Transmission Swap 6L80 to 6L90

[300 Blackout]

I have a 2014 L83 with a 6L80 4x4. Instead of rebuilding the trans, I’m considering moving up to a 6L90 if it’s possible. Does anyone have info about this or know of anyone who has done it? 

[pokismoki]

yes, its easy if your pre-2017 truck different tcus on these.  if you want the 6L90 get  one from a Camaro. 

but the better upgrade for all the laybor would be a 4L75e, easier to rebuld these, and less mass in the 4 speed. 

 

while everyone whos making big powa reccomends the heavy ass 8 speed, it shifts faster but draws more power because its just so f'n heavy

 

if your not making power just upgrade the stock 6L80 with updates and 6L90 parts, this would be less r&d work IMO

GM is running out of oil pumps for the 6L80/90 trannies, order a pump first to see if its available before attempting rebuild

Edited April 8, 2022 by pokismoki

[pokismoki]

just noticed your a 4x4, you have a different tail section on your trans, so you will have issues swapping to other transmissions. just rebuilt what you got

[300 Blackout]

Thanks for the advice pokismoki. I have no interest in the 8 speed. I like the 6L80/90. Never thought of the 4L75 and I’m not sure what that would involve to make sure I keep 4x4. I’m not really looking for the fastest truck, just a dead nuts reliable workhorse. Really great info about the oil pump, thanks for sharing. 
 

I’m running around 550 ft-lbs torque right now with plans to go higher. Spoke with Circle D Trans and TK Performance and a 6L80 rebuild is gonna be anywhere from $2500 - $4500. Then another grand for a converter.

 

I was thinking of just swapping my current tcm/valve assembly directly into the 6L90 to avoid any programming trouble. Update the tune for the 90 and fabricate the frame crossmember mounts. Trans output shaft would need to be custom ground for the transfer case along with a custom tail housing adapter. Last piece needed would be a slightly longer front driveshaft. I think that covers it but haven’t met anyone who completed it. 
 

Now that I wrote all that out, I’m in agreement with you that rebuilding the 6L80 seems like the better option. Similar cost with a known result. Now to find an oil pump…

Edited April 8, 2022 by 300 Blackout

[pokismoki]

after you acquire the pump, be sure you install the new regulator valve, as the old design causes premature wear in the bore, and causes line pressure loss to the clutches, this area could possibly be where all the metal particles are coming from on low milage trans

 

after its built get it tuned with hptuners, turn off the tcc for 1-4th gear

Edited April 8, 2022 by pokismoki

[ZachW98]

Do any of you know if there's a major difference between the 6l90 in the diesel trucks vs the other 6l90s? My 6l80 is trash and Reman Transmission has an already remanufactured one for like 2500 bucks with free shipping which is less than what I could have it rebuilt for but they also have remanned 6l90s for only like 150$ more, https://reman-transmission.com/transmission-codes/?code=6L90. The only thing is I think they only have them for the trucks they came in