Transmission swap

fossel · March 26, 2012

04 Silverado 2500HD 4X4 6.0 litre LT. 240,000 km

I have picked up a GM factory remanufactured transmission and I'm wondering if it will work in my truck? Here is the problem my 4L80E is four wheel drive the remanufactured one is two wheel. I know the output shafts are differant and the lube hole to the tail stock needs to be plugged and this involves disassembling the entire transmission. My question is, are the electronic or valve body in the transmission differant?

Both are 2004 4L80E

Truck tranny info, CASE NUMBER- p/n24208421, YELLOW TAG- BSP 04-4012

Reman tranny info, CASE NUMBER- p/n24208421, YELLOW TAG - MJP 04-4156

I got it for cheap and want to know if it is worth getting changed over, my torque convertor needs changing (TC won't stay locked when towing fifth wheel) and I don't know if the TCC valve sleeve in the valvebody is damaged. The tranny works fine otherwise but it has 240,000km on it so I'm going to change it at the same time. Also who makes a resonably priced Upgraded Torque Convertor for towing applications? What would be the best stall speed,

? (9000lbs trailer)

Any help is appriciated

Doug_Scott · March 26, 2012

Just to toss something out here, My 2000 GTP would unlock the converter if I touched the brakes. My 2010 Sierra does not do this. I don't know when GM changed this, or even if the trucks used to behave the same way, but, if your truck is supposed to unlock when you touch the brakes, you may want to make sure your brake light switch is adjusted correctly.

As for how to make it fit, if it was me, I would just take the guts from the new trans, and put them into the old trans case, reusing the output shaft from the old trans. But, I used to overhaul transmissions in a prior life.

fossel · March 26, 2012

My truck only has TC problems when I'm towing. I know there were issues with the TCC valve wearing the aluminum valvebody. I have also worked this TC and tranny pretty hard. As for the shaft they are about $80, so I figure it's worth trying to keep the original tranny in tact as a spare (why I don't know). However if the valvebody and electronics don't match I'll swap the guts. Do u know a website that decodes the ID tag. I'm very mechanically inclined, I have an idea what is involved in tearing down the 4L80E, never attempted though. With out special tools should I make an attempt?

gmtech4 · March 26, 2012

Just to toss something out here, My 2000 GTP would unlock the converter if I touched the brakes. My 2010 Sierra does not do this. I don't know when GM changed this, or even if the trucks used to behave the same way, but, if your truck is supposed to unlock when you touch the brakes, you may want to make sure your brake light switch is adjusted correctly.

As for how to make it fit, if it was me, I would just take the guts from the new trans, and put them into the old trans case, reusing the output shaft from the old trans. But, I used to overhaul transmissions in a prior life.

+1 doug,me too ,he however will not and cannot do it ,he has to pay someone alot of money to do it and if it blows up ,he is out all that money !!!!

i wish him luck and wonder if the TC was diagnosed or just someone guessed at the valve body ,either way ,i predict no fun for him and his wallet

op,every tranny is set up inside for THAT carrcus,,that means the shims for one tranny ,WILL NOT work for the other ,but good luck to ya anyways

dont do it