Bought 05 GMC Yukon...need advice “hot transmission”

[ThatRealtorGuy]

Hey there,

I just picked up an 05 Yukon XL Denali with 67k miles on it. Had about a 4.5 hour drive home afterward and about 3.5 hours into the ride back home the transmission temp gauge started increasing slowly. About 45 minutes from home the “transmission hot” came on in the dash. The gauge was not at the red but it was getting close to the red. So I pulled over and let the car sit for about 15 minutes. Checked the transmission fluid but I’m assuming it would be inaccurate since I’d been driving so long. After letting it sit I started driving and it cooled back down to just over 200 for the final 40 minutes of my drive. Any ideas or recommendations would be great! Thank you

 

[SnowDrifter]

Torque converter locking up?

Trans cooler have good airflow?

How's fluid level?

How does the fluid smell?

 

[ThatRealtorGuy]

Torque converter locking up?

Trans cooler have good airflow?

How's fluid level?

How does the fluid smell?

I haven’t noticed any shuddering or stalling or slipping to make me think it would be the torque converter. I don’t know how to check the trans cooler?

I’m going to check transmission level now. And I’ll smell the fluid too.

 

[ThatRealtorGuy]

Ok I just tested after it’s been sitting for a half hour or so. Transmission fluid smells somewhat sour? Not sure if that’s how it’s supposed to smell. But I think there is too much transmission fluid in there. It’s past the “hot” mark on the dip stick about a quarter inch.

 

[Fless]

You're reading the level with the engine idling, right, on level ground? After shifting through all the gears, letting them engage, and back into Park?

The fluid shouldn't smell burnt.

 

[Tonyrodz]

How's the color? Red--ish, cherry red or brown?
Not fun.

 

[ThatRealtorGuy]

You're reading the level with the engine idling, right, on level ground? After shifting through all the gears, letting them engage, and back into Park?

The fluid shouldn't smell burnt.

Oh, no I was reading the level with the car turned off. Let me go do it again turned on after shifting through all gears at idle. And it’s definitely not burnt. Just kind of sourish. I don’t have enough experience with transmission fluid. I’m planning on taking it to my mechanic this week to look at anyways.

 

[swathdiver]

Hey there,

I just picked up an 05 Yukon XL Denali with 67k miles on it. Had about a 4.5 hour drive home afterward and about 3.5 hours into the ride back home the transmission temp gauge started increasing slowly. About 45 minutes from home the “transmission hot” came on in the dash. The gauge was not at the red but it was getting close to the red. So I pulled over and let the car sit for about 15 minutes. Checked the transmission fluid but I’m assuming it would be inaccurate since I’d been driving so long. After letting it sit I started driving and it cooled back down to just over 200 for the final 40 minutes of my drive. Any ideas or recommendations would be great! Thank you

Normal operating temperature is 180-200 degrees. This temperature range is when you want to check the fluid level (Hot range on the stick). Something is amiss if yours is getting that high without towing unless your traveling through lots of hills or mountain passes.

With a fifteen year old truck, you'll want to have the flow rate of the transmission oil cooler and lines tested with the Trans Flow machine. This machine can also do a fluid exchange. GM dealerships are equipped with these and it is SOP in the shop manual.

Post up some photos when you can, we all love looking at trucks here!

 

[adventurenali92]

67k on a 2005 is super low mileage! Nice find! Not sure what’s up with your trans! I’ve never had that message pop up on my days before but have seen others have it happen.

 

[SnowDrifter]

Normal operating temperature is 180-200 degrees. This temperature range is when you want to check the fluid level (Hot range on the stick). Something is amiss if yours is getting that high without towing unless your traveling through lots of hills or mountain passes.

With a fifteen year old truck, you'll want to have the flow rate of the transmission oil cooler and lines tested with the Trans Flow machine. This machine can also do a fluid exchange. GM dealerships are equipped with these and it is SOP in the shop manual.

Post up some photos when you can, we all love looking at trucks here!

Tossing it out there, from my experiences:

In a stock config, Temps were 135 in the summer (80 to 90 degrees) on flat freeway. Temps would see 215 to 220 give or take in stop and go, but would drop a bit with the a/c on and level off about 180 to 185. Of note, when in stop and go, I tend to lock the transmission in either first or second depending on the speed so it's not shifting 1-2-1-2-1-2-1-2 48 times per mile