Ford 9" gears in a 9 3/8" housing

[power_by_429]

I posted this in a very old thread on the other site. Then I was informed that place is a sinking ship so I came over here. There are alot of misconceptions on this topic so hopefully this will help someone searching for the correct information like I was.

Been on this ( 9" parts in a 9 3/8" carrier ) kick for the past week. I feel like I am close. According to all of my measurements and countless checking, the key to making this work is getting the pinion deep enough. Even though the 9 3/8 pinion is larger overall, the spur itself is actually .100 thou thinner. This allows clearance between the front face of the gear and the diff case around the third pinion bearing. Running the numbers with a depth mic it seems the 9" pinion needs to go deeper than the case will allow so I have been removing material from the area above the third pinion bearing. As I have been fiddling with it. The gear pattern seems to get better and better the deeper I go with the pinion. I'm not at an acceptable wipe pattern yet but I am gaining with each test fit. I decided to post here because the fireside chats with axle gurus saying it's possible gave me the encouragement to press on and at this point I am close enough to believe this is true. My first test fit showed almost zero wipe pattern so I completely understand why others have tried and failed as it's not a just bolt it in and go solution. The plan is to use a solid spacer behind the large pinion bearing once I have the clearance taken care of and I know how thick it needs to be to get inside that envelope of acceptable gear mesh. Once I have a working unit I will post pics with specs of what worked for me.

This all started with a stripped out traction loc spider gear that is NLA and a detriot H case locker.

This is what worked for me. Your results may vary.

After playing with gear mesh for days and slowly removing material from the 9 3/8" case, I landed at 0.190" solid spacer thickness behind the large pinion bearing. This is with zero shims on the pinion carrier. If you do it right it's an easy work around for the lack of available 9.375" carrier shims. I used a speedway motors solid spacer kit that I cut to size in the mini lathe.

I would say I removed an equal amount of material from the case. My 9" pinion was just barely starting to bind on that area even with a .018 carrier shim installed and no bearing spacer. I also took .010 off the face of the pinion gear to help with clearance and surface finish to prevent binding when things heat up. With everything fully installed its got about .010 clearance in the effected area.

It's tight in there but everything's working great so far. Drove a few hours at highway speed to EJS this weekend, beat on it on the trail, drove it a few hours home. No issues. Loving that locker.

 

[Tech Tim]

Awesome! Glad you gave it a go and posted pics.

Got tired of telling people over on the old board that it can be done.

 

[rattle_snake]

What is the advantage of 9" gears in a 9-3/8 carrier? Why go to all the work?

 

[Tech Tim]

Cheap way to get a big bearing 3rd. But unless you have a 9-3/8" 3rd laying around, it really isn't worth it.

Aftermarket big bearing 3rds are fairly inexpensive these days and are stronger.

 

[power_by_429]

I guess the only real advantage is 9" parts availability and the 3/8 case is the most beefcake factory carrier available.

With the prices of aftermarket 3rds so low these days there isn't much reason to do this unless you already have a 9 3/8". I did it because I wanted to rebuild my original 9 3/8" traction loc diff but I couldn't get the correct spider gear for it. While searching for those I came across the abundance of nascar detroit lockers which have 3.25" carrier bearings. Since I couldn't buy a normal 31 spline detriot anywhere without waiting on lead times, and I already had a carrier with 3.25" journals I decided this was a good solution for me. I'm just glad I was able to find enough info saying it is infact possible (thanks Tim!) Before I gave up on it. That first attempt at a wipe pattern was a little discouraging but in the end it worked out well and this is proof that you shouldn't always believe the internet naysayers without trying for yourself.

 

[Tech Tim]

It's interesting you had to move the pinion so far out.

iirc: The one I set-up years ago needed shims under the pinion support and it was a bitch finding some. But that was twenty+ years ago, maybe I'm not remembering it correctly.

I have set up a few regular 9s over the years that didn't use any pinion support shims and we had to shim under inner bearing like you did, but nowhere near the amount you did. I'm talking like .020"-ish.

 

[power_by_429]

Haha yeah I was going a little bit at a time, It felt strange but the wipe pattern just got better and better. I wonder how much the gear ratio would change my results. The 9 3/8" 3.50 ring gear is way thicker than the 9" 3.50. Diff offset seems pretty damn close from the trac loc to the Detroit. Can't say I measured both. The pinion supports are way different obviously. Lots of things to consider. Just glad it works.

 

[bdkw1]

I did this 25ish years ago, I just cut the case down to get the pinion depth.

I only did it out of desperation lol. Didn't realize the third I had was a 9-3/8. Needed the diff back together that day. Have machine shop, will make fit.

 

[JR4X]

Refresh my memory please. Didn’t the 9.375 nodular 3rd only come in E150 vans?

 

[Tech Tim]

Some pick-ups and the bigger Lincoln cars too.


For trucks - According to BlueOvalTrucks:

Specifications:

• 9-3/8 Inch Ring Gear
• Drop Out Style Rear
• Sometimes Called a 9-1/2”
• Can Be Put In The 9-Inch Housing And Looks Nearly The Same
• 31-Spline Axle Shafts
• Removable Pinion Support

Applications:

• 1964-1975 Ford F-100
• 1975-1976 Ford E-150
• 1964-1975 Ford F-150

Notes:

Only the 1968-1972 Ford F-100’s with a 9-3/8″ rear end had 31-spline axles (there are actually TWO different 31-spline axle versions in the 9-3/8″ rear ends). One with a 1-17/32″ axle bearing journal and the larger 1-5/8″ axle bearing journal.

A 1968-1972 9-3/8″ rear with an open differential got the 31-spline axles with the 1-17/32″ axle bearing I.D. The 9-3/8″ rear end with a Traction-Lok differential got the larger 1-5/8″ axle bearing I.D.

 

[power_by_429]

this 79 bronco was ordered as a trailer special (higher gawr) with a traction loc. It came with a 9 3/8" factory. Can't speak much on the cars or vans but I would think anything of the right era could have had one depending on options.

 

[JR4X]

That’s crazy, I’ve been messing with 9”s since I was a teenager and to my knowledge I’ve never had a 9 3/8 third.

 

[Tech Tim]

That down curved rib is the way to tell a 9-3/8".

An experience eye will also note that the pinion support is bigger with a bigger bolt circle.

 

[power_by_429]

Here is s side by side for anyone who might care. 9 3/8" on the left 9" to the right.

Its bigger in nearly every possible way

 

[Byro]

I was todays years old when I learned this was a thing.

Interesting to say the least. The pinion support is considerably bigger, are the pinion bearings bigger as well?

 

[power_by_429]

Yes. Two out of three pinion bearings are bigger along with the larger carrier bearings. Inside diameter is the same so It will all fit the 9 pinion. Pinion seal is the same.

 

[YotaAtieToo]

I was todays years old when I learned this was a thing.

Interesting to say the least. The pinion support is considerably bigger, are the pinion bearings bigger as well?

Same here

Along with Nascar using Detroits

 

[Byro]

Yes. Two out of three pinion bearings are bigger along with the larger carrier bearings. Inside diameter is the same so It will all fit the 9 pinion. Pinion seal is the same.

So the 9 3/8 would accept a 33 or 35 spline carrier?

There was an old timer local to me, we called him the 9” Wizard. Basement full of pigs, gears everywhere 9”. Had him set up quite a few 3rds for me when I was still running them. He never made mention of them, he did tell me about the Nodular 3rds. Guy was a wealth of knowledge, set up the 3rds on the line for Ford. Didn’t use a dial indicator to set BL, said he could feel it. I called out on it the one time, “that’s 8” I said prove it, he dusted off the dial indicator case and sure as shit, dead nuts, he just looked at me like I told you so damn punk.

 

[Tech Tim]

So the 9 3/8 would accept a 33 or 35 spline carrier?

Yes, the 9-3/8" has the bigger 3.25" side bearing OD, just like the aftermarket HD cases.

But as mentioned above....

Cheap way to get a big bearing 3rd. But unless you have a 9-3/8" 3rd laying around, it really isn't worth it.

Aftermarket big bearing 3rds are fairly inexpensive these days and are stronger.

 

[power_by_429]

I have a 3/8 carrier shim hanging on the garage wall now making me wonder how tough they would be to produce. I have a machining background but never made anything that thin. magnetic fixture with a surface grinder? laser cut thin stock? Die cut? Anyone have experience making shim stock patterns like this? .020" down to .010"

That part seems to be the only real issue with using these housings. You can do it the way I did by manipulating the pinion bearing position but only to a point in one direction. it's a bit more time consuming and involved. Carrier shims would be nice.

 

[arse_sidewards]

magnetic fixture with a surface grinder? laser cut thin stock? Die cut?

That's exactly how I'd do it.

Mag chuck really shines for jobs like that.

Careful inspection of the edge of an OEM shim should give you some clues how they make them.

 

[Tech Tim]

I have a 3/8 carrier shim hanging on the garage wall now making me wonder how tough they would be to produce. I have a machining background but never made anything that thin. magnetic fixture with a surface grinder? laser cut thin stock? Die cut? Anyone have experience making shim stock patterns like this? .020" down to .010"

We got some of the laminated shim stock and used a water jet, that didn't work very well at all. The water jet would separate the layers and blow out the sides. A laser would probably be a lot better for that.

 

[power_by_429]

Still running this setup with zero issues. Plenty of street and trail miles on it at this point. I'm curious to see if shorter gears will want a shallow or deeper pinion.

I still say for the money the only downside is lack of pinion carrier shims available. Easy to work around with a pinion shim kit and a hobo freight lathe.

 

[OX1]

Hard to tell, but is there more meat around the 3rd pinion bearing area. That was usually the weak link for me