Gearbox woe's on 915

Bertroex · Post by **Bertroex** » Sun Jul 23, 2006 3:29 pm

Hi all,

I dont know what to do. I bought the car with 128.000 miles on her and a fantastic gearbox. Clutch was changed at 115.000 miles, the linkage was set up spot on, synchros in very very good condition.

At around 128500 metal fatigue broke the gearstick-end of the gear shift rod. It is the part where the head shift rod is attached to the gear shift rod. I was about to go on a weekend away so I asked my indy whether it could be repaired without ordering any new parts as it was friday evening.

The guy clearly said that it could only be repaired temporarily and that what he was going to do is ill adviced but considering that I wanted to take my car away, it was decided to weld the head shift rod to the gear stick rod.

When putting it all back together, I heard him on several occasions grind the first and reverse gears. The car could be used but when rushing it from 2nd to third the synchro crunched. "Okay", i thought, "lets not rush that one then " and I kept driving it.

Consequently, I bought a second hand gear shift rod and all the couplings. When the engine was rebuild at 132 454 miles I had it all changed over.
Clutch was measured and had 60% left.
First and reverse were difficult to engage but I could engage them if I waited until the car was idling. Again, I was in a hurry so I thought "b*ll*x to that, I 'll bring it in later".

Car had its 1000 mile post-rebuild service and I asked my usual independant to adjust everything and change the gear box oil with swepco. Apperently there is a "lot of play at the back with the U coupling" but I have no idea what he is on about.

The situation now, after a good drive of 1200 miles, is that
1. I cant engage 1st and reverse without switching the engine off
2. when in reverse or first, the car inches forward when i release the brakes
3. 3rd crunches below 5500 rpm. Above that, it appears fine.

I will brace myself for a £2000 gearbox rebuild but can anyone please explain to me

a) is it possible that I have slowly destroyed my synchros by having had the gear shift rod welded?
b) is it likely that during the adjusting of the linkage the synchros on 1st and reverse would go?
c) if I have the gearbox rebuild, but the problem is with the linkage, can I expect the same problem? Are gear linkages part of a gear box rebuild?
d) I presume my clutch is slipping- can this be adjusted so I can at least have the gearbox rebuild during the winter?

I never had a reputation for clutches or gear boxes for any of my cars and I have the habit of keeping my cars for a long time. I never had any of these problems with my 911 2.7 either so I feel a bit desparate.

Thanks in advance for your time.

bert

Derek · Post by **Derek** » Sun Jul 23, 2006 3:42 pm

I would start with checking your clutch cable adjustment.

1972_911t · Post by **1972_911t** » Sun Jul 23, 2006 4:16 pm

I doubt welding the shift rod could cause internal wear inside the tranny, Even if it wasnt lined up properly when welded it still needs the adjustment setting at the coupler. After checking the clutch setup as derek suggested I would move onto resetting the adjustment at the rear coupler, its possible it wasnt tightened up properly after it was last set and may have moved position making certain gears hard to reach.

Steve

davidppp · Post by **davidppp** » Sun Jul 23, 2006 5:12 pm

Panic not, Bert.

It is defintley the clutch dragging ...with resonable luck it has not yet knackered the box..

As has been suggested begin by checking the clutch cable..both for adjustment and for security of the tube and the mounts..you can reach the seemingly silly sitation where there is no freeplay at the arm but still not re;leasing..because the whole mess is loose and moving with the pedal..

Get that beautiful lady friend to work the clutch while you lie on your back underneath watching and feeling...

Well, I'm sure you can work it out for yourself..

Good luck
Davif

Gary71 · Post by **Gary71** » Sun Jul 23, 2006 5:29 pm

I'll third, or is it fourth that opinion!

Clutch, and probably shift adjustment. Third gear synchro is weak, but if the clutch is dragging you don't stand a chance of a clean shift.

All are external to the box.

Barry · Post by **Barry** » Sun Jul 23, 2006 9:19 pm

Ditto: this was what I adjusted for Early911 during CLM (to much amusment of onlookers): was crunching in 1st and reverse unless foot very hard down on clutch pedal and engine at slow idle.

Quick tip, adjust it so that the clutch is only just releasing. If you adjust it so that it's releasing towards the top of the clutch pedal travel you obviously risk the clutch slipping, but more to the point will be running hard on the release bearing all of the time. I'm sure the correct adjustment tolerences will be a the Haynes, or available here if needed (sorry I'm without a manual for the 911 at the moment

).

Bertroex · Post by **Bertroex** » Sun Jul 23, 2006 11:29 pm

Okay, now THIS is fantastic news.

I got the manuals, I got some equipment, now if I can start learning to understand what I am doing, its all systems go!

Thanks you to all for your input!

Also, I just got back from Eric Lantz and his porsche collection. Crickey, my christmas arrived early!

Best regards,

Bert

Barry · Post by **Barry** » Mon Jul 24, 2006 1:31 pm

johndglynn · Post by **johndglynn** » Mon Jul 24, 2006 3:31 pm

Just my two cents but I would adjust the linkage and the clutch too (there is a great procedure for doing the linkage on Pelican and it's a piece of cake).

You may find that, using the factory procedure for adjusting the cltuch (as per Bentley) you don't quite get the clearance you need - you will need to adjust the clevis at the pedal end also in this case. I did it on mine earlier this year and I think there is something on impact bumpers in the trans section about it, with pics.

The linkage adjustment is something I reset once a year as it's a cinch to do and and wow, doesn't it make a difference to the gearbox action.

johndglynn · Post by **johndglynn** » Mon Jul 24, 2006 3:47 pm

Found that post Bert, for info this is how it worked for me:

Have wanted to double check my clutch adjustment for some time and finally got round to it today. Easy job for me because half the interior is stripped out. If everything was in there it would be a bit more involved.

First thing to do is undo the locknuts on the cable at the gearbox, and disconnect the cable. This is easy - two 15mm spanners and a small prybar later, the cable is off. Then you adjust the clearance in the actuating arm to 1.2mm. For this you need your feeler gauge and 2 13mm spanners, try to make one really thin as the locknut here is very slim and a wide spanner won't get in there.

Reconnect the cable and adjust the cable preload to 1mm at the same point. I couldn't get this to come right, so ended up having to adjust the cable at the pedal end. Very simple; you just disconnect the clevis, wind it down the cable to the specified maximum depth (22mm), lock it up and reconnect (my locknut here was entirely loose so good to find and fix that). Went back to adjusting the gearbox end and all came together beautifully. No pics as camera was charging but the Bentley manual has some good ones. That is one indispensable book by the way.