Denali Transmission cooler failure ruins transmission

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Jim

AOL

#1 Jul 14, 2006
My 2002 Denali XL's transmission cooler failed mixing transmission fluid and coolant in the radiator. Result very quickly is slipping transmission. Car has 74000 miles, all normal family driving, never towed anything or did any off roading. The cost of the repair was over $3000; extended warranty paid $2000. I looked on the internet and quickly found this to be a common problem. Apparently the trans cooler is inside the radiator and therefore you can't detect the failure until you have a problem. One sign is coolant and trans fluid mixed in the overflow tank for the radiator, but by then your transmission will be ruined.
I called GM to see if they would help cover the cost of my portion of the repair. They ultimately came back and said no since I take the car to an independent repair shop, even though they referred this issue to a GM dealer.
I have been a loyal GM buyer, now am very disappointed. A part that is designed to extend the life of the transmission fails and causes early problems. Seems like they should own up to this. This is my last GM vehicle. If you are driving this car, watch out for this problem.
Bryan

Jacksonville, NC

#2 Dec 8, 2006
I also have a 2002 GMC Yukon Denali XL, and it has transmission fluid in the cooling system also. I will never buy GM again, because I have always had a high-dollar problem with them (1990 corvette, 1997 corvette, 1995 Suburban, 1990 Chevrolet Camaro, and now, this over-priced piece of junk!)
brandymwb

Versailles, KY

#3 Jul 16, 2007
The problem with GM transmission coolers extend to more than your models. If you ask any service center about radiator flushing you will find a high number finding slick fluids floating on top of overflow and neck of radiator. If they would put that together with the fact the transmission is over full most of the time well you could save the transmission. As far as dealers go the way they have there service set up is to make money by not doing a complete check on all points or improper training of mechanic to catch problems like this. As far as GM I have had issues with dealers repairing or so called repairing my vehicle and not do the job correct or not at all. I am with you on never buying GM again.
brandymwb

Versailles, KY

#4 Jul 16, 2007
[The problem with GM transmission coolers extend to more than your models. If you ask any service center about radiator flushing you will find a high number finding slick fluids floating on top of overflow and neck of radiator. If they would put that together with the fact the transmission is over full most of the time well you could save the transmission. As far as dealers go the way they have there service set up is to make money by not doing a complete check on all points or improper training of mechanic to catch problems like this. As far as GM I have had issues with dealers repairing or so called repairing my vehicle and not do the job correct or not at all. I am with you on never buying GM again.
Jim Rollins

AOL

#5 Aug 10, 2007
Just found oil and black stuff in my 1998 GMC Sierra's radiator. Bad news. No transmission problem yet. Will change radiator and do a trans flush, etc if I confirm a Transmission cooler leak. The truck has only 78,000 miles!
This stinks! Will not buy another GM Truck!
cha cha

Hubert, NC

#6 Aug 13, 2007
well i have a 9000 saab year of a '96 and the tranmission fluid is mixin in with the coolant.. i don't know what to do
rick hoffman

Olathe, KS

#7 Sep 2, 2007
same thing just happened to me on 03 denali. i experienced coolant overflow with transmission fluid mixed in.
Carmen

Studio City, CA

#8 Jun 19, 2008
I own a 2006 GMC Denali XL. Out of the blue my husband I heard loud clanking noise coming out of first gear. We thought we ran over something. Within the next few minutes the car would not change out of first gear. Took it to the dealer, and very upset to hear that my Denali, with only 37,000 miles, has "internal transmission trouble. This sucks.
Scrap Iron

Atlanta, GA

#9 Oct 15, 2008
My wife's 1998 Saab 900S convertible just bit the dust with radiator fluid in the transmission. No warning. No lights. Car Blue Book is $3,000. Used transmission and radiator replacement is $3,100. Sold the car to the mechanic.
RYAN

Norfolk, VA

#10 Jun 24, 2009
I have a 03' denali and on hot days im seeing my transmission temp is almost at 200 degrees, I have had tanny flush at 75,000 miles I currently have 95,000 mostly highway miles,I dont see any mixing of the tranny fluid and coolant, I have never towed anything and I dont drive it hard, I was just wondering if anybody had any ideas or solutions
JJH

Doylestown, PA

#11 Aug 18, 2009
I too own a 2006 Yukon XL Denali - only 42K miles - reliable service record, never towed anything, never off road - we took it on vacation and when pulling out from a parking lot, heard a loud clunking sound, similar to Carmen - car acted like it was in neutral, even though it was in drive following the clunk - would only drive in 1st gear. Dealership says it needs a whole new tranmission at $3000. Crazy that a $45K vehicle needs this sort of high-end repair - that clearly shows a manufacturing defect - so early in the life of the truck. I've owned many cars in my life, and have NEVER had a transmission replaced. Now, on my newest vehicle - the one I expect to go many more miles before any major issues - craps out before we even hit 50K. I can see why US car makers are all going belly up. I have a Toyota mini-van also - 2 x the mileage and 4 years older and have never had a single issue with that.
Impala owner

Mayfield, KY

#12 Dec 27, 2009
I own a 2005 Chevrolet Impala with 72000k miles. Currently waiting to be broke down somewhere due to transmission changing hard and slipping. This is a wonderful late Christmas present for us because who has over 2 thousand dollars plus now days to fix a transmission right out of the blue. This should never happen on vehicles that have 72000k. My brother works for GM but I will never buy another GM vehicle again!
Tom Smith

Alto, GA

#13 Jan 20, 2010
My 2007 Yukon has same problem at only 15,000 miles. 6 or 8 weeks ago had electronic malfunctions which resulted in RPM gauge reading correctly but speedometer is reading O (yes that is ZERO) Transmission temp registered only 107 degrees. Got to dealership diagnostics said all OK after engine turned off and gauges returned to normal read-out. Last week transmission warning "Idle Engine" transmission hot! No chime warning. Felt like in 3rd or maybe 2nd range. Took to dealer 1/18/ 2010. Told today needs new transmission and radiator. No resolution of possible electronic connection to this problem. Don't trust this vehicle and don't want the vehicle with underlying flaws. My 1996 Yukon was a far better vehicle. Lemon Law ?????
Pissed Off H2 Owner

Levittown, PA

#14 Apr 6, 2010
I have a 03 Hummer H2 and I have had the exact problem mentioned above. To make matters worse I just paid to have the transmission rebuilt about 2 months ago. It might be possible this was the problem all along. I have to say this is the most unreliable vehicle I have ever owned. I had fewer problems with a broken down honda I bought for $200 about 15 years ago.

So Far just this year I have spend upwards of $8000 in repairs and have many other problems I cannot afford to fix. Thank you GM for putting your reject engineers on your high end line of products. This fix is going to force me to not only be broke but skip a mortgage payment because money does not grow on trees.

All in all I have fixed the following problems

Air suspension failed 3 times. The problem was electrical but it seems the dealership could not figure out how to fix a $300 electrical problem for less than $3000 by replacing everything until the problem was fixed. Too bad for me no one ever told their brilliant mechanics that the distribution unit was inside the door not in the rear of the vehicle itself. I have had this problem 3 times!

The spedometer cluster has failed once before completely and now it is acting up and not working when the vehicle first starts. Acts like there is a poor power connection to the unit. Course I have to take the vehicle out of commission for 3 days because you have to mail the instrument cluster to someone to fix it because they don't trust mechanics not to roll back the odometers.

The 4WD unit has failed and no longer will engage 4WD.

The door locks, the remote fob and the passenger side controls all stopped functioning. I've had this problem twice.

All in all I have spent upwards of $15,000 on repairs in the few years I have owned this vehicle. I would strongly discourage anyone from buying one of these lemons.

And GM, if you would like to spread some of that free money around and make this right, I still have a whole list of problems that I cannot afford to fix at the moment. For normal folks like me, money does not grow on trees and this is the only vehicle I have (and cannot afford another car payment)

Thanks for the hardship GM engineers, GM testers and GM mechanics. rockin_hk@yahoo.com
Adrian

Auckland, New Zealand

#15 Jun 29, 2010
Only way to be sure you wont stuff your trans is to run an external oil cooler and not running it through the factory spot of the bottum of the rad.
jaime

Vega Alta, Puerto Rico

#16 Sep 22, 2010
i have a 1997 chevy blazer and i dont want more GM
products.theres a lots of issues with the 4l60e transmission and many electrical failures with,wiper.power windows.transmission oil cooler and they are blood sucker. i'm very mad about GMC quality.no more gmc cars in my hands.the only gm that i trust is the 1989 astro van old school technology without worries!!
Joe

Canton, GA

#17 Apr 22, 2011
Waaaaa.... Everyone threatening not to buy GM again - 1, did you follow thrpough with it, 2, do you really think it is going to hurt them??? I have an '02 Yukon with 225,000 miles on it and the only thing I have done to it is a water pump... the transmission is still going srtong...
Jim wrote:
My 2002 Denali XL's transmission cooler failed mixing transmission fluid and coolant in the radiator. Result very quickly is slipping transmission. Car has 74000 miles, all normal family driving, never towed anything or did any off roading. The cost of the repair was over $3000; extended warranty paid $2000. I looked on the internet and quickly found this to be a common problem. Apparently the trans cooler is inside the radiator and therefore you can't detect the failure until you have a problem. One sign is coolant and trans fluid mixed in the overflow tank for the radiator, but by then your transmission will be ruined.
I called GM to see if they would help cover the cost of my portion of the repair. They ultimately came back and said no since I take the car to an independent repair shop, even though they referred this issue to a GM dealer.
I have been a loyal GM buyer, now am very disappointed. A part that is designed to extend the life of the transmission fails and causes early problems. Seems like they should own up to this. This is my last GM vehicle. If you are driving this car, watch out for this problem.
Capt Glenn

Clarkesville, GA

#18 Oct 7, 2011
I have a 2002 Suburban 1500. I have towed heavily for many year with this vehicle. It has proven to be a great work horse doing what 2500's couldn't do. I just had a problem with the transmission cooler (which is inside the radiator). I was quoted a price of $3,800.00 from a trany shop in Knoxville, Tn that is where I broke down. I chose to rent a Uhaul truck and trailer to bring my favorite vehicle home. I just installed a transmission cooler and plugged the radiater. Even though my fluids are mixed there is no slippage at this time. I plan to flush both coolant and trany systems. I have heard if I had the new tranny fluid I will be ok with out a rebuild is this correct?
Capt Glenn

Clarkesville, GA

#19 Oct 7, 2011
oops I meant coolant fluid
Mike S

Shelton, CT

#20 Oct 14, 2011
My 2006 GMC Sierra Denali is currently at dealer for a failed transmission at 80,000 miles. At 10,000 miles I had the transmission and radiator replaced under warranty due to transmission fluid and radiator fluid mixing from a cracked weld in the transmission cooler. I have been working with GMC customer service in hopes of having all or part of this problem covered. I did not expect this from a 47k vehicle. Have bought and owned GMC's and Chevy's faithfully for 25 years and have not had major problems like this. Sure hope they step up to the table on this one.

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