A Guide to Installing Rear Center Axles - 1967 Chevelle
With the housing installed for the last time and the coil-overs hung and attached, I was finally ready to stick the final components together to make the rear whole again.
I’d had the center section for this project laying around for quite some time. I picked it up off our Garage Sale section of the website. This is where we sometimes sell returned or blemished items. In this case, I picked up a 3.50 posi for 31 spline axles at a decent little discount. This particular unit had been installed by a customer who found that the gear-set whined on deceleration, which is a common characteristic of Richmond gears. Sometimes the way the rear end is mounted, or even the type of transmission mount will amplify this noise.
It was inspected by our assembly team. Backlash, pattern, and runout were checked and it was given a clean bill of health. No worse for the wear, except some left-over orange RTV and gear lube residue.
When I was ready to put it to use in the Chevelle I sprayed it down with brake cleaner and scrubbed all the front side surfaces with a stiff nylon brush to remove any oil or dirt. Then I sprayed a nice, even coat of hammer tone sliver paint. This is a nice compliment to the charcoal, gloss and flat black that the rest of the undercarriage is detailed in.
I’m going to tell you this once because no matter how many times you remind yourself, you’ll forget it at least once.
PUT THE GASKET ON THE HOUSING.
There. My civic duty is done. Now that I’ve said it, I’ll tell you the dumb thing I did. Normally I like to lay everything I need out ahead of time. This saves handling stuff multiple times and crawling out from under the car. This time was no different, I laid the gasket out on cardboard under one side of the car while I got the rest of my stuff in order. This isn’t that other Project Chevelle. We work down on the floor, in the mud and the blood and the beer.
I realized what I’d done just after I had lifted the 70# chunk into place and wiggled it carefully onto the studs. I looked over and noticed that damn gasket still sitting there on the cardboard. So. . . take two. I pulled the pumpkin back out and had my son, Jonny, position the gasket on the housing for me while I held the weight on my chest.
Now I’m not sure if he was messing with me, but he sure took his sweet time putting it up there. I think he may have tried to put it on backward the first shot and then noticed the cutouts for the ring gear. At any rate, by the time the monkey motion was done, my arms were pretty tired. Fortunately, the hardest part was done. Take note, not to forget the sealing washers that go under the nylock nuts for the third member. It’s a small but infuriating amount of leakage that will happen through the press-fit studs.
The next task was to get the axles stuck into the housing. It should go without saying but there are generally two different length axles. With this housing kit, are included 31 spline dual bolt pattern axles. The bolt pattern that the ½” studs are pressed in to correspond to what the car would’ve originally had. In this case 5 on 4.75”. However, the beefier ½” studs will require the use of new lug nuts because cars typically equipped with 4.75” bolt circle are originally 7/16” studs. Anyhow, long axle, short axle. The long axle is on the passenger’s side for 9” Ford. If in doubt, try installing the long axle first. If you’re on the wrong side you’ll know it right away. Ha!
Before you go poking the axles in you’ll want to locate and install the axle seals. These housings use a pressed (hammered) in rubber and steel seal. The housing has a step machined in it for the seal to stop against. Use care to drive the seal in straight and don’t damage it. I’d suggest picking up a seal driver if you don’t have one. 910-89625 works for many different applications, including this one.
The axles have the bearings pressed on and are ready to install after a light coat of clean gear lube on the splines, gasket surface, and outer bearing race. This helps ensure that no damage occurs to the seal and aids engagement. As you slide the axle in, you’ll feel the splines in the center section. Adjust as needed to engage the splines and press the axle into the housing until the bearing begins to contact the housing end. This step requires a little bit of force, as the fit is very tight between the housing ends and bearing. A Dead Blow Hammer works quite nicely.
The bearing does not go completely flush to the flange. There remains about .125” proud after the bearing is fully seated. I used my Wilwood axle retainer brackets as a gauge. They are machined with a groove to accept the bearing.
Where you go from here depends on what you plan to use for brakes. In my case, I opted to go with Wilwood 12.19” disc brakes with Forged Dynalite Calipers. This brake kit includes axle retainers for use with the T-Bolts included with the rear end.
