[samuel0822]

I bought a 66 mustang as my high school project to take to college with me. It was original a 200 straight 6 and I am swapping to a slightly modified 302 (gt40 heads, flattop pistons, etc.). My budget is very low and was curious if it'd be possible to keep the 8 inch rear axle and put a stronger differential in it or would I have to swap to a 9 inch? If not, how much does the work to get an axle shortened cost and do you know of any good shops in the Houston area?

 

[Lizer]

You will be just fine with your 8". That's what I run with my 5.0 (also with GT40 heads and other goodies). Mine is not the original 8" that came with the car as mine was also an original straight 6. My 8" has the reinforced webbing on it and was an open 3.00. I've since upgraded it to a limited slip 3.55.

 

[Jedi]

Hey wait, I don't think any 66s with 200s came with 8" rears

 

[PB65stang]

Hey wait, I don't think any 66s with 200s came with 8" rears

Exactly. If your car still has 4 lug wheels, it doesn't have an 8" and it'll need to be replaced at the same time as the engine/trans. Either an 8" or 9" will work.

 

[GypsyR]

If the rear is stock and original then it's a 7.25" and you would need to upgrade to an 8. 9's are nice but overkill for most of us.

 

[66coupe289]

One can run the 4 lug rear end with a V8 but NOT recommended and certainly not for long term use. Using the 7.25 rear end on a V8 is kinda like running a space saver spare. It will get you from A to B in an emergency. You certainly want to factor in replacing both front and rear suspension into your budget. You might find it best to sell the 6 cyl and buy a V8 car. Looking for 8 or 9" rear ends you should be looking at 64.5-66 Mustangs and some late 50's Fords to get the correct axle width. 67-68 will be too wide...been there, done that.

My car was born a 6 cyl. It had a 289 in it when I bought it, but I had to convert everything else.

 

[du907]

I too have done a swap from 6 cylinder to 8 cylinder. Change the sway bar and springs in the front. Since you have to change the rear end no matter what, get a 9". They are not that hard to find and in the future if you keep the car (which you should, if you sell it you WILL regret it) then with the 9" you will be ready for anything that you may want to do. The 9" is indestructible and the most used in any modification, any brand. Also you will probably need to get a drive shaft made, maybe not, but check it.

 

[Stanginmatt]

What about doing an entire explorer rear end with disc brakes and everything? Cannot remember exactly what it entails, but don't think it was that big of a deal. would be super cheap

 

[Maxum96]

An 8" rear will be fine behind a slightly warmed over 302 unless you plan to drag race it. 8" axles are the same as 9" 28 spline axles.

 

[BlakeTX]

I would just find a used 8". I sold mine a few years ago when I did the Explorer swap for $110. It was a 2.80 peg leg, but it would be a perfectly workable solution on a budget. Served me well for 20+ years before I got rid of it.

I too have done a swap from 6 cylinder to 8 cylinder. Change the sway bar and springs in the front. Since you have to change the rear end no matter what, get a 9". They are not that hard to find and in the future if you keep the car (which you should, if you sell it you WILL regret it) then with the 9" you will be ready for anything that you may want to do. The 9" is indestructible and the most used in any modification, any brand. Also you will probably need to get a drive shaft made, maybe not, but check it.

9" rear ends may be plentiful, but in the width for a 65-66, ready to run, they are expensive. It's surely the most bullet proof solution, but it is also overkill in this application. Without knowing the OP's budget, I can't in good conscience recommend a 9 as the only way to go.

What about doing an entire explorer rear end with disc brakes and everything? Cannot remember exactly what it entails, but don't think it was that big of a deal. would be super cheap

For what you get in the end, an Explorer swap is great value for the money. It does require some fabrication, and by the time it's done is often more expensive than most report. I'm glad I did it and would to it again. That said, for my daughter's 66 that will have nowhere near the power that mine does, she's sticking with the stock 2.80 peg leg 8", which will be just fine.

Here's the thread on my adventure with the Explorer swap:

What does it really cost to swap an Explorer 8.8? I can...

You hear about the Explorer 8.8 swap being the most affordable path to having a super-strong rear end with disc brakes and steep gears (3.73) while driving both wheels. For context, I was coming from the stock 8 inch, 2.80 gear open diff axle with drum brakes. This swap is often described as...

www.vintage-mustang.com

 

[awhtx]

Since the OP has installed a V8 in his I6 car he has a lot more to worry about than just the rear end. What about the front suspension and steering?

 

[dacofa]

My 66 started as a 200, 3spd. Now a 331 stroker C-4, 8" 3.55 posi. I also changed the front to 5 lug and manual disc brakes. When I changed housing from the 7.25 to the 8" I found it on ebay for a 66 Stang. They have the narrow housing ends. Because I was going to rebuild it anyway I just sent it to Currie, had it straighten, cleaned powder coated, new brake assemblies, and forged axles made for it. But that's just what I did.
Get the right 65-66 housing and just rebuild it and stick it in there.

 

[wicked93gs]

8" is just fine....and for perspective, in other countries where the 8s and 9s aren't so common, plenty of people have made do with the 7.25s(its only in the US that they have a bad rep because of their much stronger big brothers) behind v8s in drag racing applications:

13 second 1/4 mile times with a 2 year life span of drag racing....not shabby for a heavy 4 door Falcon. I am not suggesting keeping the 7.25 when you have better options...just that people discount them out of hand for mild builds when they would likely hold up fine for a 250HP engine if they aren't beat on...lord knows I have pushed more power and torque than that through a 6.7" axle myself in my old RA29 Celica

 

[Israel]

8"

 

[patrickstapler]

8”

 

[myfirstcar66]

No one ever complained about my 8".

 

[patrickstapler]

That’s NOT what she said...🤣🤣🤣

 

[myfirstcar66]

That's because she was left speechless.

 

[dacofa]

That's because she was left speechless.

Now if you'd had a 9"er, you could have really put the power to her.

 

[GypsyR]

Now boys...