6L80/6L90 swap

[RDF1]

Sure they are rated for more torque on paper. But their cost to build is substantial
and is very possible the reason for their failure in higher HP applications is their complexity and nobody really knows how to make them work right.
Where a 4l80 is a simple animal where you just need 240psi apply pressure on a good waffle clutch pack and it will hold a bunch of power. And the simple stacking of solenoid for shifting vs Clutch on clutch is very very different.

 

[0xDEADBEEF]

The thing I hate most about the 6L is the first gear. It just doesn't go out of the hole unless you boot it, despite what you may think because of the gearing.

Never had one that was tuned though.

 

[bluex]

The 5 spd in my dually needs rebuilt. I've been considering a 6L instead. A bit more cost up front but maybe a better outcome in the long run. I could leave the rear gear alone maybe rather than changing it along with the NV4500 rebuild. I had a few 6Ls in factory applications now an once you realize they act way differently from the 4Ls an figure out their "normal" I didn't think they were too bad....

 

[L31MaxExpress]

The thing I hate most about the 6L is the first gear. It just doesn't go out of the hole unless you boot it, despite what you may think because of the gearing.

Never had one that was tuned though.

The heavier trucks and vans seem to roll out ok without stack shifting (technical name for shifting too early at part throttle) as you describe. Myself at 7,000 lbs empty means I am going to be booting it more just to get rolling from a stop. I am not a fan of the way GM tuned the 4 speeds either, especially the bahavior at low speeds when you are already out of first. It takes 3/4+ throttle to get back into 1st if you are over 7-10 mph. Making a turn from a stop they will slide into 2nd and stay in 2nd unless you hammer on it, same for coming out of an under highway U-turn.

 

[0xDEADBEEF]

The heavier trucks and vans seem to roll out ok without stack shifting (technical name for shifting too early at part throttle) as you describe. Myself at 7,000 lbs empty means I am going to be booting it more just to get rolling from a stop. I am not a fan of the way GM tuned the 4 speeds either, especially the bahavior at low speeds when you are already out of first. It takes 3/4+ throttle to get back into 1st if you are over 7-10 mph. Making a turn from a stop they will slide into 2nd and stay in 2nd unless you hammer on it, same for coming out of an under highway U-turn.,

This is in my wife's Yukon, so not light.

I don't think it's the shifting. The rpm just isn't being translated into wheel speed, so it feels very pokey. If you want to move out, you've got to really put some RPM change into it. I can see why everyone puts the pedal boosters on them.

Once you are going it's a fine transmission.

 

[letitsnow]

I'm hoping you guys get the bugs worked out of this swap before my 4l80e needs to be rebuilt, as I'd like to do the swap too.

 

[L31MaxExpress]

This is in my wife's Yukon, so not light.

I don't think it's the shifting. The rpm just isn't being translated into wheel speed, so it feels very pokey. If you want to move out, you've got to really put some RPM change into it. I can see why everyone puts the pedal boosters on them.

Once you are going it's a fine transmission.

I am sure I could make that alot better with throttle/shift mapping as well. Once you are rolling even 5-10 mph there is no need to be in 1st gear at very light throttle. Even my 85E is in 2nd by about 12 mph at light throttle. Sounds like a shift point vs throttle mapping issue to me.

 

[someotherguy]

Sure they are rated for more torque on paper. But their cost to build is substantial
and is very possible the reason for their failure in higher HP applications is their complexity and nobody really knows how to make them work right.
Where a 4l80 is a simple animal where you just need 240psi apply pressure on a good waffle clutch pack and it will hold a bunch of power. And the simple stacking of solenoid for shifting vs Clutch on clutch is very very different.

Can't underestimate just how much money is involved when talking about 6L rebuilds. $3500 and up. I recently read on another forum about someone paying $7K at a dealer.

Richard

 

[L31MaxExpress]

Can't underestimate just how much money is involved when talking about 6L rebuilds. $3500 and up. I recently read on another forum about someone paying $7K at a dealer.

Richard

I can order a 6L90E reman at work for a shade over 3K including the nearly 1K core.

 

[someotherguy]

I can order a 6L90E reman at work for a shade over 3K including the nearly 1K core.

So, not far off from the price I mentioned, and not including R&R. Jobber price?

Richard