Will a 8 inch rear support a nailhead?

I have a rebuilt 30 over 401 nailhead with the SP400 ****** and came across a 67 mustang 8 inch rear end with a gear ratio of 2:79:1. Will this rear end hold up to the nailhead? I want to put it in a 29 tudor with fenders. I did a search but couldn't find what I am looking for. Thanks for the help.

 

Will it hold up? I dunno.......how do you drive? Most likely, it'll be fine if you don't put sticky tires on the rear and make a habit out of launching at 5000 rpm. Some people can break anything, but then, they really work at it.

 

How big are your tires going to be? You should be just fine unless you are running big old steam roler tires, a decent traction control device and it is one helluva nailhead.

Are you sure it an 8" rear from the mustang? it was a 6 cylinder car?

 

Yep the tag is still on the housing and I looked it up. They were in 67-70 mustangs 28 spline 8 inch. I don't know yet which tires I am going to use but don't plan on any heavy launches or driving crazy just plan on driving the wife and kids around.

 

yep they had 8"in them,i got a 8" out of 65 comet

 

I ran a Maverlick 8 inch in this shubox with a VERY healthy 350 chevy/350 turbo with shift kit. I beat it like a rented mule and never suffered any breakage...spent as much time sideways as it did straight. Tires weren't very wide...I'd think a little A-bone would be a featherweight compared to my "box"...go for it

 

really any rear will work in any combo you want if its just a driver, its when you start to put the power to the ground (rocket launches) that thing start to go boom.

 

My one Son is running an 8 incher in his T bucket with a very healthy 306 sbf and he is not exactly careful with it. It has taken the abuse for 4 years now and still runs right along. I am using one also in my new rpu project with a 394 Olds and 8 inch Firestone slicks and wouldn't have used it if I thought it wouldn't take some abuse.

I wouldn't put one in a drag car with slicks, but on the street with normal tires and some reasonable driving you should be fine.

Don

 

401 nail head torque plus switch pitch multiplier vs econo-stang torque rating.

 

A big Nailhead, and a Switch-Pitch torque-converter, but no heavy launches?
Yeah, RIGHT!!!...Hahahahahaha!!!

Sorry...just bein' funny.

 

31 Vicky - That is what I am wondering. Am I asking for trouble you think. Only reason considering it is the rear is a freebe and looks to be in good shape and would fit nicely in the fenders.

 

Starting to put together a 66 425 Nailhead sp400 and looking for a rear end also.
Been looking at later model 10 bolt GM

 

I would be skeptical about the Ford factory 8" rearend holding up to the factory big block Buick 401 with 325hp/445 ft lbs tq at 2800 rpm. There is a reason Ford put the 9" behind the GT390 with with 320 hp/427 ft lbs tq. I have a 8" nodular Ford rearend behind a 302 Ford and have read the nodular Ford 8" can handle up to 300 hp. It is big block torque with traction that will quickly kill a 8" rearend. All things said, keep your foor out of it, and it should hold up. But that's no fun.

 

Slap a pinto rear in if you want, it will work and last forever if you drive normal. Though that is not what we do, usually its like for like on powertrain stuff.

 

Advertised and most likely underrated that 401 was 445 lbs tq @ 2800 rpms. what is that over the econo-stang? 100% more if it 225 ftlbstq , 50% if it was rated at 300.
Tire diameter plays a roll too.

If Ford thought for two seconds their 8" would hold up to 445 lbs of torque they would have used it in such an application.

Cerberus types way faster than I do.

 

i ran a 8 inch in a ot ranger with a stroker motor on spray and slicks no issues for me

 

It will hold up fine behind that Nailhead - Why? Because you're running it in a light 29 Tudor with skinny tires and will NEVER hook it up. A Mustang with a 390 and a Four speed was much heavier in the rear, had more tire and would launch harder. I wouldn't hesitate for a minute to run it, especially at that price.

 

I tested the hell out of one of those rears in an 11 second car in the 90s. It only had 444 point ft going to it in a 2800 lb car. The rear is now in an off topic Cutless with a stout 545 in front of it and has been seeing that combo since about 98 or 99. It doesn't get hammered as much as I hammered it.

That said they are kind of flimsy, if I was going to beat it hard I would look for a different rear but in a light car that doesn't launch wheels up everyday I might run it.

Do you catch my drift?

 

Glad you asked this question, I have the same rear going in my 30 A sedan with a 425 Nailhead and S-P trans. Almost everyone I talked with says the same as here; light car+ skinny tires= smoke show.

 

I would take the 8" and put it in to get you on the road. And keeping looking for a 9" as a replacement down the road.
RB

 

I have put years on a 8" with all the abuse I could give it! What finally got it was me forgrting to torque lug nuts ang losing a wheel at 80! Warped the axle -

 

With minimal upgrades like axles and a posi or full spool i have seen 8" rearends going in the 8's at 140 MPH+.

Lots of guys are switching to them these days due to less parasitic loss than a 9". I got a buddy with a fox body mustang. 8" rear, strange spool, currie axles and launches that thing wheels up every time off a trans brake at 4500 RPM. They are damn tough rearends.

 

Dads Got a 65 falcon falcon circuit race car with a 480HP SB Ford, never had an issue with the 8" and it gets ***holes, its been in it for 4 years, there are skinnier dia axles though which may not handle high HP.

 

I would run it, my wife's comet has the stock 8" in it and makes 362hp on a ch***is dyno. I had a 65 falcon drag car a few years ago with a blown small block, it had better axles and a spool but made double the power.

 

10 bolt GM 8.5? At the drag strip,10 second cars running 8.5 10 bolts.Granted these were auto ******s and the 10 bolt probably had billet bearing caps and an aftermarket carrier,but 550 hp in a 3400 pound car,do you catch my drift?

 

Thanks to everyone for the suggestions, I think I will run it.

 

it took my dad about 15 years of abuse to knock the pinion out of his 8".....even then it didn't wreck the axles or carrier....just the pumpkin....
33 ford 5w, mild 350, 4sp, 275/70 radials......was a 3.73?
like all have said, you will have a hard time hooking it up with all that torque....
you could paint a straight line down the axles & check them....
let us know how it works out for ya

 

IMO
8 inch’s are a waist of time
There’s plenty of 9”’s out there and way more parts availability … its basically the sbc of rears.

If you ever decide to make more power or do some showin off … you won’t embarr*** yourself and walk home

 

The 8" may be fine, however just to note Ford engineers only used the 8" to support their under 300 ft-lb motors. The 390 Mustangs and even HiPo 289 got a 9". I guess they didn't want to risk any recalls.

 

One huge advantage to the 8 inch is less unsprung weight which relates to a better ride. There are tons of cars running around with them and I bet very few of them ever gave any trouble in thousands of miles of use.

Don