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  • September 29, 2020, 10:51:54 AM

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Author Topic: Composite gasket INSTALL failure  (Read 267 times)

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Offline Canoe

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Composite gasket INSTALL failure
« on: September 04, 2020, 11:03:51 AM »
My install of the Crown/MOPAR 4295875AC transmission gasket (nylon over steel with molded-in double silicone sealing bead) failed. It was leaking in multiple places around the pan. Started as being wet, then dripping, and finally flowing when I turned the engine over. I took the pan off to inspect.

When I last installed the pan, I'd modified the pan. To add a drain hole, I'd drilled a hole through one of the bumps at a low point in the bottom of the pan, and welded a nut there on the inside (leaving a sliver between the nut and the pan unwelded to let fluid at the bottom out, instead of having to be at or above the height of the nut). Then I could use a drain bolt with a shallow head and a small magnet on the threaded end, instead of the usual undo the pan bolts and let the trans fluid leak out all around. This worked fine, and I found a collection of extremely fine particles, almost a grease, sticking to that magnet. Same for the flat donut magnet I left stuck to the bottom of the pan. After that mod, I painted the outside of the pan with an aluminum paint to protect against rust. And to protect the outer bit of the flange that the gasket sat on, I'd painted that too.

When I took the pan off, I discovered that the bottom of the pan and the lip of the flange were rust free. I could also see where the fluid had been leaking past the gasket in several places, on its top & bottom, where the gasket's silicone sealing bead had adhered to the paint on the flange, then that paint lifted from the flange, negating the seal. (I don't understand how the top of the gasket had some of the aluminum paint on its bead in a few places, as I don't recall painting the gasket contact surface of the transmission, which looks entirely paint free.)

The paint appeared nicely adhered to the pan flange, but the bead had adhered & lifted paint in more places than it hadn't. So I'm not going to play with degreasing and more paint. Count it as a fail and move on.

I cleaned up the pan (and magnets), scrubbed the remaining paint off of the flange gasket seat with steel-wool (looks like inadequate surface prep before painting). Another quick wash in dish soap, rinse & dry, then a light coat of fresh transmission fluid to the inside of the pan and flange to protect against any rust before I get to installing the pan.

Then I used some acetone on paper towel to carefully & quickly remove the paint from the gasket's silicone bead, then quickly washed the gasket in dish soap to remove any residue. Looks good for a second use (gasket should be good to use 5 or 6 times).

Since the pan is off, it will get a new transmission filter, just because.

Later today I'll get it back on and do the 150 inch pound torque, with the special fun getting those bolts in behind the exhaust pipe...
« Last Edit: September 04, 2020, 11:07:10 AM by Canoe »

Offline AMC of Houston

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Re: Composite gasket INSTALL failure
« Reply #1 on: September 04, 2020, 12:51:45 PM »
FYI; those gaskets will absolutely not work with a steel pan (they are not designed for such an uneven surface).  Need to go with an aluminum pan.
George G.
'81 Eagle Sundancer
'85 Eagle Waggie
1960 1902 Rambler Replica
'64 American
'70 AMX (Big Bad Blue), '70 AMX (White)
'77 Gremlin
'78 Pacer Coupe, '78 Pacer Wagon
'79 Pacer Wagon
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Offline Canoe

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Re: Composite gasket INSTALL failure
« Reply #2 on: September 04, 2020, 02:18:20 PM »
FYI; those gaskets will absolutely not work with a steel pan (they are not designed for such an uneven surface).  Need to go with an aluminum pan.
I had not heard that. What makes steel more "uneven" than aluminum?

Offline AMC of Houston

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Re: Composite gasket INSTALL failure
« Reply #3 on: September 04, 2020, 03:54:28 PM »
Mostly the fact that the tin changes its shape when you snug down the bolts.   I know MOPAR Performance sells a kit with this gasket and a new tin pan, but I've never seen anyone yet be able to get one to work without leaking.   Not saying it can't be done..... but if you can manage that (no leaks!); you'll be the first I've heard being successful!!

That gasket was originally designed for an aluminum panned tranny AFAIK.

Good luck with it.
George G.
'81 Eagle Sundancer
'85 Eagle Waggie
1960 1902 Rambler Replica
'64 American
'70 AMX (Big Bad Blue), '70 AMX (White)
'77 Gremlin
'78 Pacer Coupe, '78 Pacer Wagon
'79 Pacer Wagon
'73 Jensen Interceptor
'86 Audi 5000 Turbo
'98 Aston Martin DB7
'09 Nissan Titan
'10 Nissan Maxima

Offline Canoe

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Re: Composite gasket INSTALL failure
« Reply #4 on: September 04, 2020, 06:15:30 PM »
Mostly the fact that the tin changes its shape when you snug down the bolts. ...
Hmmm. Sounds credible.
That issue would be aggravated too, if it lost some material there due to rust.

Using a steel rule, my steel pan has straight edges, flat flanges, and are all flat in a single plane. Sits flat on a flat surface. That's after being torqued down on this gasket for ~six or seven years. I do remember spending some time on getting the pan that way before painting and installing it back then.

I am using the original bolts that have the captive washer. That may/may-not be a good thing.

Given how long it stayed good, I figure it's worth trying it again the same way, only no paint on the flange that takes the gasket.

Offline AMC of Houston

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Re: Composite gasket INSTALL failure
« Reply #5 on: September 04, 2020, 06:23:08 PM »
My tin pan flanges looked like a roller coaster, so I took the easy way out and got a Summit aluminum pan.  Figured the couple extra quarts of fluid couldn't hurt either.
George G.
'81 Eagle Sundancer
'85 Eagle Waggie
1960 1902 Rambler Replica
'64 American
'70 AMX (Big Bad Blue), '70 AMX (White)
'77 Gremlin
'78 Pacer Coupe, '78 Pacer Wagon
'79 Pacer Wagon
'73 Jensen Interceptor
'86 Audi 5000 Turbo
'98 Aston Martin DB7
'09 Nissan Titan
'10 Nissan Maxima

Offline Canoe

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Re: Composite gasket INSTALL failure
« Reply #6 on: September 04, 2020, 10:58:01 PM »
My tin pan flanges looked like a roller coaster, ...
That might explain why the new filter always comes with two new rubber gaskets.

... I took the easy way out and got a Summit aluminum pan.  Figured the couple extra quarts of fluid couldn't hurt either.
A nice stiff flange would certainly make that a non issue.
I'd like the extra fluid for the hot weather use, but not for the cold weather use. I'm not sure how valid that is.
If there was an aluminum pan with a nice stiff flange, but had the same stock shape & size, so I'd know it fits with the exhaust where it is, I'd get that just to know it's not going to be an issue in the future.

Online djm3452004

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Re: Composite gasket INSTALL failure
« Reply #7 on: September 05, 2020, 09:40:06 AM »
FYI; those gaskets will absolutely not work with a steel pan (they are not designed for such an uneven surface).  Need to go with an aluminum pan.



The Mopar gasket has worked fine with my stock steel pan, no leaks whatsoever.  I used the gasket only, on the bare steel/aluminum joint with no other sealant materials.  Maybe a better way of saying it would be "results may vary"... :rotfl:

David
Current Project: 1983 Eagle Wagon 258
Past AMC Project(s):  1979 Spirit Liftback 232
                                1968 Ambassador 287

Offline Canoe

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Re: Composite gasket INSTALL failure
« Reply #8 on: September 05, 2020, 12:39:30 PM »
... The Mopar gasket has worked fine with my stock steel pan, no leaks whatsoever.  I used the gasket only, on the bare steel/aluminum joint with no other sealant materials.  ...
Do you recall what torque you used on the bolts?
Or did you tighten to a visual on compressing the beads, or to 'felt right'?

Offline Canoe

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Re: Composite gasket INSTALL failure
« Reply #9 on: September 06, 2020, 02:16:12 PM »
I had everything ready to re-install, then remembered I hadn't swapped for the new filter. Dumped ATF out of the old filter onto my pile of nice clean bolts. A storm was moving in and I didn't have time to clean them off, if I wanted everything sealed before the leading wind hit and blew dust & dirt everywhere (as in, up into the bottom of the transmission).

If threads are greased, you reduce the install torque to 70% (105 inch pounds) to get the same installed tension in the bolts. I don't know how much to reduce for lubing with ATF. So I went with 80%, or 120 inch pounds. Looks good: beads are well compressed, with flanges not touching the nylon.

« Last Edit: September 08, 2020, 11:47:11 AM by Canoe »

Online djm3452004

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Re: Composite gasket INSTALL failure
« Reply #10 on: September 06, 2020, 09:04:19 PM »
... The Mopar gasket has worked fine with my stock steel pan, no leaks whatsoever.  I used the gasket only, on the bare steel/aluminum joint with no other sealant materials.  ...
Do you recall what torque you used on the bolts?
Or did you tighten to a visual on compressing the beads, or to 'felt right'?


The service manual recommends 150 in-lbs, which translates to 12.5 ft-lbs.  Since these were aluminum threads, I stuck to the spec and did 11-12 ft-lbs.  I cleaned my bolts with Brake Clean, though I do not recall cleaning the threads in the transmission case.  I have stripped WAY too many aluminum threads by taking things too tight in the past, so I was being as careful as I could. 

Thanks!
David

Current Project: 1983 Eagle Wagon 258
Past AMC Project(s):  1979 Spirit Liftback 232
                                1968 Ambassador 287

 

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