Transmission shift

[kj5zv]

I am having an issue with my 92 with auto trans. It will shift to overdrive long before it should. Then it will down shift again and pick a lower gear. If I place the transmission in a lower gear (not in OD) it has only done this maybe twice, but usually alway in OD. Oh...it also seems to work ok until it warms up. 15 min of drive time. As I am not sure what makes the decision to make the shift, I am not sure where to start to look for a fix. Thanks everyone for your assistance. Bill

 

[Hrtbeat1]

So its "hunting" for the gear it wants to be in? Shifting from 3rd to 4th and back to 3rd? The 4L60 is a little different than a 700R4. The 4L60 is computer controlled and uses servos on the valve body. If it were a 700R4 I would say it may be a accumulator spring or a band that is starting to go. How many miles do you have and when was the last timethe tranny fluid and filter were changed?

 

[RedRagTop]

Mine shifts up too quick as well (different tranny but...) and the cure seems to be to leave it in D until I know it can hold OD like on the highway.

 

[tlong]

Noticed that was your first time throwing a post at the CAC. Welcome!

The consensus I've reached is to leave it in D until over 50. I submit that the behaviour is near normal as mine 'tries' to go to OD for fuel and emission reasons, then downshifts accordingly. When did you change the fluid? Filter? Maybe you should have a vette mechanic take a spin and see if it's really acting up. Then go from there. I think the '92 is the 4l60 without the e, meaning mechanically controlled vs ecm. The experts will be along shortly. Happy vetting.

 

[kj5zv]

Thanks for the info.... 130,000 miles and a daily driver. The tranny fluid was "flushed" in May. Now that I think about it, I don't think they changed the filter only changed the fluid. That may be the best place to start. Bill

So its "hunting" for the gear it wants to be in? Shifting from 3rd to 4th and back to 3rd? The 4L60 is a little different than a 700R4. The 4L60 is computer controlled and uses servos on the valve body. If it were a 700R4 I would say it may be a accumulator spring or a band that is starting to go. How many miles do you have and when was the last timethe tranny fluid and filter were changed?

 

[MoeJr]

I believe GM suggests driving it in OD all the time. My 84 with a 700R4 does not hunt at all. In city at 34-35 it goes into od and stays there unless I stab the gas a bit to get it to downshift or I get down to like 27 it will come out. I am of the belief that with 130k your transmission may be showing signs of excessive wear. just my .02.

 

[Vettelt193]

this may be what you need: http://www.madvet.com/shop?frame=1.264.3962

the torque converter locking up feels like a shift into OD, that may be your problem, and it is a common one with your tranny.

the reason why I think it is torque converter related is I think the computer stops the converter from locking up while the car is cold.

 

[kj5zv]

You might be right about the wear. I did drive it in OD and it did not "hunt" until just recently. And it worked just great. Surprisingly for a car with that many miles, it is still as strong as can be, with very little wear. I have had the car for 2 years now. Thanks for your help..Bill

 

[kj5zv]

So you think that the computer activates the tranny/torque converter. That would make some sense as it would do it some when I had it in 3 and it would feel like it was pulling in and out. But more often when in OD. At speed in OD was never a problem only at lower speeds/ below 40. Thanks for the web page. Bill

this may be what you need: http://www.madvet.com/shop?frame=1.264.3962

the torque converter locking up feels like a shift into OD, that may be your problem, and it is a common one with your tranny.

the reason why I think it is torque converter related is I think the computer stops the converter from locking up while the car is cold.

 

[Vettelt193]

I know they didn't switch to the 4L60E until mid 1993, which is the fully electronic controlled tranny... but I am pretty sure there was minor computer control before that to help with gas mileage and other stuff (like to warm the car up). Take a close look at your temperature when the problems do/don't happen. 160 degrees should be the 'key' number, as that is the temp the computer switches 'modes' (the modes are called closed loop and open loop). If the 160 number rings true, you probably have an electronic problem instead of a tranny problem.

 

[redc4corvette]

You should check your 4 wire conector on the trans on the drivers side ,if the spedo works then I would not worry about the back two wires on the trans, the wire is not very long tight fit,sometimes the wire comes loose.

 

[kj5zv]

I'll take a quick look tomorrow and let everyone know... Thanks Bill

You should check your 4 wire conector on the trans on the drivers side ,if the spedo works then I would not worry about the back two wires on the trans, the wire is not very long tight fit,sometimes the wire comes loose.

 

[redc4corvette]

Most corvette trans are set up to shift into o = drive at about 47 mph smog and lock up converter.Normal driving.

 

[kj5zv]

Wires are good,, added just a little fluid when hot it was at the low end of the normal mark. doubt it would be low enough to made any difference. Thanks Bill

I'll take a quick look tomorrow and let everyone know... Thanks Bill

 

[Vettelt193]

Wires are good,, added just a little fluid when hot it was at the low end of the normal mark. doubt it would be low enough to made any difference. Thanks Bill

did you figure out if the 'magic number' is 160 degrees? If it is, it is something computer related. -AND- if you take the car in somewhere, 95% of the shops out there will mis-diagnose the problem and tell you to rebuild.

 

[kj5zv]

You were right on the money..... Today on the way to the office it worked fine cold temp. When I left to go,to the airport switched to temp reading and it was 175,,,bingo, transmission was hunting. I can manually go through the gears and there is no slippage, so I think the transmission may be fine. Will start looking for a computer issue. Thanks Bill

did you figure out if the 'magic number' is 160 degrees? If it is, it is something computer related. -AND- if you take the car in somewhere, 95% of the shops out there will mis-diagnose the problem and tell you to rebuild.

 

[Vettelt193]

You were right on the money..... Today on the way to the office it worked fine cold temp. When I left to go,to the airport switched to temp reading and it was 175,,,bingo, transmission was hunting. I can manually go through the gears and there is no slippage, so I think the transmission may be fine. Will start looking for a computer issue. Thanks Bill

Glad to hear it doesn't sound mechanical... did you figure out if the computer is bad, or if it is a sensor or something else? Computer problems can be a real pain on these cars

 

[Tim Scales]

My 92 had a similar problem. I took her to a tranny shop where I could get under the rack. I had 'em pull the pan. I had 115K on it at the time. Fluid and filter had NOT been changed in over 50K so I expected a lot of debris (metal shaving etc) the pan was very clean. While I was under the tranny I checked the pressure/electronic valve that controls the shift into OD or lockup. I found "Loose screws" at the point where the valve makes the seal. I had the technician remove the valve to check for cracks as it is a piece of PLASTIC. NO cracks in it and everything appeared fine. I had him reinstall it and tighten it with a torque wrench to 35 lbs. The problem was corrcted. I have driven over 5,000 miles since with NO Problems. I would strongly reccomend this be checked.
Also, if someone has "Messed" with the ASR control settings such as removing the ASR to replace the plugs and wires they may have not gotten the cables adjusted properly. By all means check this first! If the cable going to the Tranny from the ASR is just slightly out of adjustment it will cause hesitation while accelerating, a "Soft" shift instead of firm and you will loose performance on take off if all the cables are not properly set. you may e-mail me at scalestim@msn.com if you need further information on how to adjust the cables. It isn't very difficult to do but will require some "trial and error" to get it the way you like it. I want mine to "Bark" the tires between 1st and 2nd if I give it 3/4 trhottle and it definately will if it is set properly. I hope this helps, Tim