okay so ive got a 01 sd crew cab 5.4 manual tranny and 3.73 gears. its got a 3 inch lift and 35 inch tires. i dont pull very heavy loads, just a small boat. but needless to say it's left me wanting for more power. i had thought that the engine was to small for the truck but after reading countless threads, ive decided now its the gearing, and that the engine is more than capable. also i only get about 10 to 12 ish mpg. so anyway, should i get the 4.10 gears or 4.30? im not power hungry but would like to drive without down shifting on every little hill, i also dont wanna kill my mileage to bad. ive read that the 5.4's with 4.10 get just as good as the ones with 3.73, is this true. i would like to hear from those whose done this swap. thx for any advice.

 

i put 4.30 on my 2004 but im only running 285/75r16 tires. A 5.4 with 35's should have 4.88 gears that will put the truck back to stock 3.73 with stock tires. When i had 4.30 installed i actually gained 1mpg because the truck didnt up and down shift ever 1/2 second to find the right gear. For the money id go at least 4.56 with 35's if your not towing anything, but 4.88 puts you back to stock where the trucks motor needs to be....

 

+1 go at least 4:56 or 4:88. The 4:10s will have u looking for more power still.

 

OK, we can figure this out using the automotive calculators available on this site.

Automotive Calculators offer to you by Ford Trucks Enthusiasts | www.ford-trucks.com

Say the factory tires were 32 inches tall. You replaced them with 35 inch tires. You have 3.73 gears. That means you're running an effective ratio of 3.40. To return to stock, you would need a 4.08 ratio. 4.10s would be the closest.

BUT....it is often a little more complicated. You put wider tires on the truck and a 3 inch lift. That means a little more rolling resistance and a little more wind resistance. You need to compensate for that also, so I would go a little further and get the 4.30s.

 

I'd go 4.56. The 5.4L should have minimum of 4.10s with stock tires, scale that by the tire increase you have and it puts you just under 4.56. You could even go 4.88 if you rarely drive over 65.

 

This^^^ With the OD ratio on the ZF5 the 4.56 should be spot on for you.

 

4:88's dont waste your time going into those pumpkins for anything less.

4:56's is the absolute minimum, but even that will not give you the power increase you would want to see from spending that level of coin.

 

at least 4:30s if your highway cruising all the time - Id go 4:56 for all around

What kind of cost should you expect for a set of new gears installed on a 4x4?

 

^^^ ditto ^^^

IMHO...the 4.56 is your best option.


biz

 

Another way to look at it, in high gear, this is what your engine would be turing at 60 MPH with these ratios:

Gears RPM
4.10 1797
4.30 1882
4.56 1995
4.88 2136

 

I would do 4.56 gears with 35" tires. To compare, my brothers truck has factory 4.10 gears and 31" tires and his has plenty of power! To equal that power I am swapping out my 3.73 gears for 4.30's bc I have factory 33" tires. To match that with 35" tires I would at least do 4.56 gears

 

Keep in mind those RPMs are for 35 inch tires and a ZF-5 transmission final drive ratio (0.76). A 5R110W has a final drive ratio of 0.71, so the RPMs will be even less.

 

i had factory 4.30 gears installed, new bearings, seals, and had the junk LS rebuilt and it cost me $2,280.00. If i knew now six years ago i would have had 4.88 gears installed and a rear detroit locker for $2,400.00 and i would now have my 4" lift and 35's......

 

wow thx for all the responses, so it looks like 4.56 is the way to go, any paticular brand to get or to avoid?

 

I also recommend 4.56 at the least..thats what i am running with 37's but i have a powerstroke..