A friend was wondering if he could get by with 373 gears towing a13'000 5th wheel trailer 40 to 50% of the time over 430 gear,outside of gas milage any other reasons

 

I'm no expert on towing but, I think there would be an awful lot of gear hunting with that much weight everytime you tried to go over a hill.

 

With that big of a trailer and towing it half the time I'd get the 4.30's for sure! Heck, he should get the PSD if he's worried about fuel economy. The anual fuel cost between the 3.73 and 4.30 gears is prolly only $200 or less. Matter of fact, I'd say the 4.30's would get the same MPG or better as the 3.73's while towing because the 4.30's will keep the engine in a better rpm band.

 

The Ford tow manual states that the 3.73's are good for only 10,000lbs. The 4.30's for 12,000 lbs. That said, and from experience I would go with the 4.30's and put alot of consideration into the powerstroke with the 3.73's. I have the V-10 and love it, but with that much weight and the amount of time he plans on towing the oil burner may serve him better. It is what I would do if I owned a condo on wheels.. I tow a lighter trailer and it is no problem. (V-10 guys, don't call me a traitor!)

 

the F250 psd only comes with 3.73 gears. I pull a 37 ft 5th whl that is 11,850 lbs dry, with my 99' F250 psd. My trk/trlr combo will gross out at, 20,500 lbs when traveling. On the hwy 70 mph is easy, although I generally stay closer to 60, much better fuel milage.

 

one thing i forgot to mention in my previous msg; with this much wt and virtually no back pressure for deceleration an exhaust brake is highly recommended, especially if you travel some of the western mountain passes as I do each year.

 

I know the PSD is available with 4.10's , but most feel it revs to high for the diesel. Maybe only the 250 only gets 3.73's, but I thought both had gear choices.

 

what one do you recommend--thought ford did not warrantee the engine if you put a exhaust brake on it--why doesn't ford put on on as an option? ram does

 

I have a 99 f250 sd cc v10 automatic with a 4.30
rear end (came with the trailer tow package). I picked up the truck in August 98 and have about 8500 miles on it. From day one I have gotten about 10 MPG. Highway, city, Ac on, it doesn't matter, I still get 10 MPG. Is the 4.30 rearend the reason for the constant MPG? Also, what do the numbers 4.30 represent? If you had two identical SD's, one with a 3.73 and one with
a 4.3, what would be the difference in performance?

 

[Sorry for the following long winded response.. also anyone please correct me if I'm wrong]

the gear #s (3.73, 4.1, 4.3) represent the axle
ratio. It is the ratio that shows how many
revolutions the driveshaft (what connects the axle
to transmission) must turn for the axle to make
one revolution (implemented by different ring and
pinion sizes in the differential-that "pumkin" on
your axle that differentiates power between the
wheels). So 4.3 gears mean for every turn
of the axle, your driveshaft spins 4.3 times.
This makes the rpms change faster (d(rpm)/dt), or
easier for the engine to rev up, hence increasing
torque sent to wheels but top speed for each
gear will be lower than a one with a lower axle
ratio since you reach max rpm sooner with the
higher ratio. Usually the nonclemanture is
higher ratios = lower gearing; lower ratios =
taller/higher gearing i.e. the lower gears of
the transmission has higher ratios; axle ratio =
final drive ratio; axle ratio * final transmission
gear ratio (e.g. 4th/overdrive) = total final
drive ratio (though sometimes two names are
interchanged).

So yes, I think the 4.3 gears is why you're
getting the 10 mpg, probably because running
empty, you maybe tend to rev up high as it's
easier to do so and with weight, maybe you push
the throttle more, holding in lower gears longer.
I get about the same 10-12 mpg w/ superchip.
(f250 SD, SC, SB, 4x4 v10, 4.3)

 

continuing.. sorry, I forgot--the SD with 4.3
would accelerate faster, shift sooner
(timewise that is) and have lower top speed than
the SD with 3.73.. but i think the difference
would not be that great. (maybe 1 sec difference
0-60 or something)

A good feeling for the difference is when
accelerating on the highway--the 4.3 is less
likely to downshift the third than the 3.73 to
do so because is has the extra torque from the lower gearing to keep the momentum going in 4th.

 

Paul,

I have a SD, CC with the V10, AT and 4.30 gears. 10 mpg sounds a little low to me. I constantly get 11.5 - 12.5mpg. Do you have a lot of stop and go driving? Are you loaded with gear? I think I'd have to drive like heck to get my mpg to drop to 10.

 

JimV.

Thanks for the informative response. I appreciate
the explanation.

 

99 4x4 V10 5sp 4.30.constant 12.5-128
have 1500 miles on it.