07 Nbs Vmax Transmission Problem

07Sierra07 · January 30, 2011

After a 3hr road trip I stopped at my inlaws so the GF could pick up her car. When I got back onto the highway once I got up to speed and the truck shifted into 3rd the RPM's just hit the roof and the truck didn't go anywhere. Speedo dropped to 0. I put the truck in N, gave it some gas, let the RPM's settle down and put it back in D. Nothing. I put in in 3, nothing. I put it in 2, and I got power again.

Folks, WT-heck's goin on here>

I'll limp it to the dealership on Monday morning, but I'd like to have a clue beforehand.

thanks,

07Vmax-down

jandersinc · January 30, 2011

Sounds like it's time for a new tranny. That'd be my guess.

jro909 · January 30, 2011

its gone...you need the codes to get an answer to what exactley nuked in it

DwayneJ · January 30, 2011

Sounds like the third/fourth gear clutches are shot.

Put it in second and limp it to the dealership.

Here in WI if it is out of pocket a reman with 100K warranty is about $2500. Not sure where you stand on factory warranty so I thought it worth mentioning.

No idea what the going rate in Canada is or if GM treats warranty different for you.

07Sierra07 · January 30, 2011

It's under warranty. I doubt the dealer will put in a 'new tranny'. They'll replace parts but that's about it.

Nothing 'nuked' it, something broke. If there were codes, the light would have come on no? I'll plug in my obdII tomorrow and take a look.

jro909 · January 30, 2011

Sounds like the third/fourth gear clutches are shot.

Put it in second and limp it to the dealership.

Here in WI if it is out of pocket a reman with 100K warranty is about $2500. Not sure where you stand on factory warranty so I thought it worth mentioning.

No idea what the going rate in Canada is or if GM treats warranty different for you.

where in wi? 2500 for a gm trans to be put in?

07Sierra07 · January 30, 2011

Sounds like the third/fourth gear clutches are shot.

Put it in second and limp it to the dealership.

Here in WI if it is out of pocket a reman with 100K warranty is about $2500. Not sure where you stand on factory warranty so I thought it worth mentioning.

No idea what the going rate in Canada is or if GM treats warranty different for you.

Any idea what would cause the clutches to fail? With TM, I would have thought the tranny would last forever!

The truck only has 80k km. We have 'powertrain' warranty up here for 160k km. I should be ok.

hrspwr · January 30, 2011

Check out a couple things first. Check the level of the fluid, may be low and that could have caused the slip, an overheat will do the same thing. Check the colour of the fluid, should be a bright bright red. If it is brown, it is still good, but smell the fluid and see if there is a burnt smell to it. When trannys slip, the PCM will detect the slip and set a code, and most of the time when a slip is detected, it goes into a limp mode where it increases line pressure to limit the slip. It will almost act like a shift kit was added.

Clutches fail for a couple of reasons, but the most common is hauling heavy without enough line pressure. Line pressure is what keeps the clutches from slipping on one another, and will either give you a nice soft shift(factory) or a hard one(shift kits, vetter servos, larger valve body/plate). If I am not mistaken, that is what the tow/haul button does, holds a gear for longer, but also adds line pressure for a more firm shift(99% sure, but someone can correct me if I am wrong)

To add, if your truck is still under warranty, I would think the dealer would cover it as it is part of the powertrain and part of the powertrain warranty.

[email protected] · January 30, 2011

Many vmaxs were bad on trannys because they put to little of one behind a 6.0l and that's what you get.

07Sierra07 · January 30, 2011

Check out a couple things first. Check the level of the fluid, may be low and that could have caused the slip, an overheat will do the same thing. Check the colour of the fluid, should be a bright bright red. If it is brown, it is still good, but smell the fluid and see if there is a burnt smell to it. When trannys slip, the PCM will detect the slip and set a code, and most of the time when a slip is detected, it goes into a limp mode where it increases line pressure to limit the slip. It will almost act like a shift kit was added.

Clutches fail for a couple of reasons, but the most common is hauling heavy without enough line pressure. Line pressure is what keeps the clutches from slipping on one another, and will either give you a nice soft shift(factory) or a hard one(shift kits, vetter servos, larger valve body/plate). If I am not mistaken, that is what the tow/haul button does, holds a gear for longer, but also adds line pressure for a more firm shift(99% sure, but someone can correct me if I am wrong)

To add, if your truck is still under warranty, I would think the dealer would cover it as it is part of the powertrain and part of the powertrain warranty.

I'll check the fluid this morning, I doubt it's low or burnt. Last time I checked it, it was bright red, no burnt smell. If it were due to be changed, I'm positive the dealer would have suggested it. If a code were set, wouldn't I see my service engine light on? I'll plug in my OBD reader and see if theirs anything to see.

Heavy hauling, I've done some light hauling.. the truck was built with the 'Max trailer towing' package and is rated to tow over 10k lbs. My camper barely breaks the 5k lbs mark and I haven't moved it around much since I've had this truck. My 2004 with a 4.8l towed this camper alot more than this truck has...

Yeah, it'll be covered under warranty no problems there... I wonder how the dealer would re-act if I asked them to install a vette servo after they fix whatever's wrong with it ?

What bothers me the most is that I've taken good care of the truck, haven't abused it really and at 80 000km, I have a tranny problem. I've grown up with Chevy's and GMs and all of our trucks have worked harder than this one. None of them were 'built" for towing like this one and we never ever had a tranny problem like this early on in the game. Our old 2002 with a 305 pulled around landscape trailers loaded with equipment and material up and down the highway, tranny finally gave up at 200 000KM.. WHY is this one failing at 80k when it hasn't even worked? Honestly, this thing is practically a grocery getter. I goto School every morning, then to work where the truck sits in an underground parking, then home.

I just feel like the reliability of this truck is gone now. My dealer has trouble getting little things fixed on the first try, I'm dreading letting them play inside the tranny. This is going to be weeks of aggrivation I'm sure.

GMstrong · January 30, 2011

You could still be throwing codes with out the SEL on..100 bucks says gm won't put in a new one.The will just rebuild wants wrong.So the thing will happen again.

07Sierra07 · February 1, 2011

I never got around to checking the codes. Didn't go near the truck yesterday at all.

Woke up this morning, jumped in the truck to limp it to the dealership... but it ran fine! It shifted through all the gears as it should, upshifted fine, downshifted fine, no shake no slip, no nothing. I continued to the dealer anyways, and explained the situation. They checked, no codes anywhere, no leaks, fluid's perfect.. The tech went on a road test and found no fault, and then someone else from the dealership took it for an extended road test (they racked up 25km) and found no fault either.

WTF? Can anyone with solid transmission knowledge shed some insight here?

From start to finish:

07 GMT900 6.0L, GMPP CAI, Magnaflow. That's it.

I had just got back to the city from a 110km trip on the highway. I backed out of the mother in laws and started driving away. A Merle Haggard classic came on the radio so I cranked the volume a bit. I didn't initially notice that when the truck reached 3rd gear that the RPM shot up but the truck never went into 3rd. When I did clue in, I looked down, truck was definately in D. I shifted to N, gave the pedal a snap, put it back in D and again, no gear just high RPMs. I dropped it to 3, no gear, dropped it into 2nd and 2nd was there. Luckily I was only about a km from home and the speed limit was only 40-50km anyways. Then, like I said, this morning, everything was normal again.

I'm stumped, but then again, I know nothing about transmissions .

My dealership shouldn't be stumped but... they charged me to check it out and find no fault.