boosted hybrid

I want this to be the end all of which final drive ratio is the best for STREET application. I rarely, if ever run my car at the track. I do 95% of my driving on the street, so no slicks. Now here is my set-up:

Fully built b16a head (2mm ferra valves, dual valve springs, retainers, gsr cams, jg intake manifold, 70mm billet tb)
84.5mm GSR block
Custom turbo kit, 60-1/t3 .63a/r exhaust

Now i have a bunch of b-series trannies. 2 b16a's, 2 gsr's and a stock ls and custom ls tranny.

I ran the b16a tranny on my b16a block before the rod bearings let loose, and the acceleration was great, felt really good for turbo. Currently i am using a LS tranny, mated to a gsr bottom end with a b16a head. The LS gearing seems decent, but 3rd and 4th seem too long. My car does not have the same pull as the b16a tranny. That is something that i can distinctively feel about the powerband. I realize that the LS has a 4.26:1 final drive with longer 3rd, 4th and 5th gear ratios, compared with the b16a trannies.

I am using a 15" wheel with a 50 series tire. I am not sure as to what final drive i should go with a b16a tranny. The tranny will be getting a Quaife lsd, so when i have the differential out i dont mind changing the final drive. I am opting for either the 4.78:1 final drive, or the 4.929:1 ATS final drive. Top speed doesnt matter at all, my car feels sketchy over 140mph anyway. I should be able to run mid 10's with my set-up, approx 125-130mph traps. Will the 4.78:1 final drive, or even the 4.929:1 final drive in the b16a tranny hinder my overall trap speeds when i do vist the track?

earl

Do you have trouble spinning the tires in 1st gear? You will with a 4.7 or 4.9 final drive ratio. I'd go with the 4.4

EleanoR

I agree completely. Keep the stock FD. If you must change go to the JDM 4.785 and not the 4.929 because you will spin like crazy with that high of a FD.

boosted hybrid

I dont get any wheel spin at all in 1st gear. I have solid motor mounts, z10 traction bars and 700lb spring rates on the front springs, along with falken azenis tires. I make maybe 4psi in 1st gear, so its straight acceleration. I think i am going to try the jdm final drive, the ats was super extreme, but wanted to see what kind of reaction I got suggesting it.

deeeffache

newbie warning

what is final drive?? i wanna learn..

00WhiteEKy

do you have playstation 2? if you do, go rent grand turismo 3. Buy a car andgo buy the racing tranny, then before a race, go to settings and play with the tranny. try raising and lowing the final drive, you will see how the gears change. You will see that when you raise the FD, the gears cross each other more, that means that when you shift into a new gear, you will be at higher rpms. So the higher the FD, the higher rpm's you will be in. so highway driving will suck. and shifts will be faster. But the main thing is that you will stay in your powerband more. But alot of people have there different thoughts on what tranny they like the most. if you don't have suspention work done, and you have a high FD tranny, you will spin a lot, and if you have turbo, you will like a lower FD. I hope this helps you, but for real, go play with that game, you will learn a lot about how a car works on the track.


[Modified by 92hatchy, 9:57 PM 3/3/2003]

boosted hybrid

Choosing a FD goes as follows: Trap speed estimate, slick size, redline and then choose FD to carry you through the 1/4 mile line at the top of 4th gear.

J2turbo21

Use this and it will tell you where you should be at in 4th gear.

http://autocrossing.com/cgi-bin/gearcalc.cgi

In a 94+ gsr tranny with 22" tires and a 4.9fd.The max speed in 4th gear would be like 107mph.