Needs some help - Shortening 9" rear-end

[Turbo Hen]

Hi guys....need a hand on something. Car is a '69 Firebird & the rear diff is a 9"

This diff needs to be shortened so i went ahead & mocked up the wheels/tires where i wanted them to fit.

The wheels are Billet Specialties Fast Lanes 17x11 w/ 6" BS and 335/35/17 drag radials. The brakes are Wilwood Pro Street rears w/ internal parking brake.

The distance i got measuring from the mounting flange of the rim(inside quarter panel) to the other is 57"

Does this seem about right? Im going with some 33 spline axles, Ford big bearing ends & spool.

I called Moser & they told me to subtract 2 1/4" from either axle tube for the bearing ends, and subtract the thickness of the rotor hat. Is it this easy? Just looking for someone who's "been there, done that" as i'd only like to cut once!

-Carm

[quadfather]

that axle dim. doesn't sound right to me . small ford and early big ford endswith(1/2") BOLTS are 2.366 standout , and late big ford with 3/8" bolts are 2.5" standout. both dimensions are without brakes. plus you have to check pinion offset , if you you ordering a rear from moser or someone . just give them a wheel to wheel dimension and they should know the rest . if you attempting it yourself don't do it without a jig. to align the housing ends. most chassis shops do it for between 150.00 and 200.00 bucks.

[ProdigyCustoms]

With a 6" backspace you should come in at 55" flange to flange or so. Actually we do 55 1/4 with a 6" backspace.

On another note, be sure to look us up at GPSuperStore.com for your Moser needs if you want to save money.

[Turbo Hen]

Great thanks for the quick reply guys. I measured about 3 times....where i want the rims to sit gives me 57" from the inside of the rim where the face sits on the rotor face. I just dont want the rims to sit inside TOO much & make it look weird.....kind of hard to find a happy medium for me.

Quadfather i wasnt talking about the boltspacing on the mounting flange for bearing ends, i was talking about the bearing end thickness itself in relation to the overall length added onto the housing when added on.

As for doing the diff, i plan to get the axles etc.. first, assemble the pig & bolt it in, then insert the axles into the housing sliding them into the spool.....while sliding over the bearing ends to tack them in place....would this not be a good method?

[quadfather]

Great thanks for the quick reply guys. I measured about 3 times....where i want the rims to sit gives me 57" from the inside of the rim where the face sits on the rotor face. I just dont want the rims to sit inside TOO much & make it look weird.....kind of hard to find a happy medium for me.

Quadfather i wasnt talking about the boltspacing on the mounting flange for bearing ends, i was talking about the bearing end thickness itself in relation to the overall length added onto the housing when added on.

As for doing the diff, i plan to get the axles etc.. first, assemble the pig & bolt it in, then insert the axles into the housing sliding them into the spool.....while sliding over the bearing ends to tack them in place....would this not be a good method?

neither was i . the dimension i gave you was how much the axle sticks out from the housing end. not the bolt spacing. the bolt size was to help determen which style of housing ends you have . 3/8 BOLTS late style 1/2 " BOLTS EARLY STYLE. 2.875 dia. brg. small end 3.150 dia. large brg. and there all different bolt paterns.

[Turbo Hen]

Ah i gotcha....the Wilwood kit i bought has the 2.36" bolt spacing for early style big ford.

[Mark Smith]

turbo hen,saw this post this morning before i started putsin around in the garage.when i set my wheel and tire combo into position measuring for rear i came up with the same 57 inch measurement.my wheels are boze forged 11.5 inch wide with a 285 19 tire. with rear now in the car and wheels mounted the outside edge of rim is 3/4 inch for inside wheel lip.did not roll fender.I have a 9 inch rear with the same big bearings and i believe the same willwood brakes.mine have the internal parking brake.measuring from back side of axle flange to axle flange i measuring 51.5 inches.hope this helps you out.oh yea my car is dse mini tubbed.

[Turbo Hen]

Hey bro thats a great help.....i have the internal parking brake as well.

So you have 57" from the backside of the rim mounting flange to the other rim?

What backspace are your wheels?

[Mark Smith]

yea,with the tires mounted and the rims set in place 57inches.just checked the receipt for the wheels and they are 11,5 inch with 6.25 back space.one thing i would recommend would be to make the rear .5 inches wider than mine.I am running dse 3 inch drop leafs with their offset shackle and my tire only has about 3/8 inch from leaf spring. hope this will get you going.

[Turbo Hen]

Sounds good Mark....im using a ladder bar/coil-over setup so the leafs wont be in my way.

Really appreciate the help,

-Carm