poppet valve on top of tranny leaking

[seano11]

Well I orderd a new poppet valve and installed it today but its still leaking from the exhaust port of the poppet valve anyone have any idea what might cause it to leak ?

 

[doghead]

If the seal on the sprag piston is bad(2 way seal), the air couldl flow past and out the exhaust.

Why did you replace your poppet valve?

 

[73m819]

Yep what he said

 

[seano11]

If the seal on the sprag piston is bad(2 way seal), the air couldl flow past and out the exhaust.

Why did you replace your poppet valve?

I replaced the poppet valve for this reason that when In neutral the air was leaking out the exhaust port on the poppet valve but when the truck is in reverse it doesn't leak

 

[73m819]

Unless the air cut off mwo is installed the sprag can not go into neutral, when you shift into reverse the poppet valve shifts the sprag to reverse, as SOON as you shift out of reverse, the other poppet valves shifts the sprag to forward

The reason air is leaking out of the exhaust port is the seals in the xcase shift cylinder are bypassing air (leaking)

 

[seano11]

Unless the air cut off mwo is installed the sprag can not go into neutral, when you shift into reverse the poppet valve shifts the sprag to reverse, as SOON as you shift out of reverse, the other poppet valves shifts the sprag to forward

Sorry That is what I ment when the sprag is in forwards it leaks but not in reverse? how hard is it to change this seal?

 

[73m819]

Not very, can be done without pulling the front out put flange, there are some real good threads on this on SS, think FLORIDIAN had a good thread, it will show up in search if search is friendly to you

 

[73m819]

Just so If anybody that reads this thread later on down the line, If you are getting air leaking out of the exhaust ports of the poppets, it is about a 90% chance or better that it is the seal for the sprag shift cylinder, NOT the poppet valves

 

[seano11]

Is this the part that needs to be rebuilt?

 

[ChuckM]

I know you just spent money on a new poppet but why not just install a 3-way so you could have gotten a 2wd option. I was having multiple issues...plugged supply air to poppet, fixed that, then leaking air from the exhaust, removed poppet and flipped over the rubber diaphrams and got my front drive working sometimes......bypass poppet and installed a 3-way valve and I haven't had any more troubles at all.

 

[73m819]

Yes

 

[seano11]

.

I know you just spent money on a new poppet but why not just install a 3-way so you could have gotten a 2wd option. I was having multiple issues...plugged supply air to poppet, fixed that, then leaking air from the exhaust, removed poppet and flipped over the rubber diaphrams and got my front drive working sometimes......bypass poppet and installed a 3-way valve and I haven't had any more troubles at all.[/QUOTE

I installed a shut off on the main airline going to the poppet valve isn't that how you get the 4wd option

 

[73m819]

I know you just spent money on a new poppet but why not just install a 3-way so you could have gotten a 2wd option. I was having multiple issues...plugged supply air to poppet, fixed that, then leaking air from the exhaust, removed poppet and flipped over the rubber diaphrams and got my front drive working sometimes......bypass poppet and installed a 3-way valve and I haven't had any more troubles at all.

Untill you to forget to manually flip to forward when you were in reverse, or forget to put in reverse after being in forward, things WILL break

 

[73m819]

I know you just spent money on a new poppet but why not just install a 3-way so you could have gotten a 2wd option. I was having multiple issues...plugged supply air to poppet, fixed that, then leaking air from the exhaust, removed poppet and flipped over the rubber diaphrams and got my front drive working sometimes......bypass poppet and installed a 3-way valve and I haven't had any more troubles at all.[/QUOTE

I installed a shut off on the main airline going to the poppet valve isn't that how you get the 4wd option

The air shut off will put the sprag in nutural, as well as a shut off, the air switch HAS to allow the air pressure in the shift cylinder to dump, or the sprag will Stay in the last direction shifted to., this is why the deuce air switch is used for the mwo mod.

 

[ChuckM]

I agree Ron about tearing up my tcase, I rarely shift to 4wd and am very cautious as to what gear I'm in when I do...as far as staying locked in....as long as the 3-way valve vents both ports when blocked(2wd) you are good to go.

Sean are you having trouble with front wheel drive or are you just trying to fix a leak?

 

[73m819]

Air leaks

 

[73m819]

I agree Ron about tearing up my tcase, I rarely shift to 4wd and am very cautious as to what gear I'm in when I do...as far as staying locked in....as long as the 3-way valve vents both ports when blocked(2wd) you are good to go.

Sean are you having trouble with front wheel drive or are you just trying to fix a leak?

This is the KEY, a lot of air valves do not vent, just shut off, your set up is what is done when another trans is installed, though lever activating air switches could be set up to have the stick activate them

 

[seano11]

This is the KEY, a lot of air valves do not vent, just shut off

So is it ok for me to have just the main air valve shut off ? or does it need to vent?

Second 275 dollars for a new tranny valve from eastern surplus does this seem like alot ?

 

[ChuckM]

I was quoted $325 locally here so you did ok on that.......but my 3-way valve was 20 bucks

 

[73m819]

So is it ok for me to have just the main air valve shut off ? or does it need to vent?

Second 275 dollars for a new tranny valve from eastern surplus does this seem like alot ?

HAS to vent