The Ford Barn

Dyna · 05-09-2017, 09:47 AM

I hope that someone can help me figure out what is wrong. I had the rear ended rebuilt on my 1948 Merc 114. Have only driven it a few miles since. My speedometer seems to work Ok but the odometer is going backwards. I have looked at the turtle and it is on the driver's side of the torque tube. I have searched the web for a good picture of the turtle in place but haven't found something that I can take to the mechanic who did the job for me. Vanpelt drawings don't give a good indication of drivers side and passenger side. I believe that the turtle should be on the passenger side of the torque tube. I just can't wrap my head around why the speedo works and the odometer is going backwards, any thoughts? I assume it has something to do with the tach drive gear going the wrong way? Although I could live with this, I paid good money to have the rebuild and find it annoying. I would appreciate any pictures that anyone may have of the torque tube/turtle area in a car so I can show the 'mechanic' what was installed wrong. Also, is there any downside to leaving it the way it is and what would need to be done to fix it?
Thanks n advance.
Greg

JM 35 Sedan · 05-09-2017, 10:24 AM

I believe the turtle is mounted upside down. Assuming you have a left hand drive car, the turtle gear housing should be on the driver's side of torque tube, with cable mount facing down.

SofaKing · 05-09-2017, 10:44 PM

Is your odometer reset knob completely disengaged? Did the speedo/odometer ever work correctly? Turtle position shouldn't be able to drive the speedo forward and the odometer backward. I'd be looking at the gear train on the back of the instrument.

klicker · 05-09-2017, 10:57 PM

Here's the turtle on my 39. It's driver's side, cable coming in from driver's side.

Lawson Cox · 05-10-2017, 12:53 AM

Could the driven gear inside the turtle be installed backwards? Just a thought. It's been a while.

Dyna · 05-10-2017, 05:02 AM

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Thank you for the replies and great picture. When the rear end was done we used a donor set of gears, so I went from 3:54 to 3:78 ratio, also swapped the turtle gear from the donor to have as accurate a speedo as possible. Good thought about the reset gauge, I will check that today. I have read in other posts that turning the turtle around has solved their problem of odometer running backwards, but I just can't understand how their speedometer could have been working properly. I rebuilt the speedo myself, the numbers were flaking off and could not be read. I did bench test it with a hand drill and everything seemed to be working fine. I did notice that if the drill was going in the wrong direction the speedo did not work.

05-09-2017, 09:47 AM	#1
Dyna Member Join Date: Dec 2015 Location: Ontario, Canada Posts: 55	Odometer/turtle Dilemma I hope that someone can help me figure out what is wrong. I had the rear ended rebuilt on my 1948 Merc 114. Have only driven it a few miles since. My speedometer seems to work Ok but the odometer is going backwards. I have looked at the turtle and it is on the driver's side of the torque tube. I have searched the web for a good picture of the turtle in place but haven't found something that I can take to the mechanic who did the job for me. Vanpelt drawings don't give a good indication of drivers side and passenger side. I believe that the turtle should be on the passenger side of the torque tube. I just can't wrap my head around why the speedo works and the odometer is going backwards, any thoughts? I assume it has something to do with the tach drive gear going the wrong way? Although I could live with this, I paid good money to have the rebuild and find it annoying. I would appreciate any pictures that anyone may have of the torque tube/turtle area in a car so I can show the 'mechanic' what was installed wrong. Also, is there any downside to leaving it the way it is and what would need to be done to fix it? Thanks n advance. Greg

05-09-2017, 10:24 AM	#2
JM 35 Sedan Senior Member Join Date: May 2010 Location: Near Rising Sun, Maryland Posts: 10,876	Re: Odometer/turtle Dilemma I believe the turtle is mounted upside down. Assuming you have a left hand drive car, the turtle gear housing should be on the driver's side of torque tube, with cable mount facing down. __________________ *John* *"Never give up on what you really want to do. The person with big dreams is more powerful than one with all the facts". Albert Einstein*

05-09-2017, 10:44 PM	#3
SofaKing Senior Member Join Date: Jun 2014 Location: Salt Lake City, Utah Posts: 756	Re: Odometer/turtle Dilemma Is your odometer reset knob completely disengaged? Did the speedo/odometer ever work correctly? Turtle position shouldn't be able to drive the speedo forward and the odometer backward. I'd be looking at the gear train on the back of the instrument.

05-10-2017, 12:53 AM	#5
Lawson Cox Senior Member Join Date: May 2010 Location: Above the gnat line in Georgia Posts: 7,082	Re: Odometer/turtle Dilemma Could the driven gear inside the turtle be installed backwards? Just a thought. It's been a while. __________________ Life is like a roll of toilet paper. The closer to the end, the faster it goes. It is better to be seen, than viewed. "We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm".

05-10-2017, 05:02 AM	#6
Dyna Member Join Date: Dec 2015 Location: Ontario, Canada Posts: 55	Re: Odometer/turtle Dilemma Sponsored Links (Register now to hide all advertisements) Thank you for the replies and great picture. When the rear end was done we used a donor set of gears, so I went from 3:54 to 3:78 ratio, also swapped the turtle gear from the donor to have as accurate a speedo as possible. Good thought about the reset gauge, I will check that today. I have read in other posts that turning the turtle around has solved their problem of odometer running backwards, but I just can't understand how their speedometer could have been working properly. I rebuilt the speedo myself, the numbers were flaking off and could not be read. I did bench test it with a hand drill and everything seemed to be working fine. I did notice that if the drill was going in the wrong direction the speedo did not work. Last edited by Dyna; 05-10-2017 at 06:15 AM.