Wow you right... guess I never read the repeated complaints above about the lack of overdrive.

I guess that 4L80E option is only for people who don't "have a tranny already". (Top-fuel only? )

For the record, I run 4.11's in my T56 (0.50:1, double-overdrive) so I personally can't help you out. However, a buddy of mine has been runing 12's and 11's several seasons on high high-stall 4L60E, and currently pulling high 10's... most of it has been 3.73's and it's a daily driver.

Without OD, you'd probably want to stick to 3.42's if highway cruising is your concern... (and if cruising really matters to you, you MAY want to find a tranny with OD, it's all really personal preference I guess)

 

GMC: 28.9" wheels
LT1: 25.9" wheels
-----------------------
1.12:1

1.12 * 2.73 = 3.05:1 rear gear for F-body tires.

If you want the same highway rpm's in the LT1 as the truck, you need to go lower or keep the 3.42's and accept a 12% jump in rpm's over your current truck set up. With 3.42's (more agressive launch) and less weight you may be right where you want it though... it's essientally a 12% gearing gain (a normal amount in a performance upgrade).

 

Buy my th350 setup. 4200 stall Coan with reverse manual valve body.

 

Thanks for the very informative posts steve, I guess I'm a tad jumpy because all I hear is I'm an idiot for not getting an A4, (as much as using 18" wheels) well I might be, but this idiot has a TH350 and wants to try it out. If in the future I find the need to grab a white coat, my uncle's bone yard can spit out something more to my liking.

And in the other thread I was just razzin ya. But anyway, yes I would be more than happy to accept a 12% jump in RPM's, as the truck does launch nicely aside from the bog and the puny 305 but it's definately close to what I want, and if I have to sacrifice a few more revs to get my larger wheels and a nice launch, well then so be it.

Oh and Dreamer.. nice try, but wanna buy my Powerglide?

 

^ also since my motor is only a mild performance SBC motor with lt1 induction and ECU, does the 3.42/stall still seem like the best option?

 

Thanks but I already have a 6 speed to install first. If I dont like that then a PG would be next. It is the only tranny I havent tried yet