2007 Yukon Denali XL Transmission Failure

[2007 Denali XL]

My observations from these forums is that the most common failure on the 6L80 are the solenoids, which can be rebuilt at the kitchen table. After having had my transmission fluid analyzed, the fluid will be changed between 36K and 50K miles from now on and sooner with more towing.

I hear ya about the solenoids and was hopeful I could find someone who could diagnose that. But in the end I had to go the main dealer route and their diagnoses was general, not specific.

 

[2007 Denali XL]

Just when you thought your car was finally fixed....................it breaks down again!!!!!!!

about 24hrs after getting it back from the dealer, the car failed to start on the first crank. We got electrics, starter motor cranking well, and engine trying to start, no dice. Waited 5 mins cranked again and this time it started, but it needed to turn over several times before it went.

Jobs just completed by the main dealer for nearly 7K , were

• New Transmission
• replacement of the valve cover gasket due to oil leak

Now today the car failed again. I have driven it for about 30mins and as I turned into my road (quite steep) and the engine died on me. Tried to restart but same symptoms, got electrics, starter motor cranking well, and engine trying to start, no dice. This time waited about 20mins and tried again and it started on the first crank, sped up the hill to the house.

So before I call up the dealer and give him hell, are there any thoughts on if this could be something simple to diagnose. BTW, checked for DTC's and the car is clean not showing any errors.

As always thanks in advance for help offered. Hauling it back to the deal is a pain in the butt.

 

[OR VietVet]

At this point, because of the info you gave, I suspect a fuel delivery problem. I would get it back to the dealer to see if they accidentally did something during the trans replacement and the valve cover work.

 

[2007 Denali XL]

At this point, because of the info you gave, I suspect a fuel delivery problem. I would get it back to the dealer to see if they accidentally did something during the trans replacement and the valve cover work.

Thanks, I think that is the plan. It did has never experienced issues like this therefore it seems likely they did/did not do something.......I also found a large rag they left in engine which could have made it onto the manifold and burst into flames,,,,,,thanks GMC

 

[OR VietVet]

If you still have that rag put it back and take a pic and deliver that to them when you go back to check the new problem.

 

[2007 Denali XL]

If you still have that rag put it back and take a pic and deliver that to them when you go back to check the new problem.

I do and I didnt think of that, I certainly will do that

 

[2007 Denali XL]

Dealer performed a voltage drop test on the battery cables and negative cable measured 653 MV drop positive cable measures 343 MOV drop. They replaced the Negative cable due to over 1/2 Volt drop. The stall issue seems to be fixed.

Car ran well for a few days and then experienced sluggish starting after recent use and also car dying on idle after recent use. Will start a new thread on this issue as it is unrelated to the transmission job.

 

[thompsoj22]

F'ing YIKES!!!!!! Im trying hard to understand why a mech would change battery cables on a vehicle that cranks but wont run??????????????????????????????? Take a really close look at the manifold area/throttle body/injector harness connector. It will be somthing simple, Im guessing no codes is a component connector loose? they were also in the crank position sensor area so check around the starter.

 

[2007 Denali XL]

F'ing YIKES!!!!!! Im trying hard to understand why a mech would change battery cables on a vehicle that cranks but wont run??????????????????????????????? Take a really close look at the manifold area/throttle body/injector harness connector. It will be somthing simple, Im guessing no codes is a component connector loose? they were also in the crank position sensor area so check around the starter.

to be fair to the mech the dying issue has occurred after the fix on the battery. thanks for the advice, going to take a very good look at those areas now, will report back.

Should I think about swapping the plugs?

 

[thompsoj22]

to be fair to the mech the dying issue has occurred after the fix on the battery. thanks for the advice, going to take a very good look at those areas now, will report back.

Should I think about swapping the plugs?

Nope, Somthing is loose/intermittent/failing. If it wont fail for the dealer than he cant accurately diagnose it. The fact that the trans was replaced and this is a "first time occurance" In my experience there is an error on install somewhere. It will probably be somthing simple, All electrical works,Just a no start correct? Does it miss/run rough or just die? Does it die at speed or only at or approaching idle? Also check the underhood fuse box as they were leaning on that for sure.