A 42 year old car, that’s spent some time at rest, will have….issues. While a mid 60′s car is pretty dead simple to work on, a new-to-you dead simple car still takes some effort to figure out. In the 250 miles or so we’ve put on the car, a noise started making itself known. It was a howl that changed with road speed, from 0-30 mph or so, until the rest of the noises at speed drowned it out. There’s no radio to turn up and drown it out, and there’s not enough sound deadener to ignore the noise.

Based on some advice, we had to determine _where_ the noise was coming from. It sounded like it was coming from up front, but some sage advice from the Hearse Club president had me jacking the car up, front and back, testing for the noise. The front bearings were smooth and in good shape. The back end, while it made noise while up in the air, it wasn’t the same noise it made under load. 

I pulled the drain plug on the diff and dipped a coat hanger in….the oil that came out had glisteny bits. That’s never a good sign. (except this time, live and learn. But I’m getting ahead of myself)

The Axle was rusty, wet, and at this time I’d assumed that it was eating itself up. The car’s been stored a long time, no telling what shape it was in. The car’s in the garage, it’s up in the air, and I think there’s shavings in the diff lube. My copy of the 1966 Service Manual says:

NOTE: Whenever a carrier is removed because of scored gears, worn bearings, or any failure that might cause dirt or metal chips, remove axle housing from car for thorough cleaning before new carrier is installed. Also check axle shaft assemblies and clean as necessary. 

That means I’ve gotta pull the axles and fully clean the whole rear end. No problem…I’ll just cut a 1 foot square hole in the wall so I can pull the driver’s side axle. Nope. Sucker’s comin’ out. If it’s coming out, I’m having an expert look at it.

Cut off wheel, a sprained wrist, and a softball sized bruise on my wife’s upper arm later, the axle’s in the truck and on it’s way to the driveline shop.

Two days later I discover NOBODY knows ANYTHING about Cadillac Controlled Differentials. Nobody. Google, Classic car forums, my go-to GM rear-end guy, nobody. The driveline shop doesn’t even have a clue on how to begin the disassembly of the carrier and is afraid to do so. (With good reason.) One of the driveline guys has a pretty good point: “Maybe nobody knows about them because they don’t break?”

That said, the diff looks like it’s in good shape. The bearings are smooth, the gears look fine, and there’s minimal lash. I must have scraped the bottom of the carrier and picked up the shavings on the bottom from it’s initial break-in period. They diptank it, charge me a reasonable diagnostic fee and it’s back in the truck for reinstallation. (Thanks Front Range driveline, I’ll send more work your way when I have it) Worse comes to worse, I found an axle assembly at a junkyard, I can get it if necessary, but my gut is saying the noise isn’t coming from the axle. There’s still the size long segmented driveshaft and a carrier bearing, but that’s for later diagnosis. (Like I said, I couldn’t get the noise to happen with the car in the air and no load.

Which comes to the reassembly. Let’s get the out of the way: POR15 Rocks! I bought a sixpack of the paint and was a little concerned when they were these little 4 oz jobbies. Turns out I needed about 4 1/4 oz to paint everything.

Before:  After:

Before:  

After:  

Big Picture here (you really should, they’re in much higher detail…and there’s a spinning bannana)

I just have to get a few u-bolts, a shackle, some break lines, and the car’ll be back on the road.

Lessons learned: Wear eye protection and a respirator when grinding away at rust, the respirator pucks were nicely orange when I was done…and POR15 is _nasty_, don’t get it on you, and fer chrissakes, don’t breathe it!