6L80/6L90 swap

[RDF1]

Anybody gave these 6L transmissions a try in the older trucks?







I've ordered the Holley 6L80/90 Controller. Kinda curious as to what back to back to back comparisons would be with a 4l60/4l80/6l80 setup and same engine/rear gear.

 

[Alteca]

I’ve never driven a gmt400 with a 6l but I have driven other vehicles with one. The 6l will be faster off the line compared to a 4l with the same rear end ratio. The highway cruising rpm will be lower. The 6l will be better for towing. The 6l gives u the option of full manual shifts with a tap shifter or paddles. It has quicker/smoother shifts. It sounds great on paper and personally I’ve never had any problems with one but I’ve heard the trans has numerous issues. Couldn’t tell u off the top of my head what they are.

 

[Erik the Awful]

Use the search button. A friend of mine made a thread on 6L80 swapping his Centurion. It was almost a bolt-in and runs great, but requires an $800 controller.

 

[L31MaxExpress]

Use the search button. A friend of mine made a thread on 6L80 swapping his Centurion. It was almost a bolt-in and runs great, but requires an $800 controller.

I am bypassing that $800 controller by converting to GenIV engine management, building a 4x cam sensor reluctor for my L31 distributor. I am working on the harness now. I am going to get it running with a T42 controller and standalone transmission harness for my 4L85E now and when I have the engine running well with the E67 GenIV controller, I will be able to swap the 6L90E with relative ease.

GM claimed about 20% better acceleration and fuel mileage using a 6L80E vs 4L60E behind the 5.3L. GM also used a 3.08 rear gear vs 3.42 or 3.73s with the 6L80E. I am foing to keep my 3.73 gear in my Van where GM used a 3.42 gear in the 6L90E vans.

 

[618 Syndicate]

It's worth the swap if you take advantage of the deep 1st gear and your budget can handle the controller or tuning needed to run the 6 speeds.
I have a 6L90 behind an LMM in a square. Pulls great.
Brother in law has a 6L80 behind a 5.3 in a square, he's swapping from 3.08's to 3.42 for a little more pep off the line.

 

[L31MaxExpress]

It's worth the swap if you take advantage of the deep 1st gear and your budget can handle the controller or tuning needed to run the 6 speeds.
I have a 6L90 behind an LMM in a square. Pulls great.
Brother in law has a 6L80 behind a 5.3 in a square, he's swapping from 3.08's to 3.42 for a little more pep off the line.

I am definitely looking forward to that 4.03 1st gear. My 383 jumps with the 2,800 rpm converter, 2.48 1st/3.73 rear/30.5" tall tire now as it is but the 4.03 1st will be wicked getting my vans ~7,000 lbs off the line.

 

[HotWheelsBurban]

So these 6 speeds are all the good things about a 4L80E with two extra gears? Sounds like it might actually be worth the money....

 

[RDF1]

Id never say the 6L is better than the 4L80 with 2 extra gears. the 6L are all Clutch on Clutch shifting so its crazy sensitive on shift timing.

I did a search for 6L80 and it only come up with questions.

My plan is to build a 402ci and start with the 4l60 since i have a converter and driveshaft to fit the truck. Then id have to order a converter for the 4l80 to run with the 402 and already have a driveshaft for it.

my transmission guy has a fresh 6l80 that the customer has paid for in 9 months so he told me to come get it to do my testing with.
The holley controller is only $500 so got it on the way.
Its going to take awhile to get the rotating assembly for the 402 and the heads but i think it will be interesting to see what kinda differences there are at the track.

 

[df2x4]

Id never say the 6L is better than the 4L80 with 2 extra gears. the 6L are all Clutch on Clutch shifting so its crazy sensitive on shift timing.

I have heard this in other places as well. I'm no expert but my understanding is that the 6L80Es are more finicky, and as a result can be less robust than the 4L80E especially in a swap application. The extra gears would be nice, but I think it's pretty hard to beat a 4L80E in terms of simplicity/reliability.

 

[L31MaxExpress]

I have heard this in other places as well. I'm no expert but my understanding is that the 6L80Es are more finicky, and as a result can be less robust than the 4L80E especially in a swap application. The extra gears would be nice, but I think it's pretty hard to beat a 4L80E in terms of simplicity/reliability.

On paper a 6L90E is stronger than a 4L85E. It is rated for more torque, higher GVW and higher shift rpm. Real world it is going to depend on how each is tuned and integrated into the powertrain.