Rear Differential Drip

[Mark S]

I have a very small drip coming from the gasket on the differential, to the right of drain plug in photo. I cleaned the area with brake cleaner and the drip returns after a day. There is no puddle on the ground, just a very small drip. This is surprising since my Seneca is just at 4 years old and about 32,000 miles.
Freightliner is telling me it will be over $1,000 to replace the gasket and who knows how long they will take to get it done. Other truck shops in my area don’t want to work on RVs.
What are you thoughts on additive products that claim to stop differential leaks?

[Grumpy]

Originally Posted by Mark S

I have a very small drip coming from the gasket on the differential, to the right of drain plug in photo. I cleaned the area with brake cleaner and the drip returns after a day. There is no puddle on the ground, just a very small drip. This is surprising since my Seneca is just at 4 years old and about 32,000 miles.
Freightliner is telling me it will be over $1,000 to replace the gasket and who knows how long they will take to get it done. Other truck shops in my area don’t want to work on RVs.
What are you thoughts on additive products that claim to stop differential leaks?

There have been several discussions about that problem so hopefully one of the owners involved will jump in soon. Looks like someone put a jack under the differential since the drain plug appears to be pushed up. That was also discussed.

[RogerR]

NOPE on the additive. It would probably violate any warranty the MFG. has on it. Clean it again. See if it is the drain plug. If it is then get a gasket/washer/seal for the plug and a new plug.

If it is the main seal check that all the bolts are torqued properly. DO NOT OVER TIGHTEN!

I doubt it will work but you could super clean the area ( brake cleaner) and apply some kind of sealant that will stick to metal.

Before any of that see if the manufacturer or the chassis or the axle will do a warranty repair.

[craigav]

I suppose it goes without saying, find out what type of lubricant is required and get a hand pump filler tube thing that most auto supply stores sell and be sure not to let the axle get too low on oil. I had a truck years back that had a slight drip similar to your picture, it took a whole year before it dripped enough to use about half a quart. Sometimes the drip looks worse than it is. ~CA

[Colorado]

You can use a piece of Romex, roll a small loop on the end as a finger hold, simply remove the fill plug, slide in the romex and you’ll be able to monitor how much you’re actually losing...

[Rustynuts]

It does not look like the drain plug is leaking, it is a pipe thread with no seal to replace. I am going to agree with Grumpy that it looks like there is some deformation of the drain plug area, mine is not indented at all. If this area has hit something or if a Jack was used on the differential to deform it, it looks like the deformation has affected the mating surfaces of the housing and 3rd member which the gasket can no longer seal. It’s not a hard job to pull the axles and 3rd member to change the gasket BUT they are BIG and HEAVY parts, more than most people would want to tackle. I would NOT use any additive...it’s all just snake oil. Personally, I would probably first try sealing this lower area with a Permatex product called “The Right Stuff” which is like an RVT but much better IMO, it’s amazing stuff. Clean the area extremely well with brake cleaner, then again with either Xylene, Lacquer Thinner or Acetone, something that flash dries fast, and quickly apply The Right Stuff over the seam area, and I would make the coverage say from the 4-8 o’clock positions, let it dry and see what happens. This would be a cheap try that won’t hurt anything if it doesn’t work and won’t affect any future repair if needed.

Also, you would have to find out the torque spec, but you might check to see if the bolts holding the 3rd member to the housing are all tightened to spec.

Have you ever had it in for tire service where they might have jacked it up here? If you have recently, you might go back to the place that did it and discuss them covering the repair.

[Jagiven]

At a $1k, I would be doing some research to fix it right myself. First step is knowing where it is originating from.

Not sure about your rear dif lube, but many of the conventional diff lubes fluorescent under 940nm ir light. Its an easy way to see where a leak is coming originating. Then make a plan to address the issue.

[rgolding]

I had the same type of leak, but mine was under warranty. It was an overnight repair at a Truck Centers of America, to allow the new gasket cement to dry.

[Robbbyr]

I had a leak between the differential carrier and the housing, it seems the only sealer used on my 2014 was a bead of silicone. My axle was just months out of warranty and my local dealer tried escalating my case to get it covered but Freightliner said "No". So the dealer took pity on me and did the job for $650 if memory serves, including a synthetic lube refill.

It does require the axles to be pulled and the differential housing to be removed, not your average driveway job!

[SloPoke]

Originally Posted by RogerR

NOPE on the additive. It would probably violate any warranty the MFG. has on it. Clean it again. See if it is the drain plug. If it is then get a gasket/washer/seal for the plug and a new plug.

Before any of that see if the manufacturer or the chassis or the axle will do a warranty repair.

X2

Originally Posted by Rustynuts

It does not look like the drain plug is leaking, it is a pipe thread with no seal to replace. I am going to agree with Grumpy that it looks like there is some deformation of the drain plug area, mine is not indented at all. If this area has hit something or if a Jack was used on the differential to deform it, it looks like the deformation has affected the mating surfaces of the housing and 3rd member which the gasket can no longer seal. It’s not a hard job to pull the axles and 3rd member to change the gasket BUT they are BIG and HEAVY parts, more than most people would want to tackle. I would NOT use any additive...it’s all just snake oil. Personally, I would probably first try sealing this lower area with a Permatex product called “The Right Stuff” which is like an RVT but much better IMO, it’s amazing stuff. Clean the area extremely well with brake cleaner, then again with either Xylene, Lacquer Thinner or Acetone, something that flash dries fast, and quickly apply The Right Stuff over the seam area, and I would make the coverage say from the 4-8 o’clock positions, let it dry and see what happens. This would be a cheap try that won’t hurt anything if it doesn’t work and won’t affect any future repair if needed.

Also, you would have to find out the torque spec, but you might check to see if the bolts holding the 3rd member to the housing are all tightened to spec.

Have you ever had it in for tire service where they might have jacked it up here? If you have recently, you might go back to the place that did it and discuss them covering the repair.

I'm betting on the Jack on the Diff... deformed the housing and causing the leak...

Originally Posted by Robbbyr

I had a leak between the differential carrier and the housing, it seems the only sealer used on my 2014 was a bead of silicone. My axle was just months out of warranty and my local dealer tried escalating my case to get it covered but Freightliner said "No". So the dealer took pity on me and did the job for $650 if memory serves, including a synthetic lube refill.

It does require the axles to be pulled and the differential housing to be removed, not your average driveway job!

a BIG driveway job...

[Rustynuts]

Originally Posted by SloPoke

X2

I'm betting on the Jack on the Diff... deformed the housing and causing the leak...


a BIG driveway job...

Or a good time to throw in a Locker 😂

[Mark S]

Thanks for all the responses. So I crawled back under the Seneca and spent some time becoming “one with the differential”. First, while it may look like the are around the drain is indented, the area is perfectly symmetrical with no sign of ever suffering any trauma. Not even a scuff in the paint so I’m going with it is not damaged. And I’ve never had any work done where it would be lifted.

As Rob said about his, it looks like the gasket is silicon bead and perhaps is the same issue he had, although several years later than his. And way out of warranty.

When I checked the fluid level, it was just below the hole, maybe 1/2” at most.

As Brian suggested, I ordered “the Right Stuff” from my friends at Amazon. I will try cleaning really well and applying a bead around the around the contact area and see if that helps.

If I had a good Freightliner place to work with locally I would probably bring it in but they are always so backed up and never really happy to work on RVs, even M2s.

[Mark S]

Originally Posted by Rustynuts

Or a good time to throw in a Locker 😂

A locker would be good. Lol.

[SloPoke]

Originally Posted by Rustynuts

Or a good time to throw in a Locker 😂

I strongly endorse this idea!!!

[Midnightmoon]

Originally Posted by Mark S

Thanks for all the responses. So I crawled back under the Seneca and spent some time becoming “one with the differential”. First, while it may look like the are around the drain is indented, the area is perfectly symmetrical with no sign of ever suffering any trauma. Not even a scuff in the paint so I’m going with it is not damaged. And I’ve never had any work done where it would be lifted.

As Rob said about his, it looks like the gasket is silicon bead and perhaps is the same issue he had, although several years later than his. And way out of warranty.

When I checked the fluid level, it was just below the hole, maybe 1/2” at most.

As Brian suggested, I ordered “the Right Stuff” from my friends at Amazon. I will try cleaning really well and applying a bead around the around the contact area and see if that helps.

If I had a good Freightliner place to work with locally I would probably bring it in but they are always so backed up and never really happy to work on RVs, even M2s.

If you are ever in the Northeast, I highly recommend Freightliner of Maine. I'm certain that they will take care of anything you could throw at them.

[FishNFarm]

Two simple things you can do. Do not take the out. loosen all the bolts enough to clean the surfaces after draining the oil then spread a new layer of silicone in between the housing and the diff. My favorite fix is get some nylon string about twice the size of kite string. Loosen the nuts on the studs to be able to wrap the string snug against the studs. Don't tie a knot just get the wife to pull them tight and tighten the studs up. Make 3-4 wraps around the studs This is also a good time to do some male female bonding while you are both flat on your backs under the thing in the drive way. What ever you do even if you have FL repair it keep a close eve on it in the beginning. Check it with a piece of wire like someone suggested. Even though it looks like a big leak it doesn't appear to be.

[MD3]

Mine was leaking the same. I took it in to my local Freightliner dealer and they fixed it under warranty (2018 model fixed in Aug 2020). The fix was resealing the diff.

I had the same dimple in the diff at the drain plug. I can't remember if I posted here or FB but I had the same pictures and same concerns.....


_

[RVermont]

Similar leak here on my 2018. The housing looks okay and is similar to mine. I was able to get it repaired no charge sept 2020. I will try to locate the slip if I can and post it.

[javamon]

Originally Posted by craigav

... I had a truck years back that had a slight drip similar to your picture, it took a whole year before it dripped enough to use about half a quart. Sometimes the drip looks worse than it is. ~CA

Mine has had a very slow seep for about a year. My approach so far is to check it every 2500 miles and so far it requires very little gear oil. May try to get it fixed before our trip in Sept.


My diff casing looks just like Mark's.

[curver900]

Originally Posted by Mark S

When I checked the fluid level, it was just below the hole, maybe 1/2” at most.

check your manual most rear ends now are below the hole anywhere from 1/8" to 1/2" on a flat level surface blah blah blah...

This may be one of those things that isn't worth the risk to fix... breaking that seal cleaning it up and putting it back together is probably going to leak and possibly leak more...
Good luck !