I am in the process of putting a 4l80e in my truck and I wanted to get some opinions on what str ratio to go with. The '80 has a crappy 1st gear compared to the '60 and since I really dont' want to change rearend ratios I was thinking I might be able to make some of the low end deficit by going with more str. I talked to Midwest and they said I have a choice of 2.0, 2.5. or 2.7 The converter I have been using in the 4l60 had a 2.5 so I am thinking 2.7, what do you guys think?

 

I think I would opt for changing the rear gear and staying with a 2.5 personally. If you go with a 2.7 you are going to need some serious additional trans cooling.

 

what gears do you have in the truck now ?
what Size tires are you going to run ?
i actually just bought a convertor for my 4l80e today went with a mutli disk convertor from Vigialante went with a 2800 stall
should work real nice with the turbo when it arrives
it's a 9.5" convertor i beleave
Not sure on the str though
I wanted something a littlke more stock feeling than the last yank 3000k i had
Any issues making the 4l80 fit in your truck i'll be doing the swap in a few weeks
maybe we can compare notes on it

 

i dont think there will be much if any change in fluid temps, can you explain your reasoning here?

i have a py3400 with a 2.7str, i dont even have a tranny cooler yet and so far it has never gone over 200deg for the tranny fluid temps. i have a cooler but am waiting to put it on till i get a few other things sorted out(intercooler )

i like a high STR, lots of kick out of the hole. they say you will loose a litte eficiency up top but that is when you can lock up the converter if you want.

 

I got a 3500rpm Midwest coming with a 2.7str. Supposed to be here next week. GMC-I haven't actually began working on it yet-will pull the old trans this weekend and get started. I am planning on putting it on the motor with a couple bolts and then assessing the crossmember situation and the driveshaft maybe Saturday. Then when the converter comes in the fabbing will be done and it will just be a simple bolt it up kind of thing.

I have 3.73's and I just bought some 30x13.50-15 tires for this season, may be too tall now. I ran 28x13.50-15 last year. My 60fts last year were around 1.70 but it was spinning so I know it had a little left-I decided to try the taller tire but that was before I knew I was going to have a 2.48 1st gear! Just have to see how it does, I guess.