Having a diff shortened. Whats the process?

-
M

Mopartist

Well-Known Member
Joined
Mar 19, 2006
Messages
75
Reaction score
0
Location
Bend,OR
I have a 65 dart. OK; so how do I get measurements for what length my diff should be cut to? Here's what i have so far. I've cut my wheel houses to the frame rails for mini tub. I've cut the frame rails on the inside to relocate the leaf springs with relocation boxes. I've aquired new Weld wheels 15x10 4.5 backspacing. And just got a 8.75 housing out of a Manaco and a 489 sure grip chunk. I don't have my tires yet; but am fairly certain they will be 10 inch wide MTs. I will be using 11 inch drum brakes. So in measuring for the diff width so that these wheel tire combo's will work; whats the process? Any info would be much appreciated!
-Ken
 
i did pretty much identical to what you did. i can give you the measurements tuesday pm. i think the dart is the same as a 66 cuda.
 
It really depends on what axles you are using. Are you planning on re-splining the C-bod axles? That may not be an option if they are the later years tapered axles. Even so, I'd advise against re-splining. I'm sure many will say they can be done and get away with it, but a good set of aftermarket axles will be way better/stronger.
 
Ace said:
It really depends on what axles you are using. Are you planning on re-splining the C-bod axles? That may not be an option if they are the later years tapered axles. Even so, I'd advise against re-splining. I'm sure many will say they can be done and get away with it, but a good set of aftermarket axles will be way better/stronger.
Click to expand...

Oh; absolutely new good quality axles; new bearings; the works. I just have never had a diff done before; and want to gain as much room for tires; strength; and stability as I can without going to the expense of ordering a brand new Strange or Moser diff. But even if I did go with a brand new unit; I still wouldn't know exactly how to measure for width (either flange to flange; or brake to brake) And then there is the issue of the perches, and offset of the 8.75 having one side longer than the other. So......do I mount up the relocated leaf springs; and measure from there? (That'll give me the exact width for the perches) I've heard I should position my wheel/tire combination centered in the fenderwells first ; then measure the width to the mounting surface of the wheel for overall brake to brake width; and work backwards from that. Does it get down to more of a science than that? (ie. How thick is a Mopar 11 inch brake assembly? then how thick is the drum surface to get to the outside axle measurement? How far from there is it to the outer flange of the axle housing? Then how far to where the cut has to be made before the flanges are welded on? See; I don't have the info on any of this other than the wheel/tire fitment; and where the leafs will be mounted; and how far apart the perch pins on leafs will be apart.
 
When you start cutting/fabbing to move springs, tub, etc. measurements all become totally arbitrary - you can put stuff wherever you want it, providing the parts to do what you want to do are available. That's why I pointed to the axles. You could even get the axles custom made. I'd suggest shopping axles from Moser or wherever, based on your narrowed target width. Sounds like you're moving inboard around 2-3".
 
In the attached drawing; Do I have to know the measurements of "D" and "E" before contacting a shop to make the cut and ordering the new axles. Or do they normally just need the outside brake to brake width? (Item "F")

diffdrawing.jpg
 
I believe you're over-thinking this and making it more complicated than it needs to be. I just bought the axles and took everything (axles, housing and diff) to my friendly neighborhood race car builder down in Denver and asked him to cut it and make them fit. No problemo, ball's in his court, no chance of any mistakes on my part.

Another slightly more difficult way of doing it would be to start with the stock A-body axle length, decide how much shorter you want them and subract the 2nd number from the first, giving you your new desired axle length. Then get the new axles and go back to the beginning. But then you have to do a little math. :toothy7:
 
I believe you're over-thinking this and making it more complicated than it needs to be.
Click to expand...

I'm glad to hear that! :) I was kinda hoping I wouldn't have to play the part of mechanical engineer! Heh heh!
 
Prop the wheels up inside the wheel wells so they are centered and measure from the inside to the inside of the wheels. This will be your axle flange width with the drums. The stock axle offset "D" is 2.36" for the non a-body drum brakes. So for the sake of argument let say the wheel to wheel dimension was 48" to find your housing width you would subtract the drum width .125 x2 = .25 and the axle offset 2.36 x2 = 4.72 so you housing would be 43.03" wide or rounded out to 43". The axles are usually ordered after the housing is narrowed. Axles are made to the housing not housing made to the axles.

I narrow housings so if you don't have anyone yet I can do it for $250 and I will supply the housing so you only have to pay freight one way. All I need is like I said before is the width of the inside of the wheels (axle flange to axle flange), the thickness of you drums and the spring perch center to center dimension and I will narrow you one.

Since you are in central Oregon and I am in central Washington the freight would be fairly reasonable, I'm thinking around $25 - $35 dollars.

Chuck
 
Hey thanks Chuck. I'll definately give you a call once my springs are done. I'm also putting in aftermarket tubs; and new quarter panels; so once I see how much clearance I have; I'll be able to zero in on the measurements
 
You must log in or register to reply here.
-

Back
Top