Rear End Identification Help - Pics

Hey all, could use some re-***urement here. This rear was advertised as a 9" with 3.73 posi (trak loc). I got there and looked it over, appeared to be an 8" to me. No ID tag. The guy had just bought this car for parts, and who he bought it from said it was a 9", so he just ***umed it was.

Now, I know most 9's have the gear hump. This one has a rounded back. But if I am not mistaken, the pre 60's 9's had a rounded back, so....

It also has 3 vertical ribs, which most 9's I have seen have 1 or 2.

There is NO "N" or "W" on it either. I have not cracked it open, just brought it home. Can you tell by these pics what it is for sure?

EDIT: I CAN get a deep socket on every nut, including lower ones.

 

Looks like an 8" to me. Can you put a deep socket on that bottom carrier nut below the pinion? If so, it's an 8".

 

If it's a 9 there should be one bolt down by the pinion that you can't get a socket on and yes some early ones did not have the gear hump.

 

I didnt try it, but looking at it I would say yes, you can get a socket on any of them. The bottom 2 are kind of tight, but i think room for a socket. I had read that before and also mentioned to the seller that same thing. I was not sure if all 9's, including early ones, had the same socket/nut issue.

 

The 2 casting numbers, D 1 tells me that it is for a 71 model, but I can't make out the 3rd character, if there is one. Third letter would be for the car line. A= Galaxie, S=T-Bird, O=Fairlane, so forth and so on. What type car did the rear come from? Another way to tell, is if the bottom two nuts are only accessible only with an end wrench, then it is a 9-inch.

 

This rear came out of a early 70's maverick, but I ***umed it wasnt the stock rear, as the mav didnt come with a nine far as i know and I am pretty sure they didnt come with posi either. Without the tag I dont know what it came from for sure.

 

Its an 8".

 

I just went a checked, I am able to get a deep socket on ALL nuts. So if there is NO 9" made where that is possible, then its got to be an 8.

 

If it is narrow enough to work under a Maverick, and is a 9", it probably came from a high performance Mustang or Cougar. The only other narrow 9" I can think of, would have been under the '57-'59 Fords (there are probably more).
How much horsepressure are you planning to put to it? 8" rears hold up well in cars I'm familiar with that run 300-400 hp, especially with automatic trans. Hope you can figure it out and that it works out ok for you.

 

A 3:73 positrack 8 inch is still a good find.

 

yup it's an 8". still cheap though.

 

Most deff an 8 with all those ribs on the chunk !!! >>>>.

 

If the seller did not know the difference in a 8 inch or a 9 inch ( Or he is lying ) ... why trust his word on the gear ratio and the posi ???

I would have to pull the center section, count the teeth and see the posi to believe him.

 

I think the 73 maverick 8 inch I have has a 2 73 gear

 

if you measure from backing plate to backing plate it will measure 49" for the Maverick, 51" for the Mustang. And yes the Maverick GRABBER came with a 9". very rare find.

 

take a pick of the bottom bolts. i would simply pull axles and measure the ring gear so you know if its one of those wierd lincoln rears.they are like
9 1/2 or 9 1/4 (someone clarify please) and also you can check posi....good luck

 

It's an 8" for sure, and way good deal for the money. Most 8" rears are open and posi pumpkins bring double that much at the swap meets. Good Score !!!

 

Very helpful page here

http://www.kevinstang.com/Ninecase.htm

 

I agree with that, I have no idea what the gears are. I felt good about it being posi, as it functions like one (spin same direction only, hold pinion and neither will turn, etc...). So I bought it mainly for that reason, because I been looking for an 8" posi chunk to throw in my current comet 8", and they want $500 up for them because they are very hard to find, and expensive to build your own. So, hoping this will work out.

 

looks like an 8 to me

 

This is another thing. I have a (hope to be) hot 347 stroker going in the car, hoping for 350-375 rwhp. Havent decided on trans yet, leaning towards manual 5 spd. (tremec).

I found an old 65 mustang 9" also with exactly the same width as my customline 57 1/4" ($300) with 3.00 open gears. I really want posi though, so would have to spend hundreds more to achieve that. Think this 8 will hold up?

Are all 9" 28 spline chunks interchangeable like the 8's? Would it be fairly easy to find a 9" posi at a boneyard?

 

definitely an 8 !

 

Some pics of a 9".

Not the view you may need, but it may help.

If need be I can pop some pics of the housing dead on as well as a carrier on the bench.

Note that the housing bolt/gasket pattern, is a little more rounded than the 8".

Far as I know all of the early 60's half ton pickups have the rounded 57 p***enger car housing back.
Dimples too.

Most early 60's pickups, even when they run the HD 1/2" axle bolts vs 3/8" - have 28 spline axles and most have the narrower brake lining. (1 3/4" vs 2 1/4")
(There is a 2 1/2" lining width out there, but it's in later pickups and perhaps the bigger p***enger cars.









If you're running a somewhat light car and not too much horsepower 28 spline axles work fine.
The 8" 28 spline axles are virtually the same as the 9" axles 28 splines.

You can tell an undamaged open or locker diff by keeping the companion flange - where the driveshaft bolts to the pinion nose - from turning.
With the wheels off the ground, turn one wheel and watch the other.

If the other wheel turns in the opposite direction it's an open.
If they turn in the same direction it's a locker.

Be aware that damaged differentials can act the opposite from what they actually are.

Best of all is when you find a FoMoCo rear axle and the br*** tag is still on it.
It'll say something like 3L70 indicating a locker and 370 for a non-locker.

You can also check the ratio by spinning one wheel with the other on the ground and counting driveshaft revolutions.
If the driveshaft turns a touch more than twice with one turn of the wheel it's a 4.10 or 4.11 etc.

If it's a locker both wheels need to be off the ground and the driveshaft revolution will be the ratio.
IE: 3.7 turns of the driveshaft to one turn of the wheel show a 3.70 for Fords and 373 or 3.78 for other makes.

 

Thanks for the detail C9. I notice also your fill plug is in the back on the rounded back and mine is in the chunk. I believe it is an 8, and everyone here does to.

I have a 56 customline, so I guess around 3200 pounds.

When I hold the pinion still, neither wheel will turn in any direction. When not holding the pinion, both will turn in the same direction only. From what I know without actually cracking the case, this means locker.

Whats the best way to determine the gear ratio with it out of the car, no wheels or driveshaft attached? Should it be stamped on the gears if I crack it open, or do I have to count teeth?

 

count the turns on the pinion yoke it takes to rotate the wheel/drum/axle flange one full revolution. Not the best way but quick and not messy to get close at least an idea.

 

Edit: I just counted the pinion gears too, couldnt stand it anymore. 39 ring/13 pinion, shows me to be 3.00 ratio. ****s, was expecting 3.73....live and learn ehh...

Well, I thought I would post my findings, after cracking her open....

I believe everyone was right, not that I ever doubted you What i found is a casting number of C7OW A, which what I can find is an 8".

I am trying to determine the ratio now. The numbers stamped on the side of the ring gear are hard to read as seen in 1 pic below, but appears to be a 4210 (but the 1 and 0 are hard to truly make out). Which on some rears could mean 42 divided by 10 = 4.2 ratio which is possible but very rare.

I counted the ring gears, and its actually only 39 teeth (unless bud light got in the way). Did not count the pinion gears, got late on me. From what I read, 39 teeth on the ring gear on an 8" can only be 2 things, either 3.25 or 3.55. (remember this rear was said to be a 9" with 3.73 posi)

SO, setting the yellow marked tooth in a certain spot and spinning the pinion by hand, I can turn it just barely over 3 turns to get it back to where it started. So I THINK this is a 3.25 posi 8". Pics follow, what do you think?

 

I have an 8 inch in the car now with 2.79, non posi. With the motor I will be installing, the 3.00 will not be a good match, so will probably throw new gears in or keep shopping for a 9.

 

I don't claim to be an expert on this stuff but that doesn't look like a posi unit to me.

Posi units have indentations on the back of the unit (opposite side of the main ring gear). The bolts are recessed into the unit rather than a fully flat surface. Do a search on Ford 9 identification and you should come up with some pages that show the differences.

Here's the posi unit I used for my truck.

 

What kind of car is the rear axle going in?

I just put a 3.00 (with 30" tall tires) in my 32 replacing the 3.70.
The 3.70 is a great performance gear, but out here on the long desert highways the 3.00 is very nice . . . even in town.

Looks like a mileage increase as well, but the only mpg check I've done so far was running down the long grade(12 miles and steep) to Laughlin.
About a one mpg improvement there.
Running 65 - 70 mph fwiw.

Guessing perhaps a two mpg improvement on the somewhat flatter runs to Vegas or Prescott etc.

I have a 3.25 locker in the 31 on 32 rails roadster project and with 28" tall tires it should work out fairly well on the highways and in-town.

Fewer revs per mile than the 32's 3.70's and more rev's than the 3.00 along with alloy 31 splne axles.

The 31's a little more performance oriented and will have about 40 more HP over the 32 - both with 462" Buick engines so it should work well.

Fwiw, the 32 is a 2400# car (empty, but full fuel etc.) and runs 28 spline axles.

The big tires with their 8" tread width are fairly soft and grab harder than the hard slicks from back in the day.
They did well at the airport 1/8 mile drags and I did ok against a couple of big slick doorslammers.

Open diff as well, but the little car launches fairly hard all things considered.

I had the axles out a few months back and they haven't twisted far as I can tell.

I've