82sd928

From a start in 1st shifting into 2nd gear it grinds if I'm pushing it. To keep it from doing so i have to wait for the rpms to come down a bit and it slides in. For downshifting into 2nd or 1st, I have to slow the car down significantly. I guess what I'm getting at is what do i need to do to get rid of this? Anybody have similar problem?

86'928S MeteorGrey

Your syncros are probably shot. I'd check for propper clutch throw before a transmission rebuild though. Greg Brown did a fantastic tech session at Sharktoberfest last year.

Ispeed

synchros......

hacker-pschorr

Before you go tossing money at a transmission rebuild, you need to find out why they went bad which 99% of the time is a clutch not fully releasing.

There is a good chance the transmission is fine.

People are quick to dismiss the pre-85 transmission with synchro issues when in reality the main problem is mis-adjusted clutches.

I would start with the hydraulic system. The master / slave (if not both) could be waving good-buy. Using the inspection hole on the lower bell-housing you can check for full movement.
Also check the brake reservoir since it's shared with the clutch system.

Assuming the hydraulics are ok, time to tear the clutch apart. Non-releasing clutch could be:
1. Improperly adjusted intermediate disc
2. Worn intermediate disc no longer holding the above adjustment
3. Release bearing shot or retaining ring broken (happened to me)
4. Guide shaft is worn not allowing the disc's to float smoothly
5. Pilot bearing locking up
6. Ball in the upper bell-housing the fork rides on is loose (Yes I've seen this happen)
7. Bushing on the ball is worn or gone completely
8. Pressure plate is broken or worn in some way (I've never seen this on a 928 though)

My 81 was grinding same as yours, once I fixed the clutch it shifts like butter. Now with over 105,000 miles on the original transmission in a supercharged 81 making over 400rwhp.

Mrmerlin

Nice post Eric

928 obsession

^^^ Excellent post. I couldn't agree more Hacker, many of the synchro problems can be attributed to a bad clutch component or miss adjusted clutch. I'm currently in the process of replacing both clutch disks due to slight wear on the splines. Every once in awhile my clutch would stick slightly and exhibit the same effect as a worn synchro, but they are not. Hopefully the new disks solves my problem.

toofast928

Yes what Erik said. I found my slave cylinder rubber hose oozing fluid, dropping hydro clutch pressure. Its only 5 years old.

Rob Edwards

I have brand new synchros in a GTS box and a dual disc clutch that ain't right, and it shifts poorly too at high rpm. Gonna start by taking 2mm more off the nose of the clutch master piston to see whether that buys me complete releases.

hacker-pschorr

Thanks guys! Sad part is what one goes through to learn that much about the DD clutch.....
That release bearing retainer ring failure was a fun saga.

Rob - have you measured the movement of the slave?
WSM Volume II page 30-2 states the travel should be 17.4mm

Dave928S

^^^^^
Spot on original post ... I've been through the same pain with the DD.

Erik N

Double-clutch when you shift. The box doesn't like to be rushed anyway.