Too much vacuum
- Thread starter Austin86250
- Start date
IDIBRONCO
IDIBRONCO
If you think that you're getting too much vacuum, you can disconnect your vacuum lines at the VRV and see how it shifts then. My bet is that you're not getting too much vacuum. Our set ups aren't known for that. It's the opposite that happens. Is your VRV even working? Have you tried adjusting it any? If you haven't, you can try that too. How many inches of vacuum are you getting? That's some questions to help you diagnose your shifting troubles.
Austin86250
Full Access Member
How can you tell if the vrv is working?
Big Bart
Tow&Slow
Some thoughts -
Your vacuum pump on the truck should make about 20 hg of vacuum. Your VRV just lowers the vacuum going to the modulator (7-9hg as I recall.) at a specific point of travel of the IP throttle shaft. So it does not make vacuum but rather lowers it as it goes to the modulator on your transmission.
From the factory both hoses wrapped around the left side of the air cleaner, your top hose goes to the right. Make sure the VRV in hose goes to the vacuum manifold spitter on the firewall. The out goes to the modulator on the transmission.
1) Your VRV is maxed out towards the radiator, that as I recall is for a early shift like you mention. Loosen the adjusting screws and put it in the middle of its travel allotment, tighten, and drive again. Tell us if it improves. If not move as far as it will travel towards the front window. Tell us if things improved.
2) Ford says you can’t service the VRV if out of spec. (Can’t move it enough on the IP to or from to get a good shift point.). That is not true, you can carefully take off the plastic cover on the top that covers the top and the vacuum ports. Pull straight up lightly and it snaps off. Now there is a nut under the head of the VRV valve. Only the nut turns, the head and base do not, but it moves the head up and down. Be careful not to break your VRV. Now turn the nut one turn and test drive. If things get worse go two turns the opposite direction. Things get better turn 1/4 turn and test drive again. Continue to turn 1/4 turn in the direction of improvement till it shifts as you like.
Also check your vacuum line from the VRV to the modulator to make sure the rubber hoses at top and bottom are not cracked. You can also pull the vacuum line off the modulator and check for ATF. If so replace the modulator. But is far more common the vacuum pump is not working or the VRV is going/gone bad.
Also read this thread on the same topic. Discusses options for a new VRV. Also the Ford instructions on how to set a VRV.
www.oilburners.net
Your vacuum pump on the truck should make about 20 hg of vacuum. Your VRV just lowers the vacuum going to the modulator (7-9hg as I recall.) at a specific point of travel of the IP throttle shaft. So it does not make vacuum but rather lowers it as it goes to the modulator on your transmission.
From the factory both hoses wrapped around the left side of the air cleaner, your top hose goes to the right. Make sure the VRV in hose goes to the vacuum manifold spitter on the firewall. The out goes to the modulator on the transmission.
1) Your VRV is maxed out towards the radiator, that as I recall is for a early shift like you mention. Loosen the adjusting screws and put it in the middle of its travel allotment, tighten, and drive again. Tell us if it improves. If not move as far as it will travel towards the front window. Tell us if things improved.
2) Ford says you can’t service the VRV if out of spec. (Can’t move it enough on the IP to or from to get a good shift point.). That is not true, you can carefully take off the plastic cover on the top that covers the top and the vacuum ports. Pull straight up lightly and it snaps off. Now there is a nut under the head of the VRV valve. Only the nut turns, the head and base do not, but it moves the head up and down. Be careful not to break your VRV. Now turn the nut one turn and test drive. If things get worse go two turns the opposite direction. Things get better turn 1/4 turn and test drive again. Continue to turn 1/4 turn in the direction of improvement till it shifts as you like.
Also check your vacuum line from the VRV to the modulator to make sure the rubber hoses at top and bottom are not cracked. You can also pull the vacuum line off the modulator and check for ATF. If so replace the modulator. But is far more common the vacuum pump is not working or the VRV is going/gone bad.
Also read this thread on the same topic. Discusses options for a new VRV. Also the Ford instructions on how to set a VRV.
Vacuum Regulator Valve/VRV for C6 transmission: convert or replace or search for NOS?
So I'm new to the diesel specific C6 transmission, and I just realized that the one on my new truck has a cracked tube which is making it shift poorly. I did a search and it appears that as of 2019, these things were pretty scarce. I'd really like to put a factory replacement part on it, but I...
www.oilburners.net
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Last edited:
Austin86250
Full Access Member
Didn’t realize if you take the screw out there is another screw hole to adjust with now everything works perfectly I really appreciate your help
Big Bart
Tow&Slow
Glad it worked out for you!
Brian VT
Full Access Member
"2) Ford says you can’t service the VRV if out of spec. (Can’t move it enough on the IP to or from to get a good shift point.). That is not true, you can carefully take off the plastic cover on the top that covers the top and the vacuum ports. Pull straight up lightly and it snaps off. Now there is a nut under the head of the VRV valve. Only the nut turns, the head and base do not, but it moves the head up and down. Be careful not to break your VRV. Now turn the nut one turn and test drive. If things get worse go two turns the opposite direction. Things get better turn 1/4 turn and test drive again. Continue to turn 1/4 turn in the direction of improvement till it shifts as you like."
I may try to adjust my VRV tomorrow. Anyone happen to remember which direction of turning will get it to shift sooner?
Also, could I bother someone to explain what the kickdown does and how to adjust it?
I may try to adjust my VRV tomorrow. Anyone happen to remember which direction of turning will get it to shift sooner?
Also, could I bother someone to explain what the kickdown does and how to adjust it?
You want kickdown to be adjusted so that just before full throttle, the kickdown screw contacts the throttle lever, so that when it's at full throttle, it pushes kickdown. If you adjust it too much on the slide of earlier kickdown, it'll kick down with less pedal travel and won't be able to upshift properly if it's grossly maladjusted. If adjusted too much later (so it doesn't make proper contact) you may not get any kickdown at all.
So, the more the kickdown screw is threaded in, the earlier the kickdown will happen in the pedal travel.
So, the more the kickdown screw is threaded in, the earlier the kickdown will happen in the pedal travel.
IDIBRONCO
IDIBRONCO
The kick down rod helps with the down shifting. I believe that there's a hex headed screw that it rests against on the side of the IP. You can screw in toward the back of the truck for easier down shifts with less throttle. Toward the front of the truck to make it more difficult to down shift the transmission. The easier it is for the transmission to down shift, the longer it will stay in gear before up shifting too. I hope that poor description helps.
IDIBRONCO
IDIBRONCO
It sounds like I may have gotten the direction of the adjustments backward.
Brian VT
Full Access Member
Got it. Thanks.
Now just hoping to hear which way to turn the VRV nut for earlier shifting.
Now just hoping to hear which way to turn the VRV nut for earlier shifting.
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This is how it is on my F250 and kickdown works great. If I turn the screw in more (make more of the end of the screw poke out towards the camera) then it'll make it kickdown sooner with less pedal travel.
My RV's kickdown lever is facing a lot different for some reason, so it needs way more threads coming out, but that's why it has such a long adjustment screw, I guess. And I might need to give it more since kickdown barely ever works, it seems like. The F250 did get a trans rebuild and the RV probably hasn't, so maybe the RV's kickdown lever is factory positioned, and the F250's got repositioned.
Big Bart
Tow&Slow
That’s a loaded question. When the VRV is not working correctly, technically the tranny is doing a late shift, but really it is the governor forcing the shift. It is late (+/- 3,000rpm.) and shifts hard/fast.
As I recall turning the nut clockwise lowers the VRV head and it creates a earlier shift. Screwing it counter clockwise raises it and causes a later shift. I would suggest screwing it clockwise one turn, test drive. Then a seconded turn clockwise and test drive. If that does not help go the other way 3 times to see if the other way works. Maybe a 4th turn counter clockwise to see if it is the right direction. Its hard to know when the VRV is out of adjustment if the VRV is not lowering the vacuum or not letting the vacuum build. So you need to try adjusting both ways. But once you are in the zone it will start shifting better. Then start turning the nut 1/4 turn and test drive till you get the shift where you want.
Also the success of this adjustment is based on the fact the VRV is getting good vacuum, the VRV is working but not calibrated (Moving the nut only calibrates when it effects the vacuum pressure.), the vacuum line from the VRV to the modulator is in good shape, and the modulator works.
Brian VT
Full Access Member
Perfect. Thanks.
Good vacuum to VRV and a new modulator so I just need to sort out the in-between.
How much vacuum should be at the modulator at idle?
Good vacuum to VRV and a new modulator so I just need to sort out the in-between.
How much vacuum should be at the modulator at idle?
