Author Topic: Rear diff leaking  (Read 5188 times)

Offline Chadwick717

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Rear diff leaking
« on: June 30, 2014, 07:48:18 PM »
1979 k10 np203 transfer case 12 bolt rear diff, (that's all I know about the rear diff)

So I have only owned this truck since April, and have been fiddling with it since.  It runs good and I have driven it couple times a week, with the occasional 2 hour + trip thrown in.  The truck was in great shape when I bought it, but on Sunday I finally got around to greasing the driveshafts, etc to get a baseline mileage for servicing. I also changed the oil in the transfer case.  I was going to check the oil in the differential, but I didn't know it was a square plug/also didn't know I could use a socket extension.  So this morning I took it to my local lube place where they let me get under the truck with them and had them check the rear diff.  Turns out it was pretty much empty.  I had noticed a very minor leak, but I thought it was no big deal.  I had them fill it and it turns out it was only a minor leak because it must have been almost empty.  It is leaking pretty bad now that it is full.  I bought a new gasket and tmrw I plan on replacing it tmrw. 

My question is this, how bad was it that I have been driving for who knows how long with low oil in the rear diff?  I plan on changing the gasket and oil tmrw and just running with it.  Any gotchas with this plan? 

Offline bake74

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Re: Rear diff leaking
« Reply #1 on: June 30, 2014, 08:40:10 PM »
     Since you are going to change gasket and oil, when you have it taken apart, use a cleaner like brake clean and clean the inside real good.
     Then with a flash light look for any damage, chips, missing teeth.  Check for excessive blueing of the ring or pinion gears.  Check the operation of the bearing by jacking up the truck and slowly turning the axles back and forth and make sure it is smooth and no grinding or metal sound when turning.
     If everything checks out, fill it seal it and see below.
     Are you positive that the leak was not coming from the seal on the pinion ?  That would be in the front of the axle, inside the housing.  The only way to get to it is take the ring and pinion out and replace the seal.
     At this point, I would do all the above, fill it and keep an eye on it over the next several times you drive it to make sure it is not leaking from the pinion seal.
 
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#2: There is no such thing as impossible, it just takes longer.
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Offline Chadwick717

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Re: Rear diff leaking
« Reply #2 on: June 30, 2014, 08:51:53 PM »
Thanks bake.  I didn't think about the brake clean.  I can see the fluid dripping from the the bottom of the diff cover, so I'm assuming it is the gasket.

Offline Chadwick717

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Re: Rear diff leaking
« Reply #3 on: June 30, 2014, 09:47:34 PM »
Oh, and I've been assuming that my gm corporate 12 bolt is not limited slip, besides jacking up the truck and spinning one wheel, is there a way to tell with the code on the passengers side front of the diff?  I think it says 8896839N and the drivers side says GM 86.

Offline Captkaos

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Re: Rear diff leaking
« Reply #4 on: July 01, 2014, 10:22:34 PM »
On the housing or the tube?

Offline Chadwick717

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Re: Rear diff leaking
« Reply #5 on: July 14, 2014, 03:56:19 PM »
Sorry I missed this reply. It was on the housing.  But I jacked up the end and spun one side, it is not limited slip.  Got a new gasket, and checked out the inside, everything looked good so I sealed it up and ran with it. Working good so far!

Offline thefarmboy21

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Re: Rear diff leaking
« Reply #6 on: July 18, 2014, 11:03:23 AM »
Check for wet spots around your pinion yoke, where the driveshaft goes and look directly above it on the bed. My K20 had a bad pinion seal and you can see a grease line all the way across the bed floor from where it flings it from the yoke while driving.
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86 Chevy K20 Custom Deluxe-Grandpa bought it new 11/20/85
77 Chevy K10 Custom Deluxe-Dad's first truck
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