G3 TRANSGO JR 5TH GEAR SLIP

[Joelknauber]

Okay, so I've put together a few Allisons including my own which is holding 1000hp in competition for the last year really well.

I assembled a 5spd last week. I used G3 clutches, ratiotek pump spring (without the shim), and a transgo jr + the new shift valve springs.

I going back into it tomorrow because the guy said it slipped in 5th gear. The truck has a small set of injectors and a drop in turbo. Most likely 650hp or so.

On my truck i have G3s and the full trans go, never had an issue even though I know that's not the way most people are doing it now with 5spds.

This one has 7 G3s and no mods to the C2 piston. Does it need more line pressure from the shim in the pump? Or why would 7 G3s not hold that power? I'm hoping to find a cut seal on that piston to be honest.

Thanks,

 

[Chevy1925]

what are the codes?

 

[Joelknauber]

I'm not sure actually. He said it didn't actually limp but said he felt it slip and let off right away. I trusted him and said to take it back out and I'll go through it. Doesn't exactly sound right I know.

 

[Mike L.]

6 clutches will hold just fine.

 

[Joelknauber]

Thanks MIke, I appreciate it.
I guess I have a few seals to check out, and I'll probably add the shim on the pump regulator spring while I have it again.

Can you add a small vent hole to the balance piston (like with the full transgo kinda) with stock springs/inlet holes on the C2 piston? To help reduce pressure in the opposite direction? Or is that a bad idea..

 

[Mike L.]

Don't mess with that. The ballance piston is there to help stop the factory tie up on the 3/4 shift. That's why the full Transgo is no longer used by the top shops. I proved this back in '06 on Nasty Girl ( first 1000 hp Duramax.)

 

[Joelknauber]

Okay cool.
What about the spring alone vs adding the shim? Ratiotek says 800hp. I'm assuming thats accurate.
Is there any reason the spring alone wouldn't have been enough line pressure? Or am I basically just looking for a failed part somewhere to cause a 5th gear slip.

 

[Mike L.]

First of all, you don't know if you really have a slip since there is no CEL. Could be something else. As far as the spring goes; spring by itself will give you 280/290psi ( stock is 230.) That should hold up to 800hp. If the power is at around 600 and you have an aggresive driver, add a shim which will put you at 310/315psi.