2001 GMC Sierra 2500 HD Transmission

Tiny
JASONFORD99
  • MEMBER
  • 2001 GMC C2500
Mileage: 102,000. I took my truck in to my local dealership for a trans service at 85,000 miles. Up to that point, I had no problems whatsoever. Fluid nice and red but dirty. 15,000 miles after the service I noticed a low roaring noise after a 250 mile trip. I could make it stop by putting truck in neutral. I decided to check trans fluid. The fluid level was good but the fluid was as black as used motor oil. I immediately took it in to the same dealer to have it looked at. They said they had no idea what caused it. They drained fluid, replaced filter, and flushed the trans twice. Pan had NO shavings whatsoever. After driving 50 miles, the fluid still was black. Not quite as bad as previously, but still black. They told me everything checked out OK and thre had no clue as to the cause. Told me to to just drive it and watch it closely. After 500 miles it started slipping VERY badly. It barely got me back to the dealership 2 miles away. They have now told me the clutches must be worn. That's all they know. I am just wondering if there was anything that they could have done at the 85,000 mile trans service to cause the trans to fail. I have a hard time accepting it just failed, coincidentally after the service. The 102,000 miles are almost all highway miles with NO towing at all. Please give me your input.
Thank you
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Thursday, May 18th, 2006 AT 1:42 PM

3 Replies

Tiny
LOSONE
  • MEMBER
Unfortunatly it is a common story with transmission fluid changes. If a fluid looks brown it is not dirty but burned. I suspect the change and flush caused a transmission failure.

Your tranny needs to be changed every 30-45K miles.
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Thursday, May 18th, 2006 AT 4:58 PM
Tiny
JASONFORD99
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How exactly does a change and flush cause a failure?
Prior to the trans service, the fluid looked "normal" 15K miles later (after the service) it's black.
I know it should have been changed at 50K but there is no waythat extra mileage cause it to fall apart.
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Thursday, May 18th, 2006 AT 7:44 PM
Tiny
LOSONE
  • MEMBER
You do no have to believe what iI say about transmissions. After 40+ years as a garage owner I can tell you some specifics about hundreds of failed transmissions.

Flushing a transmiision with discolored fluid is an "iffy "service at best. The flush chemical loosens the deposits that have been resident in all the corner, cracks and pockets of the unit. This creates a debris field that will loosen when new fluid is added and within 5K or so miles will start to create transmission woes.

The torque converter cannot be drained unless you drill a hole and put in a bolt to seal the unit. (Ford has one built in) This leaves several quarts of transmisson fluid unchanged. Flushing is often a "gimic" transmission shops use to sell an over haul. Read the fine print on the work order and it relieves them of all liability.

The act of flushing loosens deposits on all the internal working components especially the bands and valve body. These loosened deposits get in the valve body chambers and the flush fluid often distorts the small plastic balls that chamber fluid to the correct band assembly. I have seen bands come apart as they are held together in many cases by burned material.

Internally the transmission has a plethera of working parts including seals, O rings, gaskets and most important the bands. Every time a transmission shifts a minor amount of slippage occurs. This happens so the driver doesn't feel a jerk when the gears change.

Most all transmission experts will tell you that the dark deposits are from the internal parts of the transmission and torgue converter that have been loosened by an additive. Oil change and most surely from a flush.

Remember your torgue converter also has a clutch that locks up giving you a 200 to 300 RPM drop and acts as an over drive. It is a very dark color and a little bit of debris goes a long way to discolor fluid.

Sadly the only way your problem can be corrected is to rebuild your transmission. I tell every one with a 2500 or larger vehicle to insure they have an aux transmisison oil color because heat is the real killer of most of the transmision problems as well as failure to service the units.

Sir; you are not alone in you transmission problems with forgetting to service a unit or expecting a magic bullet to cure everything when a high mileage unit is serviced.

Believe or don't believe what I have written, as a I am passing along facts based on my experience and beliefs. You are the end decision maker and very good luck to you.

Losone
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Friday, May 19th, 2006 AT 8:19 AM

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