M1009 Transmission Barfed from Dipstick

[Drock]

All my CUCV's have them as original equipment. That just makes it push out somewhere else. Like the vent tube on top of the transmission.View attachment 665241See the red transmission dipstick?

HUMMM? my M1028 has the old school style with the figure loop on it. I wonder if my trans, or just the dipstick has bin replaced? The trans & transfer case definitely looked like undisturbed originals to the truck.

 

[Drock]

If your vent tube is clogged up, the trans will build pressure from heat & fluid come out the dipstick tube.
That is why gm went to the newer dipsticks (rubber seal with flip over lever).
My dad sat & watched his new truck (84-85) burn when trans got hot & puked fluid all over the converter.
Surprisingly gm did replace the truck.

I was unaware these transmissions had vent holes? I looked quick under mine and didn't see one? Anyway I agree, the combination of a clogged vent & a severe angle would push it out.

 

[86m1028]

I was unaware these transmissions had vent holes? I looked quick under mine and didn't see one? Anyway I agree, the combination of a clogged vent & a severe angle would push it out.

upper right hand side of case (viewed from the top rear). Has a short 2-3 inch tube sticking out of the case.

 

[cucvrus]

I remember reading in an old PS comic book about switching the dip sticks to avoid dirt from entering and to prevent blown out dip sticks. If not in the PS. I know I read it somewhere. But mine have the red plastic lock dipsticks. I don't have time to look thru all them old books. Maybe someone else has the information.

 

[Rustyshackelford]

Well, I asked because in general, it's easier to overheat the transmission in high range if you are driving slow or wheeling under high power without moving much.

Well it is a M1009 with stock gears. Which is almost like being in high range.

I spoke to a transmission specialist today and he said its because it got hot. He said the TH400 is infamous for it. I asked him twice if its a possible sign of a deeper issue and he said no, its just too hot.

 

[Drock]

Well it is a M1009 with stock gears. Which is almost like being in high range.

I spoke to a transmission specialist today and he said its because it got hot. He said the TH400 is infamous for it. I asked him twice if its a possible sign of a deeper issue and he said no, its just too hot.

Well if that's the case I'd throw a trans cooler on it. Their cheap and easy to do. Here's the one I installed on my M1028... https://www.etrailer.com/Transmissi...+Pickup/1984/D13503.html?vehicleid=1984745953

 

[cucvrus]

I wish Rustystud was here. I didn't want to say this but I will. It is getting hot because something is slipping inside the transmission. I just picked up a 1998 Silverado 2500 pick up at the transmission shop and I ask the same question. I had to hear the same story the man always tells me about the TH400 being one of the best transmissions and it was used in the early 60's and it would not leak or puke fluid unless the breather is clogged or something is making it hot by slipping. I tend to believe that after 20+ years of using CUCV's and only having one do it and the fix was an overhaul. That seems to be logical. Imagine the Army using these CUCV's as hard as they did and they puked fluid when they were hot. I plow snow 24 hours straight stock cooling and the transmission never pukes fluid. Plowing snow with 3000 lbs of salt in the bed is heavy use. I am being a realistic guy. Maybe putting an auxiliary cooler is like putting a band aid on a bullet wound. It may stop the bleeding for a moment. But it just prolongs the pain and agony for the transmission. I hope that explanation is not out of line. I run is low range 8-10 hours in heavy mud and never leak a drop. No bragging explaining and trying to save you some money and it the end down time. The longer you run it and get it hot the more damage that gets done. Good Luck and peace.

 

[rustystud]

I got your PM cucvrus. I'm sorry I haven't been around much lately. I've been dealing with Kidney stones this last two weeks and will be going into surgery this Friday to remove one that is blocking my left kidney.
Now about this transmission issue. TH400's normally do "not" blow fluid out the dipstick when hot. If they are over filled they will but that is it. There are a number of reasons that fluid will "burp" out the dipstick. I'll list a few in order of severity.
1) The vent tube is plugged. Most common reason.
2) The filter is bad-either plugged or cracked and sucking air.
3) The filter "pick-up" tube is cracked. Very common with the plastic tubes. I only use the metal ones myself.
4) The oil pump is going out. Use the main pressure port to check the transmissions pressures.
5) The Torque Converter is draining back after the engine is shut-off. Only happens when the vehicle is first started.
6) The Direct Clutch seals are leaking. This will require a total rebuild.
There are other issues that will cause this to happen but these are the most common ones that I've experienced.

 

[royalflush55]

I got your PM cucvrus. I'm sorry I haven't been around much lately. I've been dealing with Kidney stones this last two weeks and will be going into surgery this Friday to remove one that is blocking my left kidney.
Now about this transmission issue. TH400's normally do "not" blow fluid out the dipstick when hot. If they are over filled they will but that is it. There are a number of reasons that fluid will "burp" out the dipstick. I'll list a few in order of severity.
1) The vent tube is plugged. Most common reason.
2) The filter is bad-either plugged or cracked and sucking air.
3) The filter "pick-up" tube is cracked. Very common with the plastic tubes. I only use the metal ones myself.
4) The oil pump is going out. Use the main pressure port to check the transmissions pressures.
5) The Torque Converter is draining back after the engine is shut-off. Only happens when the vehicle is first started.
6) The Direct Clutch seals are leaking. This will require a total rebuild.
There are other issues that will cause this to happen but these are the most common ones that I've experienced.

rustystud, Thanks for this list of reasons for "fluid burp". Good luck and wishing for a speedy recovery from your kidney stones!

 

[Rustyshackelford]

I got your PM cucvrus. I'm sorry I haven't been around much lately. I've been dealing with Kidney stones this last two weeks and will be going into surgery this Friday to remove one that is blocking my left kidney.
Now about this transmission issue. TH400's normally do "not" blow fluid out the dipstick when hot. If they are over filled they will but that is it. There are a number of reasons that fluid will "burp" out the dipstick. I'll list a few in order of severity.
1) The vent tube is plugged. Most common reason.
2) The filter is bad-either plugged or cracked and sucking air.
3) The filter "pick-up" tube is cracked. Very common with the plastic tubes. I only use the metal ones myself.
4) The oil pump is going out. Use the main pressure port to check the transmissions pressures.
5) The Torque Converter is draining back after the engine is shut-off. Only happens when the vehicle is first started.
6) The Direct Clutch seals are leaking. This will require a total rebuild.
There are other issues that will cause this to happen but these are the most common ones that I've experienced.

Thank you. I called two trans shops yesterday and both told me it was because it got too hot and it wasn't another problem. I'm going to print this list and get this checked out.

 

[Tinstar]

Maybe you got lucky and didn't hurt anything.
I would still change fluid and filter.
Also install a trans temp gauge and cooler.

 

[Rustyshackelford]

Ok is this little yellow tube the vent tube? if so, how would I check it and clean it? Does it come off?
Also wondering if it is supposed to only be 3 inches long.
f?

 

[Tinstar]

Ok is this little yellow tube the vent tube? if so, how would I check it and clean it? Does it come off?
Also wondering if it is supposed to only be 3 inches long.
f?View attachment 665619

Thats it.
Yes on length
I don't know if it comes off.
A short stout piece of wire to insert and make sure it's not clogged.

 

[Rustyshackelford]

It was definitely clogged and I pushed some wire it it. Hopefully I didn't push anything in there

 

[The FLU farm]

It was definitely clogged and I pushed some wire it it. Hopefully I didn't push anything in there

If it was plugged, you most certainly pushed something in there. What I find interesting is that the area around the vent is the only place that isn't covered with some sort of fluid residue.
Anyway, those vents are simply pressed in, as I recall.

 

[Ordak]

Hopefully cleaning out that vent line fixes your issue. If you still need pictures and information on adding a transmission cooler I can post them up. I think there is a thread about installing one but I cannot remember how far it goes into detail.

 

[rustystud]

If it was plugged, you most certainly pushed something in there. What I find interesting is that the area around the vent is the only place that isn't covered with some sort of fluid residue.
Anyway, those vents are simply pressed in, as I recall.

The vent has a "flange" on the end and is inserted into the case before the pump housing is installed. It should have a length of tubing on it going up to the firewall. That is why it is facing up. Since the tube must have fallen off and is probably lost that left the vent tube sticking up collecting all kinds of debris.
As far as the two shops who said there was no problem I wouldn't take any transmissions to them personally .
Just like that old commercial said " I always wanted to be an automatic transmission mechanic ! " .

 

[rustystud]

There is only one way to clean-out the vent tube without dismantling the transmission and that is to take out the dip-stick and using a shop air-nozzle gently blow into the tube. Most air-guns have a rubber nozzle which will seal against the tube.
Have someone at the vent and feel for any air coming out. Don't blast into the tube though ! That can blow out your oil seals !

 

[The King Machine]

Too much tequila will make any transmission barf

 

[86m1028]

The vent has a "flange" on the end and is inserted into the case before the pump housing is installed. It should have a length of tubing on it going up to the firewall. That is why it is facing up. Since the tube must have fallen off and is probably lost that left the vent tube sticking up collecting all kinds of debris.

I have never see "a length of tubing" on that vent line.
As you said that vent has a flange on it & it will rotate.