Vacuum Modulator problem?

Clutch, transmission, rear axle

Moderators: FORDification, 70_F100

Post Reply
User avatar
Pat Crash
New Member
New Member
Posts: 185
Joined: Sat Jul 16, 2011 12:07 am
Location: San Diego, CA

Vacuum Modulator problem?

Post by Pat Crash »

New problem just started today. Transmission is rough when pulling from a stop (different than last weeks problem that I posted on). I had the engine and undercarriage steam cleaned and that might have done something as this problem wasn't happening before the cleaning.

Problem: When I pull from a stop, I like to press gently on the accelerator, then I increase the pressure to get going. When I do this the transmission hits pretty hard. There is no problem when I pull from a stop an accelerate quickly. On top of this, the problem is intermittent. Also, shifter on the steering column moves moves a little to the left when I accelerate.

I check the vacuum hoses and everything seems ok - even the hose connected to the vacuum modulator.

Does this sound like the vacuum modulator?

What color modulator do I need for a C6 transmission on a 360 auto? I believe it is the one with a white stripe - this guys video says white http://www.youtube.com/watch?v=UtiY4sfFpxs. I checked on the old one and I could not see the color stripe.
1971 Ford F100 Ranger XLT Long Bed — 360 with C6 Automatic — 9" with 3.00 Gear Ratio
User avatar
forrestbump
100% FORDified!
100% FORDified!
Posts: 2140
Joined: Tue Aug 10, 2010 12:23 am
Location: California, Phelan

Re: Vacuum Modulator problem?

Post by forrestbump »

White it is! Part # C4AZ-7A377B. Your C6, assuming it's O.E.M., requires a screw in, white stripped, vacuum modulator. Brown, Purple and Green stripped vacuum modulators are for later year applications and are of the push in variety.
1970, 2WD, F-250, C/S, Dual Tanks, 390 FE (of course), C6, Power Steering, Power Disc Brakes, Dana 60 3.73, Sky View Blue, Ranger XLT

1970, 2WD, F-250, C/S, A/C, Dual Tanks, 390 FE (again, of course), C6, Power Steering, Power Disc Brakes, Dana 60 3.73, Wimbledon White & Sky View Blue, Ranger (almost twin brothers!)

"One of the greatest discoveries a man makes, one of his great surprises, is to find he can do what he was afraid he couldn't do" - Henry Ford

Larry
User avatar
Pat Crash
New Member
New Member
Posts: 185
Joined: Sat Jul 16, 2011 12:07 am
Location: San Diego, CA

Re: Vacuum Modulator problem?

Post by Pat Crash »

forrestbump wrote:White it is! Part # C4AZ-7A377B. Your C6, assuming it's O.E.M., requires a screw in, white stripped, vacuum modulator. Brown, Purple and Green stripped vacuum modulators are for later year applications and are of the push in variety.
Thank you. :D

forrestbump - does this sound like a vacuum modulator problem to you?
1971 Ford F100 Ranger XLT Long Bed — 360 with C6 Automatic — 9" with 3.00 Gear Ratio
User avatar
forrestbump
100% FORDified!
100% FORDified!
Posts: 2140
Joined: Tue Aug 10, 2010 12:23 am
Location: California, Phelan

Re: Vacuum Modulator problem?

Post by forrestbump »

Pat Crash wrote:does this sound like a vacuum modulator problem to you?
Well...could be. Where I'd begin is making sure that your vacuum line is intact and not split or pulled off either the vacuum modulator or the vacuum source on the intake manifold.

Since you pressure washed your under carriage, that was my thought. Check this FIRST before you buy a vacuum modulator that you may not need.

By the way, also be sure and check that the vacuum line is not plugged with debris/oil/dirt.
1970, 2WD, F-250, C/S, Dual Tanks, 390 FE (of course), C6, Power Steering, Power Disc Brakes, Dana 60 3.73, Sky View Blue, Ranger XLT

1970, 2WD, F-250, C/S, A/C, Dual Tanks, 390 FE (again, of course), C6, Power Steering, Power Disc Brakes, Dana 60 3.73, Wimbledon White & Sky View Blue, Ranger (almost twin brothers!)

"One of the greatest discoveries a man makes, one of his great surprises, is to find he can do what he was afraid he couldn't do" - Henry Ford

Larry
Donnie
Blue Oval Fanatic
Blue Oval Fanatic
Posts: 772
Joined: Sat Jul 30, 2011 12:22 pm

Re: Vacuum Modulator problem?

Post by Donnie »

Pat Crash wrote:New problem just started today. Transmission is rough when pulling from a stop (different than last weeks problem that I posted on). I had the engine and undercarriage steam cleaned and that might have done something as this problem wasn't happening before the cleaning.

Problem: When I pull from a stop, I like to press gently on the accelerator, then I increase the pressure to get going. When I do this the transmission hits pretty hard. There is no problem when I pull from a stop an accelerate quickly. On top of this, the problem is intermittent. Also, shifter on the steering column moves moves a little to the left when I accelerate.

I check the vacuum hoses and everything seems ok - even the hose connected to the vacuum modulator.

Does this sound like the vacuum modulator?

What color modulator do I need for a C6 transmission on a 360 auto? I believe it is the one with a white stripe - this guys video says white http://www.youtube.com/watch?v=UtiY4sfFpxs. I checked on the old one and I could not see the color stripe.
Pat, when diagnosing a tranny problem the 2 things that you want to watch are;;Is the shift on time according to your throttle position and the quality of the shift , to firm,too soft, or ok.
The harder that you push on the throttle the later your shifts will be, there is a direct correlation between, the later your shifts are the firmer they should be..Check your vacuum line fitting at the manifold with a drill bit in your hand & be sure that carbon is not building up in your manifold. pull you line off at the mod. & check for fluid. Are you using a steel line all the way from the engine down to the rubber elbow? High pressure H2o could soften your hose?? If you pull the hose at the tranny with the engine at idle, it should run rough..
I am concerned as to why your shift lever moves..engine mount??? food 4 thought.Donnie
User avatar
BobbyFord
100% FORDified!
100% FORDified!
Posts: 5342
Joined: Sun Feb 04, 2007 9:52 am
Location: Chatsworth, California

Re: Vacuum Modulator problem?

Post by BobbyFord »

Have you checked left engine mount and trans mount? ( since you said the gear selector is moving).
User avatar
Pat Crash
New Member
New Member
Posts: 185
Joined: Sat Jul 16, 2011 12:07 am
Location: San Diego, CA

Re: Vacuum Modulator problem?

Post by Pat Crash »

BobbyFord wrote:Have you checked left engine mount and trans mount? ( since you said the gear selector is moving).
Changing out all of the engine and transmission mounts this week - Thanks for the tip.
1971 Ford F100 Ranger XLT Long Bed — 360 with C6 Automatic — 9" with 3.00 Gear Ratio
User avatar
Pat Crash
New Member
New Member
Posts: 185
Joined: Sat Jul 16, 2011 12:07 am
Location: San Diego, CA

Re: Vacuum Modulator problem?

Post by Pat Crash »

So, a few years later, and still experiencing the issue. Transmission was rebuilt, linkage replaced, motor mounts replaced. Is my issue in the steering column? Any other ideas? Thank you.
1971 Ford F100 Ranger XLT Long Bed — 360 with C6 Automatic — 9" with 3.00 Gear Ratio
fordman
100% FORDified!
100% FORDified!
Posts: 22329
Joined: Sun Aug 28, 2005 8:17 pm
Location: Kansas, Ottawa
Contact:

Re: Vacuum Modulator problem?

Post by fordman »

So bothe the shifter moves. And the trans still shifts hard after rebuild? Shifyer moving is just torque pushing the worn shirt selector plate. Not sure about hard shift.
User avatar
Pat Crash
New Member
New Member
Posts: 185
Joined: Sat Jul 16, 2011 12:07 am
Location: San Diego, CA

Re: Vacuum Modulator problem?

Post by Pat Crash »

FordMan, I think you are on the right track with the skirt selector plate. I did a search on Google and this site, and I can't find the part or any info on something related to the part. Is there another name for this part as it relates to bumps? Have you seen any resources on this? Thank you FordMan! :D

***Edit*** I figured out what was meant was "shift selector plate"
Last edited by Pat Crash on Wed Feb 04, 2015 8:22 am, edited 1 time in total.
1971 Ford F100 Ranger XLT Long Bed — 360 with C6 Automatic — 9" with 3.00 Gear Ratio
User avatar
Fall_of_Olympus
New Member
New Member
Posts: 52
Joined: Mon Nov 17, 2014 12:47 pm
Contact:

Re: Vacuum Modulator problem?

Post by Fall_of_Olympus »

Mine had a blue stripe.... replacing with a white stripe in the AM actually. My parts guy was like "Blue isn't even an option!!"

Image
Post Reply