4L60E issues and questions. (LT1 Swap) - Third Generation F-Body Message Boards

Thirdgen89GTA · 08-01-2009, 08:28 PM

I've gotta say right now i'm leaning towards a mechanical problem(solenoid or other issue in the trans).. I just got my car back on the road (YAY!) But I have a few funny issues with the transmission that I don't know if they are electrical in nature, or mechanical. I'm a pessimist so I'm leaning towards mechanical.

But here's what its doing.

Issue #1: Coming off idle in OD, D, 2, or 1 the engine revs up a few hundred RPM then the car jerks forward as the trans finally catches. Once it is in gear upshifts are positive and get progressively firmer with more throttle all the way up to a WOT upshift. This jerk off idle only happens in forward, not reverse. Doesn't matter whether the selector is in OD, D, 2 or 1.

Issue #2 This is possibly PCM tune related but I'm not sure. When the selector is in OD and i'm cruising in 4th gear anywhere above 40mph if i let off the throttle to coast it downshifts to 3rd instantly. When I give it throttle, just enough to accelerate again it upshifts into 4th gear and continues on with the TC locked like it should be. 4th doesn't feel like its slipping at all. Also, while its in OD if I let off the gas the engine will throttle down to about a 500rpm idle no matter what speed i'm at. If I put it in D the engine revs will stay with the speed and drop as speed drops. So 3rd gear isn't slipping as the trans seems to respond to throttle changes as it should. TC is locked in 3rd and 4th above 40mph.

This could just be valve body related too. Though I've never had a trans do this.

Does anyone have any ideas other than rebuild the trans? Perhaps its a sticking solenoid?

Thirdgen89GTA · 08-01-2009, 09:43 PM

After looking around, the issue sounds like an either burnt/worn overrun clutch, or the overrun clutch not being applied in 4th.

Does anyone have the valve body schematics they can post or email to me?

The issue basically boils down to no engine braking in 4th gear (though why it downshifts to 3rd on coast I don't know).

Someone mentioned it could be the tune doing it.