Might be pulling the transmission again...

npe3484

npe3484

I hate ATF
Joined
May 10, 2009
Messages
792
Well I've been driving around with my rebuilt transmission for about 300 miles now. On Sunday I was towing my mom's empty horse trailer (~3000 lbs) and all was going well at first. About 2 miles from my destination I started to smell burning ATF and saw a concerning plume of white smoke behind me. The motor was running around 2300 rpm but my speed was dropping quickly. I got off on the next exit and coasted into a parking lot. After shutting it down and letting it sit for about 10 minutes, I started it back up but it would no longer move under it's own power due to the lack of fluid.

The fluid looked slightly blackened and appeared to be dripping from the lower access cover at the bottom of the bellhousing/block. Is there a seal that is the likely culprit? I'm out of town for work until the end of the month so I can't do any more diagnosing for a little while.

Pulling the transmission again is pretty much expected at this point. I'm thinking maybe I cut the pump seal when installing the convertor. Is that something that's easy to mess up?
:bang
 
the front seal probably went out. this can happen if you overfill the trans
 
98smokey said:
the front seal probably went out. this can happen if you overfill the trans
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This will be an obvious failure with the transmission on the bench, correct? It was a little bit over-filled from what I could see. I had it filled with the John Deere Hygard fluid which is almost clear and hard to read on the dipstick. Maybe I should have thrown some ATF in it as well to give it some red color.
 
It was probably puking fluid out the vent, it is located at the top of the pump.

I'd get the thing home and add oil to it and see if the thing still works.
 
mondtster said:
It was probably puking fluid out the vent, it is located at the top of the pump.

I'd get the thing home and add oil to it and see if the thing still works.
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Why would it have puked all the fluid though? When I get home from this business trip I'm going to drop the pan for a quick inspection.
 
There's probably a problem with it. At least if you put fluid in it and try to drive it you might be able to figure out what is wrong with it before it is pulled.
 
mondtster said:
There's probably a problem with it. At least if you put fluid in it and try to drive it you might be able to figure out what is wrong with it before it is pulled.
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Good point. Have you heard of the front seal blowing out due to over-filling?

What conditions would cause enough pressure to build up that it would come out of the vent?
 
If the transmission is overfilled, the gears churn the fluid into foam. This aerates the fluid and causing the same conditions occurring with a low level. In either case, air bubbles cause fluid overheating, oxidation and varnish buildup which interferes with valve and clutch operation. Foaming also causes fluid expansion which can result in fluid overflow from the transmission vent or fill tube. Fluid overflow can easily be mistaken for a leak if inspection is not careful.
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From the FSM...
 
Sounds like you need to change the fluid and carefully re-fill so you don't overfill this time around. It's worth a shot, especially since pulling the tranny again is a pain in the butt!
 
npe3484 said:
Good point. Have you heard of the front seal blowing out due to over-filling?
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No, the extra oil just comes out of the vent, which is at the top of the pump. It will go everywhere and look like a bad seal when it really isn't.

"Blowing" seals due to overfilling is a myth that has been around for years. I've seen them leak because the level is too high but they will quit leaking if the level goes down.


npe3484 said:
What conditions would cause enough pressure to build up that it would come out of the vent?
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You can usually overfill transmissions by several quarts before the oil expands and gets whipped around enough to cause the excess to go out the vent. It isn't going to be pressurized unless the vent is blocked, then it would come out of every seal on the trans.
 
I'll drop the fluid and pan on Sunday when I get home. Hopefully things will still look good and I can have an easy fix for once!
 
I'm going to check the truck out now. Keeping my fingers crossed that adding the correct level of fluid will remedy things. I'll report back with what I find out.
 
Well the fluid was darkened and smelled very burnt, but didn't have very much clutch or steel material in it. The level was normal which surprised me.

What was very weird was a 1" hole in the filter on both sides! It was close to the center of the filter and the top side had a little bigger hole. I'll get pics up asap.
 
Pics of the damaged filter.

imagejpeg_2-2.jpg


imagejpeg_2-1.jpg


imagejpeg_2.jpg
 
That almost looks like a jet of high pressure fluid shot down from the valvebody and pierced a hole through the filter. I'd carefully check the portion of valvebody directly above the hole for a leak, crack, or source of high pressure fluid jet.
 
Big Blue24 said:
That almost looks like a jet of high pressure fluid shot down from the valvebody and pierced a hole through the filter. I'd carefully check the portion of valvebody directly above the hole for a leak, crack, or source of high pressure fluid jet.
Click to expand...

This is what my dad and I were also thinking. Is the filter on the intake side or the discharge side of the pressure?
 
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