Tubalube

Hello all, new 928 owner here. Picked up a 1984 928S with a 5-speed in a straight across trade, it runs well, has tight suspension, with a clean inside and lots of new-looking parts. I am, however unsure about the transmission on whether I am having problems or this is normal operation.

My question is this; how is the 5 speed supposed to feel? Will it grind if i shift too aggressively? Do I need to double clutch, is there anything I should be doing while driving? I've never driven a manual transmission this old before. Someone told me it's a German car, so I need to shift it like it's German (I guess he meant aggressively??).

The shift **** rests naturally in between 4th and 5th. It occasionally grinds going into gear, but it seems to be a toss-up as to when it will grind. It happens generally while it is cold and goes away when it warms up (for the most part) and doesn't seem to be specific to any gear. 2nd gear always seems to grind when I shift into it, to the point where I avoid using it entirely, and sometimes 4th has a little resistance when trying to pull it out of gear. Does my clutch need adjusting, could I be low on fluid? Or am I looking at a rebuild with new synchros? What could be going on?

Thank you in advance to anyone who answers.

dr bob

The two things that commonly affect shifting as you describe will be the gear oil selection and the clutch adjustment. Adjustment includes inspecting the stub shaft that the clutch disk slides on. The spines wear and may not allow the disk to slide back clear of the flywheel when clutch is released. Related to this is a worn pilot bearing. Either will cause the disk and driveshaft to continue to rotate even when the pedal is down. The release is hydraulic so it's sensitive to air in the system. The fluid needs to be changed regularly and bled as part of that process. 2 year intervals with the brake fluid are a good idea.

Gearbox oil discussions generate lots of opinions. Swepco, Redline and Mpbil-1 are frequently discussed. Others will jump in to help I'm sure, and search is your friend. Don't remove the drain plug until you are sure you can get the fill plug out. Fair warning given.


And...

Welcome to Rennlist! No new owner can expect to get away with not sharing a little history and such about yourself and the car. Pictures are pretty much a requirement. Be sure to read the New Visitor's thread in the sticky section for a ton of essential info. All is advice and guidance from those who have driven the path before you. Saves stress and budget impacts if heeded well.

Tubalube

Thank you for the info! I'm sorry about missing the info,I will try to create a signature and in the future remember other things to help out!

I had thought a clutch adjustment and fluid change would help a lot, I am going to be paying a local reputable import shop to do it for me soon. Maybe I will have them bleed the clutch as well while they are at it.

As far as second gear goes, if I was having synchro problems would it only be second gear that is affected? Or would I be having more consistent issues with another gear?

Wisconsin Joe

Welcome.
As a 'user', you don't get a sig line. So just put the year of your car in any post that asks a question about the car.

You are allowed a certain amount of pics (it's limited by the amount of data, so post low res pics).
Membership has its advantages. Some, but not all feel it's worth the cost.

Does your 'reputable import shop' have experience with a 928? It's a somewhat 'different' car. Lots of oddities.

Bleeding the clutch, for example. It's not a straight forward process. The proper procedure is detailed on here somewhere. Is your shop willing to do the research necessary to do it right?

The clutch is self adjusting. Once it's set right, it should be good to go for a long time. But, again, setting it up properly is a bit different. The process is detailed in the WSM.

Changing the fluid is straight forward, but as Dr Bob suggested, make sure you can get the fill plug out first. Lots of so-called 'mechanics' have decided that it needs to be super tight when they put it back in (it doesn't). If you pull the drain plug and then can't get the fill plug out, you are pretty much screwed. Make sure you use an oil with a GL-5 rating. Brand is subject to lots of debate. I'm of the opinion that most are all right. Use the brand that you like.

Synchros are specific to each gear. You can wear out one and not the others. So if it's grinding worst going into second, then that synchro is likely worn the worst.
You can determine if it's clutch or synchro issue by having the car sitting still, pushing in the clutch, counting to five and selecting a gear. If it grinds, then there's a clutch issue (not releasing all the way).

Tubalube

I am not sure if they have any 928 experience. Probably not as I live in a small town, but I cant imagine that they would tell me they can do the job without doing enough research to perform the adjustment.
I will try this and report back. Thanks again for all the info, Joe!

Tubalube

Joe,

Seems as though it goes easily into every gear following the procedure you mentioned, even when cold. No grinding whatsoever. Does this signal that all of my synchros are becoming worn?

dr bob

No... That's an indication that the driveshaft is still turning. Look at clutch release, not enough release throw (air in the clutch hydraulics), disk not sliding back away from the flywheel with pedal down (splines on the stub shaft, worn/missing release lever ball), dragging pilot bearing.

The 928 has one of the easiest clutches to remove and replace, except... You'll want to insert some horseshoe spacers under the ends of the release arms so the pressure plate can come out. Warning: It's heavy! The workshop manuals have pretty good instructions on the process.

Tubalube

Okay. Thanks, Bob.

Seems I am having clutch problems then... I will have the shop do a full service on the clutch, outside of replacing it, and replacing the transmission oil. If that doesnt solve the issue, I will personally follow the clutch replacement/repair procedure mentioned in the repair manuals. This is relatively good news as I was hoping I wouldnt need to be doing any major internal transmission work.

If none of those repairs rectify the issue... I think I will just drive it avoiding 2nd gear until I can afford a rebuild.

Thank both of you again for helping me get this straightened out!

Majestic Moose

dr bob I would respectfully disagree with your diagnosis. Correct me if I am wrong, but if the clutch is not fully releasing the gears will grind whether waiting one second or one minute. I had a gearbox with worn 1st and 2nd gear synchros and the workaround when stopped was to push in the clutch and wait two seconds (for the driveshaft to stop) before I could shift to 1st smoothly. As for 2nd gear it took careful rev matching for a crunch-free experience.

There is a rubber plug at the rear of the torque tube you can remove to see the shaft inside (actually you see the coupler which you should check that the pinch bolt is torqued at 66ft lb). Either have a helper look though the hole or set up a camera to see if the shaft comes to a stop when you depress the clutch.

See this example.

Wisconsin Joe

Dr Bob - Are you sure you read that right?

I am reading that he can shift easily into any gear, sitting still, after pressing the clutch and waiting a few seconds.

That would indicate that the shaft has stopped. Right?