6 Speed Automatic Options?

[Yukon 400]

I was looking into some options of 6 speed automatic transmissions for a 3/4 ton suburban. I was looking at the TCI 6 speed 4L80e, 6L80/90e or an Allison 1000. Out of the options it seems that the TCI tranny is the easiest to work with for transplants coming in a complete package, which comes at a high cost. The Allison or GM ones would involve more work in getting the electronics to work.


Does any one have any experience with using one of these transmissions in trucks of this era along with an non-computerized engine?

[Maxxd07]

I would put big money on the allison being one of the most spendy and toughest ones to make work for you unless it came with either the factory duramax or 8.1 in front of it with all the factory wiring. All though they all will be spendy and/or tough to make work the 6l80/90 would probably be the better bet. What kind of engine are you running?

[Yukon 400]

There was a 454 in it, I would like to put in a 5.9 cummins in place of the big block.

Dose anyone know how would a 6l80/90 hold up to a mild diesel motor around 300hp?

[Maxxd07]

Im sure it would hold a diesel motor if it was built right, or maybe even stock if 300hp is all you want.

[Nova70]

Appears that you're unsure of your engine choice right now. I would figure out what motor you're using before picking a trans.... But that's me.

[Yukon 400]

I'm fairly sure of what motor's going in, either the one in my garage or one from my Dodge. I'm just trying to get some opinions and experiences from people.





Th goal would be have a reliable vehicle which could travel to most places while being able to carry a sufficient load inside for camping or towing my boat to alpine lakes, all while getting decent fuel consumption. There's already two vehicles for power, this one is going to be more for utilitarian use.

[Yukon 400]

Is there anyone that any experience with a 6 speed these trucks?

[Longhorn Man]

its not a common upgrade. You may be treading uncharted waters.
Since you are looking at a cummins swap, I would broaden the search onto ram/cummins forums too.

[Yukon 400]

Thanks Longhorn Man, I've looked over there in the past and only found that people have been mostly successful with an 4 speed 4L80e using either 92-95 6.5 diesel tcm, Compushift Unit, or PCS Transmission controller, and that's the most common Chevy tranny behind a Cummins. There are a few people with an Allison either reprogramed factory TCM or a Destroked TCM unit, and for some reason lot of people are saying this is the ultimate combo, like a majestic unicorn.

Well this is what I ended up with for now, I just hope all the wiring can be worked out at a reasonable cost.

[05crewcab]

If you just want diesel and 6-speed, I would sell that cummins combo in your garage and put the $$ + into a complete D-max/Allison combo.

The D-Max is more powerful, fuel-efficient, and quieter than a cummins, and the Allison is good to about 500hp and 700ft-lbs stock so you can run a programmer in the future and not worry about shift kits.

The 6-speed Allison became available in 2006, so you should be able to find a combo out there without too much difficulty. Keep in mind you'll also need the shift lever for the tap shift and tow/haul buttons.


Just my two cents, and I agree with the other guys... whatever way you go you'll have some big $$ into converting to diesel and 6-speed.

Good luck with your project!

[63chevyll]

i dont want to sound like captin obvious, but........ok nevermind

there are a few people who have put a duramax and trans in burbans if you really want to keep it a 3 seater towing machine

[Maxxd07]

Originally Posted by 05crewcab

If you just want diesel and 6-speed, I would sell that cummins combo in your garage and put the $$ + into a complete D-max/Allison combo.

The D-Max is more powerful, fuel-efficient, and quieter than a cummins, and the Allison is good to about 500hp and 700ft-lbs stock so you can run a programmer in the future and not worry about shift kits.

The 6-speed Allison became available in 2006, so you should be able to find a combo out there without too much difficulty. Keep in mind you'll also need the shift lever for the tap shift and tow/haul buttons.


Just my two cents, and I agree with the other guys... whatever way you go you'll have some big $$ into converting to diesel and 6-speed.

Good luck with your project!

I wouldnt try it nor would many other people that wouldnt want to spend over 3 grand on a tranny.

[63chevyll]

i would just run a 4l80 if i had about 2k to spend on it

[Yukon 400]

I ended up getting an Allison Yesterday, we'll see how it goes, if all else fails i still have the Turbo 400 that originally came behind my Cummins.

After going through all the Allison schematics in a Chevy truck they seem to be fairly straight forward and simple. I just need to find someone who is capable of reflashing the tcm for a TPS input instead of CAN Bus, tried to see what EFI Live could do and didn't get very far with that.

It seems in order to get that NP261 working might be more of a challange than the tranny.

[63chevyll]

good luck, sounds like a headache now, but when you get if figured out it should be cool