atb

Just my 2 cents Ted.
I always clamp the front pinch bolt first, just as a temporary hold for the drive shaft, then do the rear and torque to spec, then release the front and re-torque to spec.

I've had problems when pushing the drive shaft into the input shaft of the tranny, having the drive shaft shift forward in the torque tube. If you clamp the front first, you don't have this problem. Just make sure that after you've clamped the rear, you release the tension up front and re-torque.

I'm sure that forgetting this last step is a primary cause for many TBF's out in the field after a TT replacement.

Mrmerlin

Adam this is interesting advice, is this when your fitting a TT to the trans??
I can see that the driveshaft may move in the carriers when fitting to the trans though.

For simply checking the the torque of the pinch bolts, I dont see this as a concern.
But the rear cut out should be centered in the input shaft cutout,
if this isnt done then the drive shaft will carve out slots in the bolt shank, and weaken it

atb

Stan,

Yes, you are right. If the TT is already up and in place then my concern's aren't an issue.

Imo000

There is more..... halft the thread tops are missing too. See how sharp the last couple turns are at the end of the bolt? The entire thread shoud look like that. Last time when the bolt was binding and you threaded it in anyways...... what happened was that you've "machined" of a good chunk of the threads. I'm pretty sure this would reduce the clamping power of the bolt quiet a bit.

Cosmo Kramer

Yep I noticed that too. That was me re-torquing it when it was loaded with pressure from the flex plate. Would have been better off leaving it alone. Gonna order new bolts for front and back. Went to my local supplier yesterday and they only had ones that were almost completely threaded in 12.9 hardness, so gonna order them with my next batch of parts

Randy V

Seriously!?

I bought and installed P-Clamp specifically to acieve peace of mind about this problem.

So now It is still an issue with the clamp?

Dammit.

Landseer

Did you read the thread?

Boosted car, shaft not pinned quite right in the back.

Cosmo Kramer

OK guys here is an update. Year and a half later, couple trips to the dragstrip and many WOT runs with 370 whp and no movement now that the rear is pinned correctly. None zero nada...

Great product Ken!

Sorry for the crappy pic, but you get the idea.

Bill Ball

That's better. But orange paint aginst a brown/tan/grey shaft makes it hard to see if there's really any shift and break in the paint. To me it looks like there actually might have been a fraction of a mm movement, like I had once, but only one, and which is not significant.

Cosmo Kramer

Hey Bill

I think it is just the pic, unfortunately orange was all I had when I buttoned it up last time lol. But on my visual inspection under the car I didn't have any break in the paint at all.

Bill Ball

Excellent. I've been pleased with the PKlamp as well. I had one interval of over 20K miles with no movement, something I had not seen prior to the PKlamp.

safulop

This is good news, because I am not able to check my flexplate etc. myself, and my mechanic seems to not quite understand the issue with this. I am kind of running on a prayer here with my PKlamp, not sure that I can ever check the crankshaft endplay.

-Sean

Bill Ball

Uh, your mechanic is going to have to do everything just short of measuring crank endplay just to install the PKlamp. Getting the lower bellhousing cover off is the hard part - the first time the front exhaust section needs to be unfastened from the headers. He's going to have to do that to install the PKlamp. And he needs to loosen the stock TT shaft clamp to make sure the flexplate is de-tensioned as well. At that point all he needs to do is mount a dial gauge to check movement of the flywheel fore and aft as he levers it with a prybar. I'm sure he knows how to do that. He may not work on any other front engine rear transaxle cars, unless he does Corvettes, but this should be real easy.

https://rennlist.com/forums/928-foru...pictorial.html

safulop

Oh, my PKlamp was installed by the PO (well, I think Greg Brown's shop did it) in 2009, a year before I bought the car. What I meant was, I am just kind of trusting it without checking for the time being.

JET951

I have been working on Porsche 928 series since the inception of the 928 in Australia in 1978 ( 34 years), so I know a little about this subject , the problem all along has been the rear T/ Tube coupling , be it the 4 speed Auto version with its single inhex bolt design , meaning only one bolt trying to secure a try split hollow input shaft ( auto input shaft) to the solid TT quill shaft or the manual trans version ( all year types ) same idea, one bolt only holding it all together .

Subnote } the 928 3 speed auto version with its sliding sleeve covering two solid shafts & two inhex bolts gives no problems at all , same goes for the 944/ 951 series ( manual trans ) with the same sliding sleeve ( 2 inhex bolts) gives no issues at all

Lets take the 928 4 speed auto version as a good example , the rear T/Tube coupling single inhex bolt stretches way quicker( releasing clamping force) than the front of T/tube coupling inhex bolt of around a ratio of 2:1( on average) , meaning the forces ( rapid acceleration etc) is just a bit too much for the rear coupling with its single inhex bolt if left unattended(not re- torqued) for too long ( and I don't mean years), just why the rear coupling is subject to this phenomenon is not a concern to me & I don't care why I just know its always been this way , but what I am concerned about is that it can be taken care of ( maintained ) always has & always can be .

By the way , when the rear TT coupling inhex single bolt stretches ( loss of clamping force) the male splines of the TT quill shaft migrate forward to a point where the single inhex bolt flank is driven up and onto the leading edge of the splines of the half moon cut-out ( see photo of inhex bolt on previous post ) , naturally this pushes the engine flex plate forward ( this is all it is )

For many many years now we just maintain these on service intervals as routine , so every major service we re torque the rear coupling bolt and every 2nd major service we replace the front & rear coupling bolts with new ones & reset the quill shaft position , this can vary a little or a lot depending on driving style of the owner , meaning there is a lot less stretch of the inhex bolts with an owner that drives sedately as opposed to an owner why is a lead foot ( hard acceleration events) , in both driving styles its quite easy to maintain once identified.

Naturally the rear TT coupling bolt inspection hole on the 4 speed auto version has been out of sight & out of mind for most people because its hidden above heat shields and the exhaust pipes are in the way , so I can understand the reluctance to be bothered , but we can see its very very important indeed , I know because I found this out nearly two decades ago the hard way.

Interestingly Porsche were aware of this in the early 1990's , because the 944 series ( be it 944 , 944s, 944S2 & 951 ) had the 928 3 speed auto sliding sleeve with 2 inhex bolts & naturally the half moon cut-outs in the splined solid shafts to accommodate them up to the 1991 year type with no issues at all , then with the introduction of the 968 ( last of the 944 series ) 1992 - 1995 , these in 6 speed manual trans version went one step further , they still had the 2 solid shafts coming together , meaning the TT quill shaft & the trans input shaft , but this time the splines on the shaft were longer because they had a sliding sleeve with 4 ( Four) inhex bolts instead of the 2 ( two) that previously gave no trouble at all , this was a doubling of the forces that the TT coupling inhex bolts could tolerate , this was the future , the 928 if continued would without doubt had the same re engineering in this area because the 968 received it ,so it only follows that the 928 would have followed if it evolved further .

So in essence , it can be maintained perfectly , its just a service issue if one is familiar with this .

PS } we do not have any thrust bearing issues at all , never have , all along its been an low oil film strength oil issue , not a TT issue

Bruce Buchanan
Buchanan Automotive

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