Anyone Have This Issue? Seemingly Transmission Issues

DSChamber · March 30, 2010

OK... first off I'll give you some background on my truck. It's a 2010 Sierra, extended cab, 4.8L V8 automatic transmission (I believe it's the 4L60E).

Truck is new, bought it in February this year and it has only 1100 kms (approximately 700 miles) on it.

There are two issues that have me wondering if they are related.

Issue #1... I noticed that when the engine/transmission is cold (engine allowed to idle up on start up and idle down to normal idle, so it's not like I jump in, turn the key and hit the gas) I put it in reverse the truck bucks/chatters when backing up, it's almost like if I was tapping the brake, that kind of jerky motion. I can hear low knocks from the drive train underneath. Once into Drive it's like the transmission is not fully engaged, the wheels move but it's like the engine has to rev a higher to make it move. Once every thing is at operating temperature this behavior isn't an issue. This was noticed by me after a few weeks of owning the truck. Mechanic friend said for me to put 1000 kms on the engine and see if it still persists, well I'm at 1100 now and yup it still persists, maybe not as frequently but I think that is a result of the warmer ambient temperatures, now the temps some days are above 0 and I would say that this problem happens 80% of the time. Back in February when it was always sub-zero celcius it would happen every morning.

Issue #2... I noticed that while on the highway the other day and attempting to pass a slow moving car ahead of me. I stepped on the gas, I didn't mash it to the floor, just enough to make the transmission drop down a gear (maybe a little less than 1/2 throttle) and while the transmission did down shift it immediately seemed to down shift again, rpms shot up to 6000 (it was like I threw it into neutral!!), then it upshifted and went hunting for a gear, it was like the transmission had no idea what gear to be in, rpms were up and down. I could feel the transmission wasn't pulling right, you could feel that it was slipping in and out of gear or not fully engaging. All of this happened in the matter of a few seconds and it was a bit of a rush to say the least. I let off on the gas and all came back in line under normal. I was able to duplicate the issue again this evening. No codes were thrown as far as I can see (ie: no check engine light but I suppose there should be something stored in the computer?)

So after Issue #2 I am booking an appointment to bring her in to the dealer. The way I look at it, GM has 5 years or 160,000 kms to figure this out... the pain in the ass about this is losing my truck to the dealer for god knows how long and the potential battle of them saying there is nothing wrong. I can duplicate both issues, #1 will require me to leave the truck at th dealer over night so the engine/trans is cold, #2 is a simple road test, I an replicate the issue no problem. The sales guy who sold me my truck told me that any time I ever had to bring my truck in for servicing I could take his demo Sierra, so I will see if he will be true to his word this week

Anyone else have this issue? If so what was the problem afterwards? Could having the engine flash up to 6000 rpms twice for a brief second hurt the internals, considering the engine is practically brand new?

DSChamber · March 31, 2010

30 reads, almost falling off the main page and not a reply?? Nobody has ever had these issues?

ajcain79 · March 31, 2010

I have no idea what the problem is, but it definatly sounds like a warranty issue to me. My truck has never done that.

r1byker · March 31, 2010

30 reads, almost falling off the main page and not a reply?? Nobody has ever had these issues?

Nope, never had this issue. Just curious though, did you check to make sure you have transmission fluid? Maybe they forgot to put it in from the factory. Just a thought.

caddycruiser · March 31, 2010

30 reads, almost falling off the main page and not a reply?? Nobody has ever had these issues?

Nope, never had this issue. Just curious though, did you check to make sure you have transmission fluid? Maybe they forgot to put it in from the factory. Just a thought.

Or, to clarify, that the fluid level is normal? If low, things can get strange, and sometimes it happens.

music · March 31, 2010

I second checking the fluid, but otherwise... dealer visit. Most of us here aren't transmission mechanics, so you probably won't get much reply unless there's a known issue. I don't recall these specific symptoms for any "known issues"... so it's probably a faulty part (like a solenoid?). My own experience is that GM will take care of it without question.

DSChamber · March 31, 2010

Hey..thanks for the replies... yeah I know that the majority of the users on the board are not GM mechanics and are like me, GM owners. Just thought I would get some real world feedback from other owners to see if they have seen the problem.

I will check the fluid though... got a appointment for Wednesday next week. And the sales guy will be loaning me his truck for the duration (guess I will see what its like to drive a Denali, hahaha) ....

I will report back on the findings in case it helps another owner like me....

jro909 · March 31, 2010

Hey..thanks for the replies... yeah I know that the majority of the users on the board are not GM mechanics and are like me, GM owners. Just thought I would get some real world feedback from other owners to see if they have seen the problem.

I will check the fluid though... got a appointment for Wednesday next week. And the sales guy will be loaning me his truck for the duration (guess I will see what its like to drive a Denali, hahaha) ....

I will report back on the findings in case it helps another owner like me....

drive it like you stole it

Doug_Scott · March 31, 2010

I have the same truck, bought about the same time, and have about the same mileage. I do not get the low speed stuff you get, but, there is something you need to understand about how these 4 speeds work at highway speeds.

When cruising along the torque convertor will lock up (effectively becoming a clutch, no slippage). When you accelerate the first thing that will happen if the throttle is pressed far enough, is the convertor will unlock. That will feel like a downshift, but it is not really a downshift. You can also get it to unlock by just pressing the brake pedal enough to turn the brake lights on. If you press the accelerator a bit more, it may downshift to 3rd gear. That will give a sharp increase in rpms. Depending on the speed you are going, it may even drop down to 2nd gear. Chances are that is what happened to you, you were going just slow enough to allow 2nd gear. Chances are very good that you have experienced something that is normal. Not pleasant, but normal.

Do you have a tow/haul switch on the end of the shifter? If so, try engaging that for an experience. The shifting and trans actions with that engaged is just plain unpleasant. You will get used to the shifting on acceleration eventually and learn how to avoid the drop to 2nd on hard acceleration as well.

Wires · March 31, 2010

30 reads, almost falling off the main page and not a reply?? Nobody has ever had these issues?

Nope, never had this issue. Just curious though, did you check to make sure you have transmission fluid? Maybe they forgot to put it in from the factory. Just a thought.

+1 My '00 Z71 was like that. I bought it, ASSUMED it was all good, backing out of my parking lot spot and the tranny started to slip. Found it low 2 quarts. You'd think if the factory missed it that dealership would have caught it on delivery????

But to answer the OP's ?, my 6 speed has never did that.

caddycruiser · April 1, 2010

30 reads, almost falling off the main page and not a reply?? Nobody has ever had these issues?

Nope, never had this issue. Just curious though, did you check to make sure you have transmission fluid? Maybe they forgot to put it in from the factory. Just a thought.

+1 My '00 Z71 was like that. I bought it, ASSUMED it was all good, backing out of my parking lot spot and the tranny started to slip. Found it low 2 quarts. You'd think if the factory missed it that dealership would have caught it on delivery????

But to answer the OP's ?, my 6 speed has never did that.

The reason why it isn't caught often now is because there's no truly easy way to check it. No trans dipstick anymore. Takes several more steps. I know it well from having had a G8 GT with the 6L80E, and though not overly common, enough others with them having issues and their fluid being either a little or a lot low from delivery...it's too in depth to even bother with, on so many incoming new vehicles, for prep.

FarmerDave · April 1, 2010

No trans dipstick? What? There is one in my '08

DSChamber · April 7, 2010

Well guys and gals... as promised I am reporting back. Well it was down 3 quarts of tranny fluid, no signs of leakage anywhere so they chalked it up as "sent from factory low on fluid".... I was little pissed off to be honest, these things are "supposed" to be checked in the PDI. When you buy a new vehicle you expect it to be fully topped up on all fluids.... guess I have learned my lesson, next time I guess I will have to do the frigging PDI myself in the parking lot,

Anyway... I spoke to the Service Manager (whom I know personally) who is also (or was before going to management) a transmission specialist. He actually checked my truck alongside the technician.... I asked him if being down 3 qts of transmission fluid would have damaged anything... he assured me that it hadn't done any damage and that I would had to have been down a lot more before I did any damage. Well it certainly didn't help the transmission that's for sure .... I have left a v-mail to the sales guy, I want a transmission servicing done free of charge (basically a flush of the fluid and a new filter), more as a peace of mind, the dealership owes me that much I think. I know I have 5 years and/or 160,000 kms warranty on the drive train but why take the chance for less than a $100 transmission servicing. Maybe I am being paranoid, I would like to hear everyone's thoughts on that??

On the plus side... I had fun driving that Denali.... man I really really envy you guys that own this truck. I mean I like my truck, but the Denali is a whole other level of enjoyment... this thing was completely loaded with almost every possible creature feature.... I told my sales guy that he could keep my truck and I would take his demo ... lol... no deal