Modulator valve pin
Thread Starter
|
4wd Low
Joined: Feb 2023
Posts: 10
Likes: 2
Modulator valve pin
My 73 f100 with a c4 shifts very hard and only if you get to high rpm then let off the throttle so i put a new modulator valve in it but no change i was wondering if i could file the pin down a little to create faster shifts
Cross-Country
Joined: Feb 2021
Posts: 64
Likes: 32
From: Fort Knox KY
You can, did you adjust it though? When you turn the screw clockwise it shifts later and harder/firmer, when you turn it counter clockwise it shifts earlier and softer. I'd go 1/2 turn counter clockwise and test. Wash, rinse, repeat. The modulator screw should never be adjusted over 4 turns in any direction.
You can also make your own with a 1/8th inch steel rod or an 8d nail you can cut it to length round the edges with a file and you're set.
You can also make your own with a 1/8th inch steel rod or an 8d nail you can cut it to length round the edges with a file and you're set.
Thread Starter
|
4wd Low
Joined: Feb 2023
Posts: 10
Likes: 2
My modulator valve is the 2 port type and as far as i can tell there is no adjustment screw like the single port type. I have seen some people say i could replace mine with a single vacuum type but then ive seen that they dont fit as well so i dont wanna buy one not knowing if itll work
Cross-Country
Joined: Feb 2021
Posts: 64
Likes: 32
From: Fort Knox KY
Hmmm, no kidding. I've never personally seen a 2 port vacuum modulator and I've owned 4x C4s, a FMX, and 2x C6s. One the two port version, I think you only need the larger port hooked up to your vac (manifold) source. The smaller secondary port was originally connected to the EGR vacuum to make the shift softer. I wouldn't think that a 73 has EGR, but that's right at the emissions cusp. I'd verify they are both connected to the right source without and vac leaks. If your EGR stuff is gone, that might be your problem.
I would 100% replace the vac modulator with a one port green stripe and adjust it. I've never had a problem with them leaking...or rather, I've never had a problem with a replacement one leaking (some have a small gasket depending on the push in or screw in type).
I would 100% replace the vac modulator with a one port green stripe and adjust it. I've never had a problem with them leaking...or rather, I've never had a problem with a replacement one leaking (some have a small gasket depending on the push in or screw in type).
Thread Starter
|
4wd Low
Joined: Feb 2023
Posts: 10
Likes: 2
Worked like a charm
Thank you very much sir had to modify my bracket that holds it in just a little bit for the way the vacuum hooks to it and its actually shifting on its own. A little to early now i think so ill probably try adjusting the screw just a 1/4 turn and try to fine tune it but its so much better already cant thank you enough for the advice
Thread
Thread Starter
Forum
Replies
Last Post
Old Coyote
1961 - 1966 F-100 & Larger F-Series Trucks
13
Jul 4, 2017 08:58 AM
Crimsonlake
1961 - 1966 F-100 & Larger F-Series Trucks
2
Jan 12, 2014 09:41 AM
stroked 347
Clutch, Transmission, Differential, Axle & Transfer Case
1
May 3, 2008 12:23 AM
7283-F250
Clutch, Transmission, Differential, Axle & Transfer Case
9
Jun 14, 2007 11:05 PM
