Im not much of a mechanic but im very interested. Im wondering what the deal is with gears. My truck has 3.73 gears according to my window sticker. However I hear members talking about 4.56 and 4.88 gears and from what im reading most people don't like the 3.73. Whats the difference??? What do the numbers mean. I realize its a ratio but not sure how to tell what is what??
I know my truck with the 3.73 gears is geared much lower than I need. At least in the lower gears. I never use 1st. If I pull off my street in 1st I can't even get across the yellow line and I need to shift. In fact this is the first truck I have owned that I can take off from a dead stop, uphill in 3rd. I wouldn't want it any lower. What do the different gear ratios mean for power, mpg, etc...

thanks!!

 

You ever had a 10 speed bike or anything like that? A 10 speed has 5 gears up front and 2 in the back to give you 10 choices. Think of the 5 up front like the transmission and the 2 in the rear as the diff. The lower gear in the back makes pedling a lot easier but for the same amount of turns your not going as far. So for towing some heavy trailers you want the higher # gears, this gives you more torque to the wheels. However the engine will run at a higher RPM at a given speed so your gas mpg may decrease. Some argue that if your really towing a lot of weight the mpg actually wont decrease since its easier on the motor. I dont tow so cant comment there but any vehicle I have been in gets better mpg with lower # gears at least on the hwy. Oh, and the truck can potentially be quicker accelerating with the higher # gears... if you look at drag racers they all use the higher numbers.

First gear in these trucks is basically a 'granny gear' to get really heavy loads moving, or maybe pulling trees out of the ground lol. For normal driving you wouldnt use it. Heck they dont even call it 1st anymore do they? I thought it was called L and then 2nd gear was actually 1st. Think it was a 6 speed I was in last for a super duty.

 

3.73 = The driveshaft will turn 3.73 times for every revolution of the wheel....or more appropriately, the ring gear in the diff.

Good explanation by Tristan there.

 

Thanks for the great explanation guys... Im gettin a good understanding now...

 

I always like the added confusion of the number theory...the higer the number, means the lower the rear end ratio. And of course the lower the number, the higher the rear end ratio equation.

Bottom line is:

Higher the number IE 4:10, 4:30= more TQ tow grunt, lower MPG, higher RPMs at speed, great seat of the pants power.

Lower the number IE 3:55, 3:73= lesser tow grunt, higher MPG (but not by much on the V-10), lower RPMs at speed, smooth power off the line but less TQ to the cheeks.

Either way the V-10 powerplant under the hood delivers good results.

High means Low....Low means High. And if Pro means the opposite of Con....does that mean the opposite of Progress is......... Congress?

 

What I do is say 'high numerically' & 'low numerically'. Yes it's clumsy but not confusing.

For the OP, here is a calculator you can use to display the effects of gearing & tire size changes:
gear ratio calculator

 

Excellent info. Also, as you gear your truck lower (higher numerically), you gain in your ability to tow more weight without taxing your transmission as much. For instance, a 4.30 gear will tend to pull a heavy load or trailer more easily than the 3.73. Also, regarding your 1st gear question, the first gear in these manuals is pretty much intended as an extra low gear to get really heavy loads moving or for pulling stumps across a field (just for example). It really isn't intended to be used as a normal part of the shift pattern or your "starting off" gear. Most people start out in what is technically 2nd gear.

 

LMAO Oh so true!

 

you'll really notice a difference in what gear ratio does if u ever turn larger then stock tires..

with the V10 and stock 3:73's ur truck really becomes a dog when u step up to 35"s..

i had a 99 2WD V10 F250 that was like a racecar at the streetlites..

but my current truck is a outrite slouch off the line.. and esp during the 1-2shift..i really need to open the pumpkins and swap in 4:88's...

 

Thanks for the excellent info. I can say I have a decent understanding now.

so it stands to reason that the intention for putting in larger gears (smaller numerics) would be to improve mpg. It may not have worked too good but I cant see any other good reason to put in larger gears... Ford must have thought the larger gears would improve mpg enough to be worth putting in..... I would like to put larger tires on my truck this summer, I guess I will see if it makes it too doggy... Wouldn't you have to swap front gears also if you change rears in a 4x4??

 

Absolutely or you will have a catastrophic event you'll not like too well the first time you shift into 4WD. The front / rear should always match in a 4WD. I have seen some that have, for example, 4.10 in the front and 4.11 in the rear. I wouldn't vary too far though. When you put the transfer case in 4WD, the front and rear are locked with a 50/50 power distribution front to rear so theoretically, you want the two ends moving at the same speed. Otherwise, you'll have the rear trying to leap frog the front or the front pulling the rear.

 

ok what do you guys think.... i have a 2001 F250 V10... stock gears, but just put in 37 Toyos.... when i pull, it seems like i am going very slow and too high rpms.... feels like it's too forced. I see half-tons pulling toy haulers, and im just pulling a small trailer with quads.... what do you guys recommend? any help would be greatly appreciated

 

4:88's for sure...

regearing will raise ur RPM's at a given speed, but ur truck will drive/tow better for it..

and as a side benefit u wont be working the truck as hard.. esp the tranny.

 

I went with 4.56's with the stock 35" rubber. IMO I should have gone to 4.88

Now I need new rubber but unfortunately I'm going to have to stick with 35's because going larger will put me back under my powerband range...

 

what gears would you recommend? also, if i went bigger than 4:88s, would there be a problem? i'm looking at getting a toy hauler/fifth wheel and don't want to run into the same problem later... so what do you think... 4:88 or bigger???? and like i mentioned, what brand or anything for that matter would you recommend?