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Old 06-10-2019, 12:15 PM   #1
Damien8086
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Rear differential leaking from cover

A couple of questions (apologies ahead of time for my ignorance):

(1) I have a greenish colored liquid slowly dripping from the rear differential cover. Is this likely just a matter of taking the cover off and replacing the gasket or is there probably more to it? Do I need to drain the differential fluid first and if so is there a guide on here somewhere for how to drain and refill? Any gotchas or anything I should know before replacing the gasket if that is all it is? Are there stud kits for the 12 bolts and can I just use a fel-pro dry gasket?

(2) I noticed a rubber hose that appears to be connected somewhere near the front of the rear differential and the other end appears to just be tucked up in the frame. What is this for and does this look right (the hose just being tucked up into the frame like that?)

Thank you for any help.
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Old 06-10-2019, 12:20 PM   #2
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Re: Rear differential leaking from cover

That is the diff vent. It should have an actual vent valve in the end of the hose.

The leak? You need to pull the cover and reseal it. If you put any sealant on it, put it on the cover side only, and look for any scratches on the housing and clean them up.
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Old 06-10-2019, 12:24 PM   #3
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Re: Rear differential leaking from cover

Quote:
Originally Posted by demian5 View Post
That is the diff vent. It should have an actual vent valve in the end of the hose.

The leak? You need to pull the cover and reseal it. If you put any sealant on it, put it on the cover side only, and look for any scratches on the housing and clean them up.
Thanks for the quick reply. Is there a fluid reservoir somewhere or a way to check the level of the fluid? Where do I fill it with new fluid? I am assuming when I pull the cover that the fluid won't just come pouring out?
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Old 06-10-2019, 12:31 PM   #4
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Re: Rear differential leaking from cover

Order your self a tube of this. I use this on everything. It is like glue.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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Old 06-10-2019, 12:52 PM   #5
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Re: Rear differential leaking from cover

Your assumption is wrong. When you pull the cover the grease will pour out. Have a pan under it. That is the normal way to drain it. The fill plug is on the right hand side of the housing. It is a pipe plug usually removed with a 3/8 socket drive. Fill it to the level of the plug. There is no stud kit but a guy could put studs in if he wanted. I glue the new gasket to the cover with trim cement & use a thin layer of RTV on the other side.
Fill with gear lube that is specified for GL5. 90 weight or a multi weight including 90.
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Old 06-10-2019, 12:56 PM   #6
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Re: Rear differential leaking from cover

Quote:
Originally Posted by Wrenchbender Ret View Post
Your assumption is wrong. When you pull the cover the grease will pour out. Have a pan under it. That is the normal way to drain it. The fill plug is on the right hand side of the housing. It is a pipe plug usually removed with a 3/8 socket drive. Fill it to the level of the plug. There is no stud kit but a guy could put studs in if he wanted. I glue the new gasket to the cover with trim cement & use a thin layer of RTV on the other side.
Fill with gear lube that is specified for GL5. 90 weight or a multi weight including 90.
George
Thank you George for taking the time to write such a helpful reply. Sounds like I have a good weekend project ahead of me.
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Old 06-10-2019, 01:01 PM   #7
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Re: Rear differential leaking from cover

I went from a rusty cover to an original a member kindly gave me. When you look for a gasket, you might do a search for a "lube locker" brand - had good luck with mine.
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Old 06-10-2019, 01:09 PM   #8
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Re: Rear differential leaking from cover

never heard of green colored gear lube ?
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Old 06-10-2019, 01:21 PM   #9
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Re: Rear differential leaking from cover

Quote:
Originally Posted by Damien8086 View Post
Thanks for the quick reply. Is there a fluid reservoir somewhere or a way to check the level of the fluid? Where do I fill it with new fluid? I am assuming when I pull the cover that the fluid won't just come pouring out?
Loosen the bolts holding the cover, not too much, and pry the cover away at the bottom, you can loosen the lower bolts more than the upper ones. Make sure you have a drain pan under the rear end. The rear end lube will drain into the pan then you can remove the cover. After you get everything cleaned up and the cover reinstalled, don't over tighten the bolts. There is a pipe plug on the left side of the housing. You remove the plug and fill the housing with gear lube through the plug hole till it just starts to run out and replace the plug. The rear end is now filled to the proper level.
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Old 06-10-2019, 03:00 PM   #10
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Re: Rear differential leaking from cover

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Originally Posted by 54blackhornet View Post
never heard of green colored gear lube ?
Yeah it looked a bit like antifreeze almost - a green alien looking goop
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Old 06-10-2019, 03:01 PM   #11
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Re: Rear differential leaking from cover

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Originally Posted by RodnRudy View Post
Loosen the bolts holding the cover, not too much, and pry the cover away at the bottom, you can loosen the lower bolts more than the upper ones. Make sure you have a drain pan under the rear end. The rear end lube will drain into the pan then you can remove the cover. After you get everything cleaned up and the cover reinstalled, don't over tighten the bolts. There is a pipe plug on the left side of the housing. You remove the plug and fill the housing with gear lube through the plug hole till it just starts to run out and replace the plug. The rear end is now filled to the proper level.
Thanks Rudy, this is very helpful
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Old 06-10-2019, 03:35 PM   #12
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Re: Rear differential leaking from cover

my old gear oil had a greenish tinge to it
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Old 06-10-2019, 03:57 PM   #13
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Re: Rear differential leaking from cover

Before putting the cover and new gasket on make sure the mounting surface of the cover is flat. Often due to bolting the cover in place the edges of the bolt holes will get flared out which can cause the new gasket not to seal well. After cleaning up the cover take a small hammer and block of wood to tap these edges back flat with cover resting on a hard smooth surface (concrete, anvil, etc).
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Old 06-10-2019, 04:05 PM   #14
Damien8086
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Re: Rear differential leaking from cover

Thank you for the tips C-ries

Does anyone know what the fill capacity is for the rear differential so that I know how much fluid I'll need to purchase.

Has anyone tried one of the aluminum covers like this or this ?
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Old 06-10-2019, 04:06 PM   #15
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Re: Rear differential leaking from cover

This is the stuff I use in all my gear boxes and differentials.
https://lucasoil.com/products/gear-o...hetic-gear-oil
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Old 06-10-2019, 04:12 PM   #16
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Re: Rear differential leaking from cover

Quote:
Originally Posted by Damien8086 View Post
Thank you for the tips C-ries

Does anyone know what the fill capacity is for the rear differential so that I know how much fluid I'll need to purchase.

Has anyone tried one of the aluminum covers like this or this ?
Buy two quarts so that you have a little extra, just in case. Some brands come with a pump built in for easier filling.
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Old 06-10-2019, 04:31 PM   #17
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Re: Rear differential leaking from cover

Damien do you know if have posi trac? If you do, you will need to buy some posi-trac additive as well. I just did this on our 68 with the 12 bolt rear end like yours last week.

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Old 06-10-2019, 04:41 PM   #18
Damien8086
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Re: Rear differential leaking from cover

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Originally Posted by Motorfist View Post
Damien do you know if have posi trac? If you do, you will need to buy some posi-trac additive as well. I just did this on our 68 with the 12 bolt rear end like yours last week.
Not sure... it's a 1970 C10 CST V8 5.7. When I get home I'll see if it has a tag by the fill hole.

When I get to doing the job and have the cover off I'll try and take a couple of pictures of the inside and post them.
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Old 06-10-2019, 04:57 PM   #19
Damien8086
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Re: Rear differential leaking from cover

RodNRudy had mentioned not to overtighten the bolts so are you guys just hand-tightening them and then maybe a quarter turn with a socket or are you using a torque wrench?
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Old 06-10-2019, 05:21 PM   #20
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Re: Rear differential leaking from cover

I used a torque wrench at 20 Ft. Lbs. as the manual says and no leaks so far
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Old 06-11-2019, 08:41 AM   #21
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Re: Rear differential leaking from cover

Use a premium performance gear lube, like Royal Purple, that is good to go for posi. Can't go wrong. But once the cover is off you can see what you have. I just use improved lube anyway.
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Old 06-11-2019, 09:08 AM   #22
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Re: Rear differential leaking from cover

Quote:
Originally Posted by special-K View Post
Use a premium performance gear lube, like Royal Purple, that is good to go for posi. Can't go wrong. But once the cover is off you can see what you have. I just use improved lube anyway.
Can't speak about a posi rear end, but when I changed the diff fluid in my '65 Nova to royal purple it whined. Went back to Lucas GL4 90W and the whine was gone. Royal Purple makes good products, but in this particular case it was a wrong choice. Just FYI.
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Old 06-11-2019, 10:21 AM   #23
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Re: Rear differential leaking from cover

The best stuff I have found to seal the diff cover is Permatex 81182. It's made specifically for use with gear oil. I smear a thin coat of it on both sides of a gasket.

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Old 06-11-2019, 12:58 PM   #24
Damien8086
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Re: Rear differential leaking from cover

I went ahead and ordered the Toyota gasket sealant that beaterku linked to.

I haven't had a chance to pull the cover off yet, but I did get another picture of the green drip. I also looked at the vent hose and I am not seeing a vent valve in the end of it. I've attached a picture - should there be something visible in the end of the hose in the picture?

Does anyone have a good picture of the fill bolt? One post said it was on the right side and another said it was on the left side. I was looking around last night and I am not seeing one, but I am sure I am just missing it.
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Old 06-11-2019, 01:09 PM   #25
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Re: Rear differential leaking from cover

That drip looks like clean gear oil to me. Regular clean gear oil is a greenish brown in my experience. Any idea when the oil level could have been topped off, as in did you recently buy this truck and the previous owner filled it up before you bought it?

The fill plug on my 12 bolt is on the passenger side of the front/driveshaft side of differential housing, less than halfway up. It has a square head like a threaded pipe plug. You will have to crawl under the truck on the passenger side, in front of the tire to see it. I'd take a picture but my truck is at the shop getting an alignment after I rebuilt the front end.

Good luck!
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