ford 9 inch yoke

[1972SportCustom390]

I have a ford nine inch with just a regualr differential nothing special, everything looks fine, it has 3.70 gears, it worked fine when i took it out. But i noticed the yoke has a little play in it. Is that normal?

[FORDification]

What do you mean "play"? In-and-out, side-to-side, or in a circular pattern, as in the way the driveshaft would turn it? The first two are not normal...the third is, which is between pinion and ring gear, which are not supposed to be 100% meshed together. A little play is normal, a lot is not and indicates worn parts.

[1972SportCustom390]

well there is a little play side to side. nothing seem to worn out. at first glance i was thinking it couldve been missing the oil slinger. could that make it have play?

[FORDification]

So you mean you can rock it side to side, without the yoke turning? That would probably be worn pinion bearings. If this is the case then it's probably something that should be addressed before using it much. That kind of play is going to cause rapid wear of the ring and pinion, due to constant variations of the gears' engagement with each other. There is no oil slinger on the pinion gear. Here's an exploded-view schematic:

http://www.fordification.com/images/sch ... ential.jpg

[1972SportCustom390]

well i was thinking maybe a piece for 4670 was missing, is that possible for it to move with that missing?

[FORDification]

That's just a thrust washer. It'll be there....and even if it wasn't, it wouldn't cause side-to-side movement. If you can rock the pinion gear side-to-side, it's worn bearings.

[390Nut]

You may also find, depending on which carrier you have, that the hole that fits the internal pinion bearing (#4625 in the diagram) might be fractured, if the front bearing gets to much play in it. When I had my diff rebuilt for the exact same reason you are talking about, there was very little play, but it wasn't a whole lot of miles before that play was really bad slop, and lots of clunk. Ended up throwing all the gear oil out on a freeway trip, and burned up my gears.

Once I got it apart for the rebuild, it was found to be cracked at that spot, meaning a new carrier.