Roush and 3.31's or 3.55's?

[Dsquared]

Newbie and probably a repetitive FI question here... I'm having a Roush SC installed this weekend. I have MT with 3.73's and know those gears aren't the best to run with FI.. The guy doing the install of my Roush is willing to do a straight swap of his 3.55 differential (w/ 4k miles) for my 3.73 diff. (w 9k miles).. My tuner says I should go 3.31's.. Also, I will not be running it on a track. My questions are, should I do the free swap, or purchase 3.31's. Is there that much difference between the gearing? Also, is it easier to just buy a complete differential, or the just the gears and have a shop install them? I see the gear kits on LMR, but where do I find a complete 3.31 diff, and how much do they run?
Thanks!

Sponsored

 

[TooSoonJunior]

Personally for resale value I would keep your original pumpkin and source a new one with 3.31s. Otherwise when you go to sell your PP car with 3.31s you might get beat up for it.

 

[crs2879]

I have a PP car (3:73) with a Roush Phase 1 kit. I don't race the car, so "launching" is not something I care a lot about. The low rear gear has not been an issue for me. If anything, I find the 3rd and 4th gear pulls amazing.

Gears are like any mod, "beauty" is in the eye of the beholder. The day I went to pick up my car from the install shop, they had a '09 GT500 (modified to over 700WHP) on the lift replacing the factory 3:31 gears for 3:73.......my suggestion is drive it with the blower and 3:73 gear and see for yourself. If you like it, you save some $, if not, then swap it out....

 

[TooSoonJunior]

I have a PP car (3:73) with a Roush Phase 1 kit. I don't race the car, so "launching" is not something I care a lot about. The low rear gear has not been an issue for me. If anything, I find the 3rd and 4th gear pulls amazing.

Gears are like any mod, "beauty" is in the eye of the beholder. The day I went to pick up my car from the install shop, they had a '09 GT500 (modified to over 700WHP) on the lift replacing the factory 3:31 gears for 3:73.......my suggestion the blower and 3:73 gear and see for yourself.

GT500 has an entirely different trans with MUCH longer gears, 3.31 with that trans is like dragging an anchor, even 4.09's are good combo for that car.

 

[whatsup62]

GT500 has an entirely different trans with MUCH longer gears, 3.31 with that trans is like dragging an anchor, even 4.09's are good combo for that car.

Installing 4.09's as we speak. The 3.73's just weren't quite enough.

 

[Dsquared]

Thanks to all for the input. I'm going to just leave the 3.73's in for now.

 

[venumous]

If you're not tracking the car then leave them indefinitely. They have been no problem for me at 700whp, including pulling my buddy's 2010 ZR1 up to 150mph.

Sponsored