Mcglynn

Hi I have a 2004 F150 FX4. I put a 6" RCX and 37" mud grapplers. Still running my stock 3.73ls. I have a high flow exhaust, CAI, edge Eco. I need to regear to get my power back but I can't decide what gear set to do. I will have to regear both front and back so I'm thinking 4.56 or 4.88 not sure. I go through pretty thick mud and don't really tow much just my atv and some wood for fires. What's the best way to go with gears and what's the general cost of rehearing. I go to UTI so labor is no issue. Any set ups that work best. And just some info for what I'm doing in next year or so 3.9l 4c cummins and Alison 1000.

boondock

If you're only running 37's a 4.10gear would be perfect. 4.56 is a little high especially if you'll be driving on the highway at all. I wouldn't go with a 4.88 unless your strictly using it in the mud

Mcglynn

I went to an offroad shop around me and the guy said minimum of 4.56 and that if I'm regearing why go up only one gear. I drive mostly around town and sometimes to concerts and I live an hour away from home for school so I visit when I can. I might go to 40s but not for a while.

KingRanch4Life

iTrader: (2)

I'd say 4:56.. I run 35's with 3.73 with no issues. 4:88 wouldn't be optimal as a daily driver...

boondock

If you're planning on going with 40s in the future then the 4.56 makes sense.
A solid formula I saw on here one time was: (tire size/stock tire size)x stock gear ratio. It will give you a rough idea of where you should be gearing wise

06F150CFCT

I have 4.88's and love them. I am running 37's on 8" of lift and get a combined hwy/city of 13.5 mpg. I use the truck daily and it works fine. You cant go wrong with either 4.56 or 4.88 though. I wouldnt even consider 4.10. Thats a waste of time to go from 3.73. You wont notice much of an improvement in power or fuel saving.

06F150CFCT

Oh and as far as the gearing goes specifically, if you are doing the labor you have cut 75% of the cost out of it. You should be looking at spending 500 bucks on gears (average) with the master install kits. Go to diffsonly.com and email Wayne. He will get you a killer deal on everything I hear. A bunch of guys on here went that way and have nothing bad to say. Yukon gears are most popular along with Motive and US. It all depends on how good the install is on whether they whine or not. If yoiu are doing it though, then you'll be fine as you cant blame anyone but yourself if you start to hear the whine. haha.

patclarke

I run BFG KM2's 37x12.5R17 on my 05 fx4 with 4.88 gears front and rear. The truck is mostly a DD but needs to be able to get up and go off road.

buster096

488's all the way man. General rule is 410 for 33's, 456 for 35's, 488 for 37's, and 513 for 40's

KingRanch4Life

iTrader: (2)

Just stick with 35's and 3.73's and call it good...