4L80 issues... any educated guesses? CKP FMVB
04-09-2013, 11:36 PM
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4L80 issues... any educated guesses? CKP FMVB I've been fighting this particular transmission for a few rounds now. I'll save the back story and get to the details as of today.
4L80 with CKPerformance full manual valvebody. Brand new build with good parts (don't ask me what exactly, it's been so long I can't remember but they're the same parts that have been holding up in my other transmission).
From Park down to 1st it will not move unless you give it about 3000rpms. It feels like your dragging the brakes. Once it lunges forward it 'frees up' and I can shift through the gears up and down just fine. Starting in 2nd gear is sort of the same way except a little less power input is needed for it to free up. 3rd and 4th are awesome and quick.
Or...I can go from Park down to 1st and wait for about 10-15 seconds and 1st gear will start to pull on its own at idle. So it seems like I can wait this amount of time and let itself free up or I can force it to pick up pressure by giving it throttle.
Also, if I let it free up and get rolling in 1st, shift to 2nd (still at idle or slightly above) and then down shift back into first it will lock itself up solid again until I either power through it or let it sit and free up.
Compression braking on 2nd and 1st doesn't seem right either. 4th and 3rd fall down with rpms. Down in 2nd and the car does start to slow down but it's definitely not because of the compression. It's like it starts to drag on something (like putting on the brakes) in the trans even though the rpm's are already fallen way bellow the current speed. Same with 1st gear as well except if you're not going fast enough it will knock your teeth out on the steering wheel when it catches.
Again, 3rd and 4th seem perfect.
I'm asking here because the trans builder says it's the valve body and the valve body manufacturer says it's the trans builder. Of course, of course...
Here's a video starting in 1st. You can here the rpms it takes to even get rolling. I didn't touch the brakes at all anytime during this. If I would have held out the throttle a few more seconds it would have 'freed up' and kept rolling though.
4L80 with CKPerformance full manual valvebody. Brand new build with good parts (don't ask me what exactly, it's been so long I can't remember but they're the same parts that have been holding up in my other transmission).
From Park down to 1st it will not move unless you give it about 3000rpms. It feels like your dragging the brakes. Once it lunges forward it 'frees up' and I can shift through the gears up and down just fine. Starting in 2nd gear is sort of the same way except a little less power input is needed for it to free up. 3rd and 4th are awesome and quick.
Or...I can go from Park down to 1st and wait for about 10-15 seconds and 1st gear will start to pull on its own at idle. So it seems like I can wait this amount of time and let itself free up or I can force it to pick up pressure by giving it throttle.
Also, if I let it free up and get rolling in 1st, shift to 2nd (still at idle or slightly above) and then down shift back into first it will lock itself up solid again until I either power through it or let it sit and free up.
Compression braking on 2nd and 1st doesn't seem right either. 4th and 3rd fall down with rpms. Down in 2nd and the car does start to slow down but it's definitely not because of the compression. It's like it starts to drag on something (like putting on the brakes) in the trans even though the rpm's are already fallen way bellow the current speed. Same with 1st gear as well except if you're not going fast enough it will knock your teeth out on the steering wheel when it catches.
Again, 3rd and 4th seem perfect.
I'm asking here because the trans builder says it's the valve body and the valve body manufacturer says it's the trans builder. Of course, of course...
Here's a video starting in 1st. You can here the rpms it takes to even get rolling. I didn't touch the brakes at all anytime during this. If I would have held out the throttle a few more seconds it would have 'freed up' and kept rolling though.
Last edited by wcialrlter; 04-09-2013 at 11:44 PM.
04-10-2013, 01:39 PM
#2
Sounds like a possible crossleak.
I would check the rear servo 1-2 accumulator seals. I'm assuming it doesn't have a 2-3 accumulator.
The crossleak could be in the valve body or in the build, there is no way to determine it on the internet. It would have to be torn down by a savvy trans tech.
Jake
I would check the rear servo 1-2 accumulator seals. I'm assuming it doesn't have a 2-3 accumulator.
The crossleak could be in the valve body or in the build, there is no way to determine it on the internet. It would have to be torn down by a savvy trans tech.
Jake
04-10-2013, 05:10 PM
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Sounds like a possible crossleak.
I would check the rear servo 1-2 accumulator seals. I'm assuming it doesn't have a 2-3 accumulator.
The crossleak could be in the valve body or in the build, there is no way to determine it on the internet. It would have to be torn down by a savvy trans tech.
Jake
I would check the rear servo 1-2 accumulator seals. I'm assuming it doesn't have a 2-3 accumulator.
The crossleak could be in the valve body or in the build, there is no way to determine it on the internet. It would have to be torn down by a savvy trans tech.
Jake
Played with it some more. When it's sitting locked up in first and shift to 2nd there's a brief moment in between gears where it takes off forward (kinda like it's supposed to feel) before it hits 2nd gear fully. When it hits 2nd fully it locks up tight again.
04-14-2013, 07:40 AM
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Whose converter do you have? I was having the exact same problem you were and had to have the pump "modded" for more pressure at idle or something like that.
Basically my lock up converter was trying to engage because there wasn't enough pressure...triple disc lockup for me
Basically my lock up converter was trying to engage because there wasn't enough pressure...triple disc lockup for me
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04-16-2013, 10:43 AM
#8
We have seen the multi disk drag at idle in a 4L80 and it is usually because of a cross leak in the pump. But that would feel like a standard and almost kill the engine when you drop it in gear. And it would happen in all gear ranges and probably worse in reverse. So I don't think it is a converter issue. But sadly not sure what direction to point you in, very strange problem.
Chris
Chris
04-26-2013, 05:16 PM
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So what's this circled port with the torx pattern in it do? Cause it was almost totally blocked by a piece of the gasket that was covering it. The gasket has torn from the pressure above it.
04-26-2013, 05:23 PM
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