Ok, I had this big other thread where I ran to the junkyard and grabbed a replacement diff.

My truck is a 1978 F150 4x4 with 3.55 gears. I had a parts truck that was a 1979 F150 4x4 with 3.55 gears. Both axles have the clutch limited slip, big bearing ends, 3.25" tubes (tapering to 3" at the ends), and 31 spline shafts.

I pulled the '79 axle to rebuild it to go under the 78, since the tube has rusted through in a spot on the '78. The '79 axle had some water in it, and after cleaning it up I found a cut on one tube that looks like its from a cutting wheel, one spring pad is bent, and one of the shock mounts rusted off and was goober welded back together with washers. The 4 bolt flanges on the end are rusted pretty badly as well.

So I just wanted a new housing that was straight, with no rust, so I could throw my 3.55 limited slip 31 spline carrier and axles in, replace the bearings, and put it under my truck.


At the u pull I found a pristine 9" I found under a 1973 2wd. The tag off the diff is:
WDM-AC-3EA
325 9 331A

So its apparently a 3.25 open 9" from 1973. Its got 28 spline shafts. It has straight 3" tubes.

After getting the axle and looking up the info, it was looking like it should NOT have the same 4 bolt flanges as the 78 and 79 axles do. Only after pulling an axle and comparing the flanges, the housings have the SAME big bearing style 4 bolt flange. Exactly the same. the 78 and 79 have the smaller 3/8" bolts while the 73 uses the bigger 1/2 hardware, but the backing plates interchange. So I was like, wee, this will be easy, right!?

Wrong.

I pull the axle out and this is what I find for the bearings.





The first pictures for both sets are the '79 axle, easily id'd by the rust. As you can see, the 79 shaft has the usual taper style bearing, with a separate pressed in race on the housing. The seal is press on under the bearing on the shaft. The '73, on the other hand, has this cartridge style bearing that I'd not seen before. There is a seal INSIDE the tube, as you can see. There is no race on the housing, the square shoulder of the cartridge bearing rusts on the square shoulder of the tube.

Weirder still is that when I gave them the info for my '78 to get new bearings for the '79 axle, autozone tried to give me that same cartridge style bearing. I just thought I must have given them the wrong GVWR or maybe their lookup was wrong.

The OD of the shaft where the bearing seats on both axles appears to be 1.5". The ID of the housing where the race would press in appears to be the same as well (hard to tell, since I can't get the race out of the '79, I don't have a puller).

What I'm thinking is that I just try to get new cartridge style bearings for the '73, press them onto the '79 shafts, and install them, along with my 31 spline carrier off the '79, into the '73 housing.

what do you guys think? I don't have a whole lot of experience with the ford 9", but I've never used the cartridge style bearing before. It looks like some front wheel bearings I've done on rwd cars and light trucks before.

Thanks!

 

I think I'd take it back and get the right one. The ones with the seal in the housings are car or f-100 28 spline small lug bolt pattern. I have my doubts they will interchange. If you don't have a puller for the race but do have a welder lay some beads down on the race, then it will just fall out.

 

Its not autozone, its the junkyard. they don't take stuff back, they didn't have any "right ones," and besides, the chance of finding a decent 78/79 4wd housing is slim. People routinely upgrade the older housings to 31 spline axles, so I'm sure its possible.

Like I said, the axle is the same diameter where the bearings mount, and its seems like it would be easier to use the cartridge style bearings, but on the other hand, I could just buy new '79 style races and tapered bearings and tap the races into the axle... right?

This is not a truck that is going to accumulate miles. Its only used off road.

 

mysterious double post.

 

The outer race (and seal) should should be included with the tapered bearing (A20/SET20).
The race should pop out fairly easy.

If the axle OD is the same, and housing ID is the same, I'd use the tapered bearings. They were used for the higher load rated axles, must be a reason behind it. Besides, the tapered bearings are lubed by the axle oil, while the sealed bearings rely on the factory packed grease, for life, and the newer ones seem to be lacking enough grease.....

 

I will prolly try to get bearings from autozone tomorrow and see what they have. Bearing longevity isn't a real concern, with 16" wide boggers and a 460 I am doubting the shafts will last very long. I have one extra set of shafts, but Im planning on going with some bulletproof ones eventually.

 

I could just buy new '79 style races and tapered bearings and tap the races into the axle

If the axles are the same just change bearing configuration. That's what I would try to do.

 

yeah. Maybe I'll just pry out the ones on the '79 and tap them in and see how it fits.

 

The bearing and seal combination will interchange. You can swap the tapered bearing/race and the regular bearing. There is a difference in the seal and where it goes.

There were a few rear-ends that had a strange ID bearing but if the ID and OD match, just get the right seal.

 

Yep, slow to update on this, but I bought some new tapered '79 style bearings with the seal on the wheel side of the bearing and they look like they will fit right on. I still have to get the cartridge style sealed bearings off. I already pried the axle shaft seal out of the tube, I was just out cleaning the housing up right now. I'm waiting on a lube locker gasket to put the old 31 spline carrier back in, then I'll do bearings and get the axleshafts in so I can start working on the disc brackets.

If anyone needs the open carrier with 3.30's and the 31 spline axles they came with or the rusty '79 housing and can pick them up in Charles Town, WV, let me know, you can have them for $20. Otherwise they are going to the scrapper cause I have no where to keep spare parts here, and I seriously doubt I'll ever need any of that stuff as spares. I'm out of room already.