Quote:

I was rummaging thru my gear sets last night thinking about a gear change for the Dart.
I have a 3.91 open chunk that has no number on it. (489-741-742)
I was told they were the older units and were typical to the 742 cases. Anyone have any info?
I'm going to roll a clutch posi unit into it and want to make sure it doesn't have the small diameter pinion.
The Dart has slicks and the 340 makes decent power, I don't want to waste time with something that might break.



I was expecting a picture of the chuck , not the car ...

Are there any numbers or letters at all on the chuck anywhere?

The smallest part of the pinion is where the outer pinion bearing slides on , behind the yoke. The 741 and the 489 use the same bearing, 742 is the same size too, same bearing ??? ... anyway if you are worried about the pinion breaking you'll strip the teeth off the ring and/or pinion before you break the pinion stem itself.