Transmission puzzler

e_nough · 04-27-2001, 08:20 PM

Just got my rebuilt tranny back from my mechanic. (nice guy) and put it back in. It is still not right. I took it back and he drove it, and he isnt sure either, he is going to look at it on monday. Here is what it does:

when you shift there is this big CHUNK noise and no its not a grind like the syncros, they were replaced in the rebuild. it does it in all gears and it does it the most shifting from 2nd to 3rd. We tried to make it make the noise when stopped by putting it in Neutral, engaging the clutch, revving the engine up to 4000rpm, disengaging the clutch and quickly shifting into 3rd, but it wont do it, it only does it when you are moving. it doesnt matter how fast you are going. it is louder the faster you shift.

my mechanic said it is most likely the gear box, not the clutch and not the other parts of the drive train.

this is really puzzling because the tranny should be in good shape it has all kinds of new parts including syncros and some slider sleeves. also since we revved it up in neutral, pushed in the clutch and rammed the shifter into 3rd and it didnt do anything. if the syncros were shot it would make lots of noise if you did this.

my clutch should be fine. the guy i bought it from said he had a spring centered put in at about 90K and it now has 116K on it.

what do you guys think?

Porsche 951 Fanatic · 04-27-2001, 08:46 PM

Ok dont take my word for it but MABEY the cv joints are worn and the chunk is them reaching the end of there play.... and perhaps when you are going quick when you shift you most likley go from a high rpm to where the engine is idling and it has to kick back up when you disengauge the clutch and it uses the power from the wheels to speed up the engine. so i could be wrong though... does it make noise when your turning? or say when its stopped and in gear without the motor running can you push it back and forth a bit? i dunno.. all i can say is good luck and i hope i was of some help. Peace

e_nough · 04-27-2001, 08:58 PM

mechanic says the cv's are ok. he also says the clutch disc should be ok, not too much backlash when you take your foot off the gas really quickly.

e_nough · 04-27-2001, 09:00 PM

it doesnt matter if you are turning. and it doesnt have anything to do with engaging the clutch because it does it when you are shifting before you let the clutch out.

e_nough · 04-28-2001, 07:55 AM

please help!

mike944 · 04-30-2001, 05:37 AM

Well since nobody else is responding,

I don't really have a definite answer, this is a strange problem. I'm just going to throw a few ideas out there. Hopefully it'll be better than nothing.

Check the clearance between the ring and pinion, looseness here could cause a clunk.

Maybe the syncros weren't installed correctly. The lack of grinding means the syncros are engaging correctly. The syncros are there to control the freewheeling speed of the gears so that the gears are slowed down to the speed needed to mesh with the next gear. If the syncros aren't fitted to the gears correctly, they can't control the speed of the gears correctly, and noises occur.

Did your mechanic put in the correct weight gear oil?

Hopefully you'll figure it out. From the lack of response, i think everybody else is stumped as much as you are on this problem.

good luck, and let us know what the problem was when you figure it out.

Mike

1.2gees · 1.2gees's Garage

Well, I've gone through several transaxles, and this (among others) is a problem I've had with all transaxles rebuilt, or taken apart by a shop.

Do keep me updated, as I don't feel comfortable driving something that clunks like that! It also jerks slightly when in gear, and coasting (clutch in, 1st gear). It'll also jerk when taking off, or backing up (when the car first starts to move). Most of this is caused by wear in the rear end components, not just the transaxle itself (well, mostly) but also stub axle, wheel bearings, etc.

Do keep ME updated!
Ahmet