What are the stock gears in my 95 bird lx 4.6 auto. i am debating on what gears to change to ,this is a 1/4 mile car with 28in tall rear tires and thought i would go with 4.30 rear gears or is that to steep? I do drive it to the tracks and around town. 1 1/2hr to the track.
What type of modifications have you done? I think 4.30 is too steep for a near stock 4.6 SOHC with the stock torque converter or even the Mark VIII/Marauder/GT TC.
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k/n ram air, 2 1/2 true duals, dr gas xpipe/ flowmaster 40. good tune up, street tires. it went 15.11 @ 91mph not sure if thats good for these or not. Working right now on removing weight then new DOT and skinnys.
Assuming a 5500 rpm limit, with a 28" tire, your "ideal" gear ratio would be right around 5.00:1 for a 91 MPH trap speed.
Also, with a 28" tire, running 5500 rpm through the traps...
4.10's will put you at 112 MPH
4.30's will put you at 106 MPH
4.56's will put you at 100 MPH
4.88's will put you at 94 MPH
All of that being said, it really depends on what you're willing to give up on the highway in terms of "cruiseability" (yes, I'm calling that a word) and whether you want room to grow (planning more mods down the line).
4.30's will feel pretty steep, but they'll make a significant impact on your E.T. With 28" rear tires, they would be a good choice for a mostly 1/4 mile car with your current mods, IMHO.
95 V8s can have either 3.08s or 3.27s. The driveshaft won't be affected at all by the gear ratio. If you were swapping from a 7.5" to an 8.8" the driveshaft might be too long but not if you're just swapping gears.