clutch problem or gearbox problem?
 

long story short....
bought a used 915/63 gearbox, replaced all parts associated with the clutch, reinstalled into the car with new fluid. Adjusted the new clutch cable per the recommendations here on Pelican and in Bentley. The clutch pedal depresses/returns normally, and the clutch lever arm has the correct 25mm travel.

I can select any gear with the pedal in (clutch disengaged) but when letting the pedal out, I get a horrible grinding noise and the car doesn't move. This happens in all gears.

I believe the clutch was installed and cable adjusted correctly. I'm wondering now if the gearbox is bad.

any thoughts?

Yikes!!

If you haven't already, I would try adjusting the shifter coupler between the rear seats.

When you loosen the coupler on the 8mm lock bolt you can manually engage the transmission. Remember when you look at the shifter end of the trans all engagements are in reverse of the shifter for gear selection.
Bruce

horrible grinding? kind of makes you think there's a problem with the transmission. any bits in the old gear oil or in the drainplug magnet?

no metal bits in the fluid or drainplug.

i'll have to research how to adjust the gearshift coupler. Maybe that's the problem?

Seems like no matter how far out the coupler adjustment is that you should be able to get at least one gear to engage. If you can't it's likely that there is a problem within the tranny. You might try disconnecting the shift shaft at the coupler (allen head) and shift the tranny by hand with the shaft and try to get it into gear. If it won't go into gear...

Lindy

That's exactly what I was thinking this morning.
The coupler is the easiest check point since the clutch pedal seems to be adjusted correctly according to the the poster.


jmnitro-who installed the gearbox back into the car? Someone HAD to have bolted the shift rod to the coupler for the shifter to move the shift forks.....or maybe it's not moving them at all.

I installed the gearbox onto the engine and then reinstalled the motor, and did all the clutch cable adjustments.

I'm pretty sure I got the shift fork into the TO bearing groove....can I check this from below the car?

I adjusted the coupler yesterday by following the factory adjustment protocol, and it did not help. I can engage all gears with the clutch pedal in/ clutch disengaged, but when I let out the pedal, it grinds and the car won't move

If you jammed the fingers against the outside of the throw out bearing when you closed everything up the first time, you still may have problems.
Removing the engine and resetting the fingers and then closing up, your fingers may be bent from 75mm to 80mm, almost unnoticable, but the finger unit has to be replaced to properly operate.
Been there, done that..
Bruce

Based on your explanation being factual, and the assembly correct, sounds like the box is bad. Take the side cover off the diff and have a look. Its also possible that somebody took the shift fork cover off and didn't get it back on correctly.

OK thanks guys.
Being my first 911, it's possible I screwed something up putting it back together.

I've been working on the car for 3 months, and frustrated with not being able to drive it. I'll probably just take it to a shop for a lookover.

Well, youre resolved, there is 2 possibilities here.
Replacing the trans is one possibility, youre looking at a couple thousand. At a shop +R&R
of $500 to 800 plus any thing else the shop can get out of you.
My solution is a bad fork, pull the engine and measure and change, new about $150 plus a roll pin.
If you send it to the shop you havent learned anything but how to pay the bill.

Bruce

I had one with the same symptoms; it was a blown ring and pinion.

Thanks for the encouragement Bruce.
Maybe I'll give it a go when I get the "drive" to do so :)

I decided to take the SC into a local shop since my racecar project is taking up space in the garage.
the mechanic left a VM on my phone today stating that the right rear CV joint is broken.

HM.......i bet that's why the car wouldn't move under it's own power!!! Open differential with a dead CV joint means the motor is spinning the gearbox, which is dumping all the power to the one axle. I'll keep my fingers crossed the gearbox is in good shape.

That is GOOD NEWS and an easy fix.

I hope that wasn't the reason for replacing the transmission in the first place. :rolleyes:

Best,
Grady

I'm happy to report the broken CV joint has been replaced, the rear wheel bearings replaced, and the car is back on the road (if only briefly).
The fuel injector seals are leaking, and so the driveability suffers until the car warms up. So that will be on the list of things to change.

Otherwise it's good to have the car driveable. :) The clutch operates smoothly, gearbox shifts pretty well so far in the short 3 mile drive home, and the car's power seems nice. :D