I have a 2002 F-250 regular cab, auto, 5.4 and 3.73 gears. It has a four inch lift and i want to run 35x14.50 inch tires on a 16.5 inch rim. I've been told that with the high gears I will wreck the tranny. I can't afford 4.56's right now. Is this true and is there anything else in danger of faliure with the 3.73 besides being a little doggie.

 

I don't necessarily know that you are going to wreck the tranny, but yeah it does put extra stress on it and yeah you will notice a significant loss of power. I went from 3.55 to 4.56 with 33's and it is a world of difference.

You might want to go with a 16" rim instead of the 16.5's because the bead is not as secure on 16.5's when the tires are aired down low, plus there are more sizes to choose from with 16's these days.

 

i have 33's on it now and its ok but I figured with the bigger rubber it would suck. I know its harder to find tires for a 16.5 but thats what i have and i really like the way they look. how difficult is it to change the gears yourself. my dad has all the tools i'll need and a couple of dial indicators too.

 

I know what ya mean about goin with what you have, I have 16.5's on mine too. If your dad knows how set up gears and has the tools, then you're in business! Otherwise, I would take it to a shop that specializes in axle work. You dont want to ruin a brand new expensive gear set...

 

Here's a good program that tells you what your new ratio is with the tire size increase.

http://www.intercotire.com/html/tire-change.htm

If your stock tires were 30 or so inches and your moving up to 35's with an auto trans, your definately going to feel your truck bog. You'll NEED a tranny cooler installed on that for sure.

I wouldn't attempt the gear change yourself. It requires a certain bit of finesse and is not an exact science. If not done right you can damage alot more than just your pinion and ring gear.

If your stock tire was 30" and your going to just to 35"'s with a stock ratio of 3.73, if you drop 4.56 in it, it would be almost like returning your gear ratio back to 3.73 with the 30" stock tires. Should work out pretty close.

Try fooling around with that program above and see. You really will need the gear change.

My stock gears are 3.55. I currently am running 33" inch tires with 4.10 gears. This configuration is still good for me because it's like i'm running 3.73 gears on stock tires. When I go up to 35" tires (soon), that will modify my rear gears to the equivelent of running 3.51 gears on stock tires. Very close to stock and I should be in the green.

the gear sets are cheap and the install only ran me about 300 bucks. Under 500 for everything.

While they're in there you might as well get a locker installed. They wont charge you for the labor on that since they have to remove your carrier anyway to change the gears.

Tom

 

Thanks for the help. could you guys point me in the direction of a company that make good quality gear sets.

 

Hey busa01 I was reading this thread and it sparked an intrest to me. I have 3.55's now (stock) and running 285/75/16 tires w/ it, which is close to a 33". My stock tire was 255/70/16 (30") and I tow a TT. I don't have a problem pulling it, but there is always that (man if I had just a little more) saying. I'm like BennyR would this set-up that I currently have screw up my tranny?? I also thought about going to 3.73's, to make up the difference or is it worth it? I don't plan on going any bigger in tire size, the 33's are good enough for me. Any sugestions or comments welcomed.

 

Karenj, with 33's and pulling a trailer, I would do 4.10's. 4.10 is a good combo with 33's and since you most likely have overdrive, your mileage on the freeway unloaded should still be good. You could go lower than 4.10, say 4.30 if that is available, which would make your effective ratio ~4.10, but your mileage will go down some at fast speeds.

Benny, good gear brand names are: Dana Spicer, Richmond, Precision Gear, Motive, Superior, Ford Racing. Check out www.ring-pinion.com or www.precisiongear.com for more info.

 

SoCal
I called Randy's Ring and Pinion today. $713 for Yukon brand 4.56 front and rear gear sets with master overhaul kit. $877 for everything, precision gear from Reider Racing. What do you think?

 

Thanx SoCal thats some good info. Yes I do have OD. Will new gears through the spedo off//

 

Benny, I'm not familiar with Yukon gears, but I do know the Precisions are good stuff. I don't remember how much my gears plus install parts were, I just remember the gear sets themselves were $275 and $285 for Dana Spicer front and Precision rear. That was from a local axle shop who did the work. The Reider Racing price seems a little high to me but I don't know if that involves a carrier change too so it could be right.

Karenj, if your truck has the speed sensor (for the ABS system, trans, and speedo) in the rear axle that reads off the tone ring on the ring gear, like my truck has, then no, it won't affect your speedometer. I didn't have to recalibrate mine after the gear change.

 

Karen,

First you need a tranny cooler on that Automatic for towing. 3.55's with 33's and towing = 4.10 gears, big time. That's exactly my current set up right now.

Your 285's are 32.8" in diameter.

With your current set up, your actual gear ratio is 3.25 which is lower than the stock set up for sure.

You very well could burn up your rpm torque converter.

Installing 4.10 gears will bring your actual ratio up to 3.75, which is perfect for towing and pulling the rotational weight of those bigger heavier tires.

Also, if you ever decide to go up to 35's, your new gear ratio would be 3.51, which is very close to the stock ratio and would be acceptable. However going to 4.56's would be better for towing with the 35" tire.

I recommend definetely going up to 4.10 because at least that would restore you to a more towing defined ratio, be easier on your tranny and give you a bit more punch down low.

Tom

 

And yes, your speedo and odo is off right now, which may affect shift points with your auto trans. Your actually driving faster than your speedo reads. According to your current set up, when your driving 70mph, your real speed is 76.5 mph. So watch for cops.

Tom

 

Thanx everyone for the post

 

So Karen, what do you think your going to do??

Tom