How do you measure the size of a differential? My truck comes in a 7.5 and 8' but I'm not sure of the correct way to measure to figure out what I have.

Also - Is there a way to figure out the gearing?

I have not changed anything in my differential and I want to make sure that when I do start some work I have a little knowledge. Thanks

Zamboni

 

Check out this stie:

http://www.brian894x4.com/Gearratiosanddiffs.html

 

Great information. Thanks for the quick response.

 

You most likely have a 7.5" rear axle.
are you a 5 speed or 4 speed or Auto?
If 5 speed or Auto, I almost guarentee you have the 7.5"
some earlier 4speeds got the 8" (where I got mine from).
What gear ratio are you looking to go with?
I have some extra 7.5" parts if you're interested.

 

I have a manual five speed. Not sure of the gearing that I want to run. I'm running 30x9.50. If I go with bigger tires i'm sure I will have to re-gear. I'll let you know once I know what I want to do.

Here are my choices for back ends:

ARB Locker (apprx $1500)
Powertrax Limited Slip ($400)

I sure I do not want to go with a full locker right now. I drive too much on the street and I want something a little smoother and quieter.

 

You have factor in one more thing into those prices:

> ARB Locker (apprx $1500)
This option requires the use of an 8" rear (unless they changed something). From what I remember, the ARB for the 7.5" front won't work in the rear. I think it has to do with the direction the R&P turn.

> Powertrax Limited Slip ($400)
I think you'll run into the same problem with that particular model of Powertrax, but I know the EZ locker will work.

I have one more option for you - Randy's Ring & Pinion set me up with a Detroit True Trac with the gears reversed so it will work in the rear with a 7.5" axle. Since I don't have that size axle anymore, I woudn't mind selling it.

Gears:
with a 5speed, I think you have 3.56 gears (that would be a 7.5" rear). Going from stock 25.5" tires to 30" tires alone is a decent step already. The 30's are 1.18 times begger than stock. You'd benefit from going with 4.30's as is (calculation was actually 4.20, but 4.30 is better for the increased wind resistance).
That would set you up nicely for tires bigger than that too (comfortably up to about 32" I'd say).
Oh, ya I've got a set of 7.5" 4.30 v6 gears from a 92, even a spare 3rd with 3.73's in it
All you'd have to do is get the 3rd setup and do the swap in your own time (very little down time).
Hope this helps!
Todd

 

Thanks Todd - I'll PM if I am interested. Need to do a few more mods/improvements before touching the diff.

Here's the list of maintenaince items that need to happen first:

upper ball joints
lower ball joints
suspension lift
shocks
steering stabilizer
tires

 

Out of curiosity, are you keeping the body lift?
When you do the Fabtech front end, the front tires will be in a narrower track than the rear. 2 ways to solve this, different offset wheels, or a wheel spacer.
I chose to do the spacers because I didn't want to buy new wheels and have to keep track of which ones went where.
1" spacers did fine for me.
Have you decided what to do for the rear?
One suggestion, possibly do a flip of the spring perches (mount them on top like a 4x4). Quick and easy way to get 3-4" of lift in the rear while keeping stock spring rates.
This also allows you to keep the same legnth shocks in back.
For addidtional height in back, you can get extended shackles.
Ball joints are of course the first step, but that could be included in your fabtech upgrade
For me, in the future, I think I'm going to try out this setup , then add some additional height in the rear.
Have fun with the mods!
Todd

 

For the rear I have extended shackels.
As far as the front, most likely I will go with spacers. Easiest and a lot Cheaper that new rims.

As far as the body lift, I'm not sure if I will keep it or remove it. I hate to say it, but it depends on the look. If I remove it I will have to do it before I put on sliders. Most likely it will stay on, but I am still not certain.

The set-up in the link looks nice and not a bad price either.