20L8TSierra24

42k on my 24. -Valve body @ 12k -Pump, stator, and some support at right around 18. Now, it's starting to whine like a 20 yr old air conditioners capacitor when coasting to a stop.

It appears that TSB only goes to MY 22. Does it apply to newer vehicles?

So what exactly is making the knocking noise? The cover, pushrod, or the cam striking the lifter as it comes around becauseits not expanding fully?. My dealer replaced all 16 of the lifters, and 2 pushrods on my 22 L87. This morning the noise wasn't as pronounced but it was like 90° already when we started it. It doesn't do this if the engine is warm at all either. It was more of a light tap.

So would I have an issue running say 5w-30 oil?

Same garbage lifters. I traded in a 22 L87 that had the lifters done twice 7800/33k for a 25 and before the new car smell wore off, the engine's knocking. Dealer already acknowledged, and told me to get in in for repair. Guess I expected this to be resolved on the 6th year of the DFM L84's... Guess not. https://youtu.be/i8Wj6THFNJo?feature=shared

After 3 fluid changes with absolutely no improvement, they ordered a complete rear end.

My vehicle doesn't qualify for lemon law or BBB claim due to its age unfortunately.

What's frustrating is both dealers are essentially saying this is a joke... I have 400 more miles to put on it before GM will even consider replacing it.

If it were out of warranty, this would be the route I'd try. However, GM has had me waste my time with 3 fluid changes and after a couple hundred more miles, it's no better as expected. The rear end feels like I have a truck in 4WD on the pavement while turning now.

I've had ongoing Trans issues as well. Valve body was done & now a complete unit has shipped. Should have my truck repaired within a couple weeks as well. Hopefully the "updated" Trans will last more than 20k miles.

I told my wife that her Yukon converter shudder developed because of the DFM. I wasn't aware that Range had this for the T1 SUV's now. I had one on a 14 silverado 5.3 w AFM. Thanks for sharing

GM customer service has been nothing short of a waste of my time. I filed a BBB claim on the vehicle today.

I've had it at 2 different dealerships. Victory Layne Chevrolet as well as Dixie GMC. Both dealerships have said they can only change the fluids 3 times per TSB unless the part physically fails. I'm worried my wife will get stranded on a busy road and potentially get in an accident when it does lock up. I filed a BBB auto claim this morning because it has reached the 3rd attempt without resolution threshold.

Going through the exact same thing right now. GM has a TSB and they've changed the fluid 3 times now in ours. The noise never goes away even with the fresh fluid now. It's actually worse now than it was before the fluid change

My 21 Yukon with 49k miles is getting a torque converter for a nasty shudder.

Left the dealer this afternoon after the 3rd fluid change & the grinding is worse than it was when we dropped it off. I can't believe that GM won't do anything about this. I'm at a loss of words

Dropped the vehicle off again this morning. Latest oil change did absolutely nothing but make the rear end worse. This is a complete waste of time and my patience is really running thin.

Thank you for your response. I asked this question when I picked it up this afternoon. They said they do it by the book. It has been flushed twice now with a follow up appointment next week because I'm going to drive it over a thousand miles this weekend. I however have another question. They're adding an "additive" to make the clutch slip more when cold... Now will my rear end not lock up when I need it to because they're compensating for something else?? Is my rear end not working as designed now?

Haven't gone that route quite yet. Dealer is citing 3 attempts required which is lemon law, however mine doesn't qualify for that law anymore. Dealer is essentially agreeing but won't fix it because of the bulletin.

Long story short, I have 2 vehicles waiting on transmissions at the moment.... A 24 L8T w 20k miles & a 2021 Yukon with 49k miles (converter only). The Yukon also has a grinding rear end when its cold every morning which is what I'm after. The dealership has already changed the fluid once before and the problem came back much worse only 6k miles later. The dealer is telling me they're advised to keep changing the fluid until the part fails per a bulletin. The dealership also told me it's a joke & won't fix the issues but have go go "through the process". I need a corporate contact or a Southeast field engineer, or someone who can do more than GM the CS people. My dealer has been great, but has their hands tied with the rear end repair. They told me to call GM. My wife and I have wasted probably 30+ hours driving back and forth to 2 different dealers getting these vehicles repaird lately.

Mine is in the shop now with a nasty shudder and loud whine. Dealer has had it a couple days now. 12k on mine.

Dropped off today. Front diff needs disassembly to determine what's squeaking. Noise almost sounds like a washer or shim rubbing the inside of the housing. The Trans has to also be looked into further. The shudder is during light acceleration or up any incline with a trailer hooked up. The truck also has a louder than normal converter whine to it as well. It's most noticeable around 1800 RPMs or so. Almost sounds like a turbo at times. Dealer said they're going to dig into the transmission/converter to determine the problem. Owned it for 2 months and it has 12k miles on it.

I've read about several 24's squeaking at idle. Mine squeaks while in gear but not in neutral. At idle (in gear) I have had a faint squeaking sound for several thousand miles. The sound is coming from the diff right where the drive-shaft is. I can spin the forward shaft and replicate the squeaking by hand. The noise is getting louder as I put more miles on the truck. Taking it in this week for this and also a Trans shudder upon light acceleration or going up any incline with the cruise on.

Sucks that you're having these issues. Patience & the dealer are your friends in situations like this. The dealer will worl for you because they know they may be able to sell you another truck.

My Travel Trailer weighs about 9500 lbs loaded and my trans temp from SW Fla to Savannah never got over 175. I'm sure it would be higher if I had any kinds of hills.