mundo

My car has a 2.59 rear end. It seems to cruise around 1100-1200 rpm at 40 mph. I believe it's in 4th gear. I hear a rumbling sound, a vibration. I'll give it a little pedal and it will down shift into 3rd and do about 1400 rpm and the rumbling sound goes away. I suspect the engine is lugging.

My '84 with a 700r4 used to down shift to 3rd gear when I got under 40 mph at around 37 mph. Up shift to 4th at about 45 mph. I think I can adjust this tranny to act like that with the TV cable. If I adjust the TV cable can I get the tranny to down shift from 4th to 3rd at under 40 mph.

The tranny shifts from 1st to second at about 10 mph. I wanted to adjust the TV cable to hold that a bit longer anyways.

I guess the question is the tranny shouldn't be in 4th gear under 40 mph?

Any advise?

toptechx6

Perhaps trans guru Pete K will comment, but my advice is not to change the TV cable adjustment from the factory setting, clutch damage can easily result. It is my understanding that shift speeds are primarily controlled by the governor on the 700R4/4L60, the TV cable controls pressure to the clutch packs based on throttle position, if you get it too low for the torque applied damage will occur.
Also note that TV cable adjustment is unique to 92 and 93 Corvettes, they are the only vehicles equipped with ASR and a TV cable. Follow the FSM or search for one of my previous posts showing the procedure.

c-4 lhozwalte

next time it starts the rumbling sound slightly push the brake pedal down,without slowwing and see if the noise goes away.when you push the brake pedal it unlocks the converter.if the noise goes away you might be dealing with a bad converter.hopefully pete k will chime in,he is some what of a guru when it comes to trans issues.also i would agree that it sounds like your trans is shifting early.