I can drive it all week with no problems and then when I have someone ride with me it starts acting weird. I get this strange clunk or thump under very light acceleration. Sometimes it's enough to make me want to go straight home. I looked at my trans mount and torque arm mount and they look OK. I used a pry bar to move the trans and it would only move about 1/8". What could this be? It has never done it with just me in the car! Yesterday I tried a few hard stops and starts with a passenger and all I could feel was a slight thump like the trans came down right before a complete stop. I can't make it do it, it just does it every now and then with a passenger. I'm lost! Any ideas?

 

Have you checked your exhaust. The factory exhaust runs down the passenger side. The converter may be hitting. Just something else to check. What about motor mounts?

 

Haven't checked the motor mounts and I know it's not the exhaust. When it does it kinda jolts the whole car. If it was a motor mount wouldn't I feel it all the time?

 

When you have a passenger in the car, that side sits lower. If its not the trans mount, or the exhaust, it would have to be either suspension or the motor mounts. If the mounts are broke or just wore out, the motor will torque over and move when you get in the throttle. It may be enough for the bell housing to hit.

Are you running headers. I know that my Lt headers will hit on the a-arm sometimes because of needing new motor mounts. Doesnt hurt to check.

 

No headers. I just looked at the motor mounts. They look old and worn, but not broken. It doesn't do it when I floor it, just when I'm just granny driving with just very slight acceleration somewhere around the 2-3 shift. It happens at around 30-35 mph. I don't think it's when it actually shifts though. It's driving me insane! I know I'm probably going to wind up stranded somewhere.

 

I've been out driving it around trying to get it to tell me something. The only thing I can get it to do is when I brake really hard, I can feel something come down right before it comes to complete stop. It's around the trans/driveshaft area. I'm thinking it's the trans coming back down. It's kind of a soft thump. Does this sound like I need a need a new trans mount or could it be something else?

 

TTT

 

What tranny are you running?

I remember my '83 used to do the same thing. I thought it was a problem, but after investigating it was discovered that it was something else.

First of all, I had the worst tranny ever built, the fantastic
Metric 200...you've probably never even heard of it. I think it was only a Canadian option, hence the term Metric.

Anyhow, somewhere I read, whether it was in my owners manual or some other GM publication, that it had what they referred to as somewhat of an overdrive gear. It wasn't actually an overdrive gear, but when you were cruising at 50+ mph it was supposed to engage and lower your RPM. And of course, it is supposed to disengage when you brake.
It sounds to me that it is not acting correctly, if in fact, that is what is going on.

Just my thoughts. And I could not add any proof to this, so I could be totally wrong. I'll see what I can find.

 

I have a 700r4. Are you thinking of the torque converter clutch? The TCC may be trying to stay engaged during shifting or something. I'll do some searching on TCC problems.

 

I have the same exact frickin problem lol.Although I havent upgraded the tranny mount,suspension or exhaust since ive had the car.Im planning on doing all that soon so hopefully that fixes it.Regardless if it fixes it or not i still have to do those upgrades very soon

 

mine does it between the 1-2 shifts

 

Which part of the problem do you have. The thump when you stop hard or the weird thump/clunk under very light acceleration?

 

Does your TCC act up?

 

Yes, I think that is what I'm trying to describe. I did a general web search, but most things I was coming across were for Olds or Buicks.
I did find a fairly good site but it was all about rebuilding, and did not specifically describe how it all worked, just about how to rebuild it.
It does however list a whole lot of stuff. Here is the link:

http://www.bnol.com/troberts/oldsfaq/oftrn.htm


Let me know if you can figure it out. I really don't know all that much about trannies, just that I had to have the '83 rebuilt twice.

 

At what speed is the TCC supposed to lock up when everything is stock. Mine locks up at low speeds like 30 or so when the engine warms up. I'm guessing it isn't supposed to.

 

I have the early 3 speed tranny.I feel a big bang in the center consol area between the 1-2 shift when I gun it and it gets into 2nd between 3000-4000 rpm.Sometimes it bangs and sometimes it doesnt but most the time it does.Scared the ShiY out of my sister when she 1st drove the car.Anyways,I can avoid the bang if I just gently gas it from a stop and then gun it about 2 seconds in.Another thing I noticed is that it doesnt bang when I gun it from a stop on a totally flat and level st.

 

I dont feel it when I stop hard/soft or under light acceleration

 

I just figured out why it does it when I have a passenger! That is the only time I ever run the A/C. I don't have the idle stop solenoid on the carb to idle it up, so when my TCC does its' little dance at lower RPMs it lugs it down and causes this weird clunk/thump. Maybe the idle stop solenoid will fix it or maybe I should just keep it in drive at lower speeds. I think it does have something to do with the A/C and the TCC locking up though. The other day I turned off the A/C while I had a passenger, so I could hear it better and wouldn't do it!

 

I forget about this thrtead.I fixed my problem too ,tht was a while back lol.It was my tranny mount.No more clunk