#1  
Old 05-17-2022, 10:57 PM
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Default Pinion seal leak

'81 Formula with it's original 10 bolt 8.5
104K miles on it.

No gear noise but had some bearing noise and a real bad pinion seal leak when I got the car.
Took a close look at it. Noticed someone recently replaced the seal.

Definitely not leaking thru splines. It's past the seal. Flung on the tunnel and leaks when parked. Drips from behind flange on ground and runs to the cover and drips.

So, took it apart and changed the seal again using a NOS seal that even had a thin bead of sealer around the outside of the seal. Seal installed tight and thought all would be well.

Nope. Still leaked bad.

Just picked it up today from the drive line place because it needed new bearings anyway. Gave them another NOS seal and made them aware of the issue.

Brought it home and put it on jack stands at a slight angle and added about 4-6 ounces of gear lube. Leaks like a m-effer still.

When I tore the diff down before I dropped it off I inspected the seal area for any potential issues. Cracks, gouges, etc. Nothing.

Pinion flange is not grooved either. Look at the pic......it leaked THAT much at a slight angle in less than an hour.

WTF. Makes no sense.
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  #2  
Old 05-18-2022, 02:50 AM
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Just throwing this out there ... clogged vent? Don't know if it has been going through temp changes or not.

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Old 05-18-2022, 05:58 AM
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Is this the original ring and pinion gear, or a aftermarket?

Does the crush coller fit tight on the pinion?

Can you measure the OD of the pinion where the seal rides, and then measure the ID of a new seal?

The loading in of the pinion into the seal should compress it by like .030”, if not then I would think that if it’s a aftermarket pinion it was machined wrong and it will never seal right for you .

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Old 05-18-2022, 08:13 AM
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Quote:
Originally Posted by 25stevem View Post
Is this the original ring and pinion gear, or a aftermarket?

Does the crush coller fit tight on the pinion?

Can you measure the OD of the pinion where the seal rides, and then measure the ID of a new seal?

The loading in of the pinion into the seal should compress it by like .030”, if not then I would think that if it’s a aftermarket pinion it was machined wrong and it will never seal right for you .
A professional shop assembled it so I can't answer crush sleeve question.
Everything is factory original no aftermarket parts were used including the pinion flange. The pinion seal is NOS GM.

  #5  
Old 05-18-2022, 02:53 PM
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Compare the flange OD to another good one.
Try a aftermarket seal on both flanges off the rear.
The only factor the pinion would have is If the seal wasn't riding on the sealing surface one the flange is tight.

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Old 05-18-2022, 04:14 PM
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So you have confirmed that the leak is between the new seal and the cast iron case?

How tight did the seal tap in? Could it be a bad reference number and therefore the wrong seal?

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  #7  
Old 05-18-2022, 04:49 PM
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Quote:
Originally Posted by lust4speed View Post
So you have confirmed that the leak is between the new seal and the cast iron case?

How tight did the seal tap in? Could it be a bad reference number and therefore the wrong seal?
Yes it seems so, here is a pic. When I replaced the seal the first time in went in very tight. I don't have the part number handy but I got it directly from the factory 76-81 parts and illustration catalog.

I didn't want to take the flange off to check anything until I contacted the shop that assembled it. They told me to bring it back and they will find out what's going on. I just dropped it off now.

When I disassembled the diff last week before taking it to them, I did notice some marks on the inside of the pinion seal area on the driver side of the cast iron case hole, where it looked as if someone had jammed a screwdriver in to pry out the seal. I guess you could call it gouge marks but they were kinda slight and I didn't think they'd be an issue and the source of the original bad leak.

That area on the driver side of the hole is wet as pic shows and appears to be the source as it is the only wet area on the outside circumference of the seal where it meets the case.........besides the bottom area where the leak ran down.

I forgot to mention it to the shop when I first brought it to them initially. I did show them this pic and told them about it today. They said they'd pop the seal out and look at that area.

I hope that's the issue and it can be smoothed with some crocus cloth and some RTV on the outside of the seal before driving it in will fix it.

I'll update when they get back to me.

It's a bad leak for sure and I wouldn't think those marks would cause it to leak so bad but I hope I'm wrong. They are as puzzled as I am what's causing the leak as all OEM original parts were used and the area of the pinion flange where the seal rides was in good shape with no wear groove.
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Old 05-18-2022, 07:44 PM
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Sometimes the spring that keeps the lip seated against the flange can come off when assembled or the lip can get rolled under.

  #9  
Old 05-25-2022, 12:17 PM
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Just got a voicemail from the driveline place.
I am not sure what they tried to fix the leak as I won't be able to go there until tomorrow, but they claim the only way they were able to stop the leak was to replace the flange with a new one and use an "updated" two piece seal.

Can anyone clue me in to what that is exactly?

  #10  
Old 05-25-2022, 01:32 PM
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It probably did need a new flange, and a Double lip seal is a great idea. I would like to know that part number.

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  #11  
Old 05-25-2022, 03:10 PM
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I had a 12-bolt leak because the aftermarket seal was seating too deep on the end of the yolk. The side by side measurement of the original OEM seal (rubber) was 1/8" shallower than the aftermarket seal(s) so I put a 1/8" spacer (welding rod) between the aftermarket seal and the housing to keep it from being too deep. I have a picture somewhere comparing the OEM flange type seal with the aftermarket seal. I'm glad that I kept the old OEM seal or I might not have figured it out as quickly. That's what worked for me.

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