The Ford Barn

Merc Cruzer · 10-11-2010, 11:55 AM

I have a 1953 Merc with a Merc-O-Matic. The speedometer is showing 5 mph slower that I am going. It has a 20 tooth speedometer gear in it currently. Do I need to go to a 21 or 19 to correct the reading?

walter123 · 10-11-2010, 12:14 PM

I put a 19 tooth in my Merc and it worked fine. Good luck

Charlie Stephens · 10-11-2010, 12:27 PM

Unless you changed something it probably means your speedometer needs to be repaired. If you changed your rear end ratio you need to change the gear.

Charlie Stephens

37fatfender · 10-11-2010, 12:37 PM

Merc, I did exactly what you are thinking then the speedo read the other way......go figure !!!!!!!!!! Maybe Charlie's right....

Merc Cruzer · 10-11-2010, 01:00 PM

Walter:

I just checked with a local Speedo shop and he confirmed that I need to reduce the number of teeth.....however he did say that at 50 mph each tooth is worth 5% = 2 1/2 mph. I checked the parts book and it does show that an 18 tooth gear was made, but the lowest one being made today is 19, so looks like it will be the 19 tooth gear. I feel the reason for the change in the reading is the tires...went to radials....so they are not the same radius. Had to do this same thing on my wife’s 70 Cougar XR-7 when we restored it and change the tires and rims. Thank you

Frank The Plumber · 10-11-2010, 04:07 PM

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They need the rear tire diameter also, gear and rear tire.

Hughes Automotive · 10-11-2010, 08:03 PM

I found a listing in my Sacramento Vintage Ford Catalog on page 400. It lists 18-19 teeth. The 18 is part # 587-18 and cost $12.95. The phone number is 916-853-2244.

Merc Cruzer · 10-11-2010, 08:52 PM

Hughes:

Thank you I will give them a call tomarrow....

Lyle · 10-11-2010, 10:04 PM

Hello merc Cruzer I have a 53 that will be junked out wendsday. I have not removed inside stuff like switches or clock other stuff. I also have skirts in good shape not for sale just shiping cost also have, two merc O matics.If parts are needed I have them.

Merc Cruzer · 10-12-2010, 10:14 AM

Lyle:

Sent you a PM

Merc Cruzer · 10-12-2010, 04:12 PM

Hughes:

Called Sacramento Vintage Ford and was ready to order the part (by the way I did order the catalog) and they informed me that it is for a Model A 28'-31' and would not work in may 53' Merc...so it's back to the 19 tooth gear that I can get locally..thanks for the tip

10-11-2010, 11:55 AM	#1
Merc Cruzer Senior Member Join Date: Jul 2010 Location: Conifer, Colorado Posts: 2,430	Speedometer gear - wrong speed I have a 1953 Merc with a Merc-O-Matic. The speedometer is showing 5 mph slower that I am going. It has a 20 tooth speedometer gear in it currently. Do I need to go to a 21 or 19 to correct the reading?

10-11-2010, 12:14 PM	#2
walter123 Junior Member Join Date: Jul 2010 Location: N.J. Posts: 17	Re: Speedometer gear - wrong speed I put a 19 tooth in my Merc and it worked fine. Good luck

10-11-2010, 12:27 PM	#3
Charlie Stephens Senior Member Join Date: May 2010 Location: Southern California Posts: 7,046	Re: Speedometer gear - wrong speed Unless you changed something it probably means your speedometer needs to be repaired. If you changed your rear end ratio you need to change the gear. Charlie Stephens

10-11-2010, 12:37 PM	#4
37fatfender Senior Member Join Date: May 2010 Location: Mesquite, NV / Gurnee, IL Posts: 298	Re: Speedometer gear - wrong speed Merc, I did exactly what you are thinking then the speedo read the other way......go figure !!!!!!!!!! Maybe Charlie's right....

10-11-2010, 01:00 PM	#5
Merc Cruzer Senior Member Join Date: Jul 2010 Location: Conifer, Colorado Posts: 2,430	Re: Speedometer gear - wrong speed Walter: I just checked with a local Speedo shop and he confirmed that I need to reduce the number of teeth.....however he did say that at 50 mph each tooth is worth 5% = 2 1/2 mph. I checked the parts book and it does show that an 18 tooth gear was made, but the lowest one being made today is 19, so looks like it will be the 19 tooth gear. I feel the reason for the change in the reading is the tires...went to radials....so they are not the same radius. Had to do this same thing on my wife’s 70 Cougar XR-7 when we restored it and change the tires and rims. Thank you

10-11-2010, 04:07 PM	#6
Frank The Plumber Senior Member Join Date: May 2010 Posts: 693	Re: Speedometer gear - wrong speed Sponsored Links (Register now to hide all advertisements) They need the rear tire diameter also, gear and rear tire.

10-11-2010, 08:03 PM	#7
Hughes Automotive Junior Member Join Date: May 2010 Location: Washington, PA Posts: 10	Re: Speedometer gear - wrong speed I found a listing in my Sacramento Vintage Ford Catalog on page 400. It lists 18-19 teeth. The 18 is part # 587-18 and cost $12.95. The phone number is 916-853-2244.

10-11-2010, 08:52 PM	#8
Merc Cruzer Senior Member Join Date: Jul 2010 Location: Conifer, Colorado Posts: 2,430	Re: Speedometer gear - wrong speed Hughes: Thank you I will give them a call tomarrow....

10-11-2010, 10:04 PM	#9
Lyle Senior Member Join Date: May 2010 Location: Tyler Texas Posts: 226	Re: Speedometer gear - wrong speed Hello merc Cruzer I have a 53 that will be junked out wendsday. I have not removed inside stuff like switches or clock other stuff. I also have skirts in good shape not for sale just shiping cost also have, two merc O matics.If parts are needed I have them.

10-12-2010, 10:14 AM	#10
Merc Cruzer Senior Member Join Date: Jul 2010 Location: Conifer, Colorado Posts: 2,430	Re: Speedometer gear - wrong speed Lyle: Sent you a PM

10-12-2010, 04:12 PM	#11
Merc Cruzer Senior Member Join Date: Jul 2010 Location: Conifer, Colorado Posts: 2,430	Re: Speedometer gear - wrong speed Hughes: Called Sacramento Vintage Ford and was ready to order the part (by the way I did order the catalog) and they informed me that it is for a Model A 28'-31' and would not work in may 53' Merc...so it's back to the 19 tooth gear that I can get locally..thanks for the tip