1999 Chevy Silverado overdrive shift

SKINSFAN69

MEMBER
1999 CHEVROLET SILVERADO
V8
4WD
AUTOMATIC
182,000 MILES

I have a 99 silverado 4x4. I just put in a tranny with 35k on it. When I drive it shifts in and out of overdrive. Any ideas

Wednesday, March 17th, 2010 AT 10:34 PM

6 Replies

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

Hello and thanks for donating

You sure it's shifting gears? And not just locking and unlocking the torque converter clutch?
Try it with OD shut off and at a low speed i.E. 35 to 40 MPH. May need to adjust the TPS

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Friday, March 19th, 2010 AT 12:19 PM

SKINSFAN69

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3 POSTS

I drove it at 65 took it out of o/d rpm went up then I went back into o/d rpm went down it was smooth. There are no tranny codes just a bank 1 air injection code maybe thats why at a sustained speed of 45 there is a hesistation no check engine light on

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Friday, March 19th, 2010 AT 8:38 PM

BLUELIGHTNIN6

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What speed is it hunting overdrive at then? Other than the OD issue, does it shift fine?

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Monday, March 22nd, 2010 AT 1:01 PM

SKINSFAN69

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3 POSTS

It shifts fine even o/d I think I have a EGR valve that is hanging up or something related to the air injection.

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Monday, March 22nd, 2010 AT 10:00 PM

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

Could try removing the EGR valve and cleaning it along with the valve's passageway. A faulty EGR valve can effect shifting and if you have the MIL on with the code it's def. Worth a shot and free to do.