Thumping into gear

[andrewo]

Okay, I just spent a really quality couple of hours under my GT pulling out the torque tube. The transmission thumps when the clutch re-engages, and several people have told me it was likely from a bad donut.

I have a new donut, but it looks like the old one is okay. I will replace it, but I suspect it is not really the problem. I expected the one in there to be disintegrating, and it looks fine.

Where else should I be looking to track down this thump? In no particular order, the following has occurred to me:

- Rubber on the torque tube mount
- Transmission mount
- Engine mounts

For reasons of both time and money, I'd rather not just replace stuff until it goes away. Any thoughts?

Thanks,
Andrew

[Stanley_P]

Mine does the same thing. I have rebuilt and replaced everything.
Could it have something to do with drive shaft alignment?
If you find out anything let me know.

Stanley_P

[flipper]

I replaced mine a couple of months ago, and it still thumped a little. I then realised that there are three small rubber bumpers between the housing and the torque tube. the one on top is a rectangle shape, and the two on the bottom are a round cylindrical shape. if the top one is missing it will bump, if one or both of the bottom ones are missing or torn, it will thump and let the shaft vibrate on the inside of the torque tube. OGTS has all three of those for not very much. just remember, when you are installing those, you need to make sure the rear end is sitting as it would on the ground when you tighten everything back up.

[andrewo]

Are you talking about the three pieces of rubber on the mount that bolts to the body, at the front end of the torque tube assembly by the universal joint?

[greensmurf20]

i have the ever so common clunking noise now i had used rubber mounts that were in great shape and i put those in there and it took alot of it away but it still does that. the front rubber piece int he mount, is that what everyone refers to as the "donut"? mine started to pop out but its not ripped, just thinking that may be it

[andrewo]

The donut is the round rubber part inside the mount. It has a bearing in the middle of it, and is what th drive shaft is actually rotating in. One word to the wise. I changed mine out using the procedure described in the factory service manual, but there is apparently a far easier way to do it. I am sure that someone on this site can describe it.

Help anyone?

[greensmurf20]

so even if the 4 rubber mounts that hold the torqe tube in the mount are well, that just the donut alone can cause this? i've been playing with it and i can't get it to completely go away, altho its alot better and quit in reverse. can you just take the whole tube/mount/and shaft out of a part car without having to buy a gasket or something? i just ask cuz it seem slike there'd be a o ring or something between the tube and differential housing.

[andrewo]

Yes, the donut can cause it. I had the same situation as you, good rubber on the outside and a good looking donut that turned out to be in pretty bad shape one I got it out and looked at it.

There is no gasket at the rear, at least there isn't one in my '70 and it doesn't leak. You do need a special tool to remove the torque tube from the rear end, but they are sold in most auto part stores. I think I bought a set of 4 for around $20. Do not attempt to use a hex. It will not work and could damage the bolt heads. Make sure the heads are clean too, before trying to remove them.

As far as getting the whole assembly off a parts car, I wouldn't recommend it. I went that route thinking it would be easier, and realized that the rubber in the replacement I had bought was just as bad as the stuff I was taking off the car. Remeber, this is 30 year old rubber we're talking about. Once I decided to just buy a donut, I was able to get an NOS one. Seemed like a good idea at the time, as NOS is always nice to have. Bad idea though, since 30 years of sitting had dry-rotted the rubber, and it had a bunch of cracks in it.

Get a brand new repro piece. Jim at USA Opel has them in stock, that's where I got mine. I am sure some of the other parts suppliers have them as well. I think they are 30 or 40 bucks and once you see one and compare it to what is probably in your car, it will seem like money well spent. According to a couple of people who should know, the bearing never wears out, so plan on using the one you have.

[greensmurf20]

well i have a 70 GT that i have driven, beat the piss out of it for a few days to make sure a motor was going to hol dup and the torque tube never knocked or anything. i just wanted to replace the torque tube its self, instead of the whole rear end since i hear 70 is hard to get parts for. so since i knew it was well i thought just might as well get a free one if its there, and save on the 2 day wait for parts.....

[andrewo]

My car actually shifts a lot better with the new donut. When I originally pulled the tube, my rubber looked okay also. That was why I started this thread. I thought it must be something else. I replaced it anyway, and when I looked at the old and new side by side, it was clear the old one was pretty worn. The new one is much stiffer rubber, and the old had all kinds of small cracks and breaks on it that couldn't be seen until it was off the car. I am not sure of the repros are made out of harder material, or if the old one had softened with age, but I am guessing the stiffer rubber does not allow as much movement, and the cracks couldn't have been doing any good either.

My GT still doesn't shift as well as my Audi, but it was a great improvement.

[garrymc]

I replaced all the rubber parts with new parts from OGTSource. My cluncking noise went away(limited to a test drive in the backyard, no license yet!). They have a polyurethane upper bump stop that I would recommend.

While it was apart I replaced the front seal on the rear axle and the bearing in the donut. My bearing was very rough.

There is a rubber bumper and thin washer shaped thing inside the shaft. It was shot too. (22 in the picture)

http://www.opelgt.com/photos/showpho...cat=500&page=1

[flipper]

I replaced everything but the two cyclinder shaped mounts on the bottom because those looked fine. then I took the rearend out when I did all of the susp. bushings and found out one was torn all the way through. When the rearend was up, it looked normal, when it was out, they were seperated. I have orderd the "heavy duty" ones from OGTS. They will be here shortly and I will let everyone know if it gets that final little clunk out of 1st gear. I put the car up on stands and put it in 1st while it was running and I saw the torque tube go up and hit the top rubber piece. So, I can just assume that the bottom ones that are torn are not holding it down like it should. if these new ones do not work, I am going to fill in the entire are with hard rubber spacers.

[greensmurf20]

well i got my clunking to go away!!!! i thought the 2 cylindrical rubbers were to keep the tube from shifting downward, but really its just the opposite. the rubbers in my old torquetube and mount were not connected to the tube, just the mount. changed it with one that was connected at botht he mount and tube, went away, so i would say the cylndrical ones cause the most problems.