Rear Diff Stinks when hot.

So a couple months ago I began noticing a oily stink from the rear of my truck. Kept smelling it everywhere I went. I could only describe it as smelling like a hot mechanics shops. Eventually I took a 700 mile trip and when I returned home noticed a dark drip under my rear diff in my garage.

Turns out my pinion seal was leaking and diff oil was splattering all over the under side of the truck bed, fuel tank, etc. So I had that fixed. They told me at the time the diff fluid didn't appear to need replaced, that it wasn't very low, and they didn't notice any metal bits or signs the gears were shaving each other. They also confirmed my diff breather extension was not plugged. The smell stayed a couple weeks until I was able to wash the under carriage a couple times to get all the oil off.

The terrible diff oil smell is gone.... finally. However, the warm smell is present every time I drive somewhere (and it's 10F most days). It is distinct and only smells post drive (not cold in the garage). I'm taking the truck in tomorrow to have the rear diff fluids checked out, make sure the pinion seal is still good. Wondering what else I should be looking for?

Truck has 24k miles on it. Have ECGS Diffs with 4.56 Nitro Gears and ARB air lockers. Really don't want to dynamite any of those!

Any ideas?

 

For the record... someone already suggested Febreeze for the stinky truck butt...

 

Have them check the ARB install (on the outside). I think a hole needed to be drilled into the diff for the air line. Maybe that is leaking.

 

Diff oil stinks, it sounds like there is a leak somewhere. To find where the leak is coming from you could try a dye to more easily find and see the leak.
Something like this- https://www.summitracing.com/parts/..._-tracerline&gclid=CI2ippGgvdECFQ9EfgodHVQFmg
You need a UV light and it will glow.

 

I did notice the air line had oil on it when the pinion seal was spewing. I assumed it was oily due to that.... the entire underside of the bed and fuel tank were oily too.

 

If you think gear oil smells bad you should have been on the Jersey Turnpike between exit 14 and 10 back in the seventies .

If your still smelling gear oil it is being pushed out someplace.

Why any shop would replace a pinon seal and not change the gear oil

Then make sure the breather is free

 

Stink is from your pinion seal leak. I can't believe a shop changed the seal and not the fluid. Fluid is cheap Kyitty. Your gears are not. Nice build BTW and I love your truck. Your pics sold me on the bumper.

Edit. So they had to drain it to get to the seal. It was changed. And a good sign of no shavings on plug which means the gears were set right.

Edit again. I've never been into our rear Dif so it might be an outside press seal? I haven't been into a rear Dif for 15 years and remember I don't want to set up gears again. I'll pay for the work Hope this bump gets knowledge on the seal.

 

I believe it is a press seal. I know for a fact they didn't change the fluid as I asked. They said the fluid was fine and wasn't worth changing. Not that many miles on the fluid. Going in to have it checked this morning though.

 

Ok so I did have my diff checked. Fluid was good. No sign of leaks. But more oil was found up under the bed near the fuel tank. More cleaning was done.

Still smells a bit. I guess I'm gonna have to wait until Spring to do a serious cleaning under the truck....

 

Thought I'd follow up on this. My rear pinion seal leaked causing the stink. Gear oil is bad stuff.

However, here we are in April and i finally got someone to open my diff and find out why it has been making noise for a while (like the entire time I've had it regeared).





As you can see three was a reason. Theory is the pinion bearing failed (possibly installer error) which cascaded into other issues. Pinion gear moving and hitting the carrier. Pinion seal failure. Metal shavings in the diff. Small chip on one tooth on the ring gear. Fluid coming out of air locker air line.

So, if your diff makes noise and smells... don't take "it's probably fine" as an answer from local shops.

Total rebuild to occur on Thursday.

 

Oh man. Bummer. Shops suck.

 

Ouch. Damn that sucks, man. Sorry.

 

Thankfully the parts supplier and shop are both stepping up to take care of me. So aside from inconvenience, the pinion seal repair i paid for in December, and now having to borrow a company truck so mine can sit... at least I'm not footing the bill for new gears, seals, and rebuild.

Probably looking at a grand in labor and $400-$500 In parts. All because someone didn't get the preload right the first time.

 

and hopefully it didnt mess up anything else like the axle housing itself...

 

Dropped by the shop on my way home to get something from my truck. Even though parts won't be here until locker Wednesday afternoon they went ahead and took advantage of my dropping off the truck two days early.



Third member, driveshaft, and rear axle removed and waiting for parts. If parts show up early enough on Wednesday they will get to work right away.