jbrob007

WE are working on a 87 auto and need to know if there are any torque specs for the pinchbolt on the flex plate clamp???

PorKen

The original spec was 59 ftlb/80 Nm. This was increased to 66 ft lb/90 Nm at some point. (10% overtorque - not sure if this was a service bulletin or if this was an unwritten rule.)

If you are installing a PKlamp, I recommend the original spec - 59 ft lb/80 Nm.

Bill Ball

Use 66 ft lbs. The spec is stated as low as 59, but somewhere Porsche upped it a bit. Most use 62-66 range.

jbrob007

Thanks! Just saw the TSB on this.
If the P-Clamp I bought from Rodger in 09' is also being used...

what torque should be used on the P-Clamp bolts...is there a difference?

Brett (@ Joel's) & Quadcam

PorKen

PKlamp bolts - 17 ft lb/23 Nm

(If all else fails, read the manual - http://liftbars.com/docs/PKlamp.pdf )

jbrob007

Now dont go making it all EASY on us...!!!! I think we got it! Thanks to all for the info, advice, suggestions, recommendations, and most importantly DIRECTIONS!!! LOL!!!

Mrmerlin

if your setting the pinch bolts on a drive line make sure to torque the rear bolt and do it first use a dab of blue loctite on the bolt torque to 66 ft/lbs
Neglecting to do this may cause TBF as the rear pinch bolts seem to be loose more often than not

Dave928S

+928

Migration of the drive shaft forwards happens on manuals too. Renewing the bolts is also cheap insurance, as they do stretch, and you can re-torque them forever. When the drive shaft moves forward the rear pinch bolt can wreck the splines on the shaft, as the bolt rides up from the groove onto the splines.

FredR

Ken,
I introduced this concept [10% over torque] to the list around May 99 [I originally used the mailing board list] when I discovered the flexplate on my late 90 S4 was creeping inexplicably.
The saga started after I had noticed some driveline vibration and then the car snapped its torque tube just behind the front splines [May 99?] under hard acceleration whilst overtaking [or should I say trying to…]. A sickening big bang, loud whirring noise and no drive left me somewhat suspicious [never mind feeling stupid] that something cataclysmic had happened as the car rolled to a halt and the one I was overtaking disappeared into the horizon with the driver probably laughing his private parts off! Thus I was stuck in the middle of nowhere, mid-afternoon, 40 degrees C desert heat wondering why the f*&% I had purchased this “piece of crap”.
A month [& many $$’s] later after fitting a new torque tube the car felt very smooth again but within a couple of weeks back on the road I felt this vibration at 3050 rpm.
About that time I had just had my first home internet connection installed and came across this incredible resource [the Rennlist]. I then came across a thread discussing the inherent problems with TBF on the autos which explained the creeping flex plate phenomena. I complained bitterly to Porsche about the problem I experienced but they just lamely said “anyone can snap a torque tube in 5 minutes if they really want to” and denied there was any common problem with the drive line. When I retorted about the problem I experienced with the newly fitted torque tube they referred the problem to Porsche Middle East who within two hours came back with the solution to “fit ze new bolt und over torque by 10% or you will be shot at dawn”. An amazing response for a system that had “no problems” and clearly Porsche Middle East did not come up with that either. Doubtless that instruction came directly from Herman ze German but at least they did try.
I immediately fed this response back into the list, implemented it and within two weeks back to square one again- the solution was absolutely no use- the flex plate clamp was one the move once more. At that time Earl Gilstrom came up with the Loctite 260 solution. I believe I was the second owner to implement this [first one outside Earl’s garage] and I still use this solution to this day. I feel as though I owe him big time.
As an engineer, I admire the solutions that Constantine and yourself [and the Dutch chaps] have come up with and have recommended them to other owners both here and around the world. I will fit one of them one of these days if and when I need to make a driveline intervention. However, when I took on my current 928 GTS 5 years ago I tried to implement in one go all the things we 928 owners regularly have to deal with and the car has [touch wood] been totally reliable to date.
Regards

Tails

Porsche 928 S4, GT MY1990 & 1991 and GTS MY1992 & 1993 Technical Specifications Booklet states that the tightening torque for clamping sleeve to drive shaft 80Nm (59Ft. lbs).

Technical Bulletin for 928 Subject: Installing Central Tube dated May 5, 1992 states: "Then tighten the clamping screw (B in Fig 1) to 75 to 85 Nm (54-62 ft. lbs)".

10% on 59 ft. lbs = 66 ft. lbs.

I use locktite with no movement recorded for many years now.

Tails 1990 928S4 Auto

jbrob007

Thanks again to all from Joel, Pete & Brett (the MY 87 Auto owner)... We got his Shark all back together (did a TB job too) and she is purrin' like a kitten!

granprixweiss928

In a manual transmission car, does the front clamp and the rear clamp use the same bolt?

part number of pinch bolt?

Dave928S

Yes ... two for the front clamp and one for the rear, and they're all the same part number. Renew all at the same time and torque to 66 ft.lbs, after ensuring shaft is correctly located.

P/N 931 421 240 00

granprixweiss928

Thanks.