The Ford Barn

Sal · 07-04-2017, 03:24 PM

Can an engine backfire blow out a modulator so the transmission doesn't shift properly on a '68 Ford C4 transmission?

paul2748 · 07-04-2017, 07:03 PM

Check your vacuum connections - the C4 will not shift without vacuum

I doubt that an engine backfire will knock out a modulator, but replace it if its got a lot of miles and years on it.

ponymare · 07-05-2017, 06:21 AM

Easy way to tell if the modulator is blown, pull the vacuum hose off of it, if oil drips out its blown.

Sal · 07-05-2017, 07:09 AM

Thank You for your replies.

wbedwards · 07-05-2017, 11:01 AM

Could have blown the hose off =]

cohammer60 · 07-09-2017, 10:37 AM

Sponsored Links (Register now to hide all advertisements)

Just replaced my modulator and hose . Started shifting better but still a slight slip from 1 to 2 . Added Lucas oil and Been shifting good since . A cheap way for trial and error .

Alaska Jim · 07-09-2017, 11:43 PM

you might try adjusting the bands, it may help things a bit.

Sal · 07-14-2017, 06:46 AM

Thank You for your replies, I appreciate your help.

Sal · 07-16-2017, 12:30 PM

I was finally able to get under the car yesterday, I found the hose going to the modulator dry rotted and cracked. I replaced it and the transmission shifts well. Thanks to all who offered help.

dmsfrr · 07-16-2017, 02:37 PM

If any of the rubber fuel lines are even close to the same age, replace them too.

07-04-2017, 03:24 PM	#1
Sal Senior Member Join Date: May 2010 Posts: 218	C4 transmission not shifting Can an engine backfire blow out a modulator so the transmission doesn't shift properly on a '68 Ford C4 transmission?

07-04-2017, 07:03 PM	#2
paul2748 Senior Member Join Date: May 2010 Location: Midland Park, NJ Posts: 3,982	Re: C4 transmission not shifting Check your vacuum connections - the C4 will not shift without vacuum I doubt that an engine backfire will knock out a modulator, but replace it if its got a lot of miles and years on it. __________________ 48 Ford Conv 56 Tbird 54 Ford Victoria

07-05-2017, 06:21 AM	#3
ponymare Senior Member Join Date: Sep 2014 Posts: 160	Re: C4 transmission not shifting Easy way to tell if the modulator is blown, pull the vacuum hose off of it, if oil drips out its blown.

07-05-2017, 07:09 AM	#4
Sal Senior Member Join Date: May 2010 Posts: 218	Re: C4 transmission not shifting Thank You for your replies.

07-05-2017, 11:01 AM	#5
wbedwards Senior Member Join Date: Jan 2015 Location: Birmingham, Al. Posts: 339	Re: C4 transmission not shifting Could have blown the hose off =]

07-09-2017, 10:37 AM	#6
cohammer60 Senior Member Join Date: Nov 2011 Location: Silver Creek GA Posts: 100	Re: C4 transmission not shifting Sponsored Links (Register now to hide all advertisements) Just replaced my modulator and hose . Started shifting better but still a slight slip from 1 to 2 . Added Lucas oil and Been shifting good since . A cheap way for trial and error .

07-09-2017, 11:43 PM	#7
Alaska Jim Senior Member Join Date: May 2010 Location: Palmer, Alaska Posts: 1,575	Re: C4 transmission not shifting you might try adjusting the bands, it may help things a bit.

07-14-2017, 06:46 AM	#8
Sal Senior Member Join Date: May 2010 Posts: 218	Re: C4 transmission not shifting Thank You for your replies, I appreciate your help.

07-16-2017, 12:30 PM	#9
Sal Senior Member Join Date: May 2010 Posts: 218	Re: C4 transmission not shifting I was finally able to get under the car yesterday, I found the hose going to the modulator dry rotted and cracked. I replaced it and the transmission shifts well. Thanks to all who offered help.

07-16-2017, 02:37 PM	#10
dmsfrr Senior Member Join Date: Aug 2012 Location: Abq, NM Posts: 3,607	Re: C4 transmission not shifting If any of the rubber fuel lines are even close to the same age, replace them too.