Alright, I think I’ve got a handle on what the (immediate) problem is here. I’ve spent most of the past few days covered in stinky old differential fluid, doing research and watching “how-to” videos, and the diagnosis, while a bit technical, I think is pretty accurate: my rear differential is fucked.
Allow me to explain.
Our first thought (and by “our” I mean “John and I”, and by “John and I,” I mean “John”), was that maybe there was a damaged wheel bearing. Once we got Betty (I’m trying out names here) up on the jack stands, we removed the rear drum brakes and started to feel around for any excessive play in the rear bearings.
Nope. Maybe a little, but nothing that would explain the violent clunking we were experiencing.
The next thought was that maybe there was a broken axle shaft. We wouldn’t be able to see that unless we pulled them out, which would require opening and monkeying around with the rear differential or, “The pumpkin” as it is known.
The next step in the diagnostic process was to rip the lid off the rear differential. This would give me a clean look at the ring and pinion and spider gears to determine what, if anything, was off.
I had the jack stands placed securely under the frame as well as a horizontally placed tire as an added safety measure. I didn’t want to go out like Catherine the Great, crushed to death by two tons of horsepower.
(*Note of historical clarification- Catherine the Great was not actually killed mid-bestial-coitus by her horse-lover falling on her. That just a tall tale. She most likely died of a stroke. But she was incredibly fat. And legendarily lustful. This really has no pertinence to the Jeep Grand Wagoneer restoration).
There are a couple problems with working on a car in your garage. First, even on an old SUV, there really is not that much space to maneuver.
Gaining any level of mechanical advantage against old, rusted bolts while on your back has been a constant challenge. There are only so many ways you can orient yourself when you’re trying to loosen bolts on a U-joint with less than 18 inches of clearance.
I briefly considered getting a 9,000 pound hydraulic vehicle lift to make things easier, but it was not available on Amazon Prime for same-day delivery. . .and it was a shade over $1400 with a shipping weight of 1500lbs. In general, I’m a believer that having the right tool for the job is of the utmost importance but somehow I didn’t think I’d get a lot of use out of a 4.5 ton hydraulic lift.
A few other tools quickly became necessary. Shop rags. LOTS of shop rags. Things had a tendency to go from perfectly clean to utterly filthy faster than Dagny at the dog park. (Pro-tip- use oil soaked shop rags as a Firestarter for the grill! Sustainability folks. . .)
What else. . .ahh, a breaker bar. The vast majority of the nuts and bolts had spent the past 27 years torqued down tightly, further locked up by dirt, oil, and rust and needed some serious lever action (and some WD40) to loosen. I also needed a few SAE deep socket bits to access some of the bolts. . . aaaand a legitimate oil pan because apparently it’s not cool to use a Pyrex casserole dish, regardless of how stained it was or how unlikely we were to ever use it again.
And lastly, some mechanics gloves. When you are max-efforting bolts with a socket wrench and the socket slips, the last thing you want is to go knuckles first into sharp, dirty metal. After day one, my knuckles looked like I had been in a fist fight with a Vitamix.
I loosened the last of the bolts on the rear differential cover and used a very sharp wood chisel to break the seal and pry open the cover. Since the differential cover had no drain plug, once the seal was broken, the fluid poured freely into the drain pan.
There were a few problems that I noticed immediately. First, the fluid draining into the oil pan was a bit. . .lumpy. Now, as we’ve already established, I’m no seasoned mechanic, but it seems to me that seeing as the function of oil is lubrication and heat dissipation, differential fluid should not have chunks of metal in it. That’s bad right?
Secondly, and I’m not suggesting this is a problem, just that having your face 6-inches away from decades old differential fluid exposed to the light of day for the first time is. . . an olfactory experience. It smelled like Kowloon on a hot day (Yeah, I’m linking to my own blog, but it’s my blog, so I can do that. There are no rules here). Ever heard of “The Sound”? No? Go listen to this, have a laugh and come back. You’ll thank me.
That’s how I felt. It did not smell good.
I reached my hand into the mostly drained cavity, touched the oil and pulled my hand back sharply to find several shards of metal sticking out of my fingertips. I looked closely and saw a tooth missing from the ring gear, a bolt missing where it should not be, and several teeth of the spider gears all fragged up.
I put the car in neutral and started rotating each of the rear tires. As the rear left tire rotated, so too did the ring gear. That was good. When the rear right tire was rotated, the spider gears chunked, ground and slipped off each other. That was not good.
So yeah, I think it might be the differential.
I’m neither an automobile expert, nor did I stay at a Holiday Inn last night, but my guess is that the missing bolt probably came out at some point, got chewed around the gears for a while and took out a few teeth while it was at it.
So that is where we were at. My rear differential is garbage. My choices are as follows:
- I can remove the differential carrier and the pinion gear and rebuild the entire differential myself.
- I can remove the rear end completely and take it to a differential shop and have them rebuild it.
- I can find a Dana 44 rear end at some junk yard as a replacement.
Each has their own pros and cons. The chief pro of doing it myself is gaining experience and saving money. The chief drawback to rebuilding the differential is that I don’t know how to rebuild a differential. My initial impulse was, “screw it. How hard can it be?” After doing some research and talking to some people that know more than me about this, I determined that the answer to that question is, “very hard.” The problem with differential work is that you need special tools, knowledge of what you’re doing and the ability to deal with extremely tight tolerances to ensure that everything is aligned perfectly. Any misalignment with the ring, pinion or spider gears and you’re creating a ticking time bomb (not literally. More like a ticking Tranny bomb. . .by which I mean, transmission bomb. A Tranny bomb sounds like a new ISIS weapon.)
The advantage of finding a used rear end is that I could effectively just detach the existing rear end and put a new one on. Like changing a pair of shoes. This would be the cheapest and least labor intensive approach.
The problem with this is that I would know almost nothing about the condition of the differential, axle shafts or wheel bearings of this rear end. It could be in bad shape as well and I’d have no idea unless I were to take it apart.
The primary benefit of taking this to a differential shop is obvious: I would get every single shim, bearing, race, gear and axle looked at by someone who has more than a couple weeks of accumulated knowledge on automotive systems.
The problem is that this would be the most cost-intensive.
While I think it could be very interesting to try to rebuild the differential and am game for the challenge, I am not confident that I would be able to perform the repair with the level of exactitude required. I also don’t want to have to redo this work a year down the road, so I’m leaning toward removing the rear end and taking it to Northwest Differential.
Let’s do it!
* Update!
We’re in business. Removing the rear end was pretty straight forward. I disconnected the rear stabilizer bar, the two struts, the drum brakes and the U-clamps that connect the axle housing to the leaf-springs. Simple right? Sorta.
I managed to disconnect everything fairly easily until I got to the U-clamps. These sons’a’bitches were none too eager to move. After spending about 20 minutes on a single bolt, I opted to eschew brute force in favor of power tools, specifically, my trusty angle-grinder. I was intending to replace the U-clamps anyways, so there was no need to leave them intact. While I was not concerned about losing the clamps, I was concerned about the faucet of sparks inherent to metal on metal assault, particularly in the presence of flammable fluids. After glancing at a couple user forums (these could never be wrong. . .right?), I determined that as long as I didn’t aggressively grind into the fuel tank, I’d probably be ok.
Once I cut the last of the bolts, I gently lowered the jack that was supporting the axle, wrapped the rear end in a painting drop cloth, chucked it in the back of my car and dropped it off at Northwest Differential.
Now I wait to see what the damage is going to be. I have a vague idea based on sourcing some of these parts myself. Ring and Pinion kits are. . .not cheap, and this 3.31 gear ratio is a bit of an oddball, so I’m expecting a hefty price tag. My guess is that the labor will be around $500 and the parts will be another $1000 to $1200.
Now to get to work on the muffler. . .