BrianG

This has been a very informative thread. Thanks very much for the conversation

Bruce, from your post you say "Reset the position of shaft after first doing a crankshaft axial movement check ( thrust bearing wear check)" Would you be kind enough to describe the resetting the position of the shaft after having removed and replaced both pinch bolts.

Thanks!

FredR

Brian,

The logic here is check the end float, tighten the rear coupling then tighten the front coupling. Porsche would have worked on the principal that not all installations are identical dimensionally so they had to allow for this and on the later models they did it by having a front coupling that floats when the bolt is not fastened. Earlier models had a shimming system that by consensus appears to have been technically superior but somewhat fiddly to apply.

Unfortunately experience has demonstrated that the later type front coupling can [in many instances] eventually slip even though it was fastened correctly and therein lies the problem. This is further compounded by the fact that the rear pinch bolt also causes issues and therefore the problem has to be treated as a "two front attack". Wise owners heed this warning.

This thread as you can see from its title was initially perceived as a "Loctite does not work" type of thing but then as the thread opened up it became apparent that the front joint was not the issue and that it was the rear bolt that had seemingly worked loose at some time in its life and that likely caused mechanical damage.

One hopes the OP solved his issue but it seems he did not follow up on his solution methodology [unless I missed something]. I find this a bit sad as we also like to read about eventual success stories- maybe the problem was never completely resolved but each to his own as it were.

JET951

Hi Brian G , its all very simple , but first we must remember that the T Tube rear coupling ( single index bolt ) on the 4 speed Auto 928 & the manual trans ( all year models) does not loosen by undoing its self , it stretches from acceleration events ( that's what reduces its clamping force ), because there is only one bolt ( ONE )to hold everything together , its almost stupidly under - engineered , but Porsche already knew that and the later T Tube designs by Porsche ( 968 ) had 4 bolts ( same part numbered bolts ) holding a far far far far far better designed ( stronger ) rear coupling ( two index bolts on either end of a sliding sleeve joining two solid splined shafts( NO stupid hollow input-shaft) , a bit like the early 928 3 speed auto trans design but a lot better with more bolts ( problem solved )

Now back to the under - engineered rear coupling design of the 928S / S4 / GTS with the 4 speed auto trans & all manual trans versions of the 928 , meaning just one small bolt that quite understandably just stretches when its under stress (hard acceleration from a standing start mainly )

To re-set the T Tube shaft ( quill shaft ) Auto Trans 4 speed ( 1984 > ) first of all with both the front & rear coupling in hex bolts removed you simply ( if needed ) slide , push the Quill shaft backwards with a lever from the front bell housing area until the half moon cut out aligns with the centre of the rear coupling hole ( with the square clamp overlaying it ) ,with the rear clamp & coupling all aligned up , you simply apply a light coating of grease to the threads of the new index bolt and install ( do not tight just yet )
Install the new index bolt ( lightly greased threads into the front coupling ) , naturally the front flex plate is completely relaxed ( straight ) and now you can Torque up the front & rear coupling in hex bolts

Very easy stuff & easy to maintain

Bruce Buchanan
Buchanan Automotive 40 + years working on Porsche cars 6 days a week

BrianG

Bruce,

Splines dry or oiled?

And now I understand why nobody looks at the back clamp! That inspection hole is burried up under all that heat shield! Looks like the exhaust system has to come off to get there.

Bertrand Daoust

Dry AFAIC.

I never put any oil on the spline.

I want it to stay in place. At it's right place. Front and back.

BTW, it never moved since I put the PKlamp there.

Dave928S

Dry .... and the cleaner the better.