Hey Guys/Gals,

I have a b20 w/a GSR tranny (Daily Driver) and I was wondering what kind of gas mileage benefit and how much (roughly) my RPMS would drop at highway speeds. At 70mph I'm roughly at 3500 rpm w/the GSR tranny... Ive heard my gas mileage will improve if I use a longer gear etc etc...but how much???

I need to replace the clutch and fix a 3rd gear sychro on my car and figured I'd do this if it made sense. Would anyone be willing to give me any input or thoughts by chance? Is this worth while, I can get the LS final drive in the $100 range, would my gas mileage difference make up for the price tag?

Thanks, and sorry for the dumb question.

 

Unfortunately the LS FD will not fit your GSR diff.

 

Guess that answers that! HAAHH

I thought its possible for a longer 5th speed LS in a GSR tranny...I'm mixed up aren't I (is the 5th ls gear the same as a ls FD)? I've read and heard of people doing this, or so I thought.

 

5th gear and final drive are not the same thing. You can swap an LS 5th gear into a GS-R tranny. The final drive is the ring gear on the diff and the gear cast into the countershaft that it meshes with.

 

There we go, no I'm on the right track. HAHA

Would swapping the 5th gear be a good choice in gas savings and running with lower RPM at highway speeds? Would the cost outweigh the benefit in your opinion 94?..

thanks for getting me on the right path...

 

Honestly you're not going to save that much gas, the RPM drop isn't going to be that significant either, it's the LS final drive that makes a large part of the difference in the LS's lower 5th gear RPM. It will lower the noise level on the highway a bit though. If you're paying someone to pull the transmission and do nothing but swap 5th gear you'll be a long time waiting for a return on your investment. If you happen to have a good LS 5th and have some free time on your hands and feel comfortable doing the work yourself it might be worthwhile.

You're welcome

 

^^^Beautiful, can always count on my seniors for legit information. Looks like it'll be smarter to pass on this concept for the moment.

Thanks again, that is more or less the exact answer that I was looking for.