Transmission Slams into Second and Third Gear

[tvtoes]

While driving my 99 Suburban yesterday, the transmission started to Slam into gears as it uposhifted. It does not slip or delay, but feels just like i put a "shift Kit" in it.
This started while driving from a stop light. It was working normal and ever since it has been shifting hard.
What is making this happen all of the sudden?

[john8662]

Going to have to check codes, this is one of the limp modes the transmission goes into when somethings not right.

Do you have any aftermarket programming?

Vatozone (it's a joke) Autozone has scanner ability to retrieve the codes for free. Write them all down and come back here, don't let them tell you what the codes mean, cause they'll be WAY wrong on the Diesels.

J

[tvtoes]

No, i have no aftermarket parts except exhaust. There are no codes i already checked them.... Thanks

[john8662]

Next step, find someone with a Tech-2 or a snap-on or equivalent bi-directional scanner and read the codes.

The scanners that AZ uses (basic) won't retrieve codes that don't turn on the check light.

You'll need to leave the truck running after it misbehaves, then let them connect the scanner.

viewing the code "history" will help shed some light on the problem.

J

[Robyn]

Disconnect the battery + cables and wait about 10 minutes then hook back up and give it a try.
If there are no codes I suspect a glitch.

I had a 95 thqat would do that if you set at a light and messed with the throttle a bunch, (jazzing it quick without letting it rev up)

Give the unhook a try and let us know if it helps and or if it does then comes back.;)

Robyn