894 code 4L80E
 

2006 Chevy Express Van 3500 we put on 50,000 miles a year. At 128,000 Check engine light came on, and I just had the transmission full serviced about 2,000 miles ago. All hyw miles hauling 3 to 5 thousand pound daily four days a week. Dealer and Transmission shops are saying 154 to 225 rpm slip @ 55 mph. Once the van has been shut off and we do not pas 55 mph everything shifts fine. When we pass 55 mph and back to 0 mph we get hard shifts high presser line takes over. I also just replaced water pump and lower radiator hose a long with rear transmission seal. This is one of my work trucks and I’m current on all service and maintenance schedules;which is done by the dealer. I feel this is a premature failure. When I rebuild do I use stock parts or aftermarket? Or any other suggestions.

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By the way at 55 mph this Van has always surged back and fourth. Took it in at 22,000 miles and dealer had found no explanation for this surging.

Has anyone else had this problem?
 

Anyone with any info. please it would be helpful.

/me moved to Diesels In Distress

I would say the converter is slipping.

Any updates??

What's the good word??

closing due to lack of a response.