Community Forums

loydt · 01-13-2025, 09:50 AM

So last week I crawled under the back of my coach to R/R the rear rock guard since I had bent it while backing into an uneven driveway. I happened to notice oil all over the side of the engine just forward of the oil filter. Also noticed that the inside of the rock guard was stained with oil. It looks to me like gear oil which would indicate from the fan drive gear box.

About a year ago I went in and added the vent tube extension, topped off the oil, and cleaned that area up well. Back in early August while at the mothership, I had them service the fan drive box. What are the chances they overfilled it?

I dread taking that floor up again and getting to it but I guess I have no choice. I plan to check the level, add if needed, and then take it to Gaffney for a check out since they are close by. 35k miles on the coach

OMMM4747 · 01-13-2025, 10:18 AM

Was the oil filter dry or soaked? Start w/the easy stuff first ... ensure the oil filter is on tight and not cross threaded. You'll have to wipe it down and ensure there's no oil coming from it after running the engine. You may need to step on the gas to build up oil pressure.

I'm not familiar w/the 'tube extension' you mention, but call whoever serviced it and ask them if it was overfilled, how could you verify it, and where would it be porting out? Although I'm an avid DIYer, I always prefer the path of least resistance. They're the experts, ask them first.

Good luck

loydt · 01-13-2025, 10:49 AM

Its def not engine oil, you can tell my the smell and look of it. Also doesn't leak when parked in my shed.

The vent tube extension that I did was a result of what many people have discovered causing a problem with this gear box. There is a vent cap with a short extension screwed onto the top of the gear box. The issue was it was installed right in the path or the airflow coming from the side radiator fan and in some cases it was causing the gear oil to be sucked out of the box and running it dry. The extension is essentially a flexible grease gun extension that gets the actual vent piece out the airflow of the fan.

Jim_HiTek · 01-13-2025, 10:58 AM

I would look carefully at the last thing worked on. While the shop worked on fan drive box, did the tech perhaps bump into the vent extension setup? Go to the shop and ask the tech if it's possible s/he overfilled it and examine the vent tube setup. Usually, a shop will check it for you to be sure they didn't cause a problem. For free in my experience.

Dutch Star Don · 01-13-2025, 11:15 AM

Did you look to see if the extension was still there. Maybe they removed it when they did the service. Typically, when the fan drive box vent leaks, it sprays a lot of oil on the fan itself.

Reach in there with your phone from the back (outside) of the coach and snap some photos of the gear box. I like to do that and then download them to my laptop where I can enlarge them and really study what's going on.

loydt · 01-13-2025, 11:20 AM

Quote:

Originally Posted by Dutch Star Don

Did you look to see if the extension was still there. Maybe they removed it when they did the service. Typically, when the fan drive box vent leaks, it sprays a lot of oil on the fan itself.

Reach in there with your phone from the back (outside) of the coach and snap some photos of the gear box. I like to do that and then download them to my laptop where I can enlarge them and really study what's going on.

Don,

From the rear I can still see my extension is in place. I can see some dry oil residue on the fan blades, but that was there when I added the extension. I cleaned a lot of that off but did not get it all. I did get the box and area around it cleaned good with degreaser when I put that extension on. I will see what I find when I remove the floor in the rear.

NCC-1701A · 01-13-2025, 10:17 PM

The procedure to fill the gearbox is to remove the set screw up on the side and fill until it comes out that hole. If I follow that procedure, I am overfilled on the dip stick. The correct dip stick procedure is to just "set" it in on top the threads it goes in, not screw it in, then out to check level.

Even with my extension, which I ran up and over the fan box and out the back, if I use the fill procedure, it will spit out gear oil until it's to the full mark on the dipstick when just set on the threads in its hole.

So, in my case, it appears the dip stick is correct, which seems odd to me vs the location of the side hole.

If they filled it per procedure, and yours is like mine, it might be overfilled. It doesn't take a lot of overfill, in my experience.

loydt · 01-20-2025, 08:52 AM

Ok, I got in there on Saturday to check everything out. Everything was still in place from my vent extension. I did notice some oil on the actual tip of the vent extension. First thing I did was check the level in the gear box and it was just below the full mark, so by the mess I see in there I must have a leak elsewhere. I degreased everything best I could and will get it on down to Gaffney here in the next week or so to find out the leak.

Will post what they find.

OMMM4747 · 01-20-2025, 09:05 AM

Quote:

Originally Posted by loydt

I did notice some oil on the actual tip of the vent extension. First thing I did was check the level in the gear box and it was just below the full mark, ...

Sounds like -- hopefully -- only over filled and the 'mess' was created by oil spray as it vented while you were driving.

Looking forward to your report on Gaffney's findings.

Good luck

loydt · 01-29-2025, 10:10 AM

Well, Gaffney serviced everything but their comment about the oil leak is that its at the turbo, see Cummins. I was afraid of that, Cummins here in Charlotte is not my favorite place after what they did to my 400 ISL in my Monaco years ago. UGH!

OMMM4747 · 01-29-2025, 10:35 AM

Bad 4-yr old turbo?! That's not comforting for those of us w/the same engine or turbo. Still under chassis/engine warranty? If no, I'd trust but verify w/a second opinion before they start replacing and charging for unneeded repairs. Unless quality has decreased or you're extremely unlucky, turbos should last a lot longer than 4 years (presuming no frequent jack-rabbit runups to speed).

Good luck

loydt · 01-29-2025, 03:57 PM

I doubt the turbo is bad, there are several areas around the turbo that can leak oil and it's pretty common. Now if a high pressure line blew and it lost oil completely then it would be smoked. Anyway I made it home just fine and will get it to Cummins next week.

Capt. Bill · 01-29-2025, 07:36 PM

Quote:

Originally Posted by loydt

Its def not engine oil, you can tell my the smell and look of it. Also doesn't leak when parked in my shed.

The vent tube extension that I did was a result of what many people have discovered causing a problem with this gear box. There is a vent cap with a short extension screwed onto the top of the gear box. The issue was it was installed right in the path or the airflow coming from the side radiator fan and in some cases it was causing the gear oil to be sucked out of the box and running it dry. The extension is essentially a flexible grease gun extension that gets the actual vent piece out the airflow of the fan.

If indeed DEF- be sure to power wash it off really well as DEF is very corrosive. DEF will not have the lubricity of oil.

Happy Trails