differential ratio change - Diesel Forum

JDeereGn · 06-28-2008, 11:08 AM

Does anyone know what parts would have to be changed in the rear end and front end to change a 08 F-250 4x4 from a 4.10 LS to a 3.55 LS? Approximate cost using new parts?? Used??

**Scottb NY** · 06-28-2008, 03:35 PM

off the top of my head, i would say that the ring, pinion, shims, crush collar and fluid need to be changed. Personally I would not even consider using "used " parts for something like this. The gears have to be set up properly to last and not make noise. Old parts would be worn from the previous installation and may not set up correctly. Reliability is worth the difference to me and you need to find a QUALIFIED shop to install them.

dt75flh · 06-28-2008, 06:16 PM

most shops around vegas charge about 300-350 per axle to change out the gears....
most after market front gears you can get for 200-300 a set.....the ford rear set run about 500.

if you dont tow and dont mind a little gear whine in the 50 mph range you can buy cheaper rear gears after market for about the same as the fronts....

youll also need a set up kit which is usually about 100 per axle....the master kit comes with new bearings but if the truck is relativley new you shouldnt need the bearings

dt75flh · 06-28-2008, 06:17 PM

I thought you could only get the 3.73 gears in the new 08 unless you have a f-350 drw ??

**Scottb NY** · 06-28-2008, 08:41 PM

no, the latest is the 3.55

Stymie · 06-29-2008, 03:25 AM

expect to spend 600-1000 grand for parts and labor. depending on shop.

JDeereGn · 06-29-2008, 10:25 AM

I will figure on 1,000 bucks. I was hoping to just change the ring gear and use the old pinion. Not sure it would be worth it. Conversion would be on a new V-10. Just talk at this point since I haven't even ordered a new truck yet. I can not imagine why Ford will let you have a 3.73 in the V-8 but force you to go to a 4.10 in the V-10. The change to 18" wheels made all my experience with ratio's worthless.

Stymie · 06-29-2008, 01:52 PM

Quote:

Originally Posted by JDeereGn

I will figure on 1,000 bucks. I was hoping to just change the ring gear and use the old pinion. Not sure it would be worth it. Conversion would be on a new V-10. Just talk at this point since I haven't even ordered a new truck yet. I can not imagine why Ford will let you have a 3.73 in the V-8 but force you to go to a 4.10 in the V-10. The change to 18" wheels made all my experience with ratio's worthless.

the 18" wheel wont change anything, tire size will. you are only allowed 4.10's because the gas motor spins more rpm's than the diesel. Also, you can not reuse the pinion, it will be incorrect number of teeth on it, to make the correct ratio.

JDeereGn · 06-29-2008, 11:24 PM

Stymie, Since I only run OEM tires the 18" wheels and tires on the newer tucks have a larger overall circumference of about 1/6 more than the older 16" tires and wheels. I had a 2001 V-10 with the higher ratio but it had the smaller circumference wheels and tires. It only got around 10 or 11 mph overall.