Rear Gear Question
 

When it comes to rear gearing, I am not the brightest candle on the cake so, I need some help understanding the application of rear gear ratios and what the performance results of different ratios.

For example we are running a 4:56 gear and several people that I have talked to have said we are a bit over geared for our application. The people I have spoken to have said that we should be running a 4:30 gear.
My question is if we go to a 4:30 ratio gear as recommended, what performance gains should I expect? Quicker ET? Faster MPH? Both?
Also, if I changed to a 4:30 gear, does your shift RPM change? How about my 60 foot times?

Re: Rear Gear Question
 

What kind of car and class?

Re: Rear Gear Question
 

K/SA 71 Chevelle Wagon 402 big block. 4260 lbs w/driver

Re: Rear Gear Question
 

I would say, if the converter is right..That is, it flashes right around peak torque, then you might see the same 60' but more mph, then maybe gain a little ET down track.
As many here know ..there's only one way to find out for sure.

Re: Rear Gear Question
 

Powerglide or a 3 spd ? I run approx the same setup 65 Impala wagon 396-325, 400 trans 4.56 gear. If your running a powerglide I suspect you would be better off with more gear 5.57 perhaps ---Trevor

Re: Rear Gear Question
 

I run the same 402/315 but in a Camaro, it all depends on the cam, lobe sep.etc. I run a 4.56 with a tight cam,2.75 low, 4800 flash.I think you would lose 60' and ET with a heavy car like yours by changing the SLR.You can get away with a little more rpm on that motor because of more exhaust lift (.430). If you run the big hoosiers 94" as opposed to the 92.5" it will give you around 200 rpm. gsa612

Re: Rear Gear Question
 

I am surprised your only running a 4:56 and not a 4:88 . Even though it's a different combo, I have a 71 Lemans wagon I run in J/SA. To get it moving I have a 2.75 low gear and a 4:56 . Trap rpm is about 6500, I would think your 402 would turn at least that high. What rpm do you run through the lights ?

Re: Rear Gear Question
 

On mine at 3635 (G weight) in good air with the 94' tires I go through at 6700 with .56's.I can get away with .88's at altitude. You would have to check your dyno sheets and see where the motor falls off (cam type). At that weight you might be able to use 4.88's, if you have ceramic lifters make sure you have plenty of spring press, if not they might rattle at the top end with the extra rpm.

Re: Rear Gear Question
 

I agree with a 4,260 pound car.

Re: Rear Gear Question
 

I hadn't read your description yet when posting earlier.
I agree with most..4.30 is not gonna work.