Technical ford 9in.

I have a 9in. unit that has 4 spyder gears and 3 pins and no place to put the posi steels so I guess it a open unit was told it to be a limited type has 31 spline and 1966 date code don't know what the rest of code is for . any help would be appreciated ... thanks ps have some pics if would help

 

Yeah, pictures always help!

The clutch plates on a 9 inch are on only one side of the differential, not both sides like most others.

 

In todays world, there are MANY types of "posi" units out there.
As has been said, in this case, a picture would help greatly.

Mike

 

They did make a 4 pinion open carrier for the 9 inch.

 

All the factory posi carriers I have seen, have the ring gear bolts mounting surface machined and sunk into the carrier, the bolts on the open carriers are not sunk into it. If this makes any sense

 

Yes and in the 9-3/8 too...28 and 31 spline..

 

I'll add a picture. This is the easiest way to identify a factory limited slip.
It also has the crack running around to all the bolt holes, which is quite common.

 

heh...that's why I don't have any of them to take pictures of! After fixing a couple for other people, I decided I never wanted to run one.

 

It really tests your pucker power when you are hooked up and just about to the 60' lights and that carrier decides to come apart.

 

Looks like a machining mark to me.

 

The other pic..

 

Easier to see with the springs still in it.

 

Yup, that's a factory piece. A lot of upgrades/replacements available that don't do that. Often.
Think Strange, Currie, Moser, etc.

 

That must have been one drunk machinist.