I have a 2006 Ford F250 (5.4 gas engine with a 3.73 rear gear, 5 speed auto) I'm attempting to approve my towing capacity on 8500 lb TT. As I see it I have the option to replace the rear end with a 4.10 differential gear or, as I've been told by a mechanic, replace the 285/70/17 AT tires with the stock 245/70/17 tires. The mechanic said the small tire would have the same effect as a larger differential gear - better towing capacity and less strain on the TV. If this works, I'd have to invest in a set of tires not an expensive gear change.
Has anyone tried this?
And I know I should trade the TV in for a diesel but that's not an option now.
* This post was
edited 07/21/08 02:25pm by texcamper *
John - Driver
Pauline - Boss
2008 Cougar 302RLS
2006 F250 SD 5.4 V8 towing package
Yes, tire size will effect gearing. How much depends on the difference in the circumference/diameter of the tires. I imagine it would take a lot smaller tire to make up the difference between 3.73 and 4.10 gears, but you would gain some.
I did some checking and your diameter difference would be almost 13% (depending on make of tire) which is a pretty good number for towing.
I would take your mechanics advise on this one! Sure beats spending a whole bunch of bucks on new gears if you can get enough of a ratio change and it sounds like you would.
Barney
2004 Sunnybrook 30FKS TT
Hensley "Arrow" 1400# hitch
2002 Ford F250 Super Duty, 7.3L PSD
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I would save all the mod money toward the proper truck.
2003 Jayco 308fbs eagle 33' tt, towed by a 2003 Ram 3500 slt, quad cab dually, cummins diesel ho, trailer towing package, with 6 speed manual. Hauls better 1/2, 3 kids, myself, and a 2003 ez go clays car.. I have added so far, neon lights, clearance lights, back up lights, black light, lift kit, mud tires, and everything necessary to make the golf cart street legal. It's now ready to spend the winter in the garage for more mods. More neon, strobe lights, alarm, a pa system, maintance, and whatever else that comes along. This golf cart does wheelies and travels thru 7 inches of mud when need be. Two honda eu2000i gens twinned to supply the electrical power. Latest addition an 04 Honda Goldwing. [url]http://www.hometown.aol.com/rvnagain/myhomepage/profile.html[url]
These figures are not for O.D. but for 1-1. So changing tire only would have you within 71 rpm at 60 mph as using your present tires and doing the gear change. Kind of a no brainer to me. Besides you've got that truck overtired for the motor and gear you have. I'll bet the mileage will inprove also.
The Cougar 302RLS is a 9,700 lbs GVWR trailer. Your truck, with stock tires, has about a tow rating from 9,300 - 10,100 lbs. I'd say put the stock tires on and you will be okay up to the GVWR of the trailer.
Changing the size of the tires will make your truck work less when towing or hauling weight, but it will not change your gear ratio. Gear ration is the amount of times your drive shaft turns for ever one revolution of your axle. That won't change with smaller tires, but the amount of distance your truck will travel in one revolution of your axle will change with smaller tires - so it basically has the same effect. Smaller tires will result in less fuel mileage.
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