Transmission Overheating?

Hey guys, the last few times Ive driven the Riv it been acting up a bit with the transmission suddenly shifting harder and losing 4th gear. I scanned it with the computer a week ago and got a Trans Temp high code and cleared it. After letting it rest it was fine the next day and past few times driving it. Today, it did it again after driving for around a half hour. I checked again and no codes but the Trans Temp was close to 300*. Does anyone know the normal trans temp by any chance? And the temp reading was taken after the car sat for about 20 minutes so it could have been even higher. I plan on adding a Trans cooler but I still would like to get this sorted out. Any advice would be greatly appreciated.
Thanks guys!

normal operating temps for the 95 is..wait for it...190 to 200 deg F.

Thanks alot Robo, so something is definitely wrong. Shifted normal tonight when I took it for a quick ride after letting it cool off so temp seems to be causing it. Just gotta determine the cause of the high temps now!

I would definitelyput in a trans cooler.What kind of fluid are you using?
I ask because the 4T60E seems finicky regarding fluid

I believe it still has Dexron III in it but will be doing a change very soon. What would you recommend? The Dexron VI?

I will be filling it with Dex3 exclusively.I know jack shit about trannys.But I'm at the point where GM's recomedations are begining to make sense.

Sounds illogical to treat the symptom, eh? High temp is an anomaly. If you've had success with whatever coolant to date, it must be a component or degradation of a component through wear & tear, not the coolant?

Trans temp for safe operation should be under 250ºF, and even that's pretty warm. 300 is way too high, and the reason for setting the DTC. Good idea to scan and check trans temp - you've verified the problem is real.

Trans fluid will need changed after such high trans temp. Before you change it, check the fluid is at correct fill level. Also need to find out what's causing the heat. Normally trans temp should peak around 220ºF on hot days, for longer trips.

If you have access to a scanner, try to verify that the TCC lock-up is working correctly. There is a parameter that shows the status of the TCC solenoid (engaged or not). At cruising speeds on the highway, you should see the TCC is engaged. If not, your converter will remain in viscus coupling, which causes your fluid to cook on long trips. If left unchecked, this condition can cause eventual transmission failure.

I suspect this might be the issue. If caught early, you can drive the car without the TCC lock-up function, but only if you install a good trans cooler. However, you will notice highway MPG takes a hit. The loss of 4th gear I believe is a 'limp home' mode symptom caused by trans temp rising quickly in a short period of time.

Thanks again for the replies guys. I will definately take it for a ride with the scanner this and check that TCC lockup is working right. Im hoping to do the Tranny Cooler over the next week or two so Ill change the fluid then. I have access to another car for now too so I can let it rest until I am ready to do so!

Took the car out again last night being it was only 65* here and monitored tranny temp throughout the drive. My dad was reading the scanner while I drove and watched for whether the TCC lockup was occuring as well. The TCC lockup would engage for a few seconds when cruising at speed and turn back off. It wasnt the most level or straight road but being the thruway it was minor changes. We dont feel its acting correctly. The trans temp slowly climbed to about 220 and I took it back home. Left it running to check the Trans Fluid and it didnt appear or smell burned and was right at the fill line. Thermostat and cooling fans are working correctly so its just the transmission temp. Idling, it climbed to 227 and held there and I dont think sitting it was going any higher. But the car drove great, no loss of power or changes in shifting. Just gonna baby it until we put in a Tranny cooler.

220-230ºF isn't that bad. 300º is entirely different. Keep in mind, unlike the engine, the trans will usually not climb much idling in park, and at some point will reach a comfortable point, as you experienced.

I'd be more interested in what's happening on the road, and when the TCC is on, how long it's on, and why it might be unlocking on its own. Here is most likely your reason for the heat build-up. My guess is that for whatever reason the TCC was off for most or all of the time you were driving it before, causing the 300ºF fluid temp. Keep an eye on the temperature, especially on long trips, and you should be okay for a while. The trans cooler will buy you a longer time, but I imagine there will come a point when the TCC issue will become cause for a rebuild. Hope that doesn't happen, or at least a long way off.

Thanks AA. I dont drive the car all that often and I use our Pontiac Vibe for longer trips to limit the mileage on the Riv and avoid any problems with parking it in tight spots and such. lol. we have another transmission out of a parts car that I wanted to save up and have fully rebuilt if there was trouble with this one ever anyway. so hopefully the tranny cooler would be good enough to protect it for at least a few years until Im ready for that!

Dave,
I don't know your budget for all this, but I'm about to part out a '95 SC trans - 88.6K. Works just fine. $500
Will be posting soon in buy/sell section.
Chassis rot in my '95 make it a keeper for parts for my '98. I can't use the tranny.

Dont think Im going to be buying one used unless something drastic happens before we can have a rebuild done, but I will let you know if something comes up! I appreciate the offer though.

I agree it doesn't sound like your TCC is acting normally. Does your cruise control work normally, and does the TCC stay locked more if the CC is on? What TCC spec does the scanner show?

You really shouldn't _need_ an external cooler in this car. It's pretty normal for the trans fluid temp to become close to equal to the engine coolant temp, or a little higher. But TCC lockup is important and is there to help keep that fluid temp down.

A brake application, as well as heavy throttle application will unlock the converter. Might be a good idea to look at the brake switch, MAP sensor, and TPS values when the converter unlocks. 300* is very bad. ATF will degenerate quickly at that temperature. Might the transmission temperature sensor be faulty?

LARRY70GS wrote:

A brake application, as well as heavy throttle application will unlock the converter. Might be a good idea to look at the brake switch, MAP sensor, and TPS values when the converter unlocks. 300* is very bad. ATF will degenerate quickly at that temperature. Might the transmission temperature sensor be faulty?

I am thinking transmission temp sensor might be an issue but need to swap in a known good one to check.

Also thinking that the fluid is probably worn - additive wear-out reduces lubricity and mean trans temp will increase. It is entirely possible that a bit of crud is messing up the lockup. I kind of wonder if this transmission is a candidate for a power flush, HOWEVER it's have to be done by someone who really knows what they are up to because if they knock crud loose but don't remove it they will basically sentence the transmission to death.

There is a very very remote, almost nil, chance that there's an issue with the trans cooler (it's in one of the radiator side tanks). I wonder how the cooling system is performing overall?

I am also thinking that this transmission might benefit from a factory re-flash of the PCM. My GM dealer re-flashed the transmission of my Rendezvous (has the 4t65E with a power take off for the AWD) and it made a **world** of difference, IIRC there was an old TSB about reflashing the 4t60E. I wonder if this car could use that update. You could even try disconnecting the battery + lead and touching it to the - lead for a few minutes (will drain the power system and cause the car's computer modules to reset - BE SURE TO unlock the Theftlock on the radio before you do it or the radio will disable, in any event you will lose all the pre-sets. In other words it could be a gremlin.

I am finally thinking that the lack of lock-up is running temperatures up. On these transmissions it does that. installing a cooler is an interesting band-aid but won't fix the problem.

No lights or anything come on, so if the Tranny Temp Sensor was working properly, would it? And the TCC just doesnt stay engaged. And Deekster gave me an idea. The cruise control light comes on but will not set, almost as if the brake is being applied. Perhaps it is the brake switch causing this problem and it would explain the TCC problem as well! That will be the next thing I look at!

Good ideas! Hope this is something minor. CC is definately a clue.

Was the 300ºF exact, or was it any higher. Seems odd that it would be exactly that value.

The actual Temp was 278 after the car was off for 30 minutes. It doesnt seem to have a point where it levels of in temperature while driving constantly on a hot day! Ive been monitoring it and dont let it get above 220 just for safety. The CC Brake seems to be working as it turns off and stays off while moving with the cruise control on. Cruise control still does not engage, just turns off right away. And the TCC brake also seems to be working fine but when cruising today on a flat road at about 55 with constant speed, the TCC lockup turns on but then back off right away and wont come back on for another 30 seconds or so. Ill try to confirm whether or not the Trans fluid sensor is the problem also

th3fr4nchi5e wrote:

The actual Temp was 278 after the car was off for 30 minutes. It doesnt seem to have a point where it levels of in temperature while driving constantly on a hot day! Ive been monitoring it and dont let it get above 220 just for safety. The CC Brake seems to be working as it turns off and stays off while moving with the cruise control on. Cruise control still does not engage, just turns off right away. And the TCC brake also seems to be working fine but when cruising today on a flat road at about 55 with constant speed, the TCC lockup turns on but then back off right away and wont come back on for another 30 seconds or so. Ill try to confirm whether or not the Trans fluid sensor is the problem also

Brake switch or pedal position is what I was suggesting towards. Can you try pulling the brake pedal upwards with your left foot? If you do this will the CC or TCC stay engaged? You may just need to adjust the brake switch.

I'm not sure what you mean by CC Brake or TCC brake.

The trans fluid sensor is probably accurate. You need TCC lockup to control temps, and your fluid is probably burnt and therefore not cooling well anymore. Plus since your TCC isn't staying engaged your fluid is running hotter than normal.

1) fix the TCC issue (may be related to brake switch and CC operation is a hint)
2) at minimum change the fluid and filter (may require quality flush as albertj suggested above - know who is doing the flush and how they will do it before agreeing to this procedure)

Since your TCC is engaging sometimes I don't think the solenoid is stuck or failed just yet. Usually when that happens it won't engage at all.

By CC and TCC brake I meant the reading on my scanner was saying that the brake was off until I actually applied the brakes. I assume that would be based on the brake switch. Ill try lifting up on the brake just to be sure though!

th3fr4nchi5e wrote:

No lights or anything come on, so if the Tranny Temp Sensor was working properly, would it? And the TCC just doesnt stay engaged. And Deekster gave me an idea. The cruise control light comes on but will not set, almost as if the brake is being applied. Perhaps it is the brake switch causing this problem and it would explain the TCC problem as well! That will be the next thing I look at!

Look at all the brake switch wiring for a ground fault - the problem may not necessarily illuminate the lights; the short could be away from the brake pedal area. You probably need to start at pins 5 and 32 off the electronic brake and traction control modues and work out . Pin 5 has a tan wire and runs thru the part of the circuit that runs the torque converter clutch and antilock brakes. Called "brake pedal travel switch". From pin 32 there is a white wire runs to the cruise interlock and the exterior lamps.

I kind of doubt the electronic brake module is bad but I can't diagnose it from here either.

Thanks AlbertJ, Ill check all of the switch wiring as soon as possible and post if I discover something!

th3fr4nchi5e wrote:

Thanks AlbertJ, Ill check all of the switch wiring as soon as possible and post if I discover something!

be sure to check by the brake/traction control module, at the module plug. Wonder if yours got wet or if your car was in a wreck. Also wonder if we ought to be looking at the harness connector on the firewall... naah...