Dark Halo

iTrader: (14)

I got my 4L80E back saturday and everything works great but manual first. The tranny feels as if something else is engaging with it. When I first start to roll it is fine but when it gets to about 3000 to 3500 rpm's it fells like I have the brakes on. This is the same problem I had when I first got it back. The tranny is a 2003 4L80E with a PI 3500-3800 stall (it seems to flash at about 3600) and transgo shift kit. Any idea what might be going on?

James B.

iTrader: (1)

It sounds like you are getting centrifugal apply of a clutch set due to fluid not being evactuated properly. In manual first the overrun clutch is engaged. There are only three clutch sets whos pistons spin in the 4L80-E, The Forward, the Direct, and the Overrun clutch sets. In manual low (1st) the Overrun clutch and Forward Clutches are both engaged. That leaves the Direct Clutch pack as the only possibility. In first gear the Direct Clutch drum spins in the oposite direction of the forward clutch, and that clutch pack connects to the forward drum. If it were to apply then you'd have two drums going the wrong direction trying to engage and it would be trying to give you third gear, but that's impossible due to the rear band being applied, so the result would be a bind. It would feel like the brakes, as you describe. There is a checkball in the direct clutch drum that is intended to release fluid when the clutch is not applied. This should have been checked for operation.

If it does that in manual first then it's probably doing it to some extent in drive too but the amount of throttle you have to give it to stay in first over 3000 RPM exceeds the holding ability of that unapplied direct clutch, so you don't really feel it. There would be no binding in regular drive because the rear band is not applied. (That band is used only for manual first and for reverse.) If it really is doing this it will cause the clutch materials to expire more quickly than they should.

Just a theory...

Dark Halo

iTrader: (14)

that sound like it might be the problem I am going to the tranny shop today.

James B.

iTrader: (1)

Unfortunately, getting to the direct drum takes a tear down all the way to the center support.
Good luck.

Dark Halo

iTrader: (14)

UPDATE: I think it may just be a problem with the shift kit. I have brought the truck to the tranny shop and they hook it to a machine that alows you to take the control away from the computer and shift it your self. When it is held in first gear even with the lever in manual 1st it works fine. So it is looking like I have something wrong in the gear command pack