Stinky Rear End

[Stanglover]

Not what you are thinking guys. 

Recently, most will have read that I had the rear axle out over winter for a rebuild and add a Traction-Loc diff. While the axle was out, it got a total clean up and repaint. Not surprisingly, there was a 'new paint' smell, or so I thought, but it still persists after a couple of months driving. Now, I have a poor sense of smell which means I can't really tell what I am smelling or where it's coming from ( I know I'm opening a can of worms here but....). So yesterday, I took my daughter for a drive to get gas and take the long ay home carving through some bends on a favorite road. When we got home, I could smell that 'paint smell' so I asked my daughter to see if she could locate it. Definitely the rear end, but NOT paint. I used an infra-red thermometer on the diff. and brakes but all were not that hot. Then she said it smelled like old oil, not paint. Then it dawned on me what I was smelling. The Ford friction modifier stinks to high heaven and that, along with the new Hypoid gear oil, was venting from the axle vent tube under the car. Hoping that goes away soon.

Has anyone else noticed this issue?

 

[mjlan]

Where does the axle vent go?

Maybe its in a spot where the pressure is higher and the pressure differential in the cabin is pulling the fumes in.

 

[Stanglover]

It's not smelling in the cabin. I notice it after a run when everything is hot and on the outside. The vent tube goes where it's supposed to tucked into the frame rail and held by original bracket. 

The only smell in the cabin would be my rear end!!

 

[Don C]

Have you checked the gaskets and seals for any leaks or seepage? I don't believe I ever smelled it that much from the vent, even after running a vehicle hard. I have smelled it though from even some small seepage around gaskets or seals. The axle seals are good suspects, due to the increased heat from the brakes, and they have to seep a lot before it becomes noticeable.

 

[Stanglover]

Yes Don I have. All is good, no leaks on the diff anyway. I do need to pull the back wheels to check my brake work, so I'll be sure to look at the axle seals. It definitely has that horrible smell of friction modifier. The Ford dealer guy warned me not to get any of that on my clothes or hands because of the smell. By the way it is only after a drive that I smell it, but it goes away after it cools down. I'll also call my rear end guy and see what he has to say. I've only had this after the axle rebuild.

 

[Big Red Mach 1]

How much did you elect to use? I think most often its 3oz modifier per quart of gear oil. I think the bottle is 4oz so some people put in the whole bottle. Although even one drop stinks tremendously. I've used it plenty of times back when I had my SN95 Mustang, but have never had that smell after everything was sealed up. 

 

[Spike Morelli]

I would say it almost HAS TO be a leaky axle seal in the rear brake drum, if there's no visual at the pumpkin. I'm with you about the smell. That Motorcraft friction modifier is what most all rear end shops say is the best....but Whoo-Boy! Like a skunk, once you get a whif o' that funky stuff, you won't forget it. If I just take an un-opened bottle out of my chemical cabinet in the garage, my wife says she can smell it without even coming in the garage.

 

[Tnfastbk]

Yes Don I have. All is good, no leaks on the diff anyway. I do need to pull the back wheels to check my brake work, so I'll be sure to look at the axle seals. It definitely has that horrible smell of friction modifier. The Ford dealer guy warned me not to get any of that on my clothes or hands because of the smell. By the way it is only after a drive that I smell it, but it goes away after it cools down. I'll also call my rear end guy and see what he has to say. I've only had this after the axle rebuild.

Something that we just went through on my wife's car was when we installed the axles I bent one of the seals. So I ran to the local parts store and purchased a new replacement seal for a 9 inch small bearing rear end. Installed it with no issues blah blah blah, drove the car and had another issue that we had to pull the axles, too much gear. When we pulled the side with the new replacement seal as we loosened that axle, fluid immediately started leaking. Long story short I was sold the wrong seal as it did not fit the axle and I never thought to check it against the axle. But we had zero leaks on the ground but definitely had fluid going places it should not have been. We probably would have had some issues in the future. In what form I don't know just another point of view for you being you said you just replaced the axles.

 

[Stanglover]

To answer Big Red, Spike and tnfastbk at one time, thank for your input. Ford called for 1 - 4oz bottle of stinky sh*t and that's what it got. My 'guy' also says the same. Today, I'll pull the rear wheels and check the axle seals. These were all replaced when the axle was rebuilt, but there may be a slim chance that my 'guy' f'd up and put the wrong seals in. If there is a leak, then I'll have to go see my 'guy' as it's on him to fix it imo.  Before I do pull the wheels, I'll take the car out and get it hot. That way I can crawl under and try to smell the vent tube and then pull the wheels. I hope to hell that if it is the axle seals, it has not f'd up my new brakes.

I'll get back to you all with an update later today. Again, thanks to all for your input.

 

[Don C]

it's easy to damage the new seals when installing the axle shaft, especially if the seal and splines aren't lubed and if the seals are used to support the axle shaft when inserting. And, they aren't immune from the "new ain't necessarily good" syndrome.

 

[Big Red Mach 1]

it's easy to damage the new seals when installing the axle shaft, especially if the seal and splines aren't lubed and if the seals are used to support the axle shaft when inserting.

Yup. And they won't even look physically damaged sometimes, They'll just leak from being slightly out of round. Have also seen "perfect" cheapo seals leak too. I'd verify what ones they used to make sure they used quality seals.  

 

[Stanglover]

Thanks Don and Big Red, I just finished checking all the rear end over. There was no leaks from the left side axle seal, BUT there was slight leakage from the right seal, first pic.. The amount is just a trace and there was enough to wet the finger in the backer late lip. I don't know if this is enough to cause the "stinky rear end" syndrome or not. There are no leaks from the center section.

The pics show the vent tube location. The hole that the tube was in is not present on the right side. When I took it out, the clip for sure looked original. I do know that the center section had been out in the past, but that doesn't mean the axle was removed from the car. The rest are the left and right seal area. 

I will be taking the car out later so now I know where the possible areas of concern are, I'll be able to sniff out the spot.... if my nose will pick it up that is.

 

[Don C]

That's likely enough. Ever have a propane tank filled up? Even the small amount of odorant that escapes from the bleeder screw causes the tank to stink for hours.

There's a reason they add the odorants to various products, a warning that something is not right.

 

[Stanglover]

That's likely enough. Ever have a propane tank filled up? Even the small amount of odorant that escapes from the bleeder screw causes the tank to stink for hours.

There's a reason they add the odorants to various products, a warning that something is not right.

 I talked to my 'guy', Brad. Unfortunately he is not well again and unable at this time to look at it. He thinks that although he replaced the seals, I could have a worn axle shaft, but hard to tell just from a description. Now I know that there is a small leak,  I have decided not to overly worry about it, but keep my eye on it for the small amount of driving I'll be doing this year.  I don't want to get into doing a seal swop myself without proper tools. From reading my Ford manual, it can be tricky. Then again it is the Ford manual! 

I didn't get to take the car out today as company dropped by and that was that. For now, I'm confident what the smell is, just not totally sure where it's coming from. Thanks for your help, it's much appreciated.

 

[Stanglover]

Going through some of my old threads, I noticed I never closed this one off. Since the last update, I've been keeping an eye on that small leak from the right rear hub. When I was replacing the springs, I took the drum off and thankfully, the leak seems to have stopped. I will continue to monitor it, but I'm confident it is nothing to worry too much about. AND, the stink has stopped too!!

 

[Kenny nunez]

I do not like to “nit pick”but your lower brake spring is not seated properly in the respective locating hole.  The whole hooked end has to be inside the hole in the brake shoe.

 

[Stanglover]

I do not like to “nit pick”but your lower brake spring is not seated properly in the respective locating hole.  The whole hooked end has to be inside the hole in the brake shoe.

 Hmm, I don't think that's being nit-picky at all. To be honest, I really hate doing rear brakes, always have for some reason. I took pics of the old springs that were installed by a mechanic. I thought I'd got them the same. It's not the same angle, but below is a pic of the old spring install, opposite side though. Maybe the mechanic got them wrong, or I didn't copy exactly what he'd done. None the less, thanks for your input. I'll have to check them out, but that won't be till spring now. Because of the very slow seepage on that axle seal, I'll be checking that anyway. Do you or anybody else have good accurate pictures of how that spring ought to be?

Wait a minute! Did get that spring backwards? I think it might be, but just on the one side. The other pic looks ok..... I think.

 

[Kenny nunez]

The slightly blurry picture is correct.  All you need to correct yours is a good pair of pliers or vice grips to grab and pull the spring.

 

[Stanglover]

The slightly blurry picture is correct.  All you need to correct yours is a good pair of pliers or vice grips to grab and pull the spring.

 All I can say is "good eye". Thanks for spotting that error on my part. For sure it will get swapped around when the car is out of storage in Spring. Here's the other side, which looks correct.

Thanks Kenny.