Alright, so at about 6pm last night I decided to take the 3hr trip to go pick up my 9inch rear end. It was cheap, spins freely the whole nine yards. I'm going to tear into it and inspect it, but when I'm in there I want to clean up the inside as it looks like it hasn't been taken apart since 1968. First off I would like to know what kind of mustang the 9 inch came out of in 1968, like what models were offered with the 9 and also what gearing I would be looking at stock. I know it's the 28 spline.

SO questions.
-Possible gearing?
-Best way to clean it up on the inside, and also break up the rust on the outside and the best way to paint it
-Best way to build it up to handle about 400hp eventually

For now I'm keeping the 3spd in it. But it's now got the 351W in it.


Also if anyone might be interested in buying the 1974 302 that was in it, damn near complete, had to snag a couple bolts from it, oil pick up and alternator bracket let me know. Thing ran great, just wasn't enough power for me.
Or if anyone is interested in the rear end that is in my car now, believe it's an 8 inch, everything works fine, just not beefy enough. I know, don't fix something that ain't broke but I guess I'm greedy with this car haha
I live in Jacksonville, NC in case anyone is interested. I could deliever as far north as cleveland ohio if your near 77 or anywhere within a days worth of driving. Just let me know.

Thanks for all the help ahead of time

 

i would love that engine, but I could never afford shipping :-(

as for your axle. it is very easy to find out what gearing it is currently.
put the thing on blocks so the axles and pinion can rotate freely.

1st find out if it's open diff or locked in any way.
for that hold the pinion (so it cannot turn) and rotate one axle. if the other axle goes the exact other rotating direction it's an open diff.

now measure the gearing.
for this just rotate the pinion exactly so many times that one of the axles did a complete 360degree turn.
if you had to rotate 3.5 times, it's a 3.5:1 gearing

if it's open rear you have to double the measurements
so if you turn pinion in an open diff exactly 1.75 times and one side of the axle did exactly one turn then you have 3.5:1

 

um as for the 9 inch in a mustang idk

i konw for sure that my 1970 mach 1 with a 351 cleveland has a nine inch

so if a 68 came with it it could have been a 390 or at least a 302.

seems kinda over kill to put a 9 inch behind a 302 from the factory, but i guess it could have been ordered like that.

 

There's a wide array of available gears for the Ford 9". It's up to you to determine the best gear ratio for your driving style/powertrain combination. While your 2.75 gear will keep the RPMs low cruising down Western Blvd, it won't do you any favors when it comes time to do a crowd pleasing burnout. The opposite end of the spectrum would be numerically high gears... great for a burnout/acceleration, but not so great when cruising at higher speeds. A fair compromise is usually a gearset somewhere in the middle.A 3.25, 3.50, or 3.73 gearset seems fairly popular.

While the center section is removed, you can easily verify the gearset ratio by dividing the number of pinion gear teeth into the number of ring gear teeth.

It is not advisable for a novice to change gearsets. There are some special tools required andsome critical adjustments that are best made by an experienced mechanic.

The inside of the rearend housing should look pretty clean. The assembly is fairly well sealed from the elements and unless it's been drug up from the bottom of a lake/pond, should need nothing more than a good wiping down with a mild solvent such as brake parts cleaner. While inside the housing, I recommend that you change out the axle tube seals. These seals are similar to what you'd find on the front of a timing cover and can be easily "knocked out" and "tapped" back in. The seals are readily available locally at most auto parts stores.

The outside of the housing is an entirely different story. The outside can get pretty rusty. Sandblasting the exterior of the housing would be the simplest method of cleaning it up, but a wire wheel on a hand drill can get it cleaned up pretty well also. As with any bare metal, prep, prime and paint. I've used automotive paint and rattle can paint with the results being very similar. The rattle can paint should hold up fine for a number of years.

The Ford 9" is a pretty stout unit even in stock form. Building it back to stock specs should handle 400HP w/o any problems. If you anticipate spending a lot of time at the strip running drag radials, the 9" can be beefed up further by switching to 31 spline axles and carrier. I don't feel this is necessary for a daily driver that wouldn't be subjected to repeated abuse. While you have the rearend disassembled, you may want to think about replacing the "open" carrierwith a "posi"/limited slip unit. This isusually a fairly big expense, but if you're looking for better traction, it's fully justified.

Small world. I live in New Bern.

Dave

 

390 engine was the smallest it came with from the factory in 68 i believe.

 

390, and later the 68-1/2 R-code 428CJ. I'm not sure if the GT350's got it, but the GT500's surely did.

 

Thanks guys for all the information. I have so much going on with the car right now to bust it out myself in any sort of timely fashion. The next three days I'm taking a break from it.

Another question and I swear I might feel stupid. I had someone look at my rear end and he said it "looked" like an 8." I got under there today during lunch and it looks so much like my 9 inch. On the back it has three dimples, two horizontal on the bottom and one above the right one. The drive shaft also connects more to the passenger side of the car, and a "proffesional" I stress that word, claims that if it bolts in from the front, then it's a 9inch. It also appears to have eleven bolts like the 9inch. Can anyone tell off this explanation what it is, because I might have a 9 inch going up for sale.

 

... a "proffesional" I stress that word, claims that if it bolts in from the front, then it's a 9inch
nah
7.25" were integral
8" and 9" are both pumpkin style (3rd member bolted in from front)
There's a website, but I cannot say if all the info in there is correct:
http://www.kevinstang.com/Ninecase.htm

if you need to know for sure take out the diff and measure the ring

 

Exactly what I thought. They claim so much stuff at the shop I'm installing the engine, but they don't know much, so I let what they say go in one ear and out the other and do it my way. Seems to be working well.

 

To assist you in determining if you currently have a 9" rearend, here's a picture of my 9" housing. Notice the pronounced "bulge" that enables the 1" larger ring gear to fit into the housing.



This type of 9" housing would be standard issue on '67 and later Mustangs (when behind the right engine/trans combo).

Some earlier (65-66) Mustangs had a different type of housing that did not incorporate this "bulge", but instead looked similar to a "smooth" 8" housing.

In the belowpicture, you can see the carrier to housing attach studs/nuts. One sure way to determine if you have an 8" or a 9".... if you can fit a deepwell socket onto ALL of the studs/nuts, it's an 8". The lowerstuds/nuts (barely visible in the photo) on the 9" cannot be removed with a deepwell socket... the design of the 9" carrier prohibits a deepwell socket from fitting onto some of the lower ones.



Dave