M1009 Shift issues after mod

[dirtballgear]

Ok guys I need some help. I put a snorkel on my truck with a 3.5 inch intake hose that goes to the original air cleaner. Immediately after it did not like to shift. Lite throttle 1st to second would shift fine. Lift and wait to shift 2nd to 3rd. The snorkel acts as a ram air going down the road so I think I am altering the manifold pressure which is screwing with the vacuum regulator on the side of the ip.

It was building some crankcase pressure after interstate drives fixed that with new CDR. It has a k&N air filter and 40 series with 2.5 to muffler and stock 2.25 tail pipes.

Now this may all be a coincidence. But here is what I have adjusted and replaced.

• Checked all vacuum lines and replaced don't see any cracks
• The vacuum adjustment thing on the ip was replaced when I got the truck from GL in 2012
• It is adjusted all the way back for the earliest shifts.
• The vacuum pump which was facing fwd is now all the way backward at 190 degrees.
• The pump reads at this setting 25 psi at the vacuum valve on the IP at idle. It does fluctuate/bounce really fast between 8 and 25.
• I have not checked the vacuum out of the vacuum valve with the gauge but it does has suction with the finger test .
• I replaced the transmission modulator with a new recommended CUCV one (fat green stripe) New rubber connecting hose with hose clamps.
• With the new modulator on tranny it made it worse.
• Plugged and unplugged down shift solenoid

What is next:

• I will bypass the vacuum valve and go straight to the tranny from the pump
• I will hook up the vacuum gauge to the the bottom of the vacuum valve to check actual vacuum
• I will hook up the gauge to the modulator to check vacuum

My thoughts:

• My thoughts so far are my vacuum pump is weak otherwise my vacuum valve would not have to be in the softest position to start with
• My line to the modulator may have a leak.

Now before someone chimes in on why in the **** I put a snorkel on it. It was not for fording but for cold air intake and flow which is why I have the k&n and the 40 series. So can we stay on point on the shifting and not the other mods. Truck runs great other than my new shift dilemma.

Thoughts or suggestions

 

[Warthog]

The diesel engine does not create a vacuum like a gas engine does. Sounds like you have a bad vacuum pump. The pump itself should read steady about 25in hg. (not psi). It should not fluctuate.

Doesn't make a difference which direction the pump is facing.

The TH400 needs a good vacuum to operate correctly. At partial throttle the valve on the side of the IP should supply 8in hg vacuum to the modulator on the side of the transmission.

Some people like to set the IP valve by trial and error. I prefer to set it with a gauge. The TM covers how to do this.

Here is how I do it.

http://www.steelsoldiers.com/showthread.php?50568-CUCV-Throttle-Vacuum-Valve-Adjustment

 

[dirtballgear]

Update

Update:

Went back thru everything:

Gauge still fluctuates but it goes between 15-23 to vacuum valve. Steady 7-8 out of valve and at the modulator. Shifts like a Cadillac now, 13mph and 32mph. I believe the crank case pressure and the shift problem were separate but just showed up at the same time.

The diesel engine does not create a vacuum like a gas engine does. Sounds like you have a bad vacuum pump. The pump itself should read steady about 25in hg. (not psi). It should not fluctuate.

Doesn't make a difference which direction the pump is facing.

The TH400 needs a good vacuum to operate correctly. At partial throttle the valve on the side of the IP should supply 8in hg vacuum to the modulator on the side of the transmission.

Some people like to set the IP valve by trial and error. I prefer to set it with a gauge. The TM covers how to do this.

Here is how I do it.

http://www.steelsoldiers.com/showthread.php?50568-CUCV-Throttle-Vacuum-Valve-Adjustment