Driving my 96 Discovery lately, I've heard a loud unnerving sound coming from the back of the car. It happens usually from a stop in first gear. I was towing a small pickup with a car dolly today and I think the load was a catalyst.

It sounds like I'm dragging a full metal garbage can on a driveway. Lasts for a second or two, and then I let off the gas and baby it and it doesn't seem to come back. After I'm in second, I try to reproduce it by gunning a little...but can't seem to make it happen. Only from a stop.

Sounds too far back to be the transmission. Could it be the rear differential shreading? Or maybe the rotoflex? I'll get under there tonight and see if the rotoflex is hosed. Maybe someone else has had a similar experience?

Shoot..maybe there actually IS a full metal garbage can under there...

 

yeah, check for a metal garbage can first lol. I think a rotoflex going out would make more of a clunking sound. Grinding from the back could be wheel bearings going out from not getting enough gear oil.

 

I would have to agree the rotoflex is rubber and I dont see it making a loud sound like that, I would think rear diff or bearing/hub/brake areas.

 

I'll check the rear differential oil level tonight. By the sound of it, and the speed I'm going (which is almost no speed), I'd say it has something to do with the driveshaft. I mean, it really makes the sound at a stand still, but right as the truck starts rolling.

Maybe I'll just replace the differential oil anyway, see if any suspicious smells or metal fragments come from the old stuff. It's been a while...don't you just suck it out with a little pump? The drain/fill plug is near the top of the differential right?

 

it should have a drain plug at the bottom and a fill plug at the top

 

Thanks for reminding me. Now that you say that I remember draining, then filling it until it won't take anymore before I replace the fill plug. I think I even have the gear oil on hand!

 

So, I'm not certain, but I found two possible causes of the sound...both user error.

I'm pretty sure I was not using the car dolly right. I have it down now...but I was also comparing the sound I heard to the sound my wife described. Second, I found a nice thick twigish branch wedged under there from when I was last at my favorite camping spot. The sound must be one of those. because I haven't heard it yet.

The upside is, I have all the stuff I need to change the gear oil now so I'll get that done this week. Also had a look at the rotoflex, and it looks good. While it's not broken yet, I'll look into upgrading it.

Sorry for the false alarm...but thanks for the input.