Guntherx
Full Access Member
OK what color stripe for teh modulator? some say balck, some say green. what about the pin? does it get color matched too?
Vac Modulator Color Stripe
- Thread starter Guntherx
- Start date
87crewdually
Full Access Member
Not to screw you up but when I rebuilt my tranny I used a purple striped. It was adjustable so I can put it where I wanted it.
Purple Mod $15
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Purple Mod $15
Brian VT
Full Access Member
I've searched and read a bunch here about this but still not sure which stripe VM to buy. I've seen different colors suggested. And I'm not even sure that the VM is my problem. But it's cheap and easy enough to replace. Truck is new to me so I'm just starting to go through it.
Purple is the one? NAPA has white, black, and green. All adjustable.
But I can hunt down a purple if that's the one to get.
Just as an fyi, mine shifts at higher RPMs than I think it should and then it "slams" into gear. It also downshifts when I don't think it should. I suppose I could just try adjusting the one that's in there but, like I said, it seems cheap and easy to replace. I just need to know which one to get.
Purple is the one? NAPA has white, black, and green. All adjustable.
But I can hunt down a purple if that's the one to get.
Just as an fyi, mine shifts at higher RPMs than I think it should and then it "slams" into gear. It also downshifts when I don't think it should. I suppose I could just try adjusting the one that's in there but, like I said, it seems cheap and easy to replace. I just need to know which one to get.
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Brian VT
Full Access Member
Jeez. I thought this would be an easy answer but I guess not.
I really don't want to rely on "NAPA Know How". lol
I really don't want to rely on "NAPA Know How". lol
Big Bart
Tow&Slow
So if it revs high and slams into gear your system is not working. Basically it is not getting/losing vacuum at the right time and not controlling the modulator on the tranny.
So the stripes as I recall were for regular altitude and high altitude. Most use the green one.
Now the aftermarket modulators are adjustable, they have a screw inside the hole of the vacuum connection. The Ford ones were not adjustable.
The VRV valves are no longer made. They are hard to find. There are mechanical VRV’s available you can convert to. (Were made for race cars using a c6, use the throttle linkage to move the VRV.) There is a guy who also claims he makes them, not sure if they are good or not.
You will also want to check the following before replacing the VRV
1) Your vacuum pump is working.
2) You have vacuum to the VRV valve on the IP. That it has two vacuum hoses going to it. That the hoses are on it right. The “in”port hooks to vacuum pump line. “Out” port hooks to modulator on tranny. That you have no leaks between the vrv and the modulator.
3) Adjust the VRV by loosening and moving towards and away from the firewall to see if the shift point changes.
4) Ford said the VRV cannot be repaired. All you can do is adjust forwards and back on the IP. Not true, if you take off the cap on top of the two vacuum line ports you will see you can now screw the nut on the neck up or down. (Careful, just turn the nut, not the top.) Try screwing 1/2 turn at a time a couple turns up or down. Often you can adjust it back to where it is in spec and working. You can adjust further at the modulator with the screw inside the vacuum line.
Here is a link to what Ford said was how to set the VRV. Basically what you do is set the IP to a specific amount of travel, then test for a specific vacuum on the VRV valve out line. (I use a a/c evac pump to create vacuum for testing.) If out of spec then adjust the VRV by moving it towards or away from the firewall. I found it’s easier to adjust the neck of the VRV till you get it where you want it. You can do some fine adjustment with the modulator. I just drive, adjust, drive, adjust till it shifts where I like it. If you cannot get it to shift your VRV has likely had it. But read this old post for more info.
www.oilburners.net
So the stripes as I recall were for regular altitude and high altitude. Most use the green one.
Now the aftermarket modulators are adjustable, they have a screw inside the hole of the vacuum connection. The Ford ones were not adjustable.
The VRV valves are no longer made. They are hard to find. There are mechanical VRV’s available you can convert to. (Were made for race cars using a c6, use the throttle linkage to move the VRV.) There is a guy who also claims he makes them, not sure if they are good or not.
You will also want to check the following before replacing the VRV
1) Your vacuum pump is working.
2) You have vacuum to the VRV valve on the IP. That it has two vacuum hoses going to it. That the hoses are on it right. The “in”port hooks to vacuum pump line. “Out” port hooks to modulator on tranny. That you have no leaks between the vrv and the modulator.
3) Adjust the VRV by loosening and moving towards and away from the firewall to see if the shift point changes.
4) Ford said the VRV cannot be repaired. All you can do is adjust forwards and back on the IP. Not true, if you take off the cap on top of the two vacuum line ports you will see you can now screw the nut on the neck up or down. (Careful, just turn the nut, not the top.) Try screwing 1/2 turn at a time a couple turns up or down. Often you can adjust it back to where it is in spec and working. You can adjust further at the modulator with the screw inside the vacuum line.
Here is a link to what Ford said was how to set the VRV. Basically what you do is set the IP to a specific amount of travel, then test for a specific vacuum on the VRV valve out line. (I use a a/c evac pump to create vacuum for testing.) If out of spec then adjust the VRV by moving it towards or away from the firewall. I found it’s easier to adjust the neck of the VRV till you get it where you want it. You can do some fine adjustment with the modulator. I just drive, adjust, drive, adjust till it shifts where I like it. If you cannot get it to shift your VRV has likely had it. But read this old post for more info.
Adjusting shift points on C6???
So I finaly have this 1984 Van/truck machine all painted and ready to sell (6.9 with C6), However it seems like it waits too long to shift to second gear. Is there a way to adjust it? Can I fiddle with the vacuume modulator on the trans, which way should I turn the screw? Heres a link to the...
www.oilburners.net
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Brian VT
Full Access Member
Wow! I was just looking for the stripe color but thank you for all of that!
I had read bits and pieces of all that other stuff on here but very nice of you to take the time to consolidate it and type it in one spot.
Maybe that should go in the "stickies"? I've been through those and don't remember reading that.
I had read bits and pieces of all that other stuff on here but very nice of you to take the time to consolidate it and type it in one spot.
Maybe that should go in the "stickies"? I've been through those and don't remember reading that.
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Brian VT
Full Access Member
Do the VMs usually come from the manufacturer adjusted to be somewhat near where they should be and then just need fine tuning? If not, then should it be set in the middle as a starting point?
I replaced the non adjustable one on my RV because it seemed to shift late. I adjusted it some but it changed nothing, so I just gave up and figured it was an issue in the transmission.
Fast forward a couple years until this summer and I finally adjusted it more and it actually did change it. Although I need to go adjust it a bit back since it shifts just a bit sooner than I like. I'm just lazy.
Oh and I think I used a green stripe one, but it could have been black
SuperDave
Full Access Member
As far as the color stripe, my transmission guy (who built transmissions at a ford dealer for 35 years) says the black striped one is specifically for the diesel C6 trucks and that's what he installs in every one he builds. I personally always preferred the green stripe one but since he recommended the black striped modulator that's what I always run and can always get the trans to shift how I want without screwing around with the vrv.
Brian VT
Full Access Member
FYI, my NAPA black stripe VM came with the adjuster at 3 3/4 turns out from lightly seated.
And that seems to be about the middle of the adjustment range (8 turns +/-).
I guess I'll start with that.
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While looking for something, I happened across the receipt for the modulator that was stuck in a basket of misc hardware/stuff. It did get the green stripe one for my RV's C6:
It's much cheaper than the black stripe one (green $17.99 / black $30.99) and the green seems to work fine. My understanding is that the stripe color only matters for the initial setting on the modulator's adjustment screw. Considering they are adjustable, what's the point in spending $31 when an $18 one works too if you adjust it? It might have to do with the spring tension inside of it too but I'm not sure that's a problem on our rigs since it has a vacuum pump with an extra vacuum adjustment (the VRV) and doesn't rely on engine vacuum.
When I got it, it was $14.99 in March 2019. I've been running it for over 8,000 miles on a (now) nearly 37 year old transmission and it's working fine. I mean, it is possible the trans was rebuilt at some point, I don't know. But considering the engine's lower rad hose was original, I'm kind of doubting it. It did have a 4WD version filter in the trans though, so it's had the pan dropped before.
It's much cheaper than the black stripe one (green $17.99 / black $30.99) and the green seems to work fine. My understanding is that the stripe color only matters for the initial setting on the modulator's adjustment screw. Considering they are adjustable, what's the point in spending $31 when an $18 one works too if you adjust it? It might have to do with the spring tension inside of it too but I'm not sure that's a problem on our rigs since it has a vacuum pump with an extra vacuum adjustment (the VRV) and doesn't rely on engine vacuum.
When I got it, it was $14.99 in March 2019. I've been running it for over 8,000 miles on a (now) nearly 37 year old transmission and it's working fine. I mean, it is possible the trans was rebuilt at some point, I don't know. But considering the engine's lower rad hose was original, I'm kind of doubting it. It did have a 4WD version filter in the trans though, so it's had the pan dropped before.
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