixenDerPorsche; 03-11-2014 at 01:37 AM.
03-10-2014 | 07:23 PM
#29
Under the Lift
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15 years of measuring endplay and watching the TT shaft migrate backward out of the stock front pinch clamp on mine and numerous other S4 automatics, even with the bolt torqued above spec, over only a few months, creating 2-3mm of preload on the front flexplate, bowing it measurably, easily relieved but finally eliminated with the PKlamp (or Constantine's Superclamp), have lead me to believe there is something going on there. Of course, the stick shifts don't have the same TT shaft/front clamp issue but can wear the thrust bearing on the other side and crank endplay can go out of spec.
Errka, pass me some of that popcorn.
Errka, pass me some of that popcorn.
03-10-2014 | 07:38 PM
#30
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From: Helsinki, Finland
Yeah, Porsche put shims to TT front end just for hell of it in '78-84 automatics. They don't do anything at all to prevent center shaft moving forward but are very efficient in stoping clamp moving forward.