I already have 33in tires and I blew out my rear end so with my re-build Im upgrading to 4.56 gears from the stock 3.55. What Im wondering is how far off is my speedo going to be from my stock gearing with 29in tires to this set up? PS what is the break in period on the new gears?

 

With 33's and 3.55's, indicated 60 mph is 68 mph.

With 33's and 4.56's, indicated 60 mph is 53 mph.

4.10's would put you back to within 1 mph of stock.

You need a programmer.

Breakin is 500 miles, then change the fluid.

 

I would go with 4.10's if I were you. 4.56's is a bit too extreme for 33" tires, unless you plan on going to 35's anytime soon.

 

I have 33 and my speedo is not off but maybe by a mph, I only went up from 275/65/18 to 275/70/18 and my speedo is same as what gps says. How do you get it will be off by 8 mph I have stock gears 3.55

 

Thanks for the info glc. I do want to upgrade to 35s in the futur but will be stuck with my 33s for a while. I originaly wanted to do the gears and the tires at the same time but my diff exploded on me so needed to change it and thought might as well do the gears now. From what Ive read I think I should be ok with the set up for now, deffinitly going to be a big diffrence lol and c1t1d1 your size change is so little that it wouldnt have an effect but with me going up 4in from stock tires, 265\60\17 to 285\75\17, I deffinitly am off with my speedo. My tires are supose to be 34s but I measure 33s. Currently (judging from gps) it shows 40 at 45, 60 at 70, and around 90-95 at 115, dirt roads are my runways lmao

 

Read the original post - assume that STOCK was 29's.