Can some one explain how you get a t56 tranny to fit in a 99 gmc 4.8 ????

[live_to_race]

well tonight really sucked i was about to go for a swim and bang my tranny started to make some crazy noise sounded like blowing thu a peice of grass my tranny started to act up no reverse it would go in to second then skip third and go to od ?????? ok i know i drive my truck really hard so now i need a tranny i really kinda wanted to to break it anyways because i want a 5 or 6 speed can any one tell me if a t56 will fit in my truck or what i could put in it to make it go like snot i have 99 gmc sierra 2wd base model iv done a lot to it 4.56 rearend alburn posi its flash tuned with 3rd stage afi air intake and some other bolt ons some one please help

[Frenchy]

It's been done multiple times, there is a great write-up on pt.net annd there is an even better one here. Use the search button

[Wtfan18]

so based on your post i assume its a 4.8 auto. it will work but ive heard removing all the auto parts sucks to convert it. if it were a 4.8 5speed to begin with itd be pretty simple. i know the t-56 will bolt to the LSX motors as long as its off an LS1 motor. i had nelson performance redo my wiring harness to work with the t-56. not sure if the stock tranny mount would work i made a custom crossmember. drive shaft would probably need to be changed. its a lot of work but the t-56 trannys are a lot of fun.

[zebra]

if i remember right, the late 2000 & newer auto crossmember will work. since you've already got the 4.56, that'll be a little less work.

you should also consider carefully what vehicle the t-56 came out of. certain models & certain years have different gearings, and i believe the GTO transmissions used a different starter

[BSridenguy]

This is the T56 swap i did on my truck Keep in mind it was already a manual 5 speed and is an 04. I'm sure alot will be different from your truck to mine, but alot of the basics should be the same.

http://www.ls1truck.com/forums/mecha...t-56-swap.html