99 5.3l Tranny

stvdalton · September 20, 2009

I have a 1999 Chevy 5.3L z-71. Has 172K miles, have a couple problems actually.

The tranny newly rebuilt before I bought it from a friend of mine. The truck seems like it shifts so quick and especially into overdrive and lockout or whatever you call it. It will actually go into the lockout at like 40mph if I'm not getting on the gas. Trucks seems like it boggs down so much. I can push down pretty far on gas and it will finally kick down and go, but it actually kicks all the way to 3rd gear. I thought it should just kick down to overdrive and unless I really gas on it. Hope you all understand what I'm trying to say.

Other problem is, when it's kinda bogged down and it hasn't kicked down, I can sort of feel the truck jerk or misfiring. One guy seems to think it's not the convertor trying to kick in or anything, but a misfire. I do have a mis sometimes, mainly at idle. Trying to fix that also, but haven't changed anything on the mis yet. Hope you all can give a clue. Maybe normal for the tranny to shift like that. It sounds worse because the truck has a flowmaster so you can really hear the engine more if it boggs down.

Thanks for any help.

alwcurlz · September 20, 2009

You need to get the engine running smooth before trying to diagnose the drive train. It is normal for a stock transmission to shift all the way and lock into OverDrive, which is 4th gear at 4mph if you're driving with a light foot on the accelerator. It sounds like your TPS (Throttle Position Sensor) is faulty and giving erratic feedback. Also, depending on when the plugs and wires have been replaced, it may be a good idea to replace those as well. Good luck!

stvdalton · September 21, 2009

The plugs are wires were replaced about 30k ago, but may do it again. Just hate replaceing and replacing. HA! My boss feels strongly that it is O2 sensors possibly. Since it is so intermittent and mainly at idle, ever once in a while it I can feel it mis a little when taking off to get to highway speed, but not often, mostly at idle for more than 20-30sec or at highway speeds sometimes.