Help! Unusual tranny issue, '93 /auto/LT1

[five-oh]

I had something unusual happen when I drove the '93 a while ago. First some background- the car is a '93 LT1 automatic coupe with 176k miles on her. I don't know much about its service history, other than the young man that I rescued her from had used her as a daily and didn't seem to be mechanically inclined. When I test drove the car, he told me that he'd had an instance that the car would not shift into overdrive until he "popped" the gearshift lever with the palm of his hands. He said it had did that only once. I drove the car and found no issues. I've put around 1,000 to 1500 miles on it with no issues. Today, my 3 year old daughter and I went to pick up Chinese take out for the wife and the young'n wanted to take the Corvette "because it's my favoritest in the world, Daddy". Problem is, the car would not shift into second gear. First and Reverse worked great, just no second, almost like putting it in neutral. I got it home and noticed that it would "hit" really hard when putting it in first or Reverse. The shift lever really felt almost like it was binding. I parked it, figuring a rebuild was going to be the only answer. It's full of clean fluid, no burn smell or anything. After going to town and letting it set for about an hour, I came home and prepared to pull it in the shop. It seemed to shift fine with no binding feel,didn't "hit" hard or anything, so I drove it down the road. Worked great. Any idea what may have bound to cause the problem and should I plan on a rebuild soon? The car's not driven hard, just cruises on weekends. It may get a little speed, but no stop light drags. Sorry this is so long, I appreciate any help.

 

[keremarsan]

Hi !

it seems that you have high line pressure inside the hydraulic body of the transmission . I don't remember if it is a 4L60 or 4L60E for 1993 model year I think 4L60 E begins on 1996 ... ) ,

Probably it is a 4L60 which means that you have a throttle valve cable attached to the throttle body unit which controls the line pressures to shift corectly under different engine load conditions.

I think your throttle valve ( which the cable is attaced inside the transmission ) can stuck at pressured ( which can cause "hit" when putting on D or R , and in this case it will not shift up because the spring inside the throttle valve is fully compressed ) ,

Bad spring in the TV body ( in transmission hydrolic body ) or some particule inside the TV body can cause this. If your transmission does not slip on gears , you don't have to overhall it in my opinion

Hope I am not faulty in that diagnose and can help you .

kerem

 

[keremarsan]

Correction !

You transmission is a 4L60E ... you don't have a TV cable. So please forget my message but the diagnose with high pressure line still here

 

[Robertwav1]

Hold on there, I think you were correct the first time. 93 not electronic but cable controlled tranny. The issue he is having could very well be a slipped or loose cable that all connect to the ASR motor. From what I can remember the cable that controlls the TPS was loose on mine and caused similiar problem he is experiencing. Might be a good thing to check that out first...it's easy and right on top. The locks on the cable casing give out (adjustment locks). Pull the cover off the ASR motor and take a look, there should not be slack in any of the cables. FSM has the adjustment procedure. This happened to me I remember stomping hard on the throttle to keep from getting hit in the rear end. Hope it helps!

 

[surfer93]

You either lost the 2nd-3rd gear bands or your govenor is bad or low fluid.
Does the fluid have a burnt smell or is really dark?

 

[SPANISHVETTS]

The throttle cable or Governer can cause this BUT

Unless the gearbox has been rebuilt before at 160K+ miles you are probably looking at a rebuild.

Both the cable and governor are easy to check/adjust.

Release the cable with the catch on the bracket on the TB. Pull the cable out as far as you can, push the peddle to the metal and Bingo, your adjusted.

You need to pick the car up to get to the governor. Tap the governor out with a screwdriver, use some 1200 wet&dry to clean up the shaft, clean the whole thing up and tap it back in.

NOW, before doing all of this; when was the filter and fluid changed?

BUT really I think you are just putting off the inevitable. I have never gotten more than about 150K out of a GM Automatic.