hot_post in 70 Challenger 8 3/4 3rd Member Gasket Leak in Engine, Transmission & Rear End Author Topic: 70 Challenger 8 3/4 3rd Member Gasket Leak  (Read 608 times)

Offline schlett7nu1

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70 Challenger 8 3/4 3rd Member Gasket Leak
« on: January 13, 2021, 05:02:28 PM »
I've got a gasket leak on my 70 Challenger 8 3/4 sure grip 3rd member. I haven't worked on a Mopar rear in nearly 40 years. I'm very rusty. It started leaking 2 years ago. 6 years ago I replaced the pinion seal. No issues with that. Will the axles pull out easily or will I need a slide hammer?  Would it be smart to replace the inner seals?  Any specials tools to remove/install the seals?  Are there flange gaskets that should be replaced?  I was planning on using 80-90W conventional oil with Mopar limited slip additive. I'm really concerned about needing special tools. Any help before I tackle this is appreciated.
Thanks
Dereck

Linkback: https://forum.e-bodies.org/engine-transmission-and-rear-end/4/70-challenger-8-34-3rd-member-gasket-leak/19749/

Offline Dakota

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #1 on: January 13, 2021, 05:18:21 PM »
There are no “one time” tools needed.  My 2 cents would be to do the inner seals and outer gaskets while you have everything apart.   I don’t remember if I used a large socket or a loaner tool from AutoZone to set the inner seals, but either way it went in well.  There was no issue pulling out my axles, so you shouldn’t need a slide hammer. 

If you get stuck, just post a question with pictures by you’ll get quick help here. 

Offline MoparLeo

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #2 on: January 13, 2021, 11:35:52 PM »
Not complicated but dirty and takes some time. If you don't have a Factory Service Manual yet, go to the resources section of this site and download one for free. It will have illustrations and the written procedures for servicing the rear axle bearings and differential. Just basic socket set, extension and ratchet. New gaskets, gear oil, bearing grease, and  torque wrench. :tool:
moparleo@hotmail.com  For professionally rebuilt door hinges...

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #2 on: January 13, 2021, 11:35:52 PM »

Offline dodj

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #3 on: January 14, 2021, 02:48:27 AM »
 :iagree: with above responses,  and
Take the time to repack the axle bearings while you have the axles out. :alan2cents:
"There is nothing your government can give you that it hasn't already taken from you in the first place" -Winston Churchill

Offline schlett7nu1

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #4 on: January 14, 2021, 04:05:12 AM »
Thanks for all the responses. Great winter project. I'll start disassembly today and order all needed parts and supplies.

Online Floyd

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #5 on: January 14, 2021, 05:36:20 AM »

Offline Burdar

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #6 on: January 14, 2021, 08:54:17 AM »
Is a gasket even needed? Just put some gasket maker on the sealing surface and tighten it down.  It makes removal a little more difficult but how often do you need to remove the center section?  Wait until the gasket maker is completely dry.  Then trim the excess with a razor blade so it looks nice.
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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #6 on: January 14, 2021, 08:54:17 AM »

Offline davy442

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #7 on: January 14, 2021, 09:09:34 AM »
I generally use Indian Head Gasket Shellac, been using it for 40 years.  I cannot remember ever having a leak, whether using on gaskets, or on threads. Only issue is if you take it apart at a later time, it’s more difficult to clean the surfaces, but if you are not planning on disassembling it again , then i think not an issue.

Offline MOPAR MITCH

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #8 on: January 14, 2021, 12:07:26 PM »
Is a gasket needed for the carrier-to-housing?  Absolutely yes!   There is a designed thickness needed to space the carrier-to-housing... something like 0.045" when crushed.  Installing the carrier-to-housing without that thickness of the gasket throws off the perpendicular alignment of the axles within the housing to the carrier.   Long term negative effect upon the seals and bearings.

I'm a former gasket engineer from a major manufacturer and that is an old common tech/installation question. 

PS:  The design of these LubLocker gaskets incorporates a design known as print-o-seal having the rubberized beads providing extra sealing at those lines of the beads (and it pushes the same design through the material towards the opposite side of the gasket) ... no need for any supplementary sealer (shellac, RTV, etc).  The design adds considerable cost to the basic gasket, but its well worth it to those who only want the best.... easy removal, as well since, again, no supplementary sealer is needed at all.

Offline schlett7nu1

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #9 on: January 14, 2021, 12:35:28 PM »
No issues today pulling the driveshaft, axles, and 3rd member. I also dropped the 727 oil pan and changed the filter and output seal.  Very messy. I ordered a Lubelocker diff gasket as well. I won't get that until next week. I was surprised that I didn't need to remove the rear brake parts for axle removal. Upon reassembly it looks like I'll need to set the axle bearing end play to 0.008-0.018" using a dial indicator. I only see an adjuster on the RH axle.

Offline JS29

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #10 on: January 14, 2021, 02:20:51 PM »
The only adjuster it has is on the right side.  :alan2cents:

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #10 on: January 14, 2021, 02:20:51 PM »

Offline schlett7nu1

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #11 on: January 15, 2021, 01:32:32 PM »
Thanks. What would be good 727 capacity starting point after filter change?  Torque converter is full. I was planning on 3 qts as a start point then adding as needed via dipstick.

Offline rftroy

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #12 on: January 15, 2021, 04:29:28 PM »
Probably overkill, but I used one of these when I went through my 8:75.

https://www.lubelocker.com/

https://www.amazon.com/LubeLocker-Chrysler-8-75-Differential-Gasket/dp/B07JQ4ZG36

Interesting, a gasket for the 8-3/4 doesn't show up on the Lubelocker website, nor is it on the summit website.

Discontinued?  Counterfeit?
The Print-O-Seal is a very good concept, and this is the first time I've seen it on an 8.75 gasket. 
Anyone have any history or experience with this gasket, and why it doesn't show up in the Lubelocker catalog?
Robert
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Offline GoodysGotaCuda

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #13 on: January 15, 2021, 04:38:35 PM »
Probably overkill, but I used one of these when I went through my 8:75.

https://www.lubelocker.com/

https://www.amazon.com/LubeLocker-Chrysler-8-75-Differential-Gasket/dp/B07JQ4ZG36

Interesting, a gasket for the 8-3/4 doesn't show up on the Lubelocker website, nor is it on the summit website.

Discontinued?  Counterfeit?
The Print-O-Seal is a very good concept, and this is the first time I've seen it on an 8.75 gasket. 
Anyone have any history or experience with this gasket, and why it doesn't show up in the Lubelocker catalog?
Robert
My 8.75” lube locker was bought from eBay. Works great, it’s all I use.


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Offline MoparLeo

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #14 on: January 15, 2021, 11:43:17 PM »
The info about the adjuster only on the passenger axle is in the Factory Service Manual that I recommended that you download. The info on bearing service and such is also in the book. The Factory Service Manual is for just the thing is is named for. Servicing your car to Factory specs.

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Re: 70 Challenger 8 3/4 3rd Member Gasket Leak
« Reply #14 on: January 15, 2021, 11:43:17 PM »

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