Nate

I know this seems like a stupid idea but due to the horrible gas prices and the amount of highway driving I do in my civic Ive been seriously considering swapping out my S4C from my 2000 si for an LS tranny. I know Im going to get better gas mileage and its going to slow down acceleration but I would like to know a little more about this trade off. If anybody here has an LS tranny in their car, how fast are you going at your given redline in each gear. I know I currently do something like 35 in 1st, 58 in 2nd, 88 in 3rd, 116 in 4th, and Im guessing 155ish in 5th all with roughly an 8krpm redline. Basically Im trying to figure out just how laggy an LS tranny is going to feel, how badly it would effect a 1/4 time and how much better mpg I would get, especially on 200 mile highway drives which I make all the time from school to home. I know theres a way to swap out 5th gears but to be honest, changing gears inside a tranny just kinda scares me. Id much rather just swap the whole thing out and maybe make a little money in the transaction. The car is boosted running 10 psi and my turbo gets full spool around 4k-4.5k (depending on gear) currently, how much would this change? I dont do a whole lot of racing or anything but I do enjoy the short geared tranny when driving around town but If I could get 5-6 mpg better on the highway it would be tough not to make the switch and the fact that Im revving nearly 4500rpm at 80mph which is just crazy. Please discuss.

Smith-02

ls 5th/fd and be done

Nate

Dont they have to be out of a 90-91 which are supposedly next to impossible to find anymore? My biggest concern is how high will I be revving at 80 with an LS tranny in 5th and how much will it actually help mpg?

pissnuts

when i had a cable gsr tranny at 83 mph i hit vtec which was at 5100 now with the ls cable tranny im turning about 3300-3500 at 80 miles an hour.... mpg ftw

Nate

That seems insanely high for a gsr, much higher than me with the b16 tranny. You must have some low pro little tires. 3500rpm at 83 would be about perfect though. Do you guys think my turbo would fall completely out of its power band with an LS tranny? Revving to 8k seems like I would still be alright.

Nate

So is it possible to put a GSR 4th and LS 5th in my b16 SC4 tranny? This seems like the best combo of gearing possible but I dont know if its even possible to do?