Hank and the 1st gen. Chapter 1 the rear diff.

I just typed out and lost a gigantic intro before it posted

Long story short, I drained the rear diff on my new to me 05 DC and it had barely enough fluid to cover the bottom of my catch pan. The drain plug had about 1/4" of thick sludge on it. Felt gritty but not chunky with metal. I'm going to fill it up and drive it 20 miles or so, then drain and fill again. Any other advice? If it's toast I will attempt to have the dealer buy it back, but I think I'll be fooked.

 

I’m surprised you could even drive it with that low a fluid. Do you have a borescope to peak inside and look for damage? You may actually be fine if there were no metal shaving when draining. Wow.

 

1st things first, do you know if it has LSD rear-end? You should know by sticker near the fill plug unless you're rusted to hell, in which case you may have bigger problems (more info here). If you do have LSD in your diff, you can't use synthetics, Lucas 80w90 has worked for everyone on here that's tried it.

But the big question is: Why wasn't there any fluid in there?

I'm going to speculate it may've came out at the wheel seals. In which case I'd be popping off the rear wheels, removing the drum and checking for fluid traces, because you may have bigger problems at hand. If no fluid found there, I'd hit the highway, make sure I'm not hearing bad bearing sounds (wom wom wom wom wom wom), then check again for fluid under drums in 50 miles after you refill. The diff breather may be toast and forcing fluid past the seals. Hope your wheel seals and bearings are fine.

Is your truck 2WD or 4WD?

 

Sorry, most of that info was in the post I lost. 05 4wd DC 162k. Rust is not bad, truck is from florida. There was driveline whine that went away in 4wd so dealer replaced carrier bearing. Whine and clunking was still present so I greased the zerks. I'm guessing it had never been done. That seems to have reduced the clunks to only happening with the wheel turned and backing up. Whine got worse on the drive home and no longer going away in 4wd hence the drain and fill. No signs of LSD but I filled with the Lucas 80w90 anyway. There is some other noise from the rear that I was thinking was the drums not being adjusted (there is no parking brake cable) but now I'm worried it could be the bearings and seals. I'll pull of the rears and see what's going on.

 

You should rally replace the braking cable assembly if you intend to keep the truck. It's not too expensive to buy the parts OEM, others have done it. I don't think it's critical to braking in the later-model 1st gens, but in the earlier models it absolutely is, you can pull the e-brake cable to set the star adjuster in the early models.

I'd check and/or proactively replace the diff breather valve, it's the little vertical-facing nub on top of the diff, favoring the driver's side of top of diff. If that one-way valve gets clogged, the pressure buildup in the diff will force fluid to leak out somewhere, and the nearest place to leak out is at the axle seals.

I'd also be popping off the rear drums to inspect the rear brakes and check the seals aren't actively allowing fluid to pass around now you've refilled the diff (go drive and get it hot in the diff before checking), which will kill the bearings, and the bearings are a bitch to replace properly, and you'll want to replace the seals while in there.

Yes, if you're hearing noise from the rear, solid chance it's the bearings based on the symptoms: limited fluid in rear diff, whining or wub-wub noises from the rear end, etc. But it's also possible the rear-end is shot if there was no fluid.

 

Yeah, I had already ordered the ebrake parts while waiting on paperwork at dealer. I just took it for a spin to warm it up. Whine is still present, sounds like a turbine spinning up. Probably toasted the pinion bearing, I drove it almost 2 hours home like that. I'm honestly flabbergasted that the mech would go through the trouble of replacing the carrier bearing but not even check fluids in the diff.

Just found that it has those godforsaken locking lugs, so I'll have to go buy a socket to pull the wheels off...

 

There's nothing in the glovebox, center console, or overhead?

 

Noperoni.

 

The axles are easy to find at the junk yard. If there's an issue, just grab a new one.

 

For reference if your text box clears out while you've been typing just refresh the page and it should show right back up. It saves a draft every so often, just have to refresh to get it to load it back in.

 

Good to know, thanks.

 

Because everyone likes pictures, this is how much fluid I got out of the rear diff.

 

She might've been a little thirsty.

was the axle level when drained? Got a hole in the housing? Cause should be more like 3.5 qts.

 

3.5 qts is about how much I put in afterwards. Housing is good, I suspect a bad axle seal. I need to check but will need the appropriate locking lug socket to pull off the wheels. Dealer was pretty indignant when I asked about him buying it back, guess I lost the game of hot potato. Now I need to find a shop that can inspect and possibly rebuild the rear end.

 

https://www.yourlemonlawrights.com/faq/ohio

One of the few benefits of buying a used car from a dealer is that there may be remedies for such problems

 

Dealer may have drained the rear diff during troubleshooting and forgot to refill?

 

If 3.5qts of gear oil came out of a bad axle seal, you would be able to see that without having to take any wheels off. I bet the dealer drained it and forgot to refill. My brother did that once in his mustang GT. It was making a howl and he realized. Once filled the axle made a whine but ran for years after that

 

Yea, bmf's rear wheel was caked with 1/2" of dusty sludge.

 

Yikes. That's not good. Does it seem like the diff is damaged?

 

It may have drained long ago for all I know. Ive had the truck less than a week, I'm sure it was washed etc. before I purchased it. I've got an appt. lined up with a mechanic to open it up and inspect it for damage. I'm hoping that it's just the bearings but we shall see. It sounds like a turbine spooling up when I accelerate and is notably louder when applying the gas although it never goes away entirely.

 

Needs a rebuild and new gear set.

 

Put a whole qt of Lucas in it.
Jack the rear axle up and count the turns 20 of them. That will tell you the gear ratio. Then plan a visit to all the junk yards there's axles there easy to find.