Differential upgrade?

Agree - the 8" is usually strong enough for most things you throw at it for a street car, and there are options for it. If you have the smaller axle, the best/easiest upgrade would be to find an 8" from another II and swap it in. As luck would have it I have an extra 8" sitting here doing nothing - where are you located? If you're fairly close I'm sure we can work something out if you'd be interested.

Mustang II rear end upgrades

You need more than just a posi.
I like the locker a lot.
Popular posi options for the 8' and 9' inch rears are;

Locker ( can be noisy but that just means its working) Tough
Trac-loc (clutch style posi) Cheap
Trutrack (helical gear style posi) Doesn't wear out quick
Mini spool (dirt trac only, tears up axle ends on the street) Fun to look at
Full spool (Bad arse but not so great on street daily) guaranteed to squeal tires in low speed parking lot turns and rear steer car sometimes.

Sub Frame Connectors from Stumpy's Fab works are a must.(just do it)

Traction bars can be nice too;

slapper bars (universal old school)
Mustang II traction bars by Stumpy Fab works ( get to keep stock rear roll bar with these)
Calvert Cal- trac (a good drag bar available for MII)

The leaf spring to car mount is wimpy, it can have a piece of angle iron welded to it
This is post 144 from 429MII's thread


Thats the usual rear stock suspension upgrades for our M2s

Heres mine with drive shaft safety loop, stumpys subframe connectors, and shot gun style exhaust.

Come on Ed88 Post a fresh picture of your car please.

take a pic of the rear too.

Ed88 said:

Sounds dumb but im not sure which rear end i have. How do you identify them? Im also located in Southern Illinois.

Click to expand...

The easiest way to tell between the 2 is if the back of the differential has a cover or if it's "smooth." The one with a cover is the smaller rear, I think it's a 6.75 ring gear, the "smooth" differential is an 8 inch.

I took a look at the axle I have, I knew it was missing one of the brake baking plates but it's also missing an axle from the same side. I'm in the Atlanta area but I'm from Iowa, so I do travel through southern Illinois on occasion. I don't have any plans of making the drive anytime soon, but if you're not in a hurry I'm sure we can work something out if you want it. It's from a V8 car, I believe it's a 2.79 gear with an open differential.

An 8 inch for reference:




All of the II 8 inch rears that I've ever seen don't have that plug that's more centered in the housing. The fill plug is on the pinion side in the carrier.

That old car is in pretty good shape,
Looks like an original paint Mach I, Wow! neat!

What color is that ? Ginger glow? First 2 yrs only? IDK

Always liked that Mach I package. Thanks for sharing




inspiration picture