Transmission pan leaks

T

tom geiger

New member
Dec 31, 2006
673
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Ok, I’m going to take another swing at this transmission leak issue. This time I’m collecting all the info I can to address all possible leaks. O
rings, rubber gasket with RTV, I’ll re-flatten the bolt hole flanges on my OEM pan, I’ve read that the Ragusa pan still leaks and it’s not
apparently because of porosity. I’ve even read and saw a picture of someone installing a overflow bottle for the transmission fluid. Worth a try
too if it prevents it leaking. Point is, I’m wanting to cover the gambit to get this thing to stop leaking!
Any ideas welcome!! I’m tired of the old girl’s incontinence on the driveway.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
FWIW, my Ragusa pan is dry as a bone... No gasket. I use a thin layer of gray RTV on both sides, hand snug all bolts, then when the RTV has set up
for a few hours, finish tightening down to rated torque. I have a overflow on the vent line.... (Polaner all fruit jar mounted near the wiper motor).
I used to get around 1/2" or so of fluid in the jar between changes... However, since I upgraded to 3/8" transmission lines and added an auxiliary
cooler, the jar has been dry as a bone as well. Same amt of fluid on the dipstick, checked the same way. No other changes.

For a stamped steel pan, putting a straight edge and hammering the bolt holes flush from time to time is always a good idea. If you go the RTV route,
make sure the pan and trans mounting area are as fluid free as possible. Do a final wipedown with brakeleen or MEK before applying RTV.

FWIW, I use Amsoil ATF... In my experience synthetic ATFs tend to leak more as well.... So very pleased I have no leaks.
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
Be sure to check the leak at the Final drive/ trans.
Be sure to snug the bolts as the final seals the trans.

> FWIW, my Ragusa pan is dry as a bone... No gasket. I use a thin layer of
> gray RTV on both sides, hand snug all bolts, then when the RTV has set up
> for a few hours, finish tightening down to rated torque. I have a
> overflow on the vent line.... (Polaner all fruit jar mounted near the wiper
> motor).
> I used to get around 1/2" or so of fluid in the jar between changes...
> However, since I upgraded to 3/8" transmission lines and added an auxiliary
> cooler, the jar has been dry as a bone as well. Same amt of fluid on the
> dipstick, checked the same way. No other changes.
>
> For a stamped steel pan, putting a straight edge and hammering the bolt
> holes flush from time to time is always a good idea. If you go the RTV
> route,
> make sure the pan and trans mounting area are as fluid free as possible.
> Do a final wipedown with brakeleen or MEK before applying RTV.
>
> FWIW, I use Amsoil ATF... In my experience synthetic ATFs tend to leak
> more as well.... So very pleased I have no leaks.
> --
> Mark S. '73 Painted Desert,
> Manny 1 Ton Front End,
> Howell Injection,
> Leigh Harrison 4bag and Rear Brakes,
> Fort Worth, TX
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
Thanks guys on this info, this will help. Jim, I just replaced the oil and gasket on the FD. Got the correct gasket single layer gasket with the
internal breathing channel for the vent hole in it. I also made sure the vent hole was clear to breath. So I see no signs of leaking from it and
think I’m good on it sealing. Will read more to understand the sealing relationship between the FD and transmission reservoirs.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
there is two oil seals on the pinion portion of the final drive. One seals the final drive fluid in, the outer seals the transmission fluid out.
between those seals is a weep hole that goes out of the final drive near where the dipstick tube enters. so in theory if one of the seals goes bad,
you will have leak out the weep hole to let you know.

the final drive is bolted to the transmission and there is a felt gasket between the two keeping the transmission fluid inside the tranny.

Think you have the rest, there is seal on the shift arm. need the modulator to have a good o-ring. also good o-ring seal on the kickdown wire
plastic thing.(might rtv that too). and a good o-ring on the dipstick tube.

the dipstick needs to vent. and the tranny needs to be in good order as well. Had one owner chasing a vent overflow issue that would occur only
when tranny was hot. that was a bad seal internal.

--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Ah, I understand I believe. These are inner seals involved in the connection of the two and not part of the FD cover gasket. Fingers crossed I
don’t have issues with the seals. I last spring had the transmission system serviced and had the filter replaced and the service center did not
mention any issues. A month ago I serviced my FD to use the synthetic oil from Valvoline. I used the correct gasket that allowed the small vent hole
to breath. So I think I’m hopefully good pertaining to the inner seals.
As far as the O-rings, I’m going to check all of the locations after I’ve done a good washdown of the transmission. If I happen to have leakage
at the cooling lines conncetion at the transmistion, would those involve any o-rings?

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Check for leakage around the manual shifter shaft as well. When the torque converter leaks down after being parked, the fluid level can be above it.

Its not a seal like other Turbo-Hyromatics, its an O-ring, but it's not too hard to change.

Manny says a lot of rebuilders don't change it. Mine was hard and just crumbled when I removed it.

Look here for more details and a diagram.

https://www.gmcmotorhome.org/resources/the-elusive-th425-manual-shifter-shaft-seal.51/

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Tom
The cooling lines at the transmission don’t use o rings but since you are clamping a steel line against a steel casting you might have to use copper washers in the end to get a good seal.

Emery Stora
77 Kingsley
Frederick CO

>
> Check for leakage around the manual shifter shaft as well. When the torque converter leaks down after being parked, the fluid level can be above it.
>
>
> Its not a seal like other Turbo-Hyromatics, its an O-ring, but it's not too hard to change.
>
> Manny says a lot of rebuilders don't change it. Mine was hard and just crumbled when I removed it.
>
> Look here for more details and a diagram.
>
> https://www.gmcmotorhome.org/resources/the-elusive-th425-manual-shifter-shaft-seal.51/
>
>
>
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
 
Tom,

one item I have found to work really well to find leaks, is UV die. You have to be careful and really get the parts clean, but a little UV die
goes along way and you can get a light and really follow the fluid tracks.

there are different uv die products that are compatible with the different fluids, so be careful on what one you use for each fluid.

https://www.amazon.com/Interdynamics-Certified-Fuel-Systems-Ounce/dp/B002M4G24U/ref=sr_1_2?dchild=1&keywords=tranny+fluid+uv+dye&qid=1633529010&sr=8-2

--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Thanks guys, this is good. I’ll cover these areas as well. Kinda funny, moved the motorhome over to the other side I typically park it on and it
apparently has lost enough fluid that it didn’t move forward for a few seconds. So I’m going to try to calibrate the dipstick as well once I open
up and drain out the pan. All good info guys!

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Well, got the new gasket and was planning on working on this when I get back from our weekend camping trip, but now our HOA posted up in our monthly
flyer that no campers are allowed in our driveways and in addition home owners are not allowed to work on their vehicles in the driveways that on both
accounts I would be flipping the board the bird so maybe I do this all over in my storage site. Now these bylaws were written 40+ years ago when the
neighborhood was brand new and they thought they were all that and a bag of chips but that was 40 years ago. The neighborhood has changed a bit but
some, board members seemed to have lost perspective on current conditions of things. For example, the bylaws still state we are to replace our cedar
shaked roofs withe the same. Well that has fallen by the way side because of its dangers and crazy replacement costs and some insurance companies just
won’t cover it. Anyhow, some of these bylaws need to be reviewed. Times do change things.
So I’m going to comply and take up my transmission leaks over at my storage area instead of in front of my garage. Heck, just realized if I did do
it at my house I’d be violating another bylaw of the HOA. We are not to have our garage door open for any length of time. See what I mean, things
just get carried away on bylaws. Anyhow, will let you guys know how things go when I get to it over at the storage area. Cool dude that owns the
place, no bylaws there!

TG
--
Tom Geiger
76 Eleganza II
KCMO
 
I have now got the transmission pan off, flanges flattened and reinstalled back on and bolted up. While I have the fluid I thought I’d check the
other upper sources of leaks. Now I’ve done some searching and maybe not enough but I see other items identified such as cooler lines, dipstick
leak and speedo cable leak, to which I think I have. In my search I’m not seeing anything definitive on repairs for the speedo cable leak? Is it
just a new cable replacement? Also what is the best repair for cooling line leak? Is it a copper washer? I believe the dipstick leak repair is with
RTV per Jim K’s response to a post.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Ok, viewed a few videos and understand how the speedo leak gets fixed.

TG
--
Tom Geiger
76 Eleganza II
KCMO
 
I have now got the transmission pan off, flanges flattened and reinstalled back on and bolted up. While I have the fluid I thought I’d check the other upper sources of leaks. Now I’ve done some searching and maybe not enough but I see other items identified such as cooler lines, dipstick leak and speedo cable leak, to which I think I have. In my search I’m not seeing anything definitive on repairs for the speedo cable leak? Is it just a new cable replacement? Also what is the best repair for cooling line leak? Is it a copper washer? I believe the dipstick leak repair is with RTV per Jim K’s response to a post.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
The Flared Copper washer is a part we all use to get the steel Flared tube
to seal against the brass fitting.
The Commonest Chinese make the fittings with sloppy control and flood it to
us.
Never had so much issues before they started supplying them.

> Tom,
>
> The chain cover gasket was the source of the leak on mine. 'Did not
> conclude/confirm that until I addressed all other possibilities. The leak
> (mostly a "seep") was at the intersection of the chain cover with the
> transmission pan mounting flange, giving the appearance that the pan gasket
> (or something above it) was the source.
>
> The transmission has to be removed to replace the gasket (unless someone
> has found a way to do it place). 'Had the gasket replaced when I had the
> engine changed out. 'End of leak and "housekeeping mess" on my garage
> floor...
>
> HTH,
>
> Fred Hudspeth
>
>
> Fred Hudspeth
> 1978 Royale (TZE 368V101335) - Tyler, TX
> 1982 Airstream Excella (motorhome) - Cooper Landing, Alaska
>
>
>
> Message: 1
> Date: Sun, 24 Oct 2021 07:16:24 -0600
> From: tom geiger
> Subject: [GMCnet] Re: Transmission pan leaks
> To: gmclist
> Message-ID:
> Content-Type: text/plain; charset="utf-8"
>
> I have now got the transmission pan off, flanges flattened and reinstalled
> back on and bolted up. While I have the fluid I thought I’d check the
> other upper sources of leaks. Now I’ve done some searching and maybe not
> enough but I see other items identified such as cooler lines, dipstick
> leak and speedo cable leak, to which I think I have. In my search I’m not
> seeing anything definitive on repairs for the speedo cable leak? Is it
> just a new cable replacement? Also what is the best repair for cooling
> line leak? Is it a copper washer? I believe the dipstick leak repair is
> with RTV per Jim K’s response to a post.
>
> Thanks,
> TG
> --
> Tom Geiger
> 76 Eleganza II
> KCMO
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
Kinda thinking the same Fred. I want to eliminate all other sources before it gets to the hard to fix leaks. I took a quick look at the back cover
and it looks like the transmission has to be removed to get this cover off. Anyhow, will watch for it leaking when other leaks are resolved.

I do have a couple more questions. I’ve discovered the vent pipe on the top of the transmission has the elbow installed but no hose nor bottle
resevior installed. What would be the routing of hose and position of overflow bottle? Thought I’d get that installed immediately.

I’ve resealed the transmission pan and have read 2 volumes of ATF to put back in to get fluid back up to operation full levels. One post said 4
quarts, and another said 6 quarts. I have a OEM pan.

Sorry, one more question. I too am struggling on reading the dipstick after it runs. It seems to have fluid all up and down the stick so can’t say
I know for sure of its level. I have put in 4 qrts into the transmission thinking it would be full. I can do the Manny procedure if needed to
determine correct full level. I can call Jim K or Manny to go over that procedure to make sure I understand it properly. Seemed there is some
confusion on doing it “cold” in the driveway after running the selector up and down in the transmission or doing it after its been driving it a
bit.

Thanks,
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
Route the hose to the outside of the frame and attach a small 12 ounce
plastic bottle.
This will be an indication when it spits out.]

> Kinda thinking the same Fred. I want to eliminate all other sources
> before it gets to the hard to fix leaks. I took a quick look at the back
> cover
> and it looks like the transmission has to be removed to get this cover
> off. Anyhow, will watch for it leaking when other leaks are resolved.
>
> I do have a couple more questions. I’ve discovered the vent pipe on the
> top of the transmission has the elbow installed but no hose nor bottle
> resevior installed. What would be the routing of hose and position of
> overflow bottle? Thought I’d get that installed immediately.
>
> I’ve resealed the transmission pan and have read 2 volumes of ATF to put
> back in to get fluid back up to operation full levels. One post said 4
> quarts, and another said 6 quarts. I have a OEM pan.
>
> Sorry, one more question. I too am struggling on reading the dipstick
> after it runs. It seems to have fluid all up and down the stick so can’t
> say
> I know for sure of its level. I have put in 4 qrts into the transmission
> thinking it would be full. I can do the Manny procedure if needed to
> determine correct full level. I can call Jim K or Manny to go over that
> procedure to make sure I understand it properly. Seemed there is some
> confusion on doing it “cold” in the driveway after running the selector up
> and down in the transmission or doing it after its been driving it a
> bit.
>
> Thanks,
> TG
> --
> Tom Geiger
> 76 Eleganza II
> KCMO
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
When you add the vent tube, make sure it has a reverse trap (hump) in it. I had trouble with the vent hose actin like a siphon. It sucked fluid out
of the transmission until I put a longer hose on it and raised it up just after it left the elbow., then routed it to the outside of the frame as Jim
suggested, with a small bottle on the end as a test reservoir.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
Good morning Carl, thanks for the info on the siphon issue very timely I’m hunting for a small bottle to use for the reservoir. I did get 4ft of
hose so I’m hoping to have enough. So plan on doing the routing and adding the bottle this morning. We’re taking a little camping weekend at one
of our state parks nearby with other camping friends so will be able to check out the setup.
Thanks again to Jim K who spent some time with me going over the transmission issues and was very helpful in clearing up some questions for me.
I’ve used Hylomer Blue on the transmission pan and some thread seal on the pan so hoping this does the trick. I do have a washer o-ring kit for the
speedo bullet to fix that leak. So getting each of these sources of leaks taken care of one at a time. I do have a question on the back sprocket
gasket seal if thats a issue, would I need to have the transmission removed to get at that gasket seal or is there a way to do it in place?

Thanks
TG
--
Tom Geiger
76 Eleganza II
KCMO
 
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