Yukon Hybrid Issues

[atrex21]

Hi- I have a 2011 GMC Yukon Denali Hybrid with roughly 130k miles.

About a year ago, we brought it in because it was giving off an ABS code. We ended up having the module replaced along with a brand new hybrid battery. The rationale was it was worth the investment ($6k total) because of the used car market.

We got the car back for three days in March when it went into limp mode.

My mechanic was stumped so he brought it to the Chevy dealer, who told him it was a timing chain etc.

To make a long story shorter, we ended up buying a used transmission that ended up being bad; got a second used transmission and finally got the car back a couple of weeks ago.

It seemed to drive okay until after it warmed up, then the car would stop accelerating and just rev. If I turned it off and let it sit, I would be able to get it in my garage.

The next morning, it drove fine for about 20 minutes until the same problem happened again; and again later in the day after being parked.

It’s back at the shop and my mechanic is perplexed. It’s not pulling any codes according to him.

At this point, I just want it to run properly so I can sell it- it’s a great car except for this confusing issue…

 

[j91z28d1]

see if you can have your guy put a tranny pressure gauge on it. if he looks it up in his software it will show a port, I believe passenger side of the tranny right behind where the bell housing would bolt to the tranny. that will give you line pressure inside the tranny and see if lack of pressure is why it's slipping. my thought is to check its got good pressure and the scanner says it's engaging the gear it should. I have not had mine apart but with other automatic trannys, it's possible to have the cable adjusted wrong and it be half in a gear and cause it to slip. there should be a little line under the gear indicator on the dash, if the line is missing I've seen a post somewhere that that's a sign the tranny isn't communicating with a transmission control module

when the engine is off, there's an electrical pump that makes the line pressure to engage the clutch packs, once the engine starts its got a normal style tranny pump in it.. there's a check ball between the two so the fluid doesn't just flow out the back side. they electric pump has a few tsb on them.

if you have line pressure and no codes, I don't know. these trannys don't really have the reputation of failing like the 4l60e's do. maybe you can find a tranny shop to take a look?

only other thing off the top of my head is these use 2 tranny filters in the pan, not just 1. if they aren't installing them correctly maybe it's sucking air instead of fluid?

 

[j91z28d1]

I take that back, it's the driver's side.

 

[j91z28d1]

this is going to sound dumb but I just remembered an old cavalier I was given as a kid, it kinda did the same thing. tranny worked fine when cold but when it warmed up it slipped badly, then worked again after cool. turned out to be low on tranny fluid. guess we didn't know enough back then to check the fluid level when it was hot not just running haha. at one point it stopped going forward but still had reverse, so we drove it home about a mile in reverse. man the stuff we got away with as kids lol.

but for real these things take like 11.5qt of synthetic dextron 6 and don't have a converter to fill. I don't really trust shops to do anything right.

 

[T3xasR3dRum]

I realize this is an older post, but I was curious about why the hybrid battery cost you $6k. What kind of warranty came with the battery? I also wanted to mention that it took me three separate times to have my battery replaced before I finally got a good one. With that being said, I'm confident that the issue you're having with the transmission is actually related to the battery. Before you do anything drastic, like having someone work on your transmission, check the voltage on each cell of your hybrid battery. They all need to read the same; if even one is slightly different, the battery is bad, whether it's new or not. They MUST all show the same voltage. Chevy integrated every single system into this battery, which can lead you to believe that the problem is something other than what it really is. Trust me, it's the battery! I would recommend using the company I used for my battery, Green Bean Battery. They offer a fully transferable lifetime warranty in case you decide to sell your car. Plus, they come to install it at your home. The cost is only $2999.99. I added a few photos of what to look for with the voltage, this too was a brand new battery, I also added a copy of the warranty that comes with the battery I purchased. I hope this helps if not maybe it will someone who is seeking information on these Hybrids.

 

[atrex21]

I realize this is an older post, but I was curious about why the hybrid battery cost you $6k. What kind of warranty came with the battery? I also wanted to mention that it took me three separate times to have my battery replaced before I finally got a good one. With that being said, I'm confident that the issue you're having with the transmission is actually related to the battery. Before you do anything drastic, like having someone work on your transmission, check the voltage on each cell of your hybrid battery. They all need to read the same; if even one is slightly different, the battery is bad, whether it's new or not. They MUST all show the same voltage. Chevy integrated every single system into this battery, which can lead you to believe that the problem is something other than what it really is. Trust me, it's the battery! I would recommend using the company I used for my battery, Green Bean Battery. They offer a fully transferable lifetime warranty in case you decide to sell your car. Plus, they come to install it at your home. The cost is only $2999.99. I added a few photos of what to look for with the voltage, this too was a brand new battery, I also added a copy of the warranty that comes with the battery I purchased. I hope this helps if not maybe it will someone who is seeking information on these Hybrids.

The battery was $3k. It was the other work that added up to 6. Since then, without a formal investigation, it was determined that there is a camshaft or lifter issue with the engine and the car is for sale. We don't want to put any more money into it at this point, so it's been sitting for months. (Years)!

I'm not sure what went wrong, because aside from some age related issues and some normal wear and tear, the car drove fine before all this started. It's been a stressful and expensive headache.

 

[j91z28d1]

sadly the lifter issues are a problem with all these trucks with afm not just the hybrid. there's a guy right now in the engine section that just bought a non hybrid one, week later it started tapping and is getting quotes of 10-12k got a reman engine.

it's pretty brutal.

where are you located? if you decide to part the truck out. I might be in the market for a spare tranny to toss on a shelf incase mine ever goes.