Tranny temp problem???

[MadDad]

I made my first long haul with the new instrument cluster which has the tranny temp guage. I pulled our 5500# camping trailer from IL. to Custer, WY, then down to Rocky Mt. Natl Park, then home.

On the way west the highest temp I say was 225 deg. Is this to high?? I was going against a head wind, and in the rolling hills of Iowa. Occasionally the temp would dip down to 120 deg, then come right back up. This would take 5 to 10 seconds. The temp outside was @ 80. When the temp out side dropped to 70 the tranny ran at 200 deg. The fluid level is right on.

On the way home, with a very strong tail wind, really helped the gas mileage, the temp would hit a high of 190, but most of the time it would run at 120 deg., and just occasionally bump up to 200, over the course of 5 to 10 sec. then back down. I know it should be running around 200 deg. The book says the normal temp range is 180 to 200. Some of the towing was done on drive, some in 3rd gear. Mostly at 65 to 70 mph. The temp swings didn't seem to have any correlation between going up hill or down, or what gear I was in. The only thing I did notice was that it would read correctly for a while after a stop for gas, or food, but after a few miles would seem to read wrong most of the time again.

Why would the temp do this?? I have 14,000 miles on the vehicle.
Bad sending unit? Where is it located.
Bad instrument cluster? All other guages seem fine.
Bad electrical connection? Again where is it on the tranny?
Could the fluid be foaming? I don't think it got hot enough for that.

 

[RichUF]

I too just got a cluster with tranny temp gauge. I haven't towed with it, but here is how mine has behaved so far:

warms up over the course of many miles and fairly long time (>30 minutes) to stay just slightly below 200. This is city driving, no load or towing.

Occasionally the temp would dip down to 120 deg, then come right back up

Mine has never done this.

the temp would hit a high of 190, but most of the time it would run at 120 deg., and just occasionally bump up to 200

Mine has never done this either. Once it gets to near 200, it pretty much stays there.

Interested to hear what others reports as I've been wondering about this, too.

 

[Chief]

Full disclosure - I have never towed with my Avalanche, but I have had a tranny temp guage for 18 months.

On the way west the highest temp I say was 225 deg. Is this to high??

Nope - I've seen similar temps doing off-roading in 4-Lo in summer weather.

I was going against a head wind, and in the rolling hills of Iowa. Occasionally the temp would dip down to 120 deg, then come right back up. This would take 5 to 10 seconds. The temp outside was @ 80. When the temp out side dropped to 70 the tranny ran at 200 deg. The fluid level is right on.

I have found that the tranny temp is DIRECTLY related to outside temp. The cooler it is outside, the cooler my tranny runs. In the winter time I have an average temp of just 150 degrees, I have a theory that this is the main reason why the Avalanche's fuel economy goes down in cold weather.

On the way home, with a very strong tail wind, really helped the gas mileage, the temp would hit a high of 190, but most of the time it would run at 120 deg., and just occasionally bump up to 200, over the course of 5 to 10 sec. then back down. I know it should be running around 200 deg. The book says the normal temp range is 180 to 200.

I have never seen my gauge swing as wildly as you are reporting. Mine has always been slow to heat up or cool down depending on what is going on in driving conditions.

To the answer of the temp swings ~ that doesn't seem normal, but again I haven't towed. On the other hand the temp range you are reporting - even getting into 220 land appears to be quite normal. The Avalanche is well equipped and if you overheated your tranny it would take steps to protect itself. This is outlined in the owners manual.

 

[brheas]

I tow quite often with my 02 Av - probably over 15K of towing either a 4000 lb horse trailer or a 5500 lb 28' travel trailer. Everything seems pretty normal with your temps except for the fact that it is taking the sudden dips down to 120. This is not normal. You have approximately 14 pts of transmission fluid and it cannot possibly cool down that fast. Under the best conditions it can only cool down about 10 degrees in 10 minutes (rough estimate). You must have a lose connection or possibly a bad sending unit (among other possibilities).

On the way west the highest temp I say was 225 deg. Is this to high??

No, this is well within the operating range of the transmission. Temps over 260 cause the transmission fluid to start breaking down.

On the way home, with a very strong tail wind, really helped the gas mileage, the temp would hit a high of 190

This is normal based on my experiences.

Bad sending unit? Where is it located.

Can't help you there

Could the fluid be foaming?

Not very likely, most transmission fluids not start to "foam" until they reach temps above 290.

Hope this helps

Brian

 

[MadDad]

I really suspect the sending unit, or the connections to it. Just a gut feeling!! Need to find it, and clean the contacts, and if that doesn't fix it, replace it. Other than that she ran fine.

Hee, hee, if I didn't have the tranny temp guage, I would never have known of this problem. Guess I'll have to put the OEM on back on. JUST KIDDING!! Like that Denali one way to much.