re-gearing for taller tires

[Gray Ghost]

ok well in a few months i should have a 6" procomp lift with 37" tires... i have a 3" body lift on right now to fit the 37"s...once i have tires that big i know you have to re-gear it... what gears do i put in it and how much will they run? i see alot of people talk about 4.88 gears? but i have no clue what that means? will someone please school me on all this?!?!

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[jiggle]

A 4.88 gear ratio means that the driveshaft will turn 4.88 times for every 1 time the axleshafts rotate. Your stock gear ratio is probably either 3.55 or 3.73. A (numerically) higher gear ratio will make it easier for your engine and tranny to turn the big tires, but will cause your engine to run at slightly higher RPMs.

Think of a car with a manual transmission. 1st gear (the lowest gear ratio other than reverse) gets you moving very quickly and produces lots of torque, but can only be used up to maybe 12 mph for any extended amount of time.

A 4.88 gear ratio would give your truck that extra torque it needs to turn all that rubber.

It will run you anywhere from $1000-$1700 to have the truck regeared, depending on which brand and shop you go with.

[Gray Ghost]

HOLY S!!!!!!!!!!!!!!!!! 1000-1700!!! wow... i was thinking like freakin $500 at the most!!! what would happen if i put 37's on with out re-gearing it... would it get like HORRIBLE gas milage or something?

[Gray Ghost]

is this like what i would need?!?!?!? or am i way off?!?!

http://www.4wheelparts.com/PDT24542.aspx

[jiggle]

Here's exactly what you would need to buy:

Rear gearset: $170-$250
Rear master install kit: $80

Front gearset:$180-$270
Front master install kit: $90-$100

Gear oil & friction modifier: $40

Labor:$250-$500/axle


This is assuming your truck is 4wd.


Note: you should also buy rear axle seals and axle bearings because they are not included in the master install kit. The installation of these things should be included in the price to rebuild the axle.

[jiggle]

Originally Posted by Gray Ghost

what would happen if i put 37's on with out re-gearing it... would it get like HORRIBLE gas milage or something?

Your truck would be pissed. You would have pretty much NO acceleration and your mpg in the city would go to crap. Your engine and transmission would become very stressed and fail prematurely.

That's not to say that it couldn't be done, but if you plan on keeping your truck for a while then you should definitely regear.

I have a 4.6L and just putting on 33s killed what little power my truck had. I regeared to 4.56s and the difference is amazing. It's not that the truck is that much more powerful, but the engine and tranny seem so much less stressed. The next step is 35s to even out those highway rpms.

[Lumadar]

Even my 22s made my truck a dog, and they were only 6%~ taller, but noticably wider. Going to a 4.1 gear ratio helped significantly. For you, I would go with 4.88 if you're going to do it.

[sonic69]

On a 2004 F150 are you guys running 4.88's with 35's also?

[f150monster232]

i have 37 with 22 with 3.55 its not the dog it used to be but its dose ok. just a lot of money to drop

[Gray Ghost]

would i have to do the front transmition (4x4) the same time as i do the rear... becaseu my truck doent go in 4x4 much at all... i mean i go months forgetting a have 4x4... i dont do deep mudding... i just like dry off roading

[jiggle]

When I regeared I didn't have the money to do it all at once, so I bought the parts for the rear and had that done first. Then I saved up a little money and shopped around for parts for the front. I ended up finding a great deal on ebay for the front parts and saved a ton of money. When I had the money, I took it to the shop and had them do the front. In all, I think I went about a month wihtout being able to use my 4wd. If you're strapped for cash and don't NEED your 4wd that's probably the way to go.