1-2 Trans shift oddity

[tbangert]

Didnt know what else to call it, but as the title states I'm noticing a strange shifting "issue". It became apparent just after I replaced my battery a few weeks ago, figured it needed time to "readjust" but not so much.

So what happens during the 1-2 shift is it acts like a delay, the revs drop like it has shifted then a second later you feel it "engage" into second gear. Now it doesn't happen all the time, on the drive to work, 3 miles and 10 traffic lights, I'll feel it a couple times. Heavy acceleration it won't happen. All other functions of the trans appear to be normal.

I've been digging around and can't really come up with a definitive answer. I know I'm due for another trans fluid change once I get back home from a work trip (counting the days...) Auto transmissions are like Chinese writing to me...

Just so it has been stated, only modification to the trans has been an upgraded cooler.

Any help greatly appreciated!

[dvanbramer88]

I know on the 4L60E trans, there are check ball valves in the plate on the bottom of the module in the trans. The bores that the check balls ride in like to wear out and the check balls get hung up and stuck. A common fix is to install a shift kit that comes with an upgraded plate.

My truck does hard 1-2 shifts before the trans warms up. But i don't feel a distinct pause before the gear engages.

You could be facing a bad 1-2 shift servo. (Which IIRC most shift kits upgrade/replace as well)

James downing has a thread about a shift kit install, It's not terribly difficult and all the work is done with the trans still on the truck. The kits are ~$80-120 and I have a shop quote me $300 installed for a shift kit in my truck. (I never got it done)

Well anyway, thats the common things for that trans. Hopefully that helps with your research. And IDK how you're searching, but instead of searching "trailblazer 1-2 shift pause" Use 4L60E in your searches. You'll probably find more on a GMT400 forum as those trucks used the same tranny and are getting older.

[DirtyBacon04]

Mine did the same thing but from 2-3, and I had to replace the xmsn to fix it. Sounds like your just getting initial slippage on your clutch plates. Hopefully you fix it before it gets to the point of R&R. I drove on it slipping for many thousand miles with 33"s and 3.42... and no xmsn cooler... that bitch got WARM!!!