bonez

Well, I got my rear diff swapped out to 4.56's this morning. It made a huge difference turning my 35's. I will say, it's slightly over-geared now, but that will allow me to throw some larger tires on it next time I'll be getting the front done as soon as the ring and pinion becomes available.

I was a little bit surprised to learn that I have an open diff on the rear end though. All the research that I have done says that the axle code B6 is supposed to be the 3.73's with limited slip, and when we got it opened up, it's not limited slip. Anyone else run into this surprise?

Bossgame

Mine is an 07 XL 4.6 4x4 and when I serviced rear diff it was correct LS

LUVmyDUX

I never opened up mine, but I have the same axle code and know for sure I have the factory LS. I leave two tire marks when I break it loose on sand and mud.

You think 4.56 is over geared? What are you running on the hwy, speed and rpm?

bonez

I only had it up to around 65 on my way home from the shop, but I was around 2100 at that speed. It would be nice to be just under 2000 at 70, but I'll have a beater to drive soon enough so I'm not too worried about it. Then I won't need this as my daily driver and can sit back and enjoy my new found power.

uzikaduzi

i think your speedo is off... 4.56's with a final trans ratio of 0.7:1 with 35" tires at 65 should be 1992 rpms and at 70 it should be 2145

http://www.crawlpedia.com/rpm_gear_calculator.htm

bonez

I had my GPS on and at most, the speedo was 1 mph to low. That's probably due to tread wear on my tires since they are nearing the end of their life.

uzikaduzi

ahh that makes sense... I have those tires in a smaller size and i'd imagine you can loose more than an inch in diameter before they are shot. looks like if you go with 35's again, you'll be closer to where you want to be (although looks like you'd need 38's if you want to be sub 2k at 70)