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Transmission or Tcase Fluid Leak after towing

rlb

rlb

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Well I bought a boat, a 24' Albemarle. This has turned from a boat project, to a boat, trailer and now truck project. I'll explain.

The boat came with a rusty EZ loader trailer. $1000 in parts and 2 back breaking days cutting rusty parts off with an angle grinder, the trailer is refurbished w new springs, hubs, brakes, surge actuator and brake lines.

I drive 3 hours down to the coast and pick up the boat. Total weight of boat and trailer is about 6500lbs. I towed it back about 55-60mph with the transmission NOT in overdrive. When I get back home, I go to unhitch the trailer and.... uh-oh. The trailer jack is covered in fluid. The back of the suburban has a fine mist of oil/atf on it.

So, I go crawling around on my back to try and find the source of the leak. The rear axle and bottom of fuel tank is wet with fluid, but I trace the leak ahead of the axle. Driveshaft is also wet with fluid. Tcase has a drop of ATF on the bottom. Transmission has a little fluid on it from a leaking pan gasket, that has been leaking for awhile and very slowly. The biggest leak I can find is the crossmember under the transfer case is very wet with fluid. However, I can't really find the source of the leak. Both of the front and rear driveshaft seals didn't seem to be leaking.

I'm taking it to a shop this week to have it put on a lift and the leak diagnosed. Posting here because I think its strange the leak appeared after towing the heavy load. Wondering if something got hot and blew fluid out of a vent? Tcase and both axles had fluid changed recently by local mechanic. I don't have a transmission temp gauge. It does have a factory auxiliary cooler.
Here are a few admittedly crappy pics.
 
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Sent from my iPhone using Tapatalk
 
If it's no big deal taking it back to the same shop that did the work on it then start there and bring it it without cleaning any of it off. Otherwise, if you do it and you can not see where it is coming from, I would get a couple cans of degreaser on there and clean it all off. Then run the truck and go over it very frequently. You should be able to see it starting to seep. And ya, it sounds like if this started after the towing only, it got a little warm. Did you get a look at the vent tube from the trans?
 
Nope. Where is the vent roughly?

I'm going to look at it this afternoon. Check Tcase fluid level too.. If I can't find it, going back to same shop tomorrow.
 
Check your fluid levels first and see if the transfer case is low or not. Sometimes the input seal for the transfer case fails and it allows trans fluid to overfill the transfer case and it pukes fluid out.
 
THEFERMANATOR said:
Check your fluid levels first and see if the transfer case is low or not. Sometimes the input seal for the transfer case fails and it allows trans fluid to overfill the transfer case and it pukes fluid out.
Click to expand...

That's interesting. I'll look for the tcase vent.

I'm guessing if that was the case, when I pull the tcase fill plug, a bunch of fluid would run out. Correct?
 
rlb said:
That's interesting. I'll look for the tcase vent.

I'm guessing if that was the case, when I pull the tcase fill plug, a bunch of fluid would run out. Correct?
Click to expand...

Have a drain pan under the t-case when you remove the top plug. It can pour out. The front seal on the t-case keeps trans oil out of it.

The worst likely chain of events is the trans oil left as a vapor then condensed outside of the transmission. This happens when you loose static friction or can't get lockup in the selected gear and clutches/bands continue to slip generating extreme heat that vaporizes trans oil. The trans vent is on top and a hose goes to a upper bellhousing bolt as I recall. When the oil leaves as a vapor there is no "leak" to be found/seen. The Torque Converter Clutch is a likely slip point. Check the front of the converter, by dropping the rock guard cover, and look for a bluing color from the TCC slipping. Generally it's rebuild time.

Possible t-case rub through generating a leak?

How do your oil levels look now, specifically, the transmission? Any burnt smell on the trans oil?
 
Transmission was shifting well and no burning smell noted. Fluid is nice and red. I checked when it was cold and it was within range on the dipstick. Haven't had the chance to drive the truck since noticing the leak yesterday.

T-Case rub... I know there is a "pump rub fix" for certain newer models but didn't think it applied to my '94 and never bothered to look into it.
 
Pump rub doesn't apply to your 241, but they did have there own issues. Early 241's used self tapping screws to hold the extension housing on, and they could cause the rear case half to crack over time. I learned this one the hard way when my BURB took a bath of ATF on the undercarriage. The rear case half cracked right through one of the bolt holes in the top of it. It only leaked when I was driving as you had to be moving for fluid to get slung out it.
 
THEFERMANATOR said:
Pump rub doesn't apply to your 241, but they did have there own issues. Early 241's used self tapping screws to hold the extension housing on, and they could cause the rear case half to crack over time. I learned this one the hard way when my BURB took a bath of ATF on the undercarriage. The rear case half cracked right through one of the bolt holes in the top of it. It only leaked when I was driving as you had to be moving for fluid to get slung out it.
Click to expand...

Self tapping screws!! On a cast aluminum part....
 
Thanks Ferm, I wasn't sure how far back the pump rub applied.
 
WarWagon said:
Thanks Ferm, I wasn't sure how far back the pump rub applied.
Click to expand...

Pump rub became an issue when GM went to magnesium transfer cases(around 99 for some models). When MAGMA took over NEW PROCESS, there fix was to simply change from magnesium to aluminum for the case halves. Also the 2 piece cases was another cause of the issue since it held the pump in in a manner that allows it to move and rub through the case VS the older 4 piece design that held the pump in with the extension housing.
 
THEFERMANATOR said:
Check your fluid levels first and see if the transfer case is low or not. Sometimes the input seal for the transfer case fails and it allows trans fluid to overfill the transfer case and it pukes fluid out.
Click to expand...

We have a winner.

Mechanic called and said the area between the transfer case and transmission was full of fluid. He is replacing both the transmission output seal and transfer case input seal.

He told me he thought the transfer case seal might have been 'installed backwards" and that he was looking at the spring of the seal, thought it might should be in the other way Anyone have a diagram depicting the orientation of both seals?

I have a factory service manual on a CD at home but won't get a chance to look at it until later.
 
rlb said:
We have a winner.

Mechanic called and said the area between the transfer case and transmission was full of fluid. He is replacing both the transmission output seal and transfer case input seal.

He told me he thought the transfer case seal might have been 'installed backwards" and that he was looking at the spring of the seal, thought it might should be in the other way Anyone have a diagram depicting the orientation of both seals?

I have a factory service manual on a CD at home but won't get a chance to look at it until later.
Click to expand...

The area between the trans and transfer case is always full of fluid. GM doesn't use a seal on the output shaft in a 4X4 trans. There is 2 seals on the transfer case input, the first one goes in with the lip facing to keep the transfer case fluid in, and the 2nd one goes in facing out to keep the tranmission fluid out. Some late model seals are 1 piece with a double opposing lip seal design. Then there is a gasket between the trans and transfer case to keep the trans fluid in.
 
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