Transmissioon Follies Redux

[johnny]

OK. The removed transmission, sans governor, is at Garrett's. Nick/Applied is to drop-ship a rebuilt governor. I told Matt no hurry at all, all
that one will do is sit in my shop till someone needs it. Or in his shop if somebody wants to pay it in their coach instead of D I Y.
Now to the leaky transmission. Removed the pan, fluid is good and will be reused. Nothing untoward in the pan. It had a rubber gasket with no
sealer on it which made it easy to see where it didn't seal.. where I suspected. I rebent the pan so that edge was again flat - or flatter anyway -
and got a new gasket which turned out to be a Fel-Pro. Ran a bead of black hi temp rtv gasket stuff around both sides and put the pan on, tightened
it till the goo squeezed out all around. Per the instructions, wait an hour or three, then torque it up to 12 ft. lbs.
If the sumbich leaks NOW, I'll sell the coach, complete with leaky trans and a rebuilt trans in the back for the next owner. It ain't gonna leak, but
the next guy who needs to get into the transmission may need a chisel.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[johnny]

Last bit of leak chasing - a bead of J-B Weld Ultimate Black Silicone gasket goo around the lip of the dipstick tube above the O ring. Back in place,
snugged it up and tomorrow we test for leaks. And expect none...

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[bob heller]

Johnny,

Did you use an RTV that is made for automatic transmissions, like this:

https://www.permatex.com/products/gasketing/gasket-makers/permatex-automatic-transmission-rtv-gasket-maker/

If not, you may be doing the job over again in a few months.

Story: Years ago a fellow GMCer from Palatka FL mentioned to me that he had a used TH425 in his storage area and wanted to sell it. He said the trans
worked fine, it just leaked badly and after several repair attempts his mechanic was unable to make the leak stop for any length of time. He then got
another transmission, the mechanic installed it, and his GMC was fine. Shortly after, he sold the GMC.

I gave him a few dollars for the leaky trans and, figuring I would rebuild it and have a spare, while taking it apart found the leak. The chain cover
had been installed without a real gasket, only lots of black RTV on and around the sealing surfaces. The bottom third of the RTV 'gasket' had turned
to a bubble gum consistency and was oozing out wherever it was in constant contact with trans fluid. I ended up rebuilding the trans, replacing all
frictions, steels, gaskets, bearings, and bushings. Put it all together and it has been sitting in my garage now for about 8 years. I never did try it
out as the trans in my GMC still works fine and, basically, I'm lazy. I wouldn't use this trans now because it has been sitting for so long, if I ever
need it I would pull it apart again to check for corrosion and re-gasket it.

Conclusion: They make an RTV silicone specifically for automatic transmissions for a reason, apparently ATF will dissolve some RTV's.

--
Bob Heller
1974 X-Canyonlands 26ft
Original 455 exc for timing chain,
Rockwell intake, valve covers. 144k miles.
Winter Springs FL

 

[Ken H.]

Bob,

I hope you have that transmission stored "Manny Style": On the chain
housing with all the ports sealed and filled all the way to the final drive
interface with ATF, then a plate bolted on that surface. Unless it's a
switch pitch, he fills it with (and uses) Walmart ATF.

Ken H.

> ​...
>
> I gave him a few dollars for the leaky trans and, figuring I would rebuild
> it and have a spare, while taking it apart found the leak. The chain cover
> had been installed without a real gasket, only lots of black RTV on and
> around the sealing surfaces. The bottom third of the RTV 'gasket' had turned
> to a bubble gum consistency and was oozing out wherever it was in constant
> contact with trans fluid. I ended up rebuilding the trans, replacing all
> frictions, steels, gaskets, bearings, and bushings. Put it all together
> and it has been sitting in my garage now for about 8 years. I never did try
> it
> out as the trans in my GMC still works fine and, basically, I'm lazy. I
> wouldn't use this trans now because it has been sitting for so long, if I
> ever
> need it I would pull it apart again to check for corrosion and re-gasket
> it.
>
> Conclusion: They make an RTV silicone specifically for automatic
> transmissions for a reason, apparently ATF will dissolve some RTV's.
>
>

 

[johnny]

Interesting you bring that up. There were two J-B Weld hi temp black rt v gasket offerings side by side for the same money. While these claims were
similar, this one listed automatic transmission pans and the other did not. Go figure.

The chain cover has a gasket and beau coup sealant squoze out on either side. If it is leaking there I'll be sore pissed because I don't think you
can do anything with the chain case without first removing the transmission from the coach. I have had more practice in doing that than I want to. I
think George is one ahead of me, I'm not looking to tie that record.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[emerystora]

One of the problems with putting a large amount of sealant on a gasket and tightening it until it squeezes out is that it is also squeezing out on the inside of the case.
Sometimes beads of it will break loose and get lodged into transmission parts where it shouldn’t be and that can cause a transmission failure.
You are better off using a thin film of RTV on a gasket rather than a large bead.

Emery Stora
77 Kingsley
Frederick, CO

>
> OK. The removed transmission, sans governor, is at Garrett's. Nick/Applied is to drop-ship a rebuilt governor. I told Matt no hurry at all, all
> that one will do is sit in my shop till someone needs it. Or in his shop if somebody wants to pay it in their coach instead of D I Y.
> Now to the leaky transmission. Removed the pan, fluid is good and will be reused. Nothing untoward in the pan. It had a rubber gasket with no
> sealer on it which made it easy to see where it didn't seal.. where I suspected. I rebent the pan so that edge was again flat - or flatter anyway -
> and got a new gasket which turned out to be a Fel-Pro. Ran a bead of black hi temp rtv gasket stuff around both sides and put the pan on, tightened
> it till the goo squeezed out all around. Per the instructions, wait an hour or three, then torque it up to 12 ft. lbs.
> If the sumbich leaks NOW, I'll sell the coach, complete with leaky trans and a rebuilt trans in the back for the next owner. It ain't gonna leak, but
> the next guy who needs to get into the transmission may need a chisel.
>
> --johnny
> --
> 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> "I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[bob heller]

"Bob,

I hope you have that transmission stored "Manny Style": On the chain...."

Ken,

No, the trans has been sitting empty on it's pan. That's why I would not install it now without disassembling and checking for corrosion and
re-gasketing it. The innards are slathered with trans assembly lube so hopefully it's not a rust bucket but I won't know for sure unless I take it
apart and look.

Originally my plan was to install it soon after assembly but life got in the way and the trans currently in the GMC just keeps on working so the
exchange never happened. My plan now is to rebuild the existing GMC trans when it finally needs it and if I need any hard parts I can use the spare
unit as a parts store. The trans now in the GMC was last rebuilt in 1996 and I don't really want to swap out something that works well even though it
has 22 years of wear on it.
--
Bob Heller
1974 X-Canyonlands 26ft
Original 455 exc for timing chain,
Rockwell intake, valve covers. 144k miles.
Winter Springs FL

 

[johnny]

Emery, tha's the idea... but we know it was bent a bit, and you can't get it back totally flat. You hope to get it flat enough to let the gasket hit
both surfaces but bead it such that if it misses slightly it's still sealed. In the 425, you'd have to get a big enough bead chunk to plug the
filter, an unlikely happening. Unless you put half inch beads of the stuff. The idea behind the instructions - wait an hour - is for the stuff to
vulcanize enough to stay together. If I had a good flat plate tomeasure it on, I could probably get it flat enough to reuse the rubber gasket. I
don't have.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[johnny]

Update. Still dripping, so on someone's advice I've added o - rings to the pan bolts. Kept dripping. I pulled the modulator out, no o-ring or other
seal on it. I begin to wonder if it ever had one. I'll check with Matt to see if the busted one had an o-ring on it or not.
I'm gonna feel foolish if that's been the leak all along... but relieved as well.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[johnny]

Eureka!! O rings on pan bolts and modulator, and this morning after 24 hours, totally dry drip pan. I claim it sealed. Now I wonder if the other
one died from a lack of modulator seal. It was from the same build down at Ken's place. The o - ring could of got dropped checking the full level,
or not been there to begin with, who knows. However, when you get your rebuilt transmission, CHECK THE MODULATOR SEAL AND BE SURE IT'S THERE!!!!!

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[George Z]

So does this mean I can pull down all those For Sale posters I put up?

George Zhookoff
78 EL II
Atlanta

 

[johnny]

Not yet - price for the Allegro hasn't shown up.. and Paula hasn't seen it to pass judgement even if the price is right. If someone shows up for the
signs, sell them the little Escort that's in the front yard with the for sale sign on it.

We have, however found the problem. Chuck just sent me a picture of where the transmission was sitting in his shop before we installed it. On the
mat is the frickin' o-ring for the modulator. Somewhere along the line one or more of us pulled the modulator for some reason... Probably me but I
don't remember.
At least now I know what happened, and a close watch on levels kept from hurting it on the way home.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased