So I took my 2000 Expy in to get new brakes and rotors last week and the tech said the seals are going on the rear axle and they need to be replaced soon. I don't know what needs to be done as far as replacing the seals, but I'm guessing they'll be draining the rear diff and messing around with the axle... am I even close to being right?

Anyways, my question is that I'm wanting to get 4.56's installed this year. Would I be saving myself some money getting them installed at this time? Like do they have to remove the gears anyways when doing the seals?

I'm just a noob, but I'd like to save some money... plus I'm sure a lower gear ratio would help out greatly with my truck wanting to downshift on the slightest grade with the AC on.

 

yes do the gears while they have the fluid drained and cover off... Removing gears is not required to change axle seals, but your right there, might as well do em

 

4.56 will be cooking on the highway... as in your RPM will climb.. not necessailry decreasing MPG's, as it will make the load on the engine lessen...

 

I'm not too worried about losing mileage. I have 285/75R16's on currently (has 255/70R16 stock). It downshifts so much that I have to take it out of overdrive if I'm driving into the wind, or if I have the AC on and am going up hills when driving on the highway. I took a trip 2 weeks ago and cruised at 70 in 3rd gear for almost 45 mins because it was downshifting so much (and still managed to tie my best MPG fillup). I'd rather just put it in drive and forget about it!

The 1 MPG (maybe) hit I'd take wouldn't really bother me. I do lots of city driving and fill up every 1-2 weeks. I'm told 2200 rpm is the 'sweet spot' with the 5.4 and I believe I'd be darn near close if I drove 68, which I do anyways.

Plus, it would feel like I gained a bit of horsepower by going with a lower gear ratio. 4.10's would have put me close to stock, but I want to have more oomph.

 

having your same exact issue... I think I'm goin with a 4.56 though... I'm upgrading tire size after a lift..