Vacuum Lines - Missing Components

[cmroles]

I replaced my vacuum lines and Transmission Modulator today in an attempt to resolve the late-shifting issue in my M1009. When I pulled all the lines off I noticed that the hose reducers and the double-hose fitting that goes on the vacuum pump at the IP were missing. Basically the hoses were just pushed directly onto the vacuum pump and the little "T" on the emissions thing.

I can't imagine they are that important, but.....you know....

On a side-note, I lost a bit of tranny fluid when I pulled out the Trans Modulator valve. I know this may seem like a stupid question, but do I add more fluid in through the dipstick tube? I've looked through the -10 and -20 TM's for a filler, but maybe I'm just missing it....

 

[Westech]

yes add fluid using the dip stick tube. It does not matter if the adapter is there or not. I take them out when I replace my TPS valves.

 

[67_C-30]

I replaced my vacuum lines and Transmission Modulator today in an attempt to resolve the late-shifting issue in my M1009. When I pulled all the lines off I noticed that the hose reducers and the double-hose fitting that goes on the vacuum pump at the IP were missing. Basically the hoses were just pushed directly onto the vacuum pump and the little "T" on the emissions thing.

I can't imagine they are that important, but.....you know....

On a side-note, I lost a bit of tranny fluid when I pulled out the Trans Modulator valve. I know this may seem like a stupid question, but do I add more fluid in through the dipstick tube? I've looked through the -10 and -20 TM's for a filler, but maybe I'm just missing it....

Yes, you add fluid through the dipstick tube. To check your level, park the truck on a fairly level surface, and check the level with the truck running in Park at operating temperature.

On the fittings, I replaced mine because they were dry and brittle, and I had to delete the double fitting that goes to valve on IP. it was split, and I just pushed the new hoses to the barbs. Did doing this solve your shifting problem?

 

[cmroles]

Yes, you add fluid through the dipstick tube. To check your level, park the truck on a fairly level surface, and check the level with the truck running in Park at operating temperature.

On the fittings, I replaced mine because they were dry and brittle, and I had to delete the double fitting that goes to valve on IP. it was split, and I just pushed the new hoses to the barbs. Did doing this solve your shifting problem?

I haven't had a chance to try the shifting yet. I checked the fluid level after putting in the new Vacuum Modulator and it isn't even showing on the dipstick. I didn't want to risk damaging something by driving it without enough fluid.

I am the 2nd "non-military" owner of this truck and it looks like the previous owner already replaced some of the vac lines and the modulator valve. I was still having shift problems and decided it was work the $20 in parts to know for a fact it had been recently replaced.

 

[tagjeep]

What size vacuum tubing did you use? (need to replace mine when I get time)

 

[cmroles]

What size vacuum tubing did you use? (need to replace mine when I get time)

I think most of it was 9/32" tubing. I really just pulled all the old lines and took them down to the parts store to compare.

 

[cmroles]

yes add fluid using the dip stick tube. It does not matter if the adapter is there or not. I take them out when I replace my TPS valves.

I couldn't find Dexron III transmission fluid at the parts store. What I did find was Dexron VI, which says it meets the Dexron III standards. Can I top up the tranny with the Dexron VI, or would that be bad?

 

[firecontrol86]

somebody correct me if i'm wrong, but i'm pretty sure the tranny has to be warm to get the right reading. if you don't want to drive it around to warm up the tranny, put the transfer case in neutral and chock the wheels so you can warm it up in your driveway or garage. although i would think you'd still get a little on the dipstick even cold.

 

[Barrman]

Yes you can use the newer stuff that meets the older standard. Yes, the transmission should be warmed up when you check the fluid. It is also a good idea to shift into all the gears for a few seconds to let the fluid travel around and give you an accurate reading of what is still in the pan.

The difference between full and add on a transmission is 1 pint, not 1 quart like on an engine dipstick. Just something to keep in mind.

 

[cmroles]

Yes you can use the newer stuff that meets the older standard. Yes, the transmission should be warmed up when you check the fluid. It is also a good idea to shift into all the gears for a few seconds to let the fluid travel around and give you an accurate reading of what is still in the pan.

The difference between full and add on a transmission is 1 pint, not 1 quart like on an engine dipstick. Just something to keep in mind.

OK....

I've topped up the ATF, replaced the Transmission Modulator and the vacuum lines. The problem seems like it may have actually gotten worse...any ideas?

Should my next step be to rotate the vacuum pump back towards the firewall?

 

[Barrman]

You have several things in line that tell the transmission when to shift. First, there is the mechanical governor in the transmission that will shift it without any vacuum. Very high engine rpm, but it will shift.

The engine driven vacuum pump generates a constant 18"-22" of Mercury. Do you have that at the vacuum pump?

The vacuum line then goes to the injection pump where there is a throttle position sensor on the passenger side of the IP. Do you still have the specified InHg at the input to the sensor?

Next, check the vacuum at the output of the sensor.

Finally, check what you have down at the modulator. Good vacuum all the way?

If not, check all the vacuum lines. A better idea would be to replace all of the 25 year old hoses and check the metal line for cracks. Also, the -20 troubleshooting section talks you through this step by step with exact readings you should be getting at each part.

 

[cmroles]

The vacuum line then goes to the injection pump where there is a throttle position sensor on the passenger side of the IP. Do you still have the specified InHg at the input to the sensor?

Next, check the vacuum at the output of the sensor.

OK...maybe I'm a little lost. I've been looking through the -20 TM and all I've found is the section below for troubleshooting. I don't have a gauge to check vacuum, but I'll go get one in a few minutes. Is the Throttle Position Sensor the same as the "vacuum valve" (see attached picture)?

What I can see / understand:

1. Vacuum pump is on rear of engine under air cleaner. Should produce 18"-22" of Hg at all times (even at idle)

2. Vacuum hose goes from there to the Vacuum Valve on the passenger side of the IP (bottom port).

3. Vacuum hose comes out of Vacuum Valve (top port) and down to Transmission Modulator.

Do I have this right? I've been looking through the -20 TM and just am not finding the info I'm looking for...maybe I'm in the wrong part of the manual?



51. WILL NOT SHIFT PROPERLY
Step 1. Check transmission fluid indicator for proper reading. (See TM 9-2320-289-10)
Step 2. Inspect vacuum hoses, vacuum pump, and vacuum regulator valve for improper
connection, leakage, or damage.
Connect or replace vacuum hoses and vacuum pump as required. (See
paragraphs 3-21 and 3-7) Adjust vacuum regulator valve. (See paragraph
3-21.1)
Step 3. Inspect vacuum modulator (right side of transmission near base of transmission fill
tube) for leakage and damage.
Tighten mounting bolt to 20 Ib.-ft. (27 N•m). Notify your supervisor if damaged
or still leaking.

 

[Warthog]

Many times the tech manual doesn't show you how things are routed or hooked up. I use the parts diagram to help figure out the proper way.

Your discription is correct.

Bottom fitting to the vacuum pump - blue line
Top fitting to the transmission - green line

Here is a post I did about the Vacuum Valve

http://www.steelsoldiers.com/cucv/50568-cucv-throttle-vacuum-valve-adjustment.html

 

[cmroles]

I got a vacuum gauge and measured everything.

At "input" side of vacuum valve on IP: 29.5" Hg

At "output" side of vacuum valve on IP: 14.5" Hg

At Transmission Modulator: 14" Hg

It seems like I have TOO MUCH vacuum!! Would this cause my shifting issues and how do I reduce it? This started out like a normal "bad vacuum" issue with no shifting until the governor kicks in at high RPM (1st-2nd @ 35mph / 2nd-3rd @ 55mph).

Is there a way to reduce the vacuum of the vacuum pump? Can it be turned down?

 

[doghead]

The vacuum valve can be rotated(loosen 2 screws), to adjust the output .

Click on and read the thread/link that Warthog posted above.

 

[cmroles]

The vacuum valve can be rotated(loosen 2 screws), to adjust the output .

Click on and read the thread/link that Warthog posted above.

Is it normal for too much vacuum to cause a late-shift issue? From my reading I'd associated that problem with not enough vacuum.

Does the vacuum generated by the vacuum pump drop when RPM's go up, or is it constant from idle to redline? I measured with my vacuum gauge while at idle. Was that a mistake?

Rotating the valve back towards the firewall will reduce vacuum level at the valve output?

 

[cmroles]

Well....

I measured the vacuum at the TPS Vacuum Valve gizmo with a different vacuum tester and got 25" Hg with that one. Still seems a bit higher than it should be, but a little lower.

I ended up just rotating the valve body all the way towards the firewall. The shift points are now as follows:

1st-2nd: ~15-18 mph
2nd-3rd: ~35 mph

The 1st-2nd shift is very smooth (almost can't feel it) and the 2nd-3rd shift seems to be a little firmer than I would like. It also seems to make the shift to 3rd most readily if I lift of the gas for just a second. It shifts to 3rd and then put your foot back into it.

If I get a chance I'll do the correct procedure re: use the .646" block and a Mighty-Vac. Just don't have those tools handy right now.

 

[Warthog]

You can adjust the valve with the engine running and using the vacuum pump as the vacuum source.

JUST BE CAREFULL with the engine running and the fan blade turning.

 

[Barrman]

Sounds like you have it figured out. Mine will shift hard and late if I just ease up to 35 mph. If I am in the power, it shifts nice and smooth. The 1-2 shift is about like you describe.

 

[dmilkman589]

you said you were rotating something, what part is that? im having the shift problem too.