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

[SnowDrifter]

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.

For what I was asking, an external visual inspection will suffice. If you have an axillary cooler, it'll be a black, small radiator behind the Chevy logo on the front. Make sure it's clear of debris or other obstructions to airflow.

Also verify your efans fans are working, and that your coolant is at an appropriate level.

I forgot to ask, but it's important to know here: what we're your driving conditions when it overheated?

Trans fluid typically has a bit of a funky smell to it on account of additives. But it should not in any way smell burnt.

Color wise, fresh trans fluid is a maraschino cherry red. Put a drop or 2 on something white like the sticker on your airbox to help gauge color. Old fluid will tend towards more of an orange/ dirty red color, and fluid well past its service life (on these rigs) will be a gross brown color.

For the torque converter lockup, get to freeway speed and ease up, then give it a small amount of gas. Do the revs change and fluctuate? Or do they stay steady?

 

[ThatRealtorGuy]

Ok so I got my rig back from the mechanic. They did general service, checked fluids, did oil change etc. said it looks to be great shape and overall everything looks good. They said the transmission fluid looked fantastic and did not have any codes or any signs of problems they could see. Since they didn’t see anything causing concern they told me they’d reach out to the local transmission shop for more info. My mechanic just called me and said they spoke with the transmission shop and they had said it’s a known issue in these GMC rigs. You will never notice it while doing city driving, it’s only when you are in 4th gear for a long period of time the pump in the tranny causes it to heat up excessively. Long and short of it is to fix the problem the tranny needs to be dropped and pump replaced. Quoted $1,200 to do that. They said since it only has 67k miles they’re sure the transmission is in good shape otherwise, but said if I wanted to just do a rebuild while they had the tranny out it would be $3,200. I am trying to look up about these failing pumps from GMC but can’t seem to find any info yet...mechanic said it’s a known issue and GMC has put out info about them. Anyone know about this?

 

[ThatRealtorGuy]

Bump...anyone know about this “known issue”?

 

[swathdiver]

Bump...anyone know about this “known issue”?

Not me but the known issue I know of was relayed to you in my earlier post, check the cooler and lines for acceptable line pressure.

 

[Rocket Man]

Never heard of that “known issue” but the only time I got a message saying my trans was hot, it soon quit working. And I have done a lot of research on these 4l60’s as well as changing them out. Not sure what to think of that trans shop.

 

[SnowDrifter]

Second opinions are cheap. Meh.

I'd think a pump issue would rear it's head more at low speeds where fluid flow is the least. Or at WOT where stresses are highest

 

[Mr. 960]

Ok so I got my rig back from the mechanic. They did general service, checked fluids, did oil change etc. said it looks to be great shape and overall everything looks good. They said the transmission fluid looked fantastic and did not have any codes or any signs of problems they could see. Since they didn’t see anything causing concern they told me they’d reach out to the local transmission shop for more info. My mechanic just called me and said they spoke with the transmission shop and they had said it’s a known issue in these GMC rigs. You will never notice it while doing city driving, it’s only when you are in 4th gear for a long period of time the pump in the tranny causes it to heat up excessively. Long and short of it is to fix the problem the tranny needs to be dropped and pump replaced. Quoted $1,200 to do that. They said since it only has 67k miles they’re sure the transmission is in good shape otherwise, but said if I wanted to just do a rebuild while they had the tranny out it would be $3,200. I am trying to look up about these failing pumps from GMC but can’t seem to find any info yet...mechanic said it’s a known issue and GMC has put out info about them. Anyone know about this?

That doesn't sound right to me. I've driven my 06 Yukon over i70 in colorado through the highest mountains in the dead heat of summer after driving from California. I've driven through Indio at 117* My truck is has the 5.3 with a 4.10:1 rear ratio and will climb long steady grade in OD and have never had a problem. I'd get a second opinion. Have you checked the temperature of the pan with a infared temp gun to see if it is somewhat accurate with the gage? Could be a sensor that is messed up and causing all your problems.