66 diff leak

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Feb 17, 2017 | 01:14 PM

sugg60

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6th Gear

Joined: Apr 2016

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66 diff leak

I'm changing out the rear spring on my 66 coupe(HD 3:36). I removed the 4 bolts and plate that hold the spring to the diff and I now notice a few drops of gear lube coming out of one of the bolt holes. I left the bolt out for several days and it has not stopped. Is this normal or is my diff cracked? What say you.

Feb 17, 2017 | 01:40 PM

quahog

Racer

Joined: May 2003

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From: taunton mass

Quote:

Originally Posted by sugg60

No it's not normal, the problem probably is from someone putting a longer bolt in that hole than original. It's a blind hole and a longer bolt will break thru the casing , causing the leak. This can be fixed from the inside using JB weld , or replace the casting. You know how I know this... Hope this helps Jeff

Feb 17, 2017 | 01:54 PM

Powershift

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From: Bowling Green, Kentucky

Quote:

Originally Posted by quahog

Broken/cracked rear cover. Just went thru this with a good friend and his 1969 Corvette. Fortunately, he worked for a large New Orleans machining company and had the shop welders fix it for him. Pre and post weld heating required in addition to the weld itself. Now it is as good as new.

You might get by for awhile just using a thread sealant on the bolt. Heavy duty replacement rear covers are available from Muskegon Brake.........and also used originals are also out there if you search. But you may never find/get the original codes..........if that matters to you.

Larry

Feb 18, 2017 | 08:54 AM

ILBMF

Drifting

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You could try cleaning the threads with brakleen and installing a new clean bolt with sealant...worth a try.

Feb 18, 2017 | 09:38 AM

dkleather

Melting Slicks

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From: Strongsville, OH

2016 C2 of the Year Finalist

Just wondering...are all four bolts for mounting originally the same length or are two of them that go into the cover shorter? In other words, can you mix up the original bolts on an install and break the cover?

Dave

Feb 18, 2017 | 11:04 AM

Powershift

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From: Bowling Green, Kentucky

Quote:

Originally Posted by dkleather

Dave

They SHOULD all be the same length..............but you never know on a 50 year old car what is/was installed in the past.

The two bolts that thread into blind holes are the critical ones that require checking.........the other two don't really matter as long as they go thru all the rear cover threads.

Reproduction springs and reproduction spring liners are a different thickness than originals, so any changes/replacements to them will also affect the required/needed bolt length. Do not just assume that all is well.

Larry

Feb 18, 2017 | 11:31 AM

dkleather

Melting Slicks

Joined: Jul 2005

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From: Strongsville, OH

2016 C2 of the Year Finalist

Quote:

Originally Posted by Powershift

Larry

Thanks Larry, The reason I asked was that I replaced my rear spring with an Eaton a few years back and the bolts were all the same length. I put weight on the car before final tightening of the bolts. Months later I had the car on a lift and noticed some seeping from one of the cover spring bolts. I removed it and a bit more flowed out. I put a bunch of permatex on the bolt and replaced it but still have a very little seep but no drip. I wipe the spring base every six months or so.
I've wondered since how that could have happened. The bolts may have been replaced before since the spring I replaced wasn't original. Thanks for the info. Dave

Last edited by dkleather; Feb 18, 2017 at 11:32 AM.