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4l80e need alot of rpms to engage forward gear

fredbjr26

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hello all. I'm new to this forum page and am looking for help. I recently replaced the tc on my 4l80e. While I had the trans basically out I decided to take to completely out and put it on my work bench. I cleaned n check the valve body. I didn't take apart any of the solenoids I left them in. I took apart the reverse servo to clean and check if that was OK. Everything seemed to be fine. So I slapped it all back together with the new tc. I put it back in the truck. Filled it with fluid. Put it in drive, gave it gas. It don't move, put it in reverse with foot on break, engine lowers rpms, release foot off brake and i move no problem. Go back into drive rev it up. Right about 4000rpms it jumps into drive. I'm so lost on what is going on... everything worked great prior to tc swap. Now I can't drive in forward... any ideas? Also the truck is a 2000 gmc c3500hd with the 454 7.4l big block
 

Rockabillyrat

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Sounds like a forward clutch issue. Unplug the transmission connector and see if it moves. That should put it in limp mode (2nd gear). If it still wont move you have probably have a internal issue and the trans need to be removed and opened up.

Why did you replace the TC?
 

fredbjr26

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New TC from gas or diesel?
Gas tc.

I just tired to move the truck. I put it in drive and I got it to move... moved about 100 yards in drive than started slipping and not engage forward. I put it in reverse n I have no problem
 

fredbjr26

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Sounds like a forward clutch issue. Unplug the transmission connector and see if it moves. That should put it in limp mode (2nd gear). If it still wont move you have probably have a internal issue and the trans need to be removed and opened up.

Why did you replace the TC?
 

THEFERMANATOR

FRANKENBURBAN
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Are you certain you got all the check balls back into place properly? Sounds to me like one got left out.
 

fredbjr26

New Member
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hello all. I'm new to this forum page and am looking for help. I recently replaced the tc on my 4l80e. While I had the trans basically out I decided to take to completely out and put it on my work bench. I cleaned n check the valve body. I didn't take apart any of the solenoids I left them in. I took apart the reverse servo to clean and check if that was OK. Everything seemed to be fine. So I slapped it all back together with the new tc. I put it back in the truck. Filled it with fluid. Put it in drive, gave it gas. It don't move, put it in reverse with foot on break, engine lowers rpms, release foot off brake and i move no problem. Go back into drive rev it up. Right about 4000rpms it jumps into drive. I'm so lost on what is going on... everything worked great prior to tc swap. Now I can't drive in forward... any ideas? Also the truck is a 2000 gmc c3500hd with the 454 7.4l big block
Another question i have that i forgot to mention. I also pulled the reverse servo out to measure the piston on it. Could that be pushed back in to far causing the trany yk not release reverse and slipping drive due to pressure?
Are you certain you got all the check balls back into place properly? Sounds to me like one got left out.
I'll be sure to check that out first thing tomorrow.
 
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