HELP needed with GMC transmission problem

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

On Jul 5, 11:33*pm, Terry > wrote:
> 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