Yukon Transmisstion 'Forward Band'

yukon
transmissions

#1

With only 70,000 miles, the transmission on my 2004 Yukon has failed and the dealer doctor states ‘forward bands’ as the culprit.



Facing a large repair or replacement, I need to know if warranty repair done at 38,000 miles to replace the input shaft seal could have, in any possible way, contributed to this failure.



I know the transmission was opened to replace the seal and question if this could have contaminated things???


#2

I don’t understand the statement that the ‘forward bands’ are the culprits for the failed transmission. There is a ‘forward clutch’ which would cause lack of forward speeds. There is a ‘2-4 band’ that would cause those speeds to be absent and a ‘1st/reverse band’ that back up the 1st one way sprague. Usually a ‘band’ fails by breaking, wearing out its friction surface, or wearing out its corresponding drum by excessive slipping. Not knowing the specific symptoms of your failure limits opinions on what has gone wrong here.

In answer to your question, no I don’t think the previous repair introduced contamination that precipitated this problem. When the front seal was replaced, the torque converter was removed but the transmission would not have been openned unless there was some problem with the pump and/or stator support. Even if contamination were introduced, the damage would be to bushings, gears, needle bearings, and ground surfaces. Large dirt particles would have been captured in the input filter. Smaller particles that made it through the filter would have ended up in the valve body which would eventually cause valve spools to jam; clog up solenoid filter screens; and cause solenoid valves to malfunction. Ergo it is unlikely that the previous repair caused your present problem.

That is it IMHO.


#3

This transmission has one band, the intermediate band. What I see crossing my bench, would be failure in the band strut. This is the surface on the band itself where the band pin or the servo pin contact. These welded pieces break and the band no longer applies. When this happens, you lose 2nd and 4th gears. What kind of symptoms are you having?? As far as it being related to the 38k input shaft seal replacement, I seriously doubt it. If they did the repair right, they would have removed the transmission, removed the pump, disassembled the pump, replaced the stator bushing, reassembled the pump and installed new seal. Even though the band is just under the pump, the band does not need to be disturbed for this repair plus, you would have had issues long ago if the previous repair caused the failure now.

transman