Hi I currently have stock 3.55 gears and 255/70/16 tires witch is a 30.1" tire

And im interested in puttting 315/75R16 witch is a 34.6 tire

I looked up some specs and it reccoomeds installing a 4.08 gears.

And was wondering if im correct?

Please reply back thanks

 

Sounds about right.. You'll have to go to 4.10 however... That's the closest you'll get.

Mitch

 

Ok I have a 97 4.2L F150 and probably put 4.10's gears now what would that drop my top speed to?

 

Well, since you are also getting taller tires, the net effect is that you'll still be able to do what you can now. You should be ~ the same rpms in any given gear/speed as you are now.

But, those tires will be heavier and to some extent, have more rolling resistence, so how all of that factors in, I don't know exactly??

You may want to go up to 4.56 gears? Now, that will cause you to pull slightly higher rpms in any given gear/speed and you'll want to calibrate the speedo if you go that route.

Really depends on what your goals are as to which gears to go with.. If you just want to bring everything back to like it is now with the 3.55's / 255 tires, go for the 4.10's with the 315 tires.

If you want a bit more low end grunt and don't mind running a few hundred higher rpms on the hwy, go for the 4.56's..

Mitch

 

No matter what you do, you should be able to pull the same top speed, which is electronically limited to about 96 mph - as long as you put the appropriate VSS gear in if you change the effective ratio. Putting the bigger tires on and changing to 4.10's does not change this, but 4.56's would.

 

Thanks for the info

 

i would suggest 4.56 gears since you have a V6.

are you 4x4? if not i would go to 4.30 gears.

 

Yes I have a 4x4. Why would that make a difference?

 

4.30 gears are not available for the front axle in a 4x4, only the rear axle. Your choices are 4.10 or 4.56.

 

Ok probaly get the 4.10's can i just swap out the ring and pinion? or do I need more stuff?

 

If you have never done a gear swap, and don't have some one to help who has, I would probably get it done professionally. Setting up gears is not difficult just fairly involved, and require attention to detail.

 

Note that parts and labor is going to be about $1600........

 

Yes Im goin to have my mechanic change out the gears My question was can i just order just the ring and pinon. Or do I need more stuff?

 

You will need gear lube and aan install kit for each axle as well. If you have LS and significant mileage, it would be a good time to rebuild the LS as well, figure another couple hundred for that. A couple of places to check on line are Randy's Ring and PInion, and East Coast Gear Supply. The guys at East Coast are great, and are the ones who installed my gears, but do a huge mail order business as well.

 

which install kit do i need?