Hard 1-2 Shift And Pretty Bad 2-3 Flare?

Ken Z71 · March 28, 2010

Trucks an 04 1500 sierra z71 w/~170000 miles on it.

Its shifting pretty hard into 2nd and flares pretty bad from 2nd to 3rd like its searching for the gear. Also at speed when I let off the throttle for a few seconds then get back on it (nothing extreme just everyday trying to speed back up) the engine/tach flares a few hundred rpms then almost immediately back down into gear.

I took it to a local trans shop and after looking at the fluid they said its about time for a ($1400) rebuild. I don't doubt that their right because this shift flare has been going on for over a year now but I just don't think its a "hard trans component" like bands gears etc. causing this problem. (I know nothing about transmission BTW but I'm not mechanically ignorant either)

When the trans DOES find the gears, they hold fine. Ive towed many times in tow/haul and it seems like the problem goes away for the most part. Flared going up incline from a stoplight but again not all the time.

What I'm wondering is what are the possible computer/electrical causes. Like what controls the trans shifting. Changed the MAF, didn't help then MAP, nothing. Then plugs, engine oil, nothing still. The main reason I think its electrical is because it doesn't do it all the time but the majority, and sometimes its way worse than others. Sometimes it shifts and runs perfect.

This is happening at any and all temps from freezing to 110 degrees.

I will be pulling the pan soon to replace filter and fluid, should I change the solenoids while I'm in there? Anything else I could swap out/ check myself without having to drop trans?

Also not getting any trans codes but I did have P1516 and P0449 (throttle position performance & evap canister something). Fixed the 0449 but the 1516 hasn't come back on since cleared so it could have been low bat voltage or a number of other things.

Sorry its so long I'm just trying to be as specific as possible before I drop $1400+ come to find out it was a loose wire or something I could have done myself.

Thanks for sticking with me ;)

(only mods are intake and magnaflow) Diablo predator should be hear tuesday.

6in procomp lift with 305/75/16s.

Nytemare · March 28, 2010

Seeing as you have 170K on it and big tires...I would say your clutches are toast.

One check before you go for a rebuild...pull the connector on the side of the trans and ensure its not corroded.

Also, take it to a driveline only shop, these guys will likely know whats gone by driving it.

If you want a good trans that will handle the large tires etc....Try PATC...Performance auto and trans center...

http://www.transmissioncenter.net/4l60e.htm

They have the Level 3 that will handle anything your gonna toss at it....Its more cash....but its as strong as it gets, while maintaining drivability.