The Ford Barn

diyforever · 05-24-2020, 04:10 PM

It's my understanding that when an overdrive is engaged, the RPMs on the engine should decrease. However, on my 1930 A I have a laycock overdrive and a tach which shows RPMs increase when I engage. The speedometer reading goes up approx 10 mpg which I understand since speedocable is attached to original 3 speed transmission. Anyone shed some light on why engine RPMs increase?

Bob C · 05-24-2020, 04:29 PM

If the speedometer cable is before the overdrive them why would the
speedometer change when you go into overdrive?

briphaeton · 05-24-2020, 05:01 PM

You need to switch the on to off and the off to on. My speedometer and tach drops while in overdrive.

Synchro909 · 05-24-2020, 05:44 PM

Quote:

Originally Posted by briphaeton

You need to switch the on to off and the off to on. My speedometer and tach drops while in overdrive.

Yup, the switch is reversed so he starts off in O/O and then changes down.

diyforever · 05-24-2020, 06:45 PM

Bob, I'll double check the connection on the speedocable.
Just wondering about the switch connection. Does it mean that I should switch the connection on the switch attached to the transmission tower? OR ?

Jack Shaft · 05-24-2020, 07:31 PM

Sponsored Links (Register now to hide all advertisements)

Does it feel like its in overdrive?

CarlG · 05-24-2020, 08:21 PM

Overdrive installed backwards??

Synchro909 · 05-25-2020, 02:55 AM

Quote:

Originally Posted by CarlG

Overdrive installed backwards??

Or up side down????

rotorwrench · 05-25-2020, 08:44 AM

The speedometer would have to be geared in to the output shaft of the overdrive for it to give an accurate reading while in overdrive. The Laycock has to have the solenoid turned on for it to shift into OD planetary drive.

briphaeton · 05-25-2020, 01:25 PM

The transmission switch takes it out of overdrive if you try to go into reverse gear while in overdrive, because that would damage the overdrive. You need to change the plate on the dash switch that reads on and off. The position that reads on is really off and off is really on. If the speed changes in and out of overdrive the speedo is connected to the transmission. Went your in overdrive the speedo is going to read around 10 mph slower.

05-24-2020, 04:10 PM	#1
diyforever Junior Member Join Date: Oct 2014 Location: Fallbrook, California Posts: 25	RPMs increase when engage Laycock overdrive, hmmm? It's my understanding that when an overdrive is engaged, the RPMs on the engine should decrease. However, on my 1930 A I have a laycock overdrive and a tach which shows RPMs increase when I engage. The speedometer reading goes up approx 10 mpg which I understand since speedocable is attached to original 3 speed transmission. Anyone shed some light on why engine RPMs increase?

05-24-2020, 04:29 PM	#2
Bob C Senior Member Join Date: May 2010 Location: So Cal Posts: 8,741	Re: RPMs increase when engage Laycock overdrive, hmmm? If the speedometer cable is before the overdrive them why would the speedometer change when you go into overdrive?

05-24-2020, 05:01 PM	#3
briphaeton Senior Member Join Date: Jan 2012 Posts: 241	Re: RPMs increase when engage Laycock overdrive, hmmm? You need to switch the on to off and the off to on. My speedometer and tach drops while in overdrive.

05-24-2020, 06:45 PM	#5
diyforever Junior Member Join Date: Oct 2014 Location: Fallbrook, California Posts: 25	Re: RPMs increase when engage Laycock overdrive, hmmm? Bob, I'll double check the connection on the speedocable. Just wondering about the switch connection. Does it mean that I should switch the connection on the switch attached to the transmission tower? OR ?

05-24-2020, 07:31 PM	#6
Jack Shaft BANNED Join Date: Dec 2019 Posts: 1,196	Re: RPMs increase when engage Laycock overdrive, hmmm? Sponsored Links (Register now to hide all advertisements) Does it feel like its in overdrive?

05-24-2020, 08:21 PM	#7
CarlG Senior Member Join Date: Nov 2010 Location: Anchorage, Alaska Posts: 9,115	Re: RPMs increase when engage Laycock overdrive, hmmm? Overdrive installed backwards?? __________________ Alaskan A's Antique Auto Mushers of Alaska Model A Ford Club of America Model A Restorers Club Antique Automobile Club of America Mullins Owner's Club

05-25-2020, 08:44 AM	#9
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: RPMs increase when engage Laycock overdrive, hmmm? The speedometer would have to be geared in to the output shaft of the overdrive for it to give an accurate reading while in overdrive. The Laycock has to have the solenoid turned on for it to shift into OD planetary drive.

05-25-2020, 01:25 PM	#10
briphaeton Senior Member Join Date: Jan 2012 Posts: 241	Re: RPMs increase when engage Laycock overdrive, hmmm? The transmission switch takes it out of overdrive if you try to go into reverse gear while in overdrive, because that would damage the overdrive. You need to change the plate on the dash switch that reads on and off. The position that reads on is really off and off is really on. If the speed changes in and out of overdrive the speedo is connected to the transmission. Went your in overdrive the speedo is going to read around 10 mph slower.