Do i change a differential or buy a new truck?

We have a 2002 Ford F-250 Super Duty 4-door CrewCab w/6.8L gas engine, auto transmission w/4WD used mainly to tow our 24ft. travel trailer. We have discovered that this truck came with a 3.73 ratio slip rear axle instead of the 4.30 version also offered for 2002. Although we ordered the “low ratio” (4.30) for better trailer towing, we have the 3.73 rear end. We currently are limited to a towing maximum of 10,300 lbs. A 4.30 rear end would let us move up to a maximum towing of 12,500 and 13,300 for a 5th-wheel trailer.

Is it a reasonable cost and okay for long-term maintainance concerns to have the rear end changed out, or would it be better to just get a different truck?? Thanks…

You could have the ring and pinion gear changed out, but this is a somewhat technical and moderately pricy job; maybe a grand, depending.

If you ordered this truck new and it was supposed to have the 4:30 then I would be plenty hot. If you have paperwork backing this up then I would go back to the dealer you bought it from and tell them the gear change is on their dime, not yours. If they balk, a small claims judge will probably disagree with them.

It’s possible a truck like you wanted with the 4:30 was not available at the time and they simply grabbed what they could get in the interest of making the quick sale. They figured you would never discover the difference or they overlooked the ratio business.

Also, you’re going to have to find out if the rear differential is replaced, will the front differential also require replacing if you change the rear gear ratio?


Do you care about fuel mileage? Because your mileage is going to drop off SO much with 4.30s.

Also, you know, just because the factory rates the lower ratio rear for higher towing capacity, that doesn’t mean that you can’t tow a larger trailer with it. See if you can test drive a loaner trailer and pull it around a little. 3.73 isn’t exactly a stump puller, but that big V10 might be have enough torque to muscle you along okay.

About a 15% difference. But I would keep the 3.73 too, unless the trailer is over 10,300#.

But first I would contact the dealer, as OK4450 suggested. Did you buy the truck new, or was it bought used? It’s 5 years old, and you might have some 'splainin to do.

The dealer isn’t going to make any changes at this point.

Keep in mind your total GCVW allowed.

Have you put these vehicles on the weigh scales (Individually) when loaded to ensure a safe load?

I’m sure your truck can handle what you tow, but changing out the 3.73 for a bit more torque may be a waste of time and money.

That said, you may well be better off trading that truck in on one with the rear diff (AND front diff) identical. Then you can pick the one you want.

How did you find out you had the wrong rear ratio?

Changing these out after the fact is expensive as you DO need to have front the same as the rear.

I have a 3.73 in my '02 Tahoe 4x4 and after a lot of looking and reading and talking to others that had the same truck, I decided to just leave well enough alone.

I’m quite pleased with the performance and mileage I get (towing) with this 5.3L 285hp.

Going from a 3.73 to a 4.30 (both axles) would be VERY expensive and in the real world, you would hardly know the difference…

Save your money for a Diesel Duelly, an F-350, because that’s what you REALLY want and need…

Well, in answer to you questions:

If you can simply replace the ring/pinon setup, then it can be done for less than $2k by an experienced mechanic (don’t try to do this on your own unless you are experienced in setting up and ring/pinon already). If you need to replace the axles, it is more expensive, but should be less than $5k. Neither one will have any adverse impact on maintenance. The decision to replace the vehicle should be based on the overall condition and suitability of the vehicle for your use. Remember that a new deisel F250 will probably set you back a good $42k. You do the math.

Thanks Tester…I believe the low ratio issue got overlooked at the time by the dealer and I should have been more attentive to what they were doing.

Thanks Mr. Josh…I didn’t even think about the mpg when we are not towing the trailer!

Thanks Roadrunner…My wife and I were discussing moving up to a different and larger travel trailer. I wanted to verify the towing capacities of our truck with Ford factory and “Trailer Life” Magazine - Annual Towing Guide recommendations. One thing led to another and I ended up looking at the original factory window sticker listing all of the standard and optional features of the truck. I could not believe what I saw…“3.73 limited slip axle”. Ever since we bought the truck in 2001, I thought we had the 4.30 axle…!!!

Thanks Caddyman…Just what I need to do, convince her we need a “new” truck…!!

Thank you Silvergc1…great info while we decide IF we want or need the larger and heavier travel trailer and more towing capacity than our current setup.