I have a 2000 Chevy Silverado with the heavy duty trailer package. It shifts hard (clunks) when towing?

It just does it after towing for about an hour. The transmission has 2 auxilary transmission oil coolers. The temp only gets to 175 or less. The chevy people dumb up when I take it in...it only has 54000 miles on it. It does not create an error code. It has done it for the last couple of years.

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  • 1 decade ago
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    My brother's truck used to do the same thing. He would take it into the dealer and they would say that it was normal. After he had about enough of it, he traded it in on a new one and hasn't had a problem.

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  • 1 decade ago

    I worked at a GM dealership for a little over 4 years and have seen these transmissions go 300,000 miles or not even make it out of the dealership. Seriously.

    If you have an Alison built HD transmission you might be overloading it. Even with 2 tranny coolers the computer knows when its being worked too hard and it will do all sorts of things to save itself.

    In fact the extra transmission coolers might be the problem.

    If you call your GM dealership and ask to speak with the Service Manager you can usually make an appointment to talk to the guy free of charge. Make an appointment, load up your trailer and stop by the dealership and take him for a ride so he can experience the problem first hand.

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  • 1 decade ago

    are you using tow-haul feature? if you are then firm shifting is part of the rescheduling the pcm does and this is normal

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  • 1 decade ago

    you may have to take it somewhere other than a dealer and have them check the filters and pump. I'd check the u-joints also

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