Narrowing a 9” rear end on a 67 Fastback

Pbum5

Member
Oct 27, 2004
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Minneapolis, MN
I have a 67 with a 9” out of a 69/70. I think they are the same size. Anyway. I know if you narrow it a bit to 65/66 size you can use deeper dished wheels. Any one this and have pics of the look?
How much does it need to be narrowed to still fit under the stock wheel wheels?
Also what is the going rate for having the rear-end and axles narrowed? It is a 28 spline rear-end. If I wanted to upgrade it to a 31 spline would it work? I hear a lot about different bearing size 9” rear-ends.
Thanks.
 
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Pbum5 said:
I have a 67 with a 9” out of a 69/70. I think they are the same size. Anyway. I know if you narrow it a bit to 65/66 size you can use deeper dished wheels. Any one this and have pics of the look?
How much does it need to be narrowed to still fit under the stock wheel wheels?
Also what is the going rate for having the rear-end and axles narrowed? It is a 28 spline rear-end. If I wanted to upgrade it to a 31 spline would it work? I hear a lot about different bearing size 9” rear-ends.
Thanks.

A local shop told me $250- $300 to shorten the tubes. They said to get new axle shafts though as it will cost more to shorten and respline then than new ones cost.

You CAN go from 28 spline to 31 spline, but you'll need a new differential also if you do that.
 
skywalker said:
A local shop told me $250- $300 to shorten the tubes. They said to get new axle shafts though as it will cost more to shorten and respline then than new ones cost.

You CAN go from 28 spline to 31 spline, but you'll need a new differential also if you do that.

Good to know. I have been wanting to swap out gears for a posi unit. Yeah i figure if i have to get new axles then it would be a good time to step it up to 31 spline and swap out the 3rd member for a posi.
 
Pbum5 said:
So how many " inches total did you narrow the rearend from a stock 67?
i dunno :shrug: i broke (3) 8" from a 67 then found a 66 rear and stuck it in...then broke the locker and gears in that one. so i had one made 1/4" shorter. i don't remember know... :shrug:
Pbum5 said:
Do you have a low angle picture from behind to see how wide the tires are or someting that shows the clearence in the wheel well?

thanks.

you can't see nothing because of the tire tuck...

tires are 11 1/2" wide 315/35/17's nitto drag radials. had to use a BFH on the inner fender just to make sure i didn't have any rubbing. they are about an 1/4" away from the leaf spring.
 
Pbum5 said:
I have a 67 with a 9” out of a 69/70. I think they are the same size. Anyway. I know if you narrow it a bit to 65/66 size you can use deeper dished wheels. Any one this and have pics of the look?
How much does it need to be narrowed to still fit under the stock wheel wheels?
Also what is the going rate for having the rear-end and axles narrowed? It is a 28 spline rear-end. If I wanted to upgrade it to a 31 spline would it work? I hear a lot about different bearing size 9” rear-ends.
Thanks.
Just a question. Why are you going to shorten this one? You can get another one and have it shortened and sell this one, because it is the right length for someone else. It might be cheaper in the long run.
 
skywalker said:
A local shop told me $250- $300 to shorten the tubes. They said to get new axle shafts though as it will cost more to shorten and respline then than new ones cost.

You CAN go from 28 spline to 31 spline, but you'll need a new differential also if you do that.
For that price I'll sell you a 9" rear already that short. :D And throw in the 28 spline axles.
 
Jester67 said:
Just a question. Why are you going to shorten this one? You can get another one and have it shortened and sell this one, because it is the right length for someone else. It might be cheaper in the long run.

That's a good point!! That’s why I ask these questions to have someone point out a simple solution.
I’ll look into that.
 
Pbum5 said:
I have a 67 with a 9” out of a 69/70. I think they are the same size. Anyway. I know if you narrow it a bit to 65/66 size you can use deeper dished wheels. Any one this and have pics of the look?
How much does it need to be narrowed to still fit under the stock wheel wheels?
Also what is the going rate for having the rear-end and axles narrowed? It is a 28 spline rear-end. If I wanted to upgrade it to a 31 spline would it work? I hear a lot about different bearing size 9” rear-ends.
Thanks.

Currie Enterprises can get you hooked up. I had mine narrowed a couple of years ago for $350 including new axles. My '65 was able to be narrowed to specs that were 1/2" shorter on each side. No problem with rub.

Just tell them what you want and they do the rest.

HistoricMustang
www.historicmustang.com
 
HistoricMustang said:
Currie Enterprises can get you hooked up. I had mine narrowed a couple of years ago for $350 including new axles. My '65 was able to be narrowed to specs that were 1/2" shorter on each side. No problem with rub.

Just tell them what you want and they do the rest.

HistoricMustang
www.historicmustang.com

Wow. their prices must have jumped in the last few years.
axles and bearings alone are now $399 on their website.

I know they do good work.
 
Jester67 said:
You buy his and I will buy yours for the same price :D[/

I'd be up for that.
I just need to make sure the dimensions work. Can anyone confirm the size of a 1966 Merc Cyclone rear-end.
These are the dimensions I was given on it.
Spring perches Center-to-Center 45”
Housing end of flange to end of flange (where the brakes bolt up) 54 5/8”

Is that the same size as a 64/66 Stang or a 67/70 or neither?

Thanks
 
Pbum5 said:
Jester67 said:
You buy his and I will buy yours for the same price :D[/

I'd be up for that.
I just need to make sure the dimensions work. Can anyone confirm the size of a 1966 Merc Cyclone rear-end.
These are the dimensions I was given on it.
Spring perches Center-to-Center 45”
Housing end of flange to end of flange (where the brakes bolt up) 54 5/8”

Is that the same size as a 64/66 Stang or a 67/70 or neither?

Thanks


I’ve been making some calls.

For anyone that cared it will not be a direct bolt in.

Cyclones and Mustangs have different Perch widths. And a 66 Cyclone Flange-to-Flange width is the same as a 67/70 at 54”

Mustang 9” rear-ends
65/66 Flange to Flange is about 52”
67/70 Flange to Flange is about 54”