I have a 1999 7.3 psd F-450. It's rigged out for welding with a Lincoln SA-200 engine driven welder. My overall weight is approx. 11,500 lbs. and I rarely tow with it. It has a 4 speed automatic and 4.89 ratio gears in it now. I bought it with 245/70/19.5 tires. Stock size is 225/70/19.5. I am going broke trying to keep the fuel light from staying on all the time, and I am considering changing the gear ratio. My questions are; Is this a wise investment, as far as cost vs. gain? I also need to know if it may create a higher risk of other mechanical failures? I need to research what other ring and pinion ratios can be used in the ford 10.5 12 bolt rear axle. Any input would be appreciated. Money is hard to come by these days, and even harder to keep. I cannot afford a costly mistake if the funds can be more affective elsewheres. Thanks in advance. p.s. I forgot to mention this rig is stock equiped, in case anyone was wondering.

 

I wouldn't be willing to bet my life on it, but I can't imagine it would hurt anything changing to a 4.10 or even a 3.73. Many guys on here have higher gears and pull heavy 5'ers and such. Somebody much more knowledgable will be along shortly. Welcome to FTE!

 

check your parts before ordering. I thought the 450's came with a DANA 80 or 110.
AS far as gearing goes as long as its a 2wd it won't be bad with cost vs return. 4x4 doubles the amount of time it takes to get your money back. personaly with that load I wouldn't drop any lower than 4.10s. packin' that much weight it will be harder to get it moving from a stop and if you go too low you'll be using the same amount of fuel because your lugging the motor with that kinda load. My 550 like 2000 rpm cruising empty and it weighs 11K. put the 18K 5th wheel behind it and it like 2400 RPM alot better.
Welcome to FTE, stick around. alot of inexpensive things can be done to wake up your truck and get slightly better fuel mileage
Barney

 

Barney do you switch off the US Gear when towing?
.
I always find myself wishing for a 13 or 18 speed tranny when hooked up.
It's a HUGE jump between 4th and OD on the ZF6.

 

No Dan, I use the heck out of it. Its really useful on that particular gear split. 4th -4th OD-5th. its about a 500 rpm split between each gear. normally when towing I'll set the cruise at 2500 RPM(about 67 MPH) and just let it ride. then if I come to a real bugger of a hill I'll start downshifting to 4th OD, then 4th. I've found that the split between 3rd OD and 3rd is almost a push. Its alot of fun to play trucker when I have a long hill from a standing stop. then I'll row though all 12 gears just for fun!
On a side note, now that the US gear drive is no longer avaiable, do you think a 2 spd Dana 150 could be swapped into a 550?

Barney
Barney

 

Just for the next user looking at the main title (original poster is long gone) I bought a 2000 F-550 2x4 about 4 years ago, 120,000 miles (now has 200,000) w/ a 5 speed. I immeadiately regeared the Dana S-135 from the 4.88's to a Detroit Locker and 3.91's. MAN what a great choice, good mileage (12,500 "empty") and engine was not screaming. I just removed the set up (selling the truck, and bought a 2000 4x4 F-550 gasser) and drove it home from the mech. shop the engine was screaming!! So glad I did this, it not doubt saved a ton of engine wear, but also fuel expense. I originally spent $2500 for the parts and labor, and WILL reuse the locker and potentially the gears as well. I CERTAINLY do it again given my experience.

Ironwood

 

Anything is possible. I'll go and see what google turns up.


This is one of the things that I wanted to do with my 4x4 F 550, but came up empty handed when searching for a front differential of the same ratio.
In the end, I gave up on that idea because I didn't want have to convert to 2wd just to get that taller gear.
.
Another option that is available is to install a Gear Vendor on the tailshaft, but I've read you cannot put a reverse load on it while the OD is engaged so that is not really an ideal situation either.
Bottom line is I was putting off installing a US Gear box on my truck because of the expense and now it's too late.

I'm going to research that Dana 150 option. Thanks for that tip, I didn't know what to search for.

 

Dan, here is the DANA down load with axle ID. it shows that the 135-S and 150-S are the same dimensions just one has a thicker housing. It also lists part# for different ratios
AXIP-8941.pdf
I wasn't able to locate a 2sp version of the 150

Barney

 

I am in almost the same boat, I have a 99 f450 with the stock 4.88 gears and a Dana 80, I have been looking at regearing the rear end to get the Rpms down as I have a 60-80 mile commute everyday and the freeway KILLS my milage. I got 10.5 last tank. The last time I was across the scale she was just under 14,000lbs.

Here is the scenario. I have found a rear end out of a 05 E450 bus. It is the dana 80 and has 4.10 gears. The guy wants 800 bucks for it, I am wondering if the carrier and pinion will work with my truck or if I would be better off swapping the whole Axle and if so are the bolt patterns the same. I know they changed right around that time.

 

Nsaan, is your a diesel? You will not regret getting the rpms down if it is. It made a HUGE difference in the wear and tear in my engine during the 80,000 miles I owned it.

 

Thanks for that.

 

Yes its a 7.3 I just hit 180k miles this week, so I imagine that quite a few of those miles are highway miles. I know when I am on the freeway it is hardly ever under 2500rpms. usually it is closer to 2700, right around 70 mph. Unless it is rush hour... then my fuel mileage goes up, as my patience goes down.

 

My 550 with the 391's tached at right around 2000 rpm at 65-70. That was the sweet spot, and I never tried to tach over 2200-2300 EVER. I cant imagine "cruising" at 2700

Ironwood

 

I would convert to 3.91 in a heartbeat if I could find a matching FRONT differential R&P set.

 

what did it cost you for the gear set?