diff mod.

[BastardS4]

good or bad for 1/4 mile?

I have a set of washers to put in but now im getting cold feet.

chime in please.

[jutny]

i would say good, because they would allow the car to put more power to the rear wheels that have more grip when launching, as opposed to spinning the fronts uselessly when the diff cant make up for the gross difference in traction.

[SoSlow]

i would say good, because they would allow the car to put more power to the rear wheels that have more grip when launching, as opposed to spinning the fronts uselessly when the diff cant make up for the gross difference in traction.

on street tires the car launches the best on stock setup...with the 4:1 setup, the rear tires just spin wildly..

on drag radials the car slingshots the hardest with the 4:1 setup

[jutny]

good to know, and good to show that theory doesnt always previal in real world situiations.

i wonder then why, when there is wild rear wheelspin, does the diff not bias more power forwards, as thats what its designed to do. Is it simply a function of the "higher bias capable" differential causing a lack of sensitvity to torque somehow?

[MacDaddy]

not really sure what the mod does exactly, but depending on how much wheel spinning you have, playing around with tires and PSI might be a better option if your getting cold feet.

besides, a little wheel spin is good, otherwise your engine bogs off the line.

[sCeRaXn]

I agree that getting better tires and playing with pressure would yield better results than using the 4:1. Personally, i think the stock diff bias is perfect for launching these nose heavy beasts. Because so much of the weight is forward of the front axles, the weight shift from the front of the car to the back wont be NEAR as drastic as on a rwd or other awd cars. Sending a little more power to the front wheels is actually a good thing in situations like these. Even if the fronts spin a little, the backs will still be pushing the car forward. This will keep the revs up while your spinning and still making forward progress. With a 4:1, if the rears starting spinning the fronts wouldnt be able to put down enough power to create the forward momentum needed for a good awd launch.

Get some sticky tires and start playing with tire pressure. The pressure depends on the tire, but a good rule of thumb is that the psi in the fronts should be slightly lower than the rears. Dont go super low on the pressure like you would on a fwd or rwd car, because you wont be able to do a burnout thats good enough to really heat the tires(thus creating more psi in the tire). Theres alot thats overlooked when setting up and AWD car for hard launches...and this is definitely one of them. Good luck man.

[BastardS4]

bump. any other input?