Home » Public Forums » GMCnet » Chasing a transmission leak
| Chasing a transmission leak [message #228752] |
Thu, 07 November 2013 09:11  |
rcjordan
Messages: 1913
Registered: October 2012
Location: Elizabeth City, North Car...
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The Birch has what appears to be a leak due to the torgue converter draining down. While researching here for possible leak sources, I've been assembling a 'photo tour' of likely places to check for tranny leaks. Most of the photos concentrate on the drivers side and I do have a good photo of the vacuum modulator. But what are the other spots to check on the passengers side? And passenger side photos?
SOLD 77 Royale Coachmen Side Dry Bath
76 Birchaven Coachmen Side Wet Bath
76 Eleganza
Elizabeth City, NC
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| Re: Chasing a transmission leak [message #228758 is a reply to message #228752] |
Thu, 07 November 2013 09:36  |
Ultravan Owners
Messages: 443
Registered: March 2013
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This is a known problem on our Corvairs.
The fluid in the convert will drain back into the pan when it sits for a while. On a Corvair PG (automactic) it is due to the shift cable o-ring and/or the cable it self.
It is just above where the transmission pan bolts to the trans.
If the o-ring or the cable are dry/cracking it will leak once the fluid rises.
I have to say I have not spent much time under our newly purchase Olds 455 to know for sure that it is also your cause too.
However, I would look at anything that is just above where the pan bolts to the trans.
Anything else that would leak should be while it under presure/running.
If no one else chimes in - I will try to look under our coach to see what else it could be.
Good Luck, Tony
EDIT - also check to see if pan bolts need to be tightened up.
Tony (Ontario Canada)
Marie and I are blessed to have had a 2nd chance to buy our farm.
Still hoping and more importantly praying to be able to build a garage.
Our 1970 Ultravan #520 has an Olds Toronado 455 in back.
[Updated on: Thu, 07 November 2013 09:41] Report message to a moderator |
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| Re: Chasing a transmission leak [message #228763 is a reply to message #228752] |
Thu, 07 November 2013 09:55 |
Ultravan Owners
Messages: 443
Registered: March 2013
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Silly me - the shift cable on this type of trans does not go inside the trans like with a Corvair.
So that means it could be the o-ring around the shift rod going into the trans. That is the lever where the cable end mounts to.
I'm heading outside while it is not raining - to take a look at the trans for you.
Tony (Ontario Canada)
Marie and I are blessed to have had a 2nd chance to buy our farm.
Still hoping and more importantly praying to be able to build a garage.
Our 1970 Ultravan #520 has an Olds Toronado 455 in back.
[Updated on: Thu, 07 November 2013 09:56] Report message to a moderator |
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| Re: Chasing a transmission leak [message #228773 is a reply to message #228752] |
Thu, 07 November 2013 10:26 |
Ultravan Owners
Messages: 443
Registered: March 2013
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Okay, I took a peak at our Toronado setup.
Lower transmission areas that could leak when vehicle has sat for some time where the converter fluid has drained back into the pan could be:
1) Pan gasket it self
2) The shifter rod seal (found on the driver’s side of the trans where the shift cable ends and the shaft goes into the side of the trans)
3) The vacuum modulator on the passenger side of the trans.
Number 2 and 3 are the only things I could find just above the pan gasket.
• I would clean and dry the transmission then start the coach and run it until it is at operating temps. (I like to use crab cleaner if it is real dirty and then dry it off with brake cleaner. Otherwise just use brake cleaner.)
• Then check the trans fluid level. If the level is within the marks take a peek at the trans for any signs of a leak.
• Then take it out for a quick test drive and check the trans again for leaks once you get home.
• If nothing – check the level when not running. Then check for a leak once or twice a day for the next week or so and also check the level just to see if it rises.
• Once you know the fluid level has risen – if there is a leak while sitting – it should show up.
If I can be of further help let me know.
Sincerely, Tony
Tony (Ontario Canada)
Marie and I are blessed to have had a 2nd chance to buy our farm.
Still hoping and more importantly praying to be able to build a garage.
Our 1970 Ultravan #520 has an Olds Toronado 455 in back.
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| Re: Chasing a transmission leak [message #228788 is a reply to message #228752] |
Thu, 07 November 2013 11:22 |
jim kanomata
Messages: 257
Registered: March 2007
Location: fremont,ca
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This might not apply here, but always keep in mind that the transmission Fill tube that attach to the Final drive will leak.
There is a O Ring on the tube, but it does not seal well, so we use RTV Sealant to augment the seal after wiping the parts clean and make sure the mounting bracket to the tube is secured.
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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| Re: Chasing a transmission leak [message #228792 is a reply to message #228752] |
Thu, 07 November 2013 11:42 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
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| rcjordan wrote on Thu, 07 November 2013 07:11 |
The Birch has what appears to be a leak due to the torgue converter draining down. While researching here for possible leak sources, I've been assembling a 'photo tour' of likely places to check for tranny leaks. Most of the photos concentrate on the drivers side and I do have a good photo of the vacuum modulator. But what are the other spots to check on the passengers side? And passenger side photos?
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Another common leak is the pan mounting bolts. They are threaded into the case that is open to the fluid (at least some are) the bolt head doesn't have a gasket so they can weep fluid and cause you to think the pan gasket is leaking.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Chasing a transmission leak [message #228793 is a reply to message #228752] |
Thu, 07 November 2013 11:49 |
rcjordan
Messages: 1913
Registered: October 2012
Location: Elizabeth City, North Car...
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>2) The shifter rod seal (found on the driver’s side of the trans where the shift cable ends and the shaft goes into the side of the trans)
>3) The vacuum modulator on the passenger side of the trans.
>There is a O Ring on the tube
Thanks. In old threads, Armand also mentioned a weep hole near the dip tube. And numerous post say check the lines tapped into the top of the housing. Mine seems to be on the drivers side, and I'm comfortable with the diagnosis of bleed-back on the check valve but I'd like to put together a rough guide for other newbies and am wondering what I've missed on the passenger side?
Heh, the passenger side must be unphotogenic, because nobody seems to take a shot when they're pulling/replacing the tranny. Plenty of driver side, though.
SOLD 77 Royale Coachmen Side Dry Bath
76 Birchaven Coachmen Side Wet Bath
76 Eleganza
Elizabeth City, NC
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| Re: Chasing a transmission leak [message #228827 is a reply to message #228752] |
Thu, 07 November 2013 17:39 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
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RC, I had a small irritating leak on my new Manny Tranny. I finally traced it to the cooler line brass fitting. It would weep a little fluid that collected between the torque converter housing and the top of the tranny and ultimately run out that weep hole beside the final drive. Tightening up the brass fitting solved the problem although it is a pain to get a wrench in there. I finally took the line off and used a socket to get the brass fitting tight.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Chasing a transmission leak [message #228851 is a reply to message #228827] |
Thu, 07 November 2013 22:24 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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That is a perennial problem. If one looks down to the left of the
distributor at the two ATF coolant line connections on the transmission,
there's a valley in the top of the case with a "dam" at the forward end.
Obviously, any leakage from the coolant lines will collect in that area
and form a lake of red ATF. No lake, no leak, right? WRONG! The dam has
a drilled spillway at its bottom. That allows any leaked fluid to continue
to run forward, obscured from view from the top. But if you look from
underneath, there's a little shelf on the transmission housing, facing the
engine. That's where the escaped ATF from above comes out -- right down
the side of the transmission pan. Since those lines carry about the
highest pressure in the transmission, they're highly prone to leakage.
Especially if someone has replaced the fittings in the transmission case
with tapered pipe thread fittings instead of the correct straight threads.
And they are a booger to turn. In fact, I just bought a set of crows-foot
flare nut wrenches last week hoping they'll make the task easier.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL
www.gmcwipersetc.com
On Thu, Nov 7, 2013 at 6:39 PM, Kerry Pinkerton <Pinkertonk@mchsi.com>wrote:
>
>
> RC, I had a small irritating leak on my new Manny Tranny. I finally
> traced it to the cooler line brass fitting. It would weep a little fluid
> that collected between the torque converter housing and the top of the
> tranny and ultimately run out that weep hole beside the final drive.
> Tightening up the brass fitting solved the problem although it is a pain
> to get a wrench in there. I finally took the line off and used a socket to
> get the brass fitting tight.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as
> an Art Deco car hauler
> _______________________________________________
>
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Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Chasing a transmission leak [message #228852 is a reply to message #228851] |
Thu, 07 November 2013 22:33 |
armandminnie
Messages: 864
Registered: May 2009
Location: Marana, AZ
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| Ken Henderson wrote on Thu, 07 November 2013 21:24 |
The dam has
a drilled spillway at its bottom. That allows any leaked fluid to continue
to run forward, obscured from view from the top. But if you look from
underneath, there's a little shelf on the transmission housing, facing the
engine. That's where the escaped ATF from above comes out -- right down
the side of the transmission pan.
|
Ken, I think the escape path you are talking about is a different path from the one I talked about - the weep hole that is right under the transmission dip stick fitting in the final drive?
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
visit my gmc blog
click here to visit gmcws.org
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| Re: Chasing a transmission leak [message #228853 is a reply to message #228752] |
Thu, 07 November 2013 22:51 |
rcjordan
Messages: 1913
Registered: October 2012
Location: Elizabeth City, North Car...
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Armand, there is very little mention of the weep hole leak but for others following along at home (if you want to make your head hurt) here's the best thread I've found on that to date
http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&th=23155&prevloaded=1&rid=0&start=0
>the two ATF coolant line connections on the transmission
After pan/pan bolts and torque converter drain-back, my research seems to point to this as the 3rd-most common source of leaks. I found one of your earlier posts about the dam being drilled, but this is more clear. Thanks.
FWIW, I've ordered a high-definition usb borescope. My vision sucks, so maybe this will help. I have other pipe snakecams but the resolution is poor.
http://www.amazon.com/gp/product/B00EQNCMTY/
I've also ordered another steamer, as my other one finally gave up the ghost. I don't know about the borescope, but I HIGHLY recommend this steamer.
http://www.amazon.com/gp/product/B0000DF0RB/
SOLD 77 Royale Coachmen Side Dry Bath
76 Birchaven Coachmen Side Wet Bath
76 Eleganza
Elizabeth City, NC
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| Re: Chasing a transmission leak [message #228855 is a reply to message #228827] |
Thu, 07 November 2013 23:07 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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| Kerry Pinkerton wrote on Thu, 07 November 2013 15:39 |
RC, I had a small irritating leak on my new Manny Tranny. I finally traced it to the cooler line brass fitting. It would weep a little fluid that collected between the torque converter housing and the top of the tranny and ultimately run out that weep hole beside the final drive. Tightening up the brass fitting solved the problem although it is a pain to get a wrench in there. I finally took the line off and used a socket to get the brass fitting tight.
|
I had the same issue as Kerry. The weep hole was really a new one to me. Below where the cooler tubes connect to the transmission there is a little valley. At first blush one would think that if the fittings were leaking, fluid would pool in the little valley. But no, there is the tiny worm hole that allows the fluid to drain onto the top of the trans, down the right side, onto the top of the valve body. The fluid then ran forward and dripped off the bolts at the front of the transmission pan. I chased that for a while, tighten bolts and putting Right Stuff under them.
Other than that, I am with JimK. When it sits for a while the torque converter drains down and the pan gets too full. The dip stick leaks on many GMs of this vintage.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] Chasing a transmission leak [message #228870 is a reply to message #228852] |
Fri, 08 November 2013 07:44 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Armand,
You're right. I was just pointing out another common, difficult to
diagnose, source.
To prevent leakage because of damage to the FD-425 gasket, which is
generally the cause of leakage from the weep hole, I made a plastic shield
to protect the gasket during assembly. With slots for some of the bolts,
it can be removed after the FD is in place but not tightened down. Without
it, I find it all to easy to damage that gasket.
Ken H.
On Thu, Nov 7, 2013 at 11:33 PM, Armand Minnie <armand@minniebiz.com> wrote:
>
>
> Ken Henderson wrote on Thu, 07 November 2013 21:24
> > The dam has
> > a drilled spillway at its bottom. That allows any leaked fluid to
> continue
>
> to run forward, obscured from view from the top. But if you look from
> > underneath, there's a little shelf on the transmission housing, facing
> the
> > engine. That's where the escaped ATF from above comes out -- right down
> > the side of the transmission pan.
>
>
> Ken, I think the escape path you are talking about is a different path
> from the one I talked about - the weep hole that is right under the
> transmission dip stick fitting in the final drive?
> --
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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