Let's rip the bandaid off; the Avalanche ain't a real truck yadda yadda. Having gotten that outta the way, I'm looking to breathe new life into my tired *** truck.

Initially, I was going to do an interior update; focusing on modernizing the infotainment system, which then became my wanting to eliminate my column shifter in favor of a console shifter to accommodate a sizable floating screen head unit.

I bought a used 2015 Camaro AT gear shifter, and in doing my research on how to make it work with the 5.3L ECM and 6L80 TCM I found out that the shifter won't work.

Then I looked into swapping the 6L80 for the 8L90 which brought me here, so I figured this would be a good place to get some advice on what people have done to update their GMT-900 powertrains.

Some engine/transmission combos I'm considering are 6.xL/8L90, TT3.6/8L90 for performance and fuel efficiency improvements, with newer 5.3L/8L90 as a last resort because I don't feel that they offer enough additional HP to justify the money spent.

So, what powertrain conversions have you fine folks done on your GMT-900s?

 

Fortunately we cater to all full size vehicles. Hell even Trailblazers

Okay I would NEVER EVER EVER swap a 6 speed for an 8 speed. The 10 speeds look really nice but I probably would keep the 6 speed for a while longer yet. **** the 8 speeds. They are garbage transmissions. I do not know if you could get a TT3.6 to work however I honestly don't see why not. I would recommend just throwing in a 6.0 or a 6.2 if you really want a new engine or going ahead and supercharging or turbocharging what you have.

 

Where you're probably hurting is the 3.23 or 3.42 axle that thing has. That will take some of the pressure off the trans when trying to move that 5500lb beast. I loved my avalanche but no 6.0/6.2 option and the Escalade EXT only came with a 5.3 in 2WD form. Agree with the above, though. Asking for trouble on the 8 speed and you can make a robust 6 speed with what you would spend trying to make the 10 speed work. Also, yes, a drop in 6.0 or 6.2 would get the truck back on the road sooner and reliable.

 

I agree about the 6l80, they can be built to last now. The 8 speed detonates at factory power levels. If you want a bad *** trans factory buy the ford 10 speed.

 

Aren't the 8 speeds still processing class action suit? As others said, I would keep the 6L over the 8 or 10 speeds. Swap 5.3 for 6.0 or 6.2, maybe swap the 6L80 for 6L90 from a 3/4 ton truck if you can get a good pullout for more power potential.

 

There's a company in Houston that does 10-speed conversions for your truck. Someone just got it done over at the TahoeYukon forum and loves it.

Replace your 5.3 with an L9H 6.2 and you'll be smiling all day long.

Is this a RWD Avy or a 4x4? 3.08 gears or 3.42s?

 

Long story short:
You want a 6.2L. You'll get so much more bang for your buck upgrading the axle gears to 3.73 or 4.10.
If you tow / haul HEAVY, or otherwise work / play with your truck HARD, seriously consider upgrading the entire rear axle as well.

Long story medium:
It's not nearly as simple as you'd like to imagine / hope to swap in an 8L90.
Cherry on top is that the 8L90 is not worth that electrical / programming effort anyway, nevermind the time and expense.
By the time 'they' figure out how to rebuild 8L90s properly to withstand real power, the 10L80 / 10L90 may have made the 8L90 almost completely irrelevant.

 

I’d just do a 6.0, they make the same power as a 6.2 and can handle more power overall vs the 6.2. If I was to do it all over again I’d build my old 5.3 with forged internals and strap a huge supercharger on top with a built 6l80 with a circle d converter.

 

I was checking that website and they list anything GMT900+ as a 10 speed candidate. I believe it has to do with the 58X reluctor wheel Gen IV requirement for those transmissions, right?

OP's truck is a Gen IV, I think 🤔

https://www.powertrainswapsolutions....07-2014-gm-suv