SeanR

And there ya go.

I post a thread telling people to check it and everyone can see how it turns out. Welcome to Rennlist.

OTR18WHEELER

When I discovered my cracked front flex plate...the rear pinch bolt was tight, and was unmarked, it was still centered in the shaft groove.

Tazzieman

Answering for Bruce , the thread screws go the other way downunder , and the only virgins here are Americans on student tours

bureau13

Not to keep inserting my ignorance into this thread, but is there a write-up or pretty pictures anywhere that would indicate what needs to be done with a 5-speed car to check this? I don't see anything in the WSM about checking/tightening anything in this area, which is not surprising given the fact they didn't seem to know or care too much about it. I did find what I think is the coupling and bolts...80 nM torque? That's what it says, unless I have the wrong ones. Not sure how you access it....from discussions I'm guessing there's an access point. It definitely seems like something I should check though, I wouldn't be surprised if it had never been done on my car.

soontobered84

It turns out that probably everybody needs to check their rear pinch bolt torque and you may be the one person who raised our consciousness and awareness to the problem. Even if you keep just one 928 owner from trashing their TT, you may have saved that car.

I think I'll have a beer tonight and just raise a toast to you. Cheers

dr bob

A couple decades ago when I was buying a new Saab, I questioned why the local dealer felt the need to charge a few $hundred extra for checking tightness of critical fasteners. Dealer couldn't give me a list of what they were going to 'check' so we negotiated that cost away. But it spooked me enough that I picked the car up as it came off the trailer, and spent an afternoon checking a long list of things shared by the service manager. Then let them 'inspect' everything to 'validate the warranty'. Craziest car purchase ever, but it set a new standard for me and all car purchases.

I just didn't know about this rear bolt issue on my 928. I learn every day from this group.

polecat702

Why has no one mentioned the torque specification of the pinch bolt, what is it?

Chalkboss

Thanks Sean for bringing this up. I am going to check mine regularly now.

bureau13

If you see my post a couple posts above yours, I mention that I found what I THINK is the proper bolt, listed at 80 nM...but I'd like someone to verify it. And I still am not 100% sure how to get to it...

Mrmerlin

factory torque on the bolt is 59 Ft/lbs,
the TSB issues increased the torque by 10% so 66 Ft/lbs is the new torque

polecat702

Thanks Stan!

depami

Be careful on the front one if you have a PKlamp as the PKlamp bolts only want 17 Ft/lbs. I had a brain fart and tried to torque the PKlamp bolts to 66 and those bolts don't like that.

I replaced them with hard bolts bought locally, used blue Loctite, and torqued them to 17, maybe slightly more. I hope they'll be alright.

ROG100

Volume wise the "stretch" bolt is one of our biggest sellers at $8.94 each

Dave928S

Constantine mentioned that he believes that the bolts just loosen ... I and Bruce Buchanan believe they stretch.

On thinking about the issue, I think it's conceivable that both may occur.

Constantines proposition that splines may 'settle in' a little is possible, which leads me to think that, just like a timing belt, a check after the initial installation/re-installation is worthwhile.
Owners just not torquing bolts properly, as he states, is also possible.

The original paint mark, which happened to also go a little onto the clamp body, on my GTS, clearly showed that bolt had stretched and not loosened, and this seems to be supported by the 0.45 mm extra bolt length. I say seems, because it could, of course, have been longer to start with.

As I said in my previous post .... "Nothing short of measuring a bolt when it goes in new, and then measuring that same bolt when it comes out, after loosening, will categorically tell if it has stretched, or just rotated loose.

The bottom line is that the bolts loosen. It doesn't really matter through what process that occurs. They should be routinely checked, and I think they also warrant replacement, to rule out the possibility of stretch.

This is not a new issue.

I've mentioned it on multiple occasions in past threads, where I put the view that I'm putting now, Bruce Buchanan has mentioned it on numerous occasions in TBF, TT, and flexplate threads (and got a dismissive response each time), and Stan has been recommending checking it for a long time also. Here's just one post I pulled up from 4 years ago ... https://rennlist.com/forums/928-foru...ml#post8217916 Edit: There are dozens more threads and posts on this issue, before and after this one.

Check/replace the rear pinch bolts at the same time as you check the front ones. At that time you should also be checking that the shaft is correctly located in the TT, and hasn't slid forward. It's a waste of time having the front ones tight/ superclamp/pklamp if the rear clamp allows the shaft to move.

Edit: Be sure to fit the correct grade and size bolts, which you can get from one of our suppliers. Lower grade bolts will stretch.

Dave928S

Here's an abbreviated summary ...

1. Remove the access plug and you can see the clamp.
2. Transmission in neutral and clutch depressed, will allow you to rotate the shaft to see/access the bolt head.
3. Loosen the bolt. Highly likely it will be difficult to rotate from pressure on the side of the shaft groove.
4. Remove the clutch lower bell housing cover, and pry the shaft back to align/centre the rear clamp/bolt, and then the rear bolt will easily come out.
5. Slide rear clamp out of the way and carefully check gearbox input shaft for cracks.
6. Align rear clamp, fit new bolt and torque to 66 ft/lbs.
7. Remove front clamp bolts.
8. Check alignment and location of front clamp, and that stub shaft is at correct position into pilot bearing.
9. Fit new front bolts and torque.

I agree with Bruce that loktite shouldn't be used on the bolt (post #43), as that would give you a false sense of security that it is still correctly torqued, if it stretches.

Here is the access plug on a 5 speed ...