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NOT a just live with it deal!
You will kill what is left of the synchro for 2nd gear.
Find out what is wrong with the clutch or the hydraulics. Either the clutch is slightly out of adjustment, meaning the intermediate plate, and/or the slave cylinder is not fully releasing the clutch.
As well, could be the ball cup bushing on top of the release arm.
Go through the entire clutch system, make sure it is right.
An OB 5spd that is in good condition is a rare thing.
Don't ruin it.
Now...better experts will be along soon to give you better details.
If the clutch master cylinder has ever been replaced it would be wise to remove the piston and see if it’s been shortened,
also replace the flex line and the hard line that goes to the slave with a Greg Brown flex hose, this is a must do upgrade.
NOTE if the car sits in a damp environment there’s a good chance that the spline shaft is rusted to the disks,
it would be prudent to drop the clutch assembly down and put fresh grease on the stub shaft so the disks slide,
also inspect all the pieces.
NOTE as suggested by Seth the release arm bushing should be replaced.
1. Verify clutch isn't dragging.
Dual clutch is tricky to setup and may come out of spec over time. A warped disk, misadjusted intermediate plate, incomplete clutch arm travel, sticky clutch disk shaft, oval'd pilot bearing can all cause clutch dragging. An experienced 928 shop will have a clutch cover with a hold drilled in it for a visual inspection.
2. Verify Torque Tube bearings arn't dragging
If the torque tube bearings are bragging or stiff or out of alignment it can make it difficult for the synchros to do their work
3. Try Synthetic ATF in the transmission (Mobile 1, Redline, etc.)
Reducing oil drag can help and buy you some time
After all that your 2nd gear still might be crunchy and worn out from an extended time with 1 and 2 or just age and use. Important to do all this so that If you do choose a rebuilt it wont be destroyed quickly. All Porsche's were known for this issue and Porsche redesigned their synchro system across their range in 1985 but the long torque tube and long warm up cycle of the 928 put lots of stress on the early synchro design.
Last edited by icsamerica; 04-02-2021 at 01:43 PM.
After having gone through all of this a year ago on my ‘78, I agree with what everyone here is saying. Start small and work big.
Since there’s no synchro, reverse gear is usually a gear that grinds if one or both clutch discs are dragging and thus letting the torque tube shaft still spin with the clutch pedal pressed down. Does your reverse ever grind when you try to shift into it?
At startup after the car had been sitting for a day...
Originally Posted by islaTurbine
After having gone through all of this a year ago on my ‘78, I agree with what everyone here is saying. Start small and work big.
Since there’s no synchro, reverse gear is usually a gear that grinds if one or both clutch discs are dragging and thus letting the torque tube shaft still spin with the clutch pedal pressed down. Does your reverse ever grind when you try to shift into it?
... following a 10-mile test drive (after a clutch re-bleed) with little if any grinding, the grinding returned this morning. It wasn't possible to get the car into any gear, no matter what I tried.
... following a 10-mile test drive (after a clutch re-bleed) with little if any grinding, the grinding returned this morning. It wasn't possible to get the car into any gear, no matter what I tried.
I’d personally concentrate on the movement and adjustment of the intermediate plate. If that doesn’t resolve it then I’d remove the clutch assembly and properly lube everything with the expensive Porsche grease. At the same time with the clutch removed, spin the torque tube shaft to see how it feels and sounds. If that doesn’t work, I’d take then take a look at your shifter alignment and it’s front and rear bushings.
Don't forget the pilot bearing in the end of the crankshaft. They get old/stiff/corroded even when not driven. If they don't roll smoothly and freely, you won't see the full effective release and get the symptom you describe.
As others recommend, start with the release mechanism and the hydraulics. With a helper pushing on the pedal, you can see the release after removing the bottom bellhousing cover. The intermediate plate is self-centering when set up per the WSM procedure. The disks may hang on the sliding splined shaft especially if the shaft is corroded or the grease has stiffened with age. Drop the clutch, clean and relubricate everything, put it back together carefully. Assemble the splined shaft so it sits back from fully seated/bottomed in that new pilot bearing.
Hydraulics are critical. The system needs clean dry fluid (read: new...) and is extremely sensitive to air in the system. Replace the original "blue hose" between the brake fluid reservoir and the clutch master cylinder. Bleeding the system is a challenge, one made easier if you use the Greg Brown hose under the engine oil pan, and by reverse-flushing the system. There's a very interesting recommendation for connecting a front caliper bleeder to the clutch slave cylinder bleeder with a hose, and let the brake system push fluid backwards so any bubbles go uphill to the reservoir.
The release arm pivots on a plastic bushing that fits over a ball stud at the top right in the bellhousing. Replace that bushing while you have the clutch out. The release bearing is rebuildable.
The 928 is the second-easiest clutch to replace as far as access, but it's heavy and will fall on you if you aren't careful; be careful.
No, the yellow MG TD is not mine. It's the shop for springtime service, new wire wheels, new green-leather upholstery, and some minor repairs. The shop--Eclectic Motorworks in Holland, Michigan--is a classic-car artisan operation. I "work" there two mornings a week doing mostly menial and go-fer stuff (including refreshing parts (brake equalization valves, starter, front grille, and more on the 928 included). Being able to see the work on my cars up close and learn a few things is a real delight. Over the years, they've sorted two 924S cars, an '87 911 coupe, and a 944 Turbo S of mine and an '89 BMW 325is of my son's. Their primary mechanic was trained by Porsche in the 80s and is a real talent and a fun guy. I told him, without him being there, I would not have purchased the 928.
Came across this thread as I too have the 2nd gear grind. Just purchased my 82 a couple weeks ago. Unless at a stop 2nd is almost a "no go" when cold and 4th has slight grind. All other gears engagements are fine including reverse. Once warm, 2nd has no grind if "eased" into and 4th is fine. Do these symptoms point to anything or at least eliminate some of the possible issues? Thanks!
The parts for these early transmissions are getting/have gotten crazy expensive. A slider to engage 2nd and 3rd or 4th and 5th (which wears as it travels over the synchro) retails for over $450 (each). A first gear/reverse slider for the later G05/G08 transmissions does not exist...and we have to create one.The 5th gear ball bearing (which has to "deal" with the metal debris suspended in the gear oil) retails for over $700. If the engaging teeth on the 2nd gear gets trashed, a 1st/2nd gear set is over $4000, now.
Doing just "rough" calculations, each and every time one of these transmissions "crunches" into a gear costs a minimum of $25.....in the beginning.
As things get worse and the crunching turns into a grinding, it's more like $50 per crunch/grind.
By the time the engaging teeth start wearing on the gear, it's closer to $200 per grind.
A new second gear synchro retails for just a smidge over $100.
You "catch" the crunch in the begging, probably all you need is a synchro or five.
Quick review......crunching/grinding gears is expensive.
Synchros are relatively cheap, compared to the rest of the pieces.
The labor to rebuild is the same...New bearings, new gears, new sliders, new synchros costs the exact same amount of labor as only a new synchro.
Thanks, Greg. With the "h" adjustment made, tnew clutch pack installed, and gear oil changed, the car drives well. Still "grind" into second, but I simply do not use second. I'll continue this way until the fall when the transmission will get pulled and sent off to you.
04-01-2021, 09:21 PM
Best courses of action for a "grind-y" 2nd gear?
