Three days ago I became a first-time Vette owner with a 76 Stingray. I may have a tranny problem already that did not show itself at the test drive or inspection. But, since I am a rookie, maybe just ignorance is to blame. My first car was a 67 Chevy but not a Vette. That was many years ago and a long time since I worked much on cars. Now since I have jumped back in the water (or fire), better learn how to do it again. I have an L48 w/automatic T. When I put her in 3 on the shifter & take off, I'm not hearing or feeling any gear shift. RPMs go way on up there before I back off. After backing off, it sounds & acts like I am in neutral (can't accelerate) until falling back under 30mph where it begins to accelerate again if I give it gas. But, if we start off at 1, then shift into 2 followed by 3 at the appropriate times - all is fairly smooth, no noises/knocks, and I cruise on. What am I doing wrong? Or, what is wrong? How serious? Thanks for any help/assistance/advice in advance to this rookie.

 

That is too strange, my 76 is doing the exact same thing you describe. It's like driving a standard transmission. I don't know the problem, I'm just going to upgrade mine to 4 speed automatic.

Good luck.

 

I appreciate your response and hope it is not catching! I think I may have stumbled upon my problem. Years ago on my old 67 Chevy, I had a very similar problem that I only remembered this afternoon. That time it ended up being a vacuum hose that had been pulled loose accidentally by my mechanic at the time. I found the dangling hose, plugged it back in to the vacuum line leading to the tranny and everything from there on was fine. In talking to the seller this afternoon by phone, I suddenly remembered a little hose that broke off on Saturday morning when I took the air cleaner off for some normal clean-up. I could never find where the hose went so I just ignored it when putting the air cleaner back on later. Now, I am thinking that is the answer but it will have to wait until I can get home and into the garage later. You might want to check around the carb or intake manifold for a deteriorated or disconnected hose that runs down to the modulator which sits on the side of the auto tranny. Hope this answers it and hope yours can be addressed without getting the new one before you have to....big expense! Thanks again.

 

I checked the hoses already (4 times actually) but couldn't find anything out of the ordinary. Hoses are all new, just totally rebuilt the engine a year and a bit ago.The problem popped up only after I had stomped it down hard driving home. I never heard any noises, but it started acting funny after I got home. It was ironic, because I had just been asking a performance shop about 4 speed trannys 15 minutes before my problem popped up. I was planning on changing it anyway.

 

This might be a stupid question, but have you checked the tranny oil level?

 

Problem sounds like vacuum modulator or low/no vacuum to the modulator. While in park with engine running and someone holding on the brakes, check that you have a decent about of vacuum to the modulator. This will of course mean that you have to elevate the car. The vacuum should be located to a direct connection on the intake manifold. Sometimes there is a restriction on the tubing where it meets the intake that becomes clogged. I usually cut the restriction off with a tubing cutter. If the vacuum is good at idle, I would replace modulator which usually leaks trans. fluid out the hole the line connects to when bad but not always.

 

If you're asking me, yes I did. I didn't start original thread, so I'm not sure, since I have the same problem if advice is for me or original poster.
thanks either way.

One thing I noticed, when I tried to drive up ramps the motor seemed to be trying to stall, but when I put it in first it went up no problem, I'm going to check those vacuum lines again, I think I missed something.

 

I found the vacuum leak. It was near the firewall where the hose goes through for the lights, there was a plastic t fitting that a hose goes to the manifold from, anyhowrehooked the hose, went for a test run and it works.
I'm still going to swap tranny's though, but I can wait a couple months more.