My 8.8 has always had a slight whine to it and its finally getting on my nerves. I've been thinking about building a budget 9 inch. I'm partially a Ford man and have a spare 9 inch 3.90 31 spline posi centersection in the garage. I was thinking about buying a Moser rear end housing, axles, and a torque arm bracket. Then using this 3.90 centersection or visiting a local salvage yard to get a cheap 31 spline 3.50 posi centersection out of a pickup. Does anyone see a reason this won't work? I'm hoping i could buy the Moser parts for about $1000 shipped then get a used centersection for another $200 at the most and be good to go. I really want to get a used centersection out of a Ford vehicle so it will be nice a quiet. What do you guys think?

 

i considered doing something similar: Getting a 3.50 open diff out of a ford truck just to run for the winter. One minor drawback is that depending on your driveshaft you will need to run a 1310-1330 or 3r-1330 conversion ujoint. i'm not suggesting that isn't strong enough, just that if you plan to eventually upgrade to the moser you will need to then buy another conversion u joint. I have 2 driveshafts so that wouldn't have been that big of a deal.

I also wasn't sure how many fords had the 31 spline axles. I was told that all 4wd trucks and all 3/4 ton and above 2wd trucks would have it, but that is free second hand advice so take it for what its worth. I didn't know how to tell if it was a posi or open diff without pulling it out of the truck either.

In the end parts cost + risk of getting a bad center section + plus pain in the *** of doing the swap and disconnecting the torque arm mount + working outside in the winter detered me. I just sucked it up and ran the 3.89 spool, errrrr i mean posi all winter. If i were you i'd worry a lil more about the posi being worn out, since i was looking for an open diff that was less of a concern for me.

Your situation is somewhat different than mine though, so it sounds like it could be a good option for you.

 

I did a build simular to what your wanting to do. I bought the moser rear housing with T/A bracket and 31 spline axles. I also got 3.90 gears and a spool from moser. If I were to do it agian I wouldn't get moser gears, they wine like hell
I have heard that moser gear sets do that, Ford motorsport would have been a better choice. Anyway, I got the housing, T/A mount, axles, gear set, and spool from moser. I found a center section from a junkyard that I was pleased with and had the rear set up. Total cost with all labor, shipping and parts was around $1800.

 

Being a Ford man i know how to tell 31 spline axles on 9 inches without pulling the stuff. I'm also lucky enough to have a book on how to decode the tags on the 9 inch that tells what the rear is packing without pulling it. I also have a deal worked out at a local salvage yard where i can have pretty much anything for free so i can get 9 inches for free. I was thinking even if i get a junk posi or one thats a non posi at least if it has 3.50+ gears i can get a different posi and hopefully have the Ford gears reinstalled for a nice quite rear. I was just wondering if there was any reason this wouldn't work, mainly i'm not sure how Moser does the torque arm bracket.

 

You get them for free! Hook me up with a 3.50 open diff.....

I think the moser instructions make mention of the possibility of needing to *slightly* clearance/grind the webbing of the centersection. I think that was actually in reference to their own centersections though and mine didn't require anything.

I couldn't find a picture, but i'll try to describe it. Its basically 3 "Sch 800 XXXXS pipes", 1 above and 2 below the axle. They are all parrelel to each other and are welded to the side of the housing pointing towards the front of the car. From there a large cast piece which is the actual TA mount uses bolts, something like 22 mm, threaded into to the three pieces of heavywall pipe. This removeable TA mount is how you can get the center section in and out.

Go for it, you shouldn't have any problems.

Do a search on the moser axle shims though. You will find some posts about how moser jerks you around with them. I.E. not sending them and not telling you when they are really required.

-brent

 

Ok thanks Brent. I think this is gonna be a summer project for me. I do really get parts for free. The 3.90 31 spline posi centersection i have laying around is out of my 69 Mach 1 because i wanted some better highway gears. I just went to the local salvage yard and popped out a 3.50 open rear for free. I did have to carry it from the rear of the yard to the front of the yard by myself which was almost payment enough. The part that sucks is the salvage yard is only 1940's-1980's stuff no 4th gen Fbodies. Can i ask why you want a 3.50 open centersection?

 

not sure why he does... but I'd like to get a hold of a 35 spline open diff so I can install a powertrax locker in it and get rid of the 35 spline detroit locker in my car. The slack in the detroit locker makes it a major annoyance on the street, especially with a 6 speed.

 

It was kinda buried in my first post, cause a tight posi in a daily driver in the snow sucks!

 

I don't think you can get an open 35 spline diff. The biggest Ford made stock was 31 spline. I haven't heard of any aftermarket open diff.

Anyone else use their own centersection with an Aftermarket 9inch housing
and have any feedback?

 

1959-1986 F100 and F150 with special high performance 35 spline axle option. The powertrax locker part number for this is 92-0690-3500.

They wouldn't make a locker for installing in this open diff if the open diff didn't exist.

 

Hmmm i've never heard of those and i'm a pretty big Ford guy at heart. I can't believe it would come in the 100 or 150s maybe the 350's or something. Oh well you learn something new every day.

 

Yup. It was only the F100-F150 that got them. The 250 and up with Ford rear ends got 8.8, 9.75, 10.25, and 10.5 -- but no 9" (there were also some dana rears too).

The 35 spline option was rare, and that's why it's been so hard for me to locate a 35 spline open diff... If you ever run across one, drop me a PM and I'll pay good money for it.

 

Ok i'll keep that in mind. I know how to tell a 31 spline axle and 28 spline axle with out pulling it from a car. I wouldn't know how to tell a 35 spline axle with out pulling it. I've probably walked past some before in my day and just left them because i didn't know wtf they were. Hmm thats just really odd that they have 35 spline axles on 9 inches. I've even owned two 9 3/8" rears and both of them were only 31 spline but they were the biggest beefiest stock axles i've ever seen. By the way did you buy your 9 or build it yourself?

 

I bought a moser with nodular iron center section, 3.70 gears (typical whiney moser gears), detroit locker, 35 spline axles, arp 1/2-20 screw-in studs, etc... I wanted something that I couldn't break.

The biggest problem you'd run into using a center section from something old will be the pinion support. That's why I just went ahead and bought it all from Moser.

 

Why would the pinion support cause it from not working? I'm not arguing i just don't know. I don't think i would be able to break a 31 spline 9 inch with a stock case. I don't think i got enough power to break the gears or axles. My buddy was running a stock center section case into the 8's before he broke it clean in two. Now he is finally at least running an N case.