My 2000 Sierra just started having a problem with a server jump from
1st to 2nd gear. When starting from a dead stop and my automatic goes from 1st to 2nd on take-off, I get a very bad jumping jerk of the truck. All other gears are good.To get around the problem I began starting off in 2nd gear from a dead stop.
Any help is appreciated. Terry in Texas
Do you have a 4L60E transmission? Is this a 1/2 ton truck? If so, this could be the dreaded P1870 code. Get the codes scanned because iirc the P1870 does not always trip the check engine light. This has something to do with the valve body boring out the valve sleeve. If the trans isn't too far along, a Sonnax valve-sleeve installed by a good, independant transmission shop might save you from a complete rebuild. I am sure someone else in this group can explain it better as I am certainly no transmission guy.
HTH,
Derek
My son had the same problem with his 97 GMC K1500. He had the trans rebuilt and the problem was still there. They replaced the valve body with a new updated one from GM and it worked perfectly. He said that after the valve body was replaced the trans never shifted better. You may be able to just replace the valve body on your's and not have a complete rebuild. If you do it yourself, there are allot of steal balls on top of the valve body when you take it down, be careful not to tip it over and misplace any of the balls. Hope the info helps.
Warren
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