Performance difference b/w 4.56s and 4.10s???

[HotRod929]

I have 4.56 gears in my truck and was wondering if I would notice and off line performance drops if I go to 4.10s and a posi? It would also bring my highway rpms down some. Thanks

HotRod

[Old Chevy Lover]

What RPM are you turning on the highway with 4.56's? Last thing I had on the street with a decent motor and gear was a 64' Chevy II.. Had a 327, t350 tranny, 4.11 gear, and running 235/60/14's (which equates to about a 25" tall tire).. turned about 2950 rpm's at 55...

[HotRod929]

Old Chevy Lover: about 3500rpm @ 65mph with 30.6" tall tire.

Anyone know if I will notice any difference with the 4.10 gears and a locker?


HotRod

[Old Chevy Lover]

Here is a website that shows the difference calculations for Rpm, Speed, Tire Height, etc.. you can calculate the difference.
http://www.mrt-wheels.com/formula.html

according to the RPM calc, it would drop you about 300 RPM at the same MPH..

[HotRod929]

Im actually more worried about off the line performance. Will it drop a lot with 4.10s?

HotRod

[Old Chevy Lover]

I think it kind of depends on what type of a motor that you have put together. If its basically stock, then you will not have that intial 'jump' off of the line like you do now. But then again, if your running an open rearend now, and have any wheel spin off of the line, then going with the 4.10 and a posi will launch you better/faster than you are now. I think the biggest thing you will notice is that it will take a little longer to wind out the motor when your going through the gears. It doesn't neccessarily mean its that much slower, just the motor having to labor a little harder.
In my 72 Nova drag car, I went from a 4.56 to a 5.38 gear (have 33" tall slicks) and really didn't notice a big difference like I thought I would out of the hole. Biggest thing was getting down the track (1/8th mile), the motor wound out a lot quicker, and I picked up a little bit of time because it wasn't having to work as hard to move the car.

[sakohntr]

The posi is irrelevant to this question. You will notice a difference in acceleration. I would much rather have a car (or truck) that went to 100mph in a short period of time than a car that will top out at 140. No engine can make up for a lack of steep gearing.. good luck

[bigjimzlll]

its all about your usable rpm range..if your motor stops making power at 4500 rpm, the higher gears(4.10s) will actually help performance..allowing the motor to be in its usable rpm range for a longer time..the lower your max torque is the higher gear you will need..the higher up in the rpm range your max torque(HP) is the lower gear you will need ..of course this has to take into account the track your running on..1/8 or 1/4 mile.. right now your probably running out of usable power at the 800 foot mark in the 1/4(depending on your engine)..either build the engine to rev and make power up to 7000 rpm, or stick some higher gears in.
Jim