Hey,
I was directed to that same story that Tech Tim had said. So anyway I called Currie Ent. and they haven't heard of doing that with the 9 3/8". I did call my local bearing shop and there are crossover bearings to fit a 35 spline spool to fit the 9 3/8" carrier. I've been trying to track down those ellusive pinion shims to make the 9 inch pinion gear work in the 9 3/8" pinion support, but no luck as of yet. I did send a PM to Tech Tim and Gearman but nothing back thus far. I called Unitrax who has been in business for a while and do nothing but differentials and they haven't heard of the conversion either. I can't find anything on the internet either. So anyway untill I come up with some confirmation on what to do with the pinion I'm skeptical to say the least. I wouldn't go rushing out to find one as of yet. hahaha

 

TeenyCar, I posted in your buildup thread directing you tothat link. I figured you wern't really looking into it to hard because you had already built a 9" rear. Thanks for sharing what You have learned.

I figured this post would get a little more vissibility. It is really wierd that there isn't more info on the net, if this works. If we don't get some resolution soon I'm gonna go to the local pick and pull and stick some 9" gears in a 9-3/8. There are quite a few of them out there.

 

I tried to put a 35 spline detroit, richmond 4.88 street gears and a new 3.25" bearing kit in what I thought was a free 9" big bearing 3rd.

It wound up being the 9 3/8" that you refer to. I was excited to see the billet bearing adjusters and what seemed like really heavy duty caps. Unfortunately, I couldn't get it to jive for the life of me.

I tried for a while, and wish I could remember why physically it wouldn't work ever and I felt I had to break it to my wife that now I absolutely needed a $450 strange case. If I could have avoided that I would.

 

I talked to Sandy Cone about these, he said it was bitchen set up but pretty much a dead end road, he's tried everything with them. They just dont make gears for them and you cant use 9" gears, the pinion is offset lower than a 9" the lowest gears made were 4.10. He came across 500 brand new cases for cheap but couldn't do anything with them. There is a 10" R&P that fits in a 9" third with some major clearancing, this is what all the off road race trucks use.

 

Thanks GOAT that's what I needed to hear. If sandy couldn't make em work, then I can stop thinking about it.

 

I figured it was just another dead end rumor with little to no truth. GearMan also confirmed that they are pretty much useless. Thanks for the further research.

 

I pulled a 9" from a '67 Ford custom cop car for our '55 Chebby since it was 31 spline, and it wound up being a 9-3/8". My local speed shop narrowed the housing, then found out no gear sets were avaliable for it also! The speed shop went ahead and gave me some $$ for it (shafts and center section)anyway claiming it had a value to some street rodders looking for a 31 spline carrier and stock gears.

 

There is a value to the 9 3/8 housing, but not the center section. You can put a 9" 31 spline center section in the 9 3/8 housing as an easy way to get 31 spline axles and big bearings in a narrow housing. Plus most of the 9 3/8's I've ever seen are setup for a coil sprung 4 link setup. Real nice for traction.

I have a 9 3/8 in my 67 thunderbird with 3.0's and if i ever want 3.5's I can just toss my 31 spline truck center section in there.

Justin

 

Super old thread resurrection... Just adding some tech to this in case anyone is searching in the future.

This came up in a discussion around the campfire lately. It got rather involved and I was sent this thread a few days later.

Going from memory, all this was done back in 1998-2000-ish. Plus, I'm getting old and senile :flip-off: , so forgive me if this isn't 110% correct.

Reality Check:
The 9-3/8" really is a dead end. The aftermarket big bearing cases (Yukon, PME, etc) are so cheap these days it just doesn't make sense to waste the time or money to do it. Back when they were $800-900 for a Strange case they kind of made sense for the budget builder.

The pinion shims are not available and are the biggest bitch in doing this setup, unless you have lots of the 9-3/8" 3rds lying around to rob them from.

The side bearings are nothing special, only the race is different and they commonly available.

Yes, 9" gears fit the 9-3/8" case. This was an old school circle track trick that Jason Bunch from Tri-County gear in Pomona clued me in on.

Yes, you will **** around a bit to get them to fit. But they do work.

No, the pinion offset is not different between the 9" and 9-3/8", it is the same.

I had long talks with both John Currie and Sandy Cone about this back in the day, Currie didn't know about it until I brought it up with John. He later went out to the gear bench, checked it out and called me back to say yes, it works. I don't remember what Sandy had to say about the swap. It wasn't anything hugely negative or I wouldn't have continued down the path.

I did swap 9" gears into a 9-3/8" third member (that John Currie sent me after our discussion) with an ARB Air Locker just as a test. There was a bunch of fiddling to get it all to work, but it did work.

And yes, I know, this post is useless without pics...... Unfortunately, after all these years, I do not have the pics anymore. Thought I had posted them up in a thread somewhere on PBB, but couldn't find them.

 

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.

In the end I had no choice but to run the thinner 9" support bearing. The old 9.375" third bearing is too thick. I also ended up with very little room for the stock style lock ring. I guess if that bothered someone enough they could install the bearing with some holding compound. I have used that stuff on giant ski lift gear boxes with plenty of success. It seems like I removed a ton of material but if you have never seen a 9 3/8"case I assure you it will be fine. There is still way more material in this area than on a standard 9" housing and these are nodular iron cases.

Very satisfied with how this all worked out. Super cheap solution for a very strong 3rd member.

 

Sweet @power_by_429, glad you took up the challenge and posted pics!