I want to build up a 9" for my 79 Ranchero and it would be nice to know if it's a 28 spline or 31 spline,d axels. Bone stock at this point with a 302 FMX and a 2.75 open rear. I want to keep it running till the 3rd member 3:89 Traction-Loc is finished and just do a weekend swap out. The rear is the first of the drive train upgrades, later will be the 331 EFI and C6 with OD TIA
Also, I learned the hard way that the 28-spline axles in my 78 are a few 1000s larger than axles from a 9" in a T-bird, and the bearings are HD rollers, not ball bearings. Learned this changing out a cracked housing. Good luck.
Just look at the outside between the studs...31 splines will be flat with two little holes, 28 spline will be hollowed-out.
Thats the way I used to ID the axels, like on my 64 post car, but I think you can't rely on that menthod on the 70s and later. I just purchased new side gears and spiders in 28 spline and am waiting for bearings. If the old marking system still holds true in 79 I'm screwed as mine has the dimples.
I'm building this up from my parts stock. The only goodTract-Loc cover I had was for 1.78 ID bearings. no problem as I had a G case in stock that takes the matching 3.06 OD carrier cup. here is the rub??? Even though the carrier uses the larger bearing ID, a 31 spline axel won't go through the carrier, only 28 will?????
it's probaby a little too late, but I just came across this post. When I was rebuilding my 9", my axles looked the part of a 31 spline; fit all the descriptions. But of course I took them out and even counted them...28 spline. I have heard of a lot of similar cases since then.
By the way, I ended up putting in an Auburn Gear Pro series; drives like a locker, turns like an open. Also put in Richmond 3.70 gears (with 275/60R15 tires to turn). This goes behind my 350 hp 302 w/ TCI C4 tranny (I still have the 2.75 open diff. & FMX tranny sitting in the garage just in case...). Anyway, it's a good move changing out that rear end, that is unless you're planning on highway driving. Have fun!
and I'm glad I get the email heads up when an answer is posted. My planned build up will be a slow one since I'm old and pretty crippled up from a tough "paper route" as they say. The chunk shown below will be finished tomorrow it's a 3:50 tract-lok big bearing G case and 28 spline. Next to build is a C6 I have hanging around and it will get the wide ratio package along with a Gear Vendors O/D. For power I have a good running 89 5.0 HO that I'l tear down for an inspection and add the new cam? and the new GT40P heads I already have. On top of the 5.0 I may shot the lock off the wallet and get the Mass-Flo EFI system since I've come to like FI over the years.