Transmission slipping in second gear

1999 GMC

LVLIKEG

MEMBER
3 POSTS

I have a 1999 GMC Suburban with a 5.7l v8 and 56,000 miles on it. A couple of months ago the transmission started slipping it only did it in second gear. It would go straight form first gear to third gear and take a long time to pick up speed. When I took it to a transmission shop the mechanic told me I would have to rebuild the transmission. I recently got the transmission rebuilt and it is still doing the same thing now he says that the PCM is burned out and I need to get a new one. Is it possible to burn out the computer with such low miles?

Nov 10, 2007 at 10:59 AM

CHEVY22

✓ASE Certified Mechanic
1,375 POSTS

is it 4x4??

jim

Nov 10, 2007 at 11:31 AM

LVLIKEG

MEMBER
3 POSTS

No it's Not.

Nov 10, 2007 at 12:28 PM

KASEKENNY

✓ASE Certified Mechanic
18,907 POSTS

I would challenge the idea that the PCM is failed at this point. It very well could be but I would want to see the proof after being told it was a transmission and that was not correct.

The idea of what is happening is the vehicle appears to skipping shifts most likely due to inputs to the PCM. This is most likely the throttle position sensor because this is a major input that is needed to determine proper shift points and correct gear.

So if the throttle position is not operating properly then the PCM will not correct it.

Again, if there is a reason that the PCM is failed, they should be able to show that. If not, then I would seek a second opinion if you are not going to look into this yourself.

Please come back and update us on what happened with this and we can go from there. Thanks

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Mar 26, 2020 at 4:34 PM