04gtoBMXracer

iTrader: (26)

Now, I know I need a rebuild blah blah blah...

I would like to know what exactly is wrong with this trans.

2004 GTO 4l60e

Car will not move if manually shifted to 1 or 2 (If I am rolling and try to downshift, car will idle, when gas is pressed the motor will just rev). When it is placed in 3, it engages but kind of feels like it's slipping at high rpm. When the car is in D, the trans works perfectly!

I have searched and searched but cannot find an answer. I have spoke to a few "Transmission Experts" and cannot get the same answer out of them. They all have different theory's. Any input?

Do not have access to a scanner to read trans codes btw.

mrvedit

I think you posted your question on another thread already (which I have since deleted). I didn't reply to that one because it has me stumped too. I have probably answered a 1000+ questions here, but never than one. (Usually its the opposite - the OP can manually shift 1->2->3->OD, but nothing in OD - this indicates a failure of the forward sprag. Doesn't sound like your problem.)

To confirm, with the shifter in [D4]/[OD], the trans shifts properly through all gears?

Dumb question - then why not just leave it in [D4]?
Is the trans stock?

bbond105

Maybe the overrun clutches have gone out and the OP is not revving the engine high enough to make it stop coasting and accelerate? Just spit balling here. This is an odd one.

04gtoBMXracer

iTrader: (26)

I figured the same. I was thinking if I rev high enough it might build enough line pressure to engage but it would just hit the limiter.

I have a TH400 now so it's not a big deal, but I was just curious because I've never even heard of this problem happening to anyone before.


One of these days I'll open it up and check everything out.

bbond105

Would it take off from a standstill in manual 1st?

04gtoBMXracer

iTrader: (26)

No it will just idle. If I press the gas, it still doesn't move. Even at high rpm.

bbond105

That doesn’t make sense. In over drive the low roller clutch holds for 1st gear and in manual 1st/low the only difference is that the low/reverse clutches come on also. With it shifting through all of the gears when the shifter is in overdrive that tells us the low roller clutch is working. With the trans working in reverse that tells us the low/reverse clutches are good. Is the shifter actually pulling the manual valve into low?

04gtoBMXracer

iTrader: (26)

The linkage was fine. I actually took a video before I took the trans out. I will post it tonight when I get home.

bbond105

Do you have some way to see want the solenoids and Manifold Pressure Switch are doing when you are manually down shifting, like a scanner or HP Tuners or something? I suspect that maybe the Manifold Pressure Switch is not reading the correct gear command.