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Temps have been dropping a bit since I last drove my 928. The past week, I've been having a lot of trouble shifting, with reverse, 1st, 2nd grinding almost constantly. If I let the car sit for over 30 minutes warming up, I slowly get access to more gears, starting with 3rd and 4th, then 5th, then 2nd, then 1st and reverse. When it's cold it's almost as though I don't even have a clutch.
Tomorrow I'm going to be changing out the gear oil for Redline 75w90, hoping that helps at all. Anyone have any ideas on where else I should look for sorting this issue out? Clutch hydraulics are to be inspected during the gear oil change.
Sounds a like you're not getting complete disengagement of the clutch, and when the gear oil is cold and more viscous you're getting hydraulic connection of gears within the gearbox, and less so as the oil becomes hotter and less viscous. Getting your clutch intermediate plate adjusted correctly so that both driven plates disengage is you first step to sorting your problem.
And adjusting the clutch intermediate plate is...
remove bellhousing cover, use flathead screwdriver and move the 3 T-adjusters as far back as they'll go, correct?
The adjustment is discussed to death in this thread . . . . https://rennlist.com/forums/928-foru...te-ers-11.html
You'll find the answers in posts by knowledgeable members answering the original poster . . . it's worth skimming through the whole thread, which covers other issues as well There are other things that may add to the problem like intermediate shaft spline wear, lack of lubrication, hydraulic issues, or gearbox wear, but getting this adjustment right should go a long way to solving the grinding.
Adjusting the clutch plates is a good place to start. But IMO I'd drop the clutch and inspect everything. I've now had 4 back to back 928's with similar shifting issues and all of them had something wrong with the release bearing.
It's a wear item and when it's not functioning properly, you can get intermittent shifting issues.
Also, I feel every double disc clutch 928 owner should buy a second lower bellhousing cover and cut a hole in it for adjusting / inspecting the intermediate disc. Here is mine installed in my 81:
Ok, I work at a dealership so I just threw it on the lift during my lunch break.
Checked over hydraulics and slave cylinder function, has about 1" of travel, and there's no sign of any leaks.
Removed bellhousing and adjusted intermediate plate after reading through the sent threads as well as looking it up on youtube to help me visualize it, and buttoned the car up, including fresh gear oil.
Car now shifts smoothly! even 2nd has no issues, can even downshift from 3rd to 2nd without grinding at all. Before I avoided downshifting beyond 3rd for fear of 2nd gear synchro issues. Reverse engages well too. I would like to do a full clutch job, but currently I need to have my 928 running, as it's in my daily driver rotation. When I can get a clutch kit and have a free weekend I'll probably take it apart for that.
Awesome news.
I haven't bought any clutch parts for a while, not sure what's available new. I know @ROG100 @ 928's R Us has a disc rebuild service and can get any new parts. 928 International sells new and rebuilt parts and the go to for any parts not available new, like the intermediate disc
Ok... so I'm back scratching my head. I've tried adjusting it to WSM spec of 1mm gap but it's still dragging if I don't let the car warm up for at least 15 minutes. After that it seems to be shifting fine. Is it my gear oil?
Ok... so I'm back scratching my head. I've tried adjusting it to WSM spec of 1mm gap but it's still dragging if I don't let the car warm up for at least 15 minutes. After that it seems to be shifting fine. Is it my gear oil?
If you're in a colder area you can try a thinner oil. I've had good luck with Mobil1 Synthetic gear oil but any of the thinner high quality synthetics will work. My transmission shifts very good but can feel a bit stiff and cranky when temps are near freezing, the synthetic gear oil helped that a'lot and the crankyness went away much quicker. I've heard of replacing some of the gear oil for ATF. This is a bit drastic but can thin out the fluid a lot if you're in a colder climate. I'd try the synthetic and nurse it until it warms up.
I don't think its gear oil. I have had this cold temp problem in the past. Never really solved it, but I felt that a little more clutch travel would have helped. Would be interesting to leave it outside all night on a cold night a roll it onto a lift before it warms up to see what's happening.
I'm in Atlanta, but temps were in the 30s at the time.
Temps have gotten into the 60s now, and on days where it gets into the 70s it doesn't need to warm up at all. It's most certainly temp related, though like you said karl, a bit more clutch travel would likely help. Very strange issue indeed.
There's a strong chance that the clutch is going out of adjustment again, to give you exactly the same problem as you experienced before, due to the H adjusters being a bit worn/loose . . which is very common. Replace the rivets with a bolt (or drill and pin the adjusters) to stop them adjusting themselves out of correct position. Which is what I did to mine, after going crazy constantly adjusting it, and it proved to be a lasting remedy . . . . https://rennlist.com/forums/928-foru...l#post12283310
There's a strong chance that the clutch is going out of adjustment again, to give you exactly the same problem as you experienced before, due to the H adjusters being a bit worn/loose . . which is very common. Replace the rivets with a bolt (or drill and pin the adjusters) to stop them adjusting themselves out of correct position. Which is what I did to mine, after going crazy constantly adjusting it, and it proved to be a lasting remedy . . . . https://rennlist.com/forums/928-foru...l#post12283310
Isn't this treated steel? How would I go about drilling and pinning the adjusters?
Pinning can and has been been done by some, as you'll see in some of the never ending posts on this topic, but I haven't done it and wouldn't do it as it's a bit 'shade tree mechanic'. I should have noted that in my last post, but included it because you'll see it mentioned and shown a lot in clutch threads. It's just drilling a 1/8th hole near the original rivet head going through the adjuster and fitting a long 1/8th rivet.
I strongly suggest you just pull the clutch pack, which is not a massive job, and fit the bolts with spring washers as shown, but also check all your other components, refit and lubricate to fix it once properly . . . and avoid the never ending story of a bit at a time, which will take you much more time and cause much more frustration in the long run. The time has come to pull it out and get it right (see post #6) . . . there will undoubtedly be something else which needs attention, and at the very least proper lubrication.
Last edited by Dave928S; Feb 25, 2023 at 10:11 PM.
Reason: sp
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Early 5spd shifting issues
