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Leaky rear diff 2002 mustang gt #4512747
09/10/17 10:17 PM
09/10/17 10:17 PM
Joined: Oct 2011
Posts: 70
Az
daemontrym Offline OP
daemontrym  Offline OP
Joined: Oct 2011
Posts: 70
Az
I have a leaking rear diff that leaks in the bottom left corner no matter what I have tried.
I used a paper gasket with alitttle bit of ultra black rtv to hold it in place. Then it started to leak
In a couple of months. Then picked up a felpro gasket that I followed the instructions on not using any
Rtv and it's still leaking. Both surfaces have been scraped clean of old material and cleaned off with brake cleaner and wiped it dry. I torqued the cover into place per what the manual said which is 28ft lbs. I just saw a couple of drops on the driveway when going to put gas in it. The surfaces are not gouged or has any damage I can see. So I am at a loss

I did not use rtv because the sway bar is very close to the diff over. I have to do a lot of shimmying to get the diff over off.

Thanks

James

Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512751
09/10/17 10:21 PM
09/10/17 10:21 PM
Joined: Sep 2005
Posts: 5,664
MIchigan
Warstud Offline
Warstud  Offline
Joined: Sep 2005
Posts: 5,664
MIchigan
Try tightening the bolts down a bit more.

Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512752
09/10/17 10:22 PM
09/10/17 10:22 PM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline
Merkava_4  Offline
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Never use RTV and gaskets together. That's your problem.

With paper gaskets, use Permatex 2B.

Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512755
09/10/17 10:32 PM
09/10/17 10:32 PM
Joined: Jun 2005
Posts: 11,319
Santa Barbara, CA
bdcardinal Offline
Happy Birthday bdcardinal  Offline
Joined: Jun 2005
Posts: 11,319
Santa Barbara, CA
Make sure both the cover and housing are flat. Also make sure all the bolt holes are cleaned out. How is your diff vent? If it is clogged then you can have leaks. Also when you use RTV how long do you wait to fill the housing?


2014 Ford Mustang GT Track Pack
1995 Ford Mustang GT

Ford/Mazda Parts Counter
NRA Benefactor Member
Opinions expressed are my own.
Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512766
09/10/17 10:56 PM
09/10/17 10:56 PM
Joined: Oct 2005
Posts: 86
Boston, Massachusetts
Exit32 Offline
Exit32  Offline
Joined: Oct 2005
Posts: 86
Boston, Massachusetts
Best solution for differential covers is a Permatex product called "The Right Stuff" and it's available from Amazon:

http://a.co/8B9ziAh

"The Right Stuff" is a gasket-maker product, so don't use a separate gasket with it. I believe newer differentials are sealed at the factory with a similar product. I've never had a leak after using "The Right Stuff."


2018 Explorer 3.5 EcoBoost
2004 Buick Rainier V8
2002 T-Bird
1999 F250 V10
1967 Camaro
1966 Shelby Cobra
1966 Pontiac GTO
1965 Rambler American
1957 T-Bird
Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512767
09/10/17 10:57 PM
09/10/17 10:57 PM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline
Merkava_4  Offline
Joined: Jan 2007
Posts: 17,501
Clovis, CA
With a paper gasket, lay it out over some flat newspapers. Take your finger and apply an even layer of gasket dressing like if you were frosting a cake. Install the gasket to the differential housing and then frost the other side of the gasket that's facing you.

Do the same with cork gaskets if you ever get any. (don't use it on rubber gaskets)



Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512774
09/10/17 11:21 PM
09/10/17 11:21 PM
Joined: Aug 2014
Posts: 502
WA
SnowDrifter Offline
SnowDrifter  Offline
Joined: Aug 2014
Posts: 502
WA
Fan of lube locker gaskets here. Have 'em on my diff and tranny pan

Last edited by SnowDrifter; 09/10/17 11:21 PM.

2005 Tahoe - 135k
2003 Forester(the swagger wagon) - Rehomed
1999 Passat - Rehomed
Re: Leaky rear diff 2002 mustang gt [Re: SnowDrifter] #4512786
09/10/17 11:35 PM
09/10/17 11:35 PM
Joined: Oct 2011
Posts: 70
Az
daemontrym Offline OP
daemontrym  Offline OP
Joined: Oct 2011
Posts: 70
Az
I let them sit overnight with rtv and the bolts were hand tight.

When I put the felpro gasket I just lined it up with the top 3 bolts. I installed it dry in between the cover and diff.

The cover does not look bent at all or damaged. The diff besides the machine tooling marks their is not
Damage I can see.

I will check the vent tomorrow when I get home from work. Because looking at the pictures of people with that issue. It seams fluid is in the same place both times it started leaking right near the center forward the drivers side. From looking at google the vent is at the top d/s axle.

Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512788
09/10/17 11:37 PM
09/10/17 11:37 PM
Joined: Jul 2017
Posts: 309
PR CA, USA
2strokeNorthstar Offline
2strokeNorthstar  Offline
Joined: Jul 2017
Posts: 309
PR CA, USA
If you are using a Limited slip additive it will eat away some RTV. Use the gear oil specific rtv.

Re: Leaky rear diff 2002 mustang gt [Re: Exit32] #4512810
09/11/17 12:26 AM
09/11/17 12:26 AM
Joined: Aug 2006
Posts: 9,799
Central Washington
Colt45ws Offline
Colt45ws  Offline
Joined: Aug 2006
Posts: 9,799
Central Washington
Originally Posted By: Exit32
Best solution for differential covers is a Permatex product called "The Right Stuff" and it's available from Amazon:

http://a.co/8B9ziAh

"The Right Stuff" is a gasket-maker product, so don't use a separate gasket with it. I believe newer differentials are sealed at the factory with a similar product. I've never had a leak after using "The Right Stuff."


Yeah, I have a big tube of this stuff in a caulk gun type apparatus. I keep it in the garage freezer when Im not using it to keep it from setting up.
Its 5 minute setup time. So I lay out a bead on the cover, throw it on, tighten it down to an approximation of 20 ft-lbs. Then I go have a drink or whatever, come back and fill it up. Drop it off the jack stands and drive away. No leaks yet.

Last edited by Colt45ws; 09/11/17 12:28 AM.

-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2
Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512868
09/11/17 05:09 AM
09/11/17 05:09 AM
Joined: Sep 2009
Posts: 325
Rockies
Scdevon Offline
Scdevon  Offline
Joined: Sep 2009
Posts: 325
Rockies
Originally Posted By: daemontrym
what the manual said which is 28ft lbs.


Wait.......... you're torquing the bolts on a stamped steel diff cover with a paper gasket to 28 FOOT pounds? Are you sure the spec isn't in inch pounds?
Most stamped steel cover bolts usually get torqued to something like 80 to 120 INCH pounds which is in the 10 Ft. Lb range.


2003 Mustang Mach 1. 32V 4.6 Liter. Motorcraft Syn Blend 5W30
1970 Mustang Convertible 302-2V Auto (Stock) M/C 10W30
1970 VW Beetle 1600 DP
Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4512872
09/11/17 05:23 AM
09/11/17 05:23 AM
Joined: Jan 2011
Posts: 2,714
N.Ohio
Lubener Offline
Lubener  Offline
Joined: Jan 2011
Posts: 2,714
N.Ohio
Check the cover for distortion. Did you pry, to get it off?


The "thinking" man's friend.
Re: Leaky rear diff 2002 mustang gt [Re: Scdevon] #4513064
09/11/17 09:56 AM
09/11/17 09:56 AM
Joined: Dec 2016
Posts: 189
Wisconsin
emmett442 Offline
emmett442  Offline
Joined: Dec 2016
Posts: 189
Wisconsin
Originally Posted By: Scdevon
Originally Posted By: daemontrym
what the manual said which is 28ft lbs.


Wait.......... you're torquing the bolts on a stamped steel diff cover with a paper gasket to 28 FOOT pounds? Are you sure the spec isn't in inch pounds?
Most stamped steel cover bolts usually get torqued to something like 80 to 120 INCH pounds which is in the 10 Ft. Lb range.


This.

Cover's flange is probably bent now.


2011 Ford Crown Victoria LX 4.6L V8 auto
2009 Chevrolet Malibu LT 2.4L I4 auto
1974 Dodge D200 360 V8 4 speed manual
Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4513070
09/11/17 10:07 AM
09/11/17 10:07 AM
Joined: Dec 2014
Posts: 485
MB - Manitoba
FastLane Offline
FastLane  Offline
Joined: Dec 2014
Posts: 485
MB - Manitoba
You are torquing them way too high. The cover is probably bent now. Lay it on a flat surface and take a look.

All I use on my Mustang is Permatex Black. It never leaks. 75W140 gear oil.


2010 Silverado 4.8 4x4 Mobil 1 5W30 ACDelco PF48E
2002 Mustang GT 4.6 Mobil 1 5W30 MC FL-820S
1966 Cessna 150 Phillips 20W50
2013 Mercury 30hp Mystic 25W40
Re: Leaky rear diff 2002 mustang gt [Re: daemontrym] #4513277
09/11/17 01:54 PM
09/11/17 01:54 PM
Joined: Oct 2012
Posts: 50
Marysville, WA
ABursell Offline
ABursell  Offline
Joined: Oct 2012
Posts: 50
Marysville, WA
I don't know why the idea that the torque is too high, IIRC from my Ford days the spec is 25-35 foot-pounds (so 30 is nominal).

I don't think I saw it mentioned but tighten in a star pattern, like you are tightening lug nuts. It helps to make sure that the cover seats evenly. And I think all the service manuals call for that as well.

Clean, clean, clean. I use a air die-grinder with a scotchbrite on it for cleaning and it works beautifully. I understand that not everyone has that, so you have to make do with what you have. Razor blades, scotchbrite, maybe even a fine sandpaper. Clean is critical to getting the RTV to seal correctly. Both sides. I use brake cleaner as well but as a final wipe I use acetone just to be sure there is no residue left and I wipe until my rag comes back clean. Then I am ready to seal.

Directions for RTV have changed over the years, the last time I used it, it now says to apply within 5-minutes and torque, no re-torquing necessary. No more waiting for it to skin over or hand-tight then come back and re-torque or any other methods. Not to say that still wouldn't work, but the directions don't say to do that. I do still wait as long as possible before filling with fluid though. Try for a full day if possible.

Don't remember the last time I had one leak. I only need to change when it's time to change fluid.

With all this said, next time I do one I am going to try a lube-locker.

Adam

Last edited by ABursell; 09/11/17 01:56 PM.
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