Transmission shift modulator difference?
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Transmission shift modulator difference?
Went to the parts store to grab a new transmission shift modulator for my 3sp automatic 78 f150 and it had two different ones listed that looked exactly the same as mine. One was listed with brown/black stripe and one with purple stripe, but I can't figure out which one I have. Any ideas guys?
Hotshot
Joined: Apr 2009
Posts: 14,333
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From: Stanley, VA
The difference is the spring that's inside the modulator. Most modulators can also be adjusted by inserting a small screwdriver in the nipple where the vacuum line goes to fine tune it. For your application, go with the black/brown stripe.
Fleet Mechanic
Joined: Sep 2014
Posts: 1,626
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From: NE Texas
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Black is the most common. Green is more for Diesels and Purple is sometimes used for low vacuum engines. There is also a White Stripe too (not the rock band)
Also you can adjust the length of the modulator pin.
There are 4 pin lengths.
1) 1.601-1.611
2) 1.634-1.644
3) 1.650-1.660
4) 1.666-1.677
Both of the above were copied from one of the first entries when I did a quick search for 'C6 vacuum modulator" - I may be a bit of a jerk for saying so, but if you search the forums before asking a question, you may be able to find the answer on your own - which is also considerably faster.
Also you can adjust the length of the modulator pin.
There are 4 pin lengths.
1) 1.601-1.611
2) 1.634-1.644
3) 1.650-1.660
4) 1.666-1.677
Both of the above were copied from one of the first entries when I did a quick search for 'C6 vacuum modulator" - I may be a bit of a jerk for saying so, but if you search the forums before asking a question, you may be able to find the answer on your own - which is also considerably faster.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
Be very careful when removing the modulator valve, the throttle control rod (modulator pin) could fall out unnoticed.
btw: The OP has a 1978 F150, but failed to mention the size of the engine or if it has a C4 or C6.
btw: The OP has a 1978 F150, but failed to mention the size of the engine or if it has a C4 or C6.
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Both of the above were copied from one of the first entries when I did a quick search for 'C6 vacuum modulator" - I may be a bit of a jerk for saying so, but if you search the forums before asking a question, you may be able to find the answer on your own - which is also considerably faster.
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,194
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From: S/W Missouri, Polk county
There is some talk about it here too...Trans issues? https://www.ford-trucks.com/forums/1...l#post14696866
I believe I got this from mikeo0o0o0 in the 1st place.
I believe I got this from mikeo0o0o0 in the 1st place.
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