70 N Case Rear Housing

I parted out a 70 Standard H code recently. When I pulled the rear axle out from under the car I was surprised to see it had a Nodular case in it. It is an open axle and the tag reads correct for the car according to make and date. It does have the N caps on the inside but it has 28 spline axles in it.

My question is will the N caps and pinion work with a 31 spline set up if I decided to build a posi unit out of this? And could this have come in this car originally?

Pretty sure you can put a 31 spline carrier in that housing. I know that different housings have different sized side bearings (there are two sizes as I recall) so you’d have to get the right bearings for the housing but that should be no problem.

100% compatible with a 31-spline carrier and axles.
I don’t know why an H-code would have received an “N” case differential from the factory, do you know when your car was built? Its possible they were using up excess inventory, like the 8,000 RPM tachs that show up in some non-Boss/non-Eliminator Cougars from late in the '70 model run.

The N case has one or two places where a date code is cast. Does it jive with the build date of the car?

Yes, that is correct for 2.75 open, 1969/1970, 28 spline per your tag. The “N” is a bit strange to find but there’s nothing that says it’s right or wrong.

It looks like the date is 9K23 on the case. I do not have a build date on the car since the door tag sticker was almost unreadable but the rear end tag and the washer jar both had june dates on them and the VIN is 565407 which should be fairly late in the run. The mechanical parts of the car were very much untouched with the OK stamp still on the front of one valve cover, a complete CA emissions set up still inplace and the rear end and drive shaft looked original too. So you never know, it could have come with the car. The K date on the case seems a little early for a june or july built car to me but you still never know. My 69 Q Code built in May had a K intake manifold on it and it is original to the car.

I’m glad to hear it will work to suit my needs and build a good posi or track loc unit for my 69 Q Code project which has an N Case just like this one only its a 3.00 peg leg, I have not looked to see if it has 28 or 31 spline axles though. I’ll have to pop a hub cap off and take a look.

That tag is correct for a 69/70 Cougar/Mustang with open 2.75 and 28 spline axles. If the copper washers are in place behind the stud nuts it is likely original. Can’t make out the date on the tag to see if it works with the case cast date though. First nodular with 28 spline axles I have ever seen.

Kerry, looking at the tag in the pic, it looks like OFC for '70, F-June, C-3rd week to me. John

Thanks John the tag is not original to the case with an 8 month later tag. I would venture to assume the tag is off the original non Nodular case that was in the car when it left the line.

Have you spun the wheels/driveshaft up in the air to check the ratio? If one side goes forward and the other backwards it’s an open. If they both turn together someone changed it to posi. Pull the wheel and look at the axle end at the drum – post a picture. Very obvious how many splines from a pic.

I have the axles out and they are typical 28 spline axles. The unit is definitely an open. I have the whole chunk out of the axle housing but its been sleet, snow and rain for the last 6 weeks here so not much happing outside right now.

I am going to rebuild it as a 3.25 or a 3.50 locker for my 69 Q Cat and keep the 3.00 open N case that is in that car now as original equipment that stays with the car.