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speedo help.... not reading right #1334297 11/12/12 03:20 PM 11/12/12 03:20 PM
Joined: Jan 2009 Posts: 813 Ontario,Canada brads70 OP super stock
brads70 OP super stock Joined: Jan 2009 Posts: 813 Ontario,Canada	Hello all! I replaced the speedo in my 70 Challenger with another one off e-bay after I screwed mine up trying to replace the speedo needle. ( standard gauges, not ralley) It just swung limp at the bottom of the speedo. So I bought another cluster off e-bay. Problem is the odometer is working perfectly but the speedo is out by around 20 MPH? I have a new speedo cable already installed. Needle moves nice, not jerky. Any idea's? Thanks Brad Last edited by brads70; 11/19/12 10:40 AM.

Re: speedo help.... not reading right [Re: brads70] #1334298 11/12/12 03:25 PM 11/12/12 03:25 PM
Joined: May 2003 Posts: 15,487 Florida S scratchnfotraction I Live Here
scratchnfotraction I Live Here S Joined: May 2003 Posts: 15,487 Florida	was it correct before swaping the speedo cluster? maybe a speedo pinion gear in the trans could be changed to adjust the needle to the road speed.

Re: speedo help.... not reading right [Re: scratchnfotraction] #1334299 11/12/12 03:33 PM 11/12/12 03:33 PM
Joined: Oct 2006 Posts: 7,365 Iowa burdar Owen's Dad
burdar Owen's Dad Joined: Oct 2006 Posts: 7,365 Iowa	I think I have the same problem. I havn't verified it with GPS yet though. My cluster was rebuild. I also went from a 2.76 gear to a 3.23. I changed out the speedo gear from a light blue/green(original) to a yellow gear. I don't remember the tooth count off hand but it's the correct one for 3.23. Dad was following me for the cars first trip out of town since the restoration. I set my foot to 60mph but dad said I was very close to 70mph. I was turning 3000 RPM. The online RPM calculators say I should be turning less then 3000 at 60 with 3.23's and stock F70x14 tires.

Re: speedo help.... not reading right [Re: brads70] #1334300 11/12/12 04:48 PM 11/12/12 04:48 PM
Joined: Feb 2004 Posts: 1,012 indiana M mcmopars super stock
mcmopars super stock M Joined: Feb 2004 Posts: 1,012 indiana	do you have the right gear?just a thought

Re: speedo help.... not reading right [Re: brads70] #1334301 11/12/12 05:01 PM 11/12/12 05:01 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Quote: Problem is the odometer is working perfectly but the speedo is out by around 20 MPH? If the odo is reading correctly (checked by the interstate mile markers, go past 5 of them) then the speedo assy needs to go into a speedo specialty shop to be recalibrated. If the odo is off then you would 1st need to get the correct trans speedo pinion in there so the odo reads correct (checked as mentioned) then check the speedo with a digital roadside MPH sign (or GPS) & if it's incorrect then take the assy in & have the magnetic gismo recalibrated. I picked the correct tooth pinion gear by using the MP chart in the archives which only asks for tire dia and rear gear ratio. I measured ACTUAL dia by placing a piece of flat stock across the top of one of the rear tires then measuring from the underside of it to ground. I have been advised to use "rollout" instead as in putting either rear tire valve stem at 6 o'clock then measure with a tape the rollout to get the stem back to 6 o'clock which'll be ~7 or 8 feet then dividing Pi (3.1416") into that to get actual dia but how I measured mine worked for me in this instance. #1 get the odo correct 1st with the right pinion then check the speedo live every 24 hour block of time like it's your last day on earth

Re: speedo help.... not reading right [Re: scratchnfotraction] #1334302 11/12/12 11:55 PM 11/12/12 11:55 PM
Joined: Jan 2009 Posts: 813 Ontario,Canada brads70 OP super stock
brads70 OP super stock Joined: Jan 2009 Posts: 813 Ontario,Canada	Quote: was it correct before swaping the speedo cluster? maybe a speedo pinion gear in the trans could be changed to adjust the needle to the road speed. I swapped in a Keisler A41 auto OD kit. I'm pretty sure the gear in the tranny is ok as like I mentioned the odometer is correct. Anyone know a speedo shop were I could send it? I'm in Canada about 2 hours north of Buffalo NY Thanks Brad

Re: speedo help.... not reading right [Re: brads70] #1334303 11/19/12 09:40 AM 11/19/12 09:40 AM
Joined: Jan 2009 Posts: 813 Ontario,Canada brads70 OP super stock
brads70 OP super stock Joined: Jan 2009 Posts: 813 Ontario,Canada	No speedo experts/experiance on here? I went for a drive yesterday and double checked the odometer and it is correct. speedo IS out about 20 MPH I'm wondering if it's lubrication issue? a spring somewhere wore out? or?.... Not looking forward to removing it again...

Re: speedo help.... not reading right [Re: brads70] #1334304 11/19/12 10:50 AM 11/19/12 10:50 AM
Joined: Jul 2007 Posts: 1,526 North Carolina cjskotni pro stock
cjskotni pro stock Joined: Jul 2007 Posts: 1,526 North Carolina	Quote: No speedo experts/experiance on here? I went for a drive yesterday and double checked the odometer and it is correct. speedo IS out about 20 MPH I'm wondering if it's lubrication issue? a spring somewhere wore out? or?.... Not looking forward to removing it again... From what I understand, the speedo works off of the odometer. If you are sure the odemeter is moving correctly, then there is soemthing that needs to be repaired within the speedo itself. The fact that the odometer reads correctly, rules out any speedo cable or speedo gear issue. I could be wrong here but that how I understand these clusters. Maybe somebody else here will chime in but it may be time for a rebuild of the cluster itself. Good luck

Re: speedo help.... not reading right [Re: cjskotni] #1334305 11/19/12 10:58 AM 11/19/12 10:58 AM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Unfortunately the speedo magnetic gismo has the delicacy of a swiss watch. No other option but to take it in or get another used one which might be cheaper depending on what's available to you live every 24 hour block of time like it's your last day on earth

Re: speedo help.... not reading right [Re: brads70] #1334306 11/19/12 12:17 PM 11/19/12 12:17 PM
Joined: Oct 2006 Posts: 427 Sweden Mopar Guy mopar
Mopar Guy mopar Joined: Oct 2006 Posts: 427 Sweden	You can recalibrate the magnet in the speedo if you can find some one that have that eqipment !

Re: speedo help.... not reading right [Re: RapidRobert] #1334307 11/19/12 12:19 PM 11/19/12 12:19 PM
Joined: May 2003 Posts: 15,487 Florida S scratchnfotraction I Live Here
scratchnfotraction I Live Here S Joined: May 2003 Posts: 15,487 Florida	if the odo is correct then the gear may be wrong size. if it is 20 mph over road speed you need more teeth to slow the speedo needle down. if it is 20 mph slower then you need less teeth to speed it up. I changed from 27 tooth speedo gear with a 2.76 gear and 29" tire to a 38 tooth speedo gear and 3.91 gear and 29" tire it could very well be the cluster but I would look at the speedo gear to see what tooth count you have in there the see what it would call for with gear x tire size. then retry speed/mile marker test and speed with a GPS. thats the way i understand it.

Re: speedo help.... not reading right [Re: Mopar Guy] #1334308 11/19/12 03:00 PM 11/19/12 03:00 PM
Joined: Sep 2003 Posts: 1,168 Vancouver, WA MoparMarq super stock
MoparMarq super stock Joined: Sep 2003 Posts: 1,168 Vancouver, WA	Quote: You can recalibrate the magnet in the speedo if you can find some one that have that eqipment ! www.tacomaspeedometer.com They made a nice reduction gear assembly for my Toyota when I swapped rear gears (speedo drive pinions don't interchange on the different transmissions on the Supra). Probably someplace closer to you just like it that can properly tweak your speedo...

Re: speedo help.... not reading right [Re: MoparMarq] #1334309 11/19/12 05:48 PM 11/19/12 05:48 PM
Joined: Jan 2009 Posts: 813 Ontario,Canada brads70 OP super stock
brads70 OP super stock Joined: Jan 2009 Posts: 813 Ontario,Canada	Thanks for the replies guys! I have a buddy that works as a mechanic for the local police station. I'll check with him and see if he knows of a shop. I know it's not the gears in the tranny or the cable as the odometer works perfect.

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