Transmission trouble, can't figure it out

I have a 1996 Riviera with a 4t60e transmission and something is wrong with it.
When it gets hot the torque converter will lock up at the wrong times,
and when in 2nd gear it will lock 3rd at around 2000rpm dragging the
rpm down to about 900-1000. Same with 3rd to 4th. It only does that
when it is hot, but will not do it if I drive on the highway. Just
frequent stop and go. When the transmission is cool it will shift
semi-normally but the torque converter will slip if I let off the gas
and get back on it, as well as being sluggish to lock in the gears.

dtrumbo wrote:

I have a 1996 Riviera with a 4t60e transmission and something is wrong with it.
When it gets hot the torque converter will lock up at the wrong times,
and when in 2nd gear it will lock 3rd at around 2000rpm dragging the
rpm down to about 900-1000. Same with 3rd to 4th. It only does that
when it is hot, but will not do it if I drive on the highway. Just
frequent stop and go. When the transmission is cool it will shift
semi-normally but the torque converter will slip if I let off the gas
and get back on it, as well as being sluggish to lock in the gears.

what is the condition of the fluid?

It's definitely above par, when I changed it the first time it was red, a little dark, but absolutely no black particulate and no burnt smell. I changed it again recently and changed the filter stem sleeve, the sleeve I got from a parts store seems to be a little loose fitting and I am going to buy one from the dealership when I am able to so I can replace it. I believe this can be the problem, but I am unsure.

We will see what you find. Also make sure no one messed with the vacuum modulator.

And finally make sure there is no wiring problem at the harness to the transmission and there's nothing stupid going on like your shift indicator is maladjusted or disconnected, or the wires are misrouted and got burnt or shorted. Also IIRC the transmission "reads" the indicator position and if the signal's wrong the tranny won't shift right. But don't quote me on that check the FSM (if you have it).

Okay, where is the wiring harness located? If you have pics that would be absolutely wonderful, I have messed with the modulator to see if I could adjust it to change the shifting, but nothing changed when I adjusted it. And how would I check the shift indicator? I know it's alot of questions, but I would love to not have to change the tranny.

dtrumbo wrote:

Okay, where is the wiring harness located? If you have pics that would be absolutely wonderful, I have messed with the modulator to see if I could adjust it to change the shifting, but nothing changed when I adjusted it. And how would I check the shift indicator? I know it's alot of questions, but I would love to not have to change the tranny.

first you need to put the modulator back as it was - might need a Tech II to make that adjustment.

Then (I know this sounds kinda funky) need to look for **Other** vacuum leaks, like at the power brake booster. The idea is that other vac leaks affect modulation.

As for the wiring start at the part of the transmission just under the radiator overflo tank near the ABS motor and work your way around.

I was looking at rebuild kits for the 4t60e transmission, and I was wondering if this is something a person without experience in rebuilding a transmission. But I can turn nuts and bolts. Haha..

I've been told the work is not simple, and the special tools needed for the rebuild might cost more than paying someone to do the work.

Good to know. While looking into used transmissions, I found that not a lot of transmission are interchangeable with the SC riviera, because the 4th gear has an odd ratio. But I don't think that the transmission itself is at fault. It seems like a problem outside of it (modulator, vaccuum leak, etc.) I just cannot figure it out. I am selling the car, and it would be alot easier to sell if the trans didn't act up like this.

dtrumbo wrote:

Good to know. While looking into used transmissions, I found that not a lot of transmission are interchangeable with the SC riviera, because the 4th gear has an odd ratio. But I don't think that the transmission itself is at fault. It seems like a problem outside of it (modulator, vaccuum leak, etc.) I just cannot figure it out. I am selling the car, and it would be alot easier to sell if the trans didn't act up like this.

contact moradpartscompany.com, see if Ed Morad has any 4T60E trans sitting around. Pricing is pretty good, if you're like some others you may end up keeping the car...

From Wikipedia:

A heavy-duty 4T60-E HD was produced only in 1996 for the supercharged GM 3800 engine. The 4T60-E was phased out in favor of the 4T65 beginning in 1997.

The 4T60-E featured a 245mm torque converter with varying stall speed and gear ratios. Stall speed is the rpm(revolutions per minute) that the converter reaches maximum efficiency and is correlated with the engine and vehicle weight for the best combination of power and efficiency for the vehicle. (For example a '95 Beretta features a 1650rpm stall converter as opposed to '99 Century converter with a stall of 2095rpm.) Gear ratios are remarkable in the 4T60 family in that there are two points in which the transmission can have different gearing (the drive-chain sprockets and the differential) resulting in up to 12 different available gear ratios. The combined gearing of the two is the overall transaxle ratio and is called the "Final Drive Ratio", and the different ratios allow the use of the transmission in multiple applications based on the engine and vehicle.

Replacing a complete transaxle should only be done if a unit is verified to be the same as the unit it replaces, as in addition to the up to 12 variants of the Final Drive Ratio, different applications and years can and will have incompatible electronics. The use of an incorrect transaxle will result in undesired operation, up to and including total non-functioning of the transaxle.

What I wonder is, did your car have a bum transmission and before you bought it someone swapped in a 4T60 from a different model GM car? (that is, has it always done this stuff since you got the car? did you have earlier transmission work?) If you agree that this might be the case, then you might get back to your buddy the GM tech and check the numbers on that transmission.

You are looking for the metal tag on the transmission case - see this site:

http://www.gmtuners.com/transmission/index.htm

and once you find that you can look up what trans the car is supposed to be in at the links on the GMTuners site for instance here is one such page for 1995 4T60E:

http://www.gmtuners.com/transmission/1995_4T60-E.pdf

If I am not mistaken you can change one over to another internally but I do not know what all is involved.

Albertj

And yes, the car has been acting like this since I have bought it, and when my brother had it as well. The guy who owned it before us liked to jerry rig things, like he cut off the cat converter and duct taped a tie rod end, so I would not doubt this would be the case if he replaced the trans, but I cannot find my tag plate, it says it's on the rear of the transmission, but where would that be while it's attached?