Rear differential drain plug has a drip

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Rear differential drain plug has a drip

August 12, 2021, 11:19:33 am

Good morning everyone
Just noticed a drip coming from the rear differential drain plug and upon a closer look I saw that there are like three threads exposed on this plug.
I'm pretty sure that no threads should be exposed on this plug.
I tightened it a little bit but need to find the torque value for it. I still have about 1 1/2 to 2 threads exposed. Hopefully it's written In one of the books that I have

Re: Rear differential drain plug has a drip

Reply #1 – August 12, 2021, 11:26:31 am

That's is pipe thread and it looks fine to me. Tightening may stop it from leaking
but it may have to be taken it out and put pipe dope onto the treads to stop it from
leaking.

Re: Rear differential drain plug has a drip

Reply #2 – August 12, 2021, 11:49:10 am

Quote from: Lt403 – August 12, 2021, 11:19:33 am

I'm pretty sure that no threads should be exposed on this plug.
I tightened it a little bit but need to find the torque value for it. I still have about 1 1/2 to 2 threads exposed. Hopefully it's written In one of the books that I have

As OldGuy says, it's a pipe thread and will have threads exposed. The photo is at an angle but it almost looks as if the plug is at a bit of an angle itself with more threads visible on one side.

Pierce

Re: Rear differential drain plug has a drip

Reply #3 – August 12, 2021, 11:56:15 am

Use white teflon permatex on threads.

Re: Rear differential drain plug has a drip

Reply #4 – August 12, 2021, 12:09:40 pm

I thought the same as Pierce on the threads.sure looks cross threaded to me. Any records of when it was serviced?

Re: Rear differential drain plug has a drip

Reply #5 – August 12, 2021, 12:32:58 pm

Will need to look at my service records and see if I find it.
Don't understand why have exposed threads that can be damaged.

Re: Rear differential drain plug has a drip

Reply #6 – August 12, 2021, 12:49:48 pm

Pictures can fool the eye. Use a breaker bar and back it out a half turn and if it moves easily put it back in tighter and wait to see if the drip stops before draining and using thread sealant.

Re: Rear differential drain plug has a drip

Reply #7 – August 12, 2021, 01:02:53 pm

Pipe thread is a tapered thread so there is almost always thread exposed.
Do what Craneman said.

Re: Rear differential drain plug has a drip

Reply #8 – August 12, 2021, 01:25:49 pm

Thanks everyone,
Differential fluid has been changed twice since we have owned the couch for two years.
Both times at MOT.
last service January 18 of 21

Re: Rear differential drain plug has a drip

Reply #9 – August 12, 2021, 01:32:41 pm

Probably just didn't get tightened enough. Hard to cross thread pipe threads doubt a MOT mechanic would do so.

Re: Rear differential drain plug has a drip

Reply #10 – August 12, 2021, 01:46:32 pm

Quote from: Lt403 – August 12, 2021, 01:25:49 pm

Thanks everyone,
Differential fluid has been changed twice since we have owned the couch for two years.
Both times at MOT.
last service January 18 of 21

Twice in two years...... haven't changed ours in 6. And 50,000 miles. Am I way... behind.

Re: Rear differential drain plug has a drip

Reply #11 – August 12, 2021, 01:49:41 pm

You are not behind they just are changing it too soon

Re: Rear differential drain plug has a drip

Reply #12 – August 12, 2021, 04:19:20 pm

You need some good diesel rated or oil rated pipe dope to put on the threads to stop the leak. It doesn't take much torque to put it in, you over torque it and it will be a real pita to get it out.

Re: Rear differential drain plug has a drip

Reply #13 – August 14, 2021, 08:01:02 pm

Quote from: Bob & Sue – August 12, 2021, 01:46:32 pm

Twice in two years...... haven't changed ours in 6. And 50,000 miles. Am I way... behind.

Sadly, FT's maintenance schedule in the owner's maintenance book has "Change Differential Lubricant" every 12 months or 14,000 miles, whichever comes first

There's a lot of folks who have likely had this done wayyyyy... more often than it actually needs to be done.

Re: Rear differential drain plug has a drip

Reply #14 – August 14, 2021, 08:08:41 pm

Which reminds me..............I need to rotate the air in my tires.

Re: Rear differential drain plug has a drip

Reply #15 – August 14, 2021, 08:40:27 pm

I have not changed my muffler bearings yet at 43K miles. Hmmm

Re: Rear differential drain plug has a drip

Reply #16 – August 14, 2021, 11:36:35 pm

Quote from: John & Genni – August 14, 2021, 08:40:27 pm

I have not changed my muffler bearings yet at 43K miles. Hmmm

Sounds like you and hillbilly deluxe need to get together and do some maintenance. 😂

Re: Rear differential drain plug has a drip

Reply #17 – August 15, 2021, 06:54:22 pm

Quote from: Lt403 – August 12, 2021, 12:32:58 pm

Will need to look at my service records and see if I find it.
Don't understand why have exposed threads that can be damaged.

Aaaaarrrrggggghhhh!

THAT is a tapered pipe thread pipe plug. Without the taper you would just wind the plug through into the inside and it would fall in and break the gears. The taper is designed in for positioning. tightening it does not stop it from leaking. Pipe Dope, or Teflon tape stops the leak.

Assembled thread systems have two leakage paths designed in and it is not a flaw, it's a feature. When the male and female parts are screwed together there exists a spiral groove where the crest of one thread meets with the root of the other. Hence two spiral paths for leakage.

For something like a pipe plug use pipe dope, or a paste thread sealant. The problem with Teflon tape is that pieces end up inside with repeated assembly and assembly.

Rector Seal #5 is good with hydrocarbons.

https://www.lowes.com/pd/RectorSeal-No-5-Pipe-Thread-Sealant-Sealant/3134515?cm_mmc=shp-_-c-_-prd-_-plb-_-google-_-lia-_-142-_-plumbingconnectionsandsupport-_-3134515-_-0&placeholder=null&ds_rl=1286981&gclid=CjwKCAjw9uKIBhA8EiwAYPUS3M93znMrMesp3V4hfrBGQYxH0nqKdGQcXk3-6id5pzy3z5OoJtBsGBoC6EUQAvD_BwE&gclsrc=aw.ds

Re: Rear differential drain plug has a drip

Reply #18 – August 15, 2021, 06:59:27 pm

Quote from: Lt403 – August 12, 2021, 01:25:49 pm

Thanks everyone,
Differential fluid has been changed twice since we have owned the couch for two years.
Both times at MOT.
last service January 18 of 21

Seriously? There's a saying about having a knowledgeable customer running around somewhere in the back of my mind.

Re: Rear differential drain plug has a drip

Reply #19 – August 15, 2021, 07:01:11 pm

Have never needed sealer on any of my truck or crane differentials and they don't leak. When you tighten it up the thread contact area stops the leaks. Same with car differentials I have owned.

Re: Rear differential drain plug has a drip

Reply #20 – August 15, 2021, 07:08:36 pm

Quote from: craneman – August 15, 2021, 07:01:11 pm

Have never needed sealer on any of my truck or crane differentials and they don't leak. When you tighten it up the thread contact area stops the leaks. Same with car differentials I have owned.

It's more a matter of the high pressure additives* in differential oil. The spiral paths are always present except in the case of the dryseal tapered pipe thread standard. And that one is not reusable.

* In the good old days that would have been lead oxides.

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