Is this a vacuum test port?

[doghead]

You will need the screws that hold it on also.

 

[roveroverme]

You will need the screws that hold it on also.

Do you know the size of them? Thank you, Doghead

 

[doghead]

The TM does.

Let me look.

 

[doghead]

part number, MS51869-28

http://www.parttarget.com/5305-01-211-7464_5305012117464_MS51869-28.html

 

[roveroverme]

Thank you, Sir !!!

 

[roveroverme]

How is this valve being adjusted? was searching through the TM's but I could only find replacement not adjusting it.

 

[doghead]

Simple answer is, rotate the valve and test the shift firmness and timing.

The -20 TM covers replacement and adjustment.

TM 9-2320-289-20
3-21.1. TRANSMISSION VACUUM VALVE REPLACEMENT.
This task covers: a. Removal b. Installation
INITIAL SETUP:
Equipment Condition Too/s/Test Equipment
Air cleaner removed. Valve gage block, J-33043

 

[Warthog]

Or read post #9 with the link on how to adjust it per the TM.

 

[Tow4]

With .456 gears, it really doesn't matter if it goes straight from first to third. My valve was bad so I by-passed it. If you need to accelerate faster, you can shift it into second manually. I think I have done that twice.

I really don't notice much difference in acceleration manually shifting through the gears or letting it shift automatically which only hit's second briefly before going to third. That's why I decided to by-pass it. Now if you have .308 gears, you would probably want to replace it.

 

[cucvrus]

This is advise I got from the transmission shop. It is hard on the transmission if it does not receive the proper vacuum signal to the modulator. I had one with the bad VCM and it shifted poorly and quickly. I ignored it thinking oh well. It was really poor shifting when you were loaded and pulling out on an incline. It eventually ruined the transmission. My thought is they GM put it there for a reason and if it works it is better then not knowing what is happening if it is not hooked up. I have no documentation to prove this but I think when it is hooked up and working properly these vehicles run and drive so much better then when the valve is bad or missing. I like to be able to pull out stomp it and have smooth even shifts with the valve hooked up. With out the valve I pull out stomp it and it just shifts when ever and how ever it wants. Very indecisive. It almost goes from 1st to slipping thru 2nd and then slides into 3rd. Not very nice and sounds like the trans has issues. I say hook it up on my trucks. You do what you want it is just my opinion.

 

[roveroverme]

My Idea of it is… if the part was there before, I'll put it back. like CUCVrus said, it's there for a reason.

 

[Nowhereman]

I replaced mine a few weeks ago and it does make a difference. It shifts smoother, mine shift from 1st to 2nd at around 15 mph then from 2nd to 3rd 30 mph. The old one didnt shift until the engine rpms started screaming. When I pulled the old one off it was all gunked up.