I got new rims and tires for my duster and i was wondering if i had to recalibrate my speedometer..
The back ones are 15x10 and im not reall sure of the front probrably 8 or 6.. And if i do have to recalibrate it.. How?

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1974 Plymouth Gold Duster

It's not the rim size, but the tire diameter.............


Compare the original rear tire diameter to the new rear tire diameter and see what the the percentage difference.............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

You will need to know the tire diameter (size) and the axle ratio. Then get the proper speedometer pinion gear for your transmission. See http://www.moparts.com/Tech/tech/pages/speedo.html for the proper gear. The gear is located on the driver side of the transmission.

Cool Thanks guys...

Dave

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1974 Plymouth Gold Duster

or if you would like to convert to a electric speedo get the sender from a 93-97 ram pickup which uses the same gear drive location. then get a autometer speedo and calibrate.

zedpapa

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1970 dodge dart w/225 /6 bored .040" over, holley 390cfm w/vac. sec., compcams 252s, clifford shorty headers w/2.5" exhaust w/flowmaster, f-body 11" front discs, aluminum A-833OD, 8 1/4 w/3.21 SG
soon to have 5 gears!!!

Are these gears still available from MOPAR? And how does one go about changing them out?

Jerry

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There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

Speaking of speedo problems. Mine didn't work at all. It was disconnected, and for good reason. The speedo head was a twisted mess of metal. Sent the head for to be repaired. (Auto Instruments $185) Got it back and installed it. It works now but it has two problems. 1st, it ticks just a little at low speeds. 2nd, the speed is off. Used my GPS and found the following:
Speedo = Real speed
45 = 48
50 = 54
55 = 60
60 = 66
65 = 72
70 = 78
75 = 84
I can live with the ticking but do you think the speedo is wrong or maybe its the gear in the trans thats wrong? The trans numbers match the car.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

The ticking is either the cable is slightly tweaked (bent or too long) or the speedometer fix is really fixed............

The speedo being off could be:

rear-end ratio numerically too low (should be 2.93 or higher)
tire diameter to large
wrong speedo pinion in tranny

combination of above

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I've opened up several Mopar speedometers to fix their odometers; generally, the speedomters have little to go wrong. Changing gears is the way to calibrate; usually (if memory serves) 2000rpm cable speed = 60mph.

The speedometer works by spinning a pair of magnets around and inducing an eddy current in an aluminum cup - a picture is in http://www.tidewatermoparclub.com/TECH/odo3c.pdf. The cup is connected to the needle and a spiral spring.

Small adjusments to the calibration could be made by changing the tension on the spring or adjusting the strenght or position of the magnets, but it'd be by trial-and-error w/ the speedo on a workbench run by a drill or something similar.

The clicking is very likely due the speedometer cable. If losening the nut or clip to give a little play eliminates the noise, the cable has been slightly stretched and needs to be shortened (I use a Dremel & #409 blade); otherwise, it the cable may be damaged or need lubrication.

So, do you simply unscrew the cable end from the transmission, pluck out the pinion, and drop another one in? Or is it more complicated than that? I found out that to change the one on my brother's Jeep I am working on requires removal of the drive shaft and dig into the guts. His is off about 20 mph.

Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

Check the odometer. If the odometer is off the same percentage as the speedometer, then it's a simple gear change.

If they're off by different amounts, the speedometer wasn't calibrated correctly........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

When I got the speedo back from the rebuilder I found that if it was rotated by hand it sometimes ticked and sometimes not. The clearance in there is so tight that it hits the support. I needed (wanted) to go to a car show so I put it in and hoped for the best. I didn't get the best. You can't hear it if the radios on. The speed is off. Never thought about checking odometer. What size tires did this car origanal come with. Could it be a tire size problem. I am running 215-70-14

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Almost that simple. You don't need to unscrew the cable from the trans. You remove the bolt and retainer that hold the speedo pinion adaptor into the transmission, then pull the adaptor and pinion assembly out of the trans with the cable still attached. Swap to the new pinion (simply remove/replace), pay careful attention to the condition of the adaptor O-ring so as to avoid a fluid leak, make sure the tooth count of your new pinion falls within the range of the indicated orientation of the adaptor (this will make sense when you see the tooth ranges cast into the adaptor) and reinstall. Do this with the car jacked up by the left rear corner so the trans fluid runs forward-rightward, away from where you're working. Unless you like trans fluid showers!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan,
Sounds fairly straightforward. Another site had a chart indicating a 28-tooth pinion, based upon Aaron's 2.76 rear end ratio and his rear tire diameter. Sixteen bucks at our MOPAR dealer will get us a new one. I think I'll give it a try.

Thanks,
Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.