I have the pro-comp 6in lift with 35 inch tires. The 3.73 gears in my fx4 are really not cutting it. This thing downshifts into second at 75mph. The performance has taken a dive as well, as expected. I have done some calculating and plan to have 4.56 gears installed. If my calculations are correct this should be similar to a 3.83 gear ratio with stock tires (hope that makes sense). With these gears and 35 inch tires, I should be able to cruise at 75-80 mph @ 2500 rpm in overdrive. A shop said they could do it for around $1375. Does this seem awful steep? Any input as far as my calculations, and where I can purchase cheaper gear sets would be greatly appreciated.

 

I was quoted $1600 with tax (which is $1476 w/o tax) so you're price is within range. This is from the most reputable off road shop here in San diego (i.e pricey).

Make sure they use the same synthetic gear oil that is in the originals. If you plan on mudding or going through water you should have it checked after each encounter in case it needs replacing. The synthetic should be good for the life of the truck.

 

Here in California we have a place located in the Sun Valley here's the info.

Hooper's Rear End Exchange Inc.
12201 Branford St.

Sun Valley, CA 91352

818 - 899 - 2515

Fax 818 - 897 - 0952

Differentials and rear end parts for cars, trucks, rv's and racecars - Since 1976

they did a rebuild on my 71 Dodge pickup for just under 400.00 and I got an estimate from another shop for 1800.00

Good Luck GG

 

The price seems reasonable for 4WD.

Have you considered spending that klind of money on in other areas liek intake, exhaust, tuner, headers and maybe e-fans? That is another way to get some more torque and maybe have better fuel economy too.

 

I am having the same issue with the tranny after installing the procomp 6" lift and 35's. The shop I am using quoted about the same $1,500 for front and back. And 4.56's seems to be the way to go with this configuration. I do not have the funds to do it yet but if you have it done before I get a chance please post results. I will do the same.

 

hey big ody
im getting 35's aswell. 4 wheel parts has the 4.56 gears but what is the size back there. 10 and a half or 8.8" or whatever. appreciate it, thanks

 

o yeah, another thing. what does the installation of these gears involve? how difficult is it to do on your own

 

Hey Ristuccia,
The rearend is a 9.75 inch and the front is some kind of 8.8. The cheapest place i've found to purchase gears is from http://www.jawsgearandaxle.com/ you have to call them to get the info on our trucks (866) 617-5297.
As far as installing the gears yourself you can forget about it. There is a lot of work in it and specialized tools such as a dial-indicator that are expensive.

 

thanks