9inch diff axel worn

[Chocosmith]

Hi,

I have a ford 9inch 31 spline large bearing diff. I needed the bearings replaced on each side, they were both in bad shape.

The machine shop rang and said that once the retaining/wedding ring had been removed the bearings basically fell off. He said the axels are too worn and there isn't enough meat left on them to put news ones on without risking them spinning and killing the housing as well. He suggested getting second hand ones, or new.

Questions:
I thought if the wedding ring was pushed up snugly to the bearing then the risk of the bearing spinning would be minimal?
also don't understand how axels wear other than if the bearings spun?
If bearings spin isn't catastrophic failure within about 50miles?

Cheers,
Choco

[1972hiboy]

I wouldnt depend on the ring holding the bearings from spinning. Things wear out in the oddest ways sometimes. Maybe its had a few sets of bearings put on in its lifetime? I would test fit the new bearings, if they do indeed slip over the axle without the need for pressing then its most likely a good idea to source some other axles.

[Busboy]

I disagree, You can peen the journal surface upon which the inner bearing race resides. This can be done with a good quality punch. Just put a dozen or so punch marks on the shaft. I'd then use some Loctite stud and bearing mount compound. The retaining ring should in fact prevent the inner race from spinning on the shaft but the peening will help also. Unless the axle bearing locks up there is no tendency for the inner bearing race to spin on the shaft.

[cep62]

The problem with worn axles is the bearing holds the axle retainer in place.
if the ring and bearing slip , the axle will slide out .
At best you stop moving , at worst you'll peel your box side .
I had an old plow truck that saw few road miles and I tack welded the ring to the axle but that's not recommended.
If you trust your shop then follow their recommendation.

[Busboy]

You've got it backwards, the retainer holds the bearing in place, not the other way around.

[ultraranger]

BOTH the axle bearing and the bearing retainer ring gets pressed onto the axle (both should have a very tight fit on the axle journal). Something must have been really wrong if the I.D. of the axle bearing was spinning on the journal of the axle.

You mentioned having a Ford 9-inch with 31-spline axles. Are these custom axles? Reason I ask is because none of the Ford 9-inch truck rear ends before 1973 came with 31-spline axles. All truck 9-inch rears before 1973 had 28-spline axles.

There was a Ford 9-3/8" rear end available in the 1968-1972 Ford F100s. While it's a very close cousin to the 9-inch, the 9-3/8" rear end is not the same. The 9-3/8" rear ends came with 31-spline axles. In fact, they came with two different versions of 31-spline axles. It just depended on what differential was in the rear end as to which 31-spline axle version the rear end got. If a 9-3/8" rear end came with a Traction-Lok differential, the 31-spline axle bearings measured 3-9/64" O.D. by 1-5/8" I.D. If the 9-3/8" rear end had an open (single track) differential, the 31-spline axle bearings measured 3-9/64" by 1-17/32" (same axle bearing dimensions as the 28-spline axles in the 9-inch truck rear ends).

I have a pair of 31-spline axles in my stock '69 F100 9-inch rear end housing that came from a '71 F100 9-3/8" rear end with an open differential. I replaced my stock '69 C7AW-E single vertical rib 9-inch 28-spline 3.50 geared single track 3rd member for a Ford Daytona 9-inch N-case 3rd member with a 31-spline 4-pinion Traction-Lok differential with 3.50 gears that I pulled from a '75 F150 4x4.

[Chocosmith]

Hi all thanks for the replies.

I'm not able to measure the bearings but from the housing has the turn down on the rib so it looks like it is a 9 3/8th diff (see the attachment). If this isn't 100% accurate does anyone know of another measurement that works?

I'll ask the shop to see if the retainers stick on hard and fast, if so I think I'll try my luck with peening the surface. That way I'll have more time to keep my eye out for a good 9 inch centre and axels.

Cheers,
Choco

[ultraranger]

Hi all thanks for the replies.

I'm not able to measure the bearings but from the housing has the turn down on the rib so it looks like it is a 9 3/8th diff (see the attachment). If this isn't 100% accurate does anyone know of another measurement that works?

I'll ask the shop to see if the retainers stick on hard and fast, if so I think I'll try my luck with peening the surface. That way I'll have more time to keep my eye out for a good 9 inch centre and axels.

Cheers,
Choco

The rear end you have pictured is definitely the 9-3/8" rear end and not a regular Ford 9-inch rear end. If the axle journals are damaged, I would not advise peeing the axles to try and make the bearings and retainer rings tightly grip the axles. If the bearings and retainer rings do not have a good, solid surface to be pressed onto, you will be at great risk of the axle and wheel sliding out of the housing. If this happened, I think you can figure out the type of damage this would inflict.

You can put a 9-inch 3rd member in a 9-3/8" housing but you can't put a 9-3/8" 3rd member in a 9-inch housing --at least not without notching the 9-inch housing to install the larger 9-3/8" 3rd member. The next problem with putting a 9-inch 3rd member into a 9-3/8" housing would be the 31-spline axle issue --if the 9-inch 3rd member has a 28-spline differential. Dentside ('73-'79) 31-spline axles will not fit in an earlier, narrower, '68-'72 9-inch rear end housing.

'68-'72 F100 9-3/8" 31-spline axles are narrower than Dentside axles (9-3/8" 31-spline axles are the same width as '68-'72 F100 9-inch 28-spline axles.

You will have to know what differential is in the 9-3/8" rear end to get the correct axles/axle bearings. As I mentioned, the O.D. of both versions of the 31-spline 9-3/8" axles are the same as the axle bearing O.D. for the 28-spline axles in the 9-inch rears (3-9/64") but, depending on what differential is in the 9-3/8" rear end will determine if the axle bearings have a much larger 1-5/8" I.D. or whether they have the smaller 1-17/32" I.D.

I put the 31-spline axles under my '69 F100 and I pressed my own axle bearings and bearing retainer rings on. I've pressed a lot of axle bearings off/on over the years and I can tell you that most definitely the 31-spline and 28-spline axle bearings in these trucks BOTH should have a VERY TIGHT grip on the axle when they are pressed on --not just the retainer rings.

The axle bearings and the retainer rings should NOT be pressed on together at the same time. The axle bearing should be pressed on and fully seated first, followed by the retainer ring being pressed on. Pressing axle bearings and retainer rings onto the axle is a one shot deal. If you got a brand new set of axle bearings and retainer rings, pressed them on and then realised you forgot to put the stamped steel 4 bolt axle retainer on first, you can go ahead and throw the brand new axle bearing and retainer in the trash. They will be no good. The act of pressing the bearings/retainers onto the axle stretches their I.D. If you have to remove the axle bearings/retainer rings (whether they are brand new or not or whether they have zero miles on them) they will never be that tight on the axle journal again, if you have to remove them for any reason. They are trash can material if they are removed after having been installed.

[cep62]

You've got it backwards, the retainer holds the bearing in place, not the other way around.

I was talking about the axle retainer , it is held in place by the bearing ,and then the bearing retainer ring.

[ultraranger]

Both the bearing and its retaining ring grip the axle to keep it from sliding out through the center of the stamped steel 4 bolt hole axle retainer. The stamped steel axle retainer bolts to the housing's end flange and keeps the axle from coming out of the housing.

If the axle bearing and its retainer ring lets go of the axle, the axle will slide out the center opening of the stamped steel retainer and then bad noises will follow.

[carnuck]

I recall a repair bearing that came with a built in seal, slightly smaller ID and Loctite Red Stud and bearing mount. Last one I did was around '97.

[Busboy]

Peening of journal surfaces is a common repair procedure done everyday in shops everywhere. DON'T BE SCARED OF IT. By the same token pistons are knurled to raise the surface on worn skirts. Valve guides are knurled for the same reason. Probably the most common use of this procedure is in wheel bearing hubs that have a slightly loose race in the bore. Works perfectly. Remember there is no inherent force trying to spin the inner race on the axle shaft. Again only if the bearing starts to lock up would there be a force testing the press fit of the inner bearing.

[carnuck]

Skirt knurling is okay for low RPM motors, but builders usually won't do it anymore in practice due to the high failure rate of pistons afterwards in "modern" engines. Aside from that, 100% agreement on the peening the bearing seat to keep it from moving if needed.

[radioactivelarry]

Sounds to me that he is telling you the axles at the bearing surface are worn. Most likely the bearings froze and spun on the axle surface itself wearing the surface where the bearing seats on the axle. That's why they are pressed on. the retainer is your insurance policy the bearings don't ride out of the axle and having it slide out of the housing. If the axle surface is worn the axle will move up and down killing the seal. The retainer won't keep that from happening.

[Chocosmith]

An update

I went ahead and got them to pen the axle and put in new bearings.

I did a 5 mile slow round trip (I'm on a farm so private roads and paddocks) and when I got back the wheel had moved out a quarter of an inch. I could hit the retainer and bearing back to correct position with a piece of pipe, so it's now very lose.

I checked if the shop used the correct I.D bearing 1 5/8" and they have.

So I'm on the hunt for a 9 3/8 axle of a wreckers, so far very unsuccessful as Australian wreckers don't seem to have bump side f100, only dent side and newer .

Other options are

an xc ford fairmont with disk but it had an off centre pumpkin and is 61", I'm not sure if this is a problem. I'd need new rims for the 4.5" bolt spacing

The other is a 74 F100 9". But I'd also have to cut and move the spring and shocker perchers maybe have to purchase new rims anyway due to offset anyway.