What would happen if a 2-4 servo exhaust passage in a 4L60e gets blocked ? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 04-30-2011, 06:10 AM
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What would happen if a 2-4 servo exhaust passage in a 4L60e gets blocked ?

I am just trying to understand what would happen if the the exhaust passage of the 2-4 servo in a 4L60e is restricted or blocked.

Mine was fairly blocked before cleaning.

What problems could this have caused?



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Old 04-30-2011, 08:39 PM
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let me try to guess what might happen.

this is an air exhuast if I'm right. Blocking it will cause a build up of air pressure inside the servo chamber.

So, partially or completely block that hole, means the servo can't engage 4th gear propperly.

Does this sound right ???
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Old 05-01-2011, 04:38 AM
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Quote:
Originally Posted by old yukon
let me try to guess what might happen.

this is an air exhuast if I'm right. Blocking it will cause a build up of air pressure inside the servo chamber.

So, partially or completely block that hole, means the servo can't engage 4th gear propperly.

Does this sound right ???
theres no air in there, just fluid taking up space that has to go somewhere. its not a high pressure release, kinda like a vent, its gotta relieve pressure. in all my years, ive only seen it blocked a couple times by people who tried to use silicone to seal the pan.
it could present a excessive 2-3 flare shift. or maybe even a 2-3 bind. what did you find obstructing the hole?
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Old 05-01-2011, 07:12 AM
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Thanks tnsmith10 for that helpful info.

Silicon and old gasket material, I got the thing 2nd hand. This things is full of surprises.

Could that then in anyway lead to clutch slipping or overheating issues, somehow done the line ??
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Old 05-01-2011, 03:48 PM
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Looks like there's no Fluid in there unless some leaks past the Seals, that and air has to escape somehow.
Good Servo operation diagram here about 7/8 way down Pg.>> http://www.transmissioncenter.net/700r4.htm
Could cause a Bind or Flare.
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Old 05-01-2011, 09:34 PM
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which one is right ?

Thanks again guys for the productive feedback, this is what great discussion forums are all about.
I just want to clarify how this servo works.

We have 2 different view, which one is right ?

"....there's no air in there, just fluid taking up space that has to go somewhere."

and

"Looks like there's no Fluid in there unless some leaks past the Seals, that and air has to escape somehow"

Now I am diving in way over my head here.

I am probably totally wrong on this but from my reading of the servo apply, it seems that if there are no leaks on the seals there should be no fluid in the servo cavity above the that exhaust vent between the 4th and 2nd apply pistons.

As the 2nd apply piston is applied, that chamber's volume is increased allowing air to be drawn in from the pan.
As the 2nd apply piston is released, the air exhausts back out of the servo chamber into the pan.

In the 4th apply, the air is exhausted out of the servo chamber into the pan, and drawn back in when the 4th apply piston is released.

If we have leaks both air and fluid with travel this path.

if the exhaust vent is fully blocked, it would create a slight vacuum effect on 2nd apply, meaning less apply, and resistance on 4th apply, again less apply.

I just want to understand how this things works.

How does this sound to you guys with the real world experience??

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Old 05-03-2011, 07:30 AM
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so it it air or ATF fluid ?

Does anyone out there know ??
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Old 05-03-2011, 05:03 PM
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every time i drop the pan on a 700r4/4l60e i always have fluid come out of that hole. never very much, but always some. theres probably some air in there anyways, but theres always been a bit of fluid from there.
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Old 05-03-2011, 08:20 PM
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there is fluid in there.

generally when the exhaust hole at the pan is covered, the loss of over drive happens.

the other operations of the servo is not affected since there are paths for the fluid to exhaust out internally..... like that little check ball device in the servo bore
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Old 05-03-2011, 08:23 PM
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cool!

thanks for the clarification guys.
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