'71 Challenger speedometer questions

[goldengladiator]

I searched and didn't find my answers so I figured I will post something here.

My speedometer in my '71 Challenger doesn't work properly. It works, but the actual speed and the speed on the gauge don't mesh up. It seems to climb high than your actual speed. So, for instance, on the freeway my speedometer might say 90 when I'm going 55.

Any clues as to the issue? It's a rally gauge cluster, '71, 360, automatic, no gear changes that I know of.

If something is wrong, who do you recommend for a rebuild or a replacement?

[MEK-Dangerfield]

The speedometer gear in your transmission needs changed. Just find where the speedo cable goes into the tranny under the driver's side seat. There is a clip holding the gear in the housing. The clip is held on by one bolt. I had the same issue. I was reading 80-90 at 55MPH. I had a 26 tooth gear, and needed a 34... so you'll need a bigger gear too.


  Mike

[71chally416]

http://home.earthlink.net/~mopared/speedo.htm

[goldengladiator]

So I should just change my gear? My issue is that I don't know what's going on in my rear axle. I haven't touched it during restoration. Wheels are 15" but same size overall...

Oh, I also disconnected my odometer because it wasn't working. Would that be an issue as well?

Thanks for the replies. As you can see, I'm not a gauge expert. Ha ha.

[73Chally]

The odometer disconnected won't make a difference.  You need to figure out what your rear gear is.  Jack up the rearend so both wheels are off the ground (support with jackstands), and spin one tire one complete revolution.  As you do this, have someone count the revolutions of the drive shaft.  The number of revs of the shaft will be your gear (ie 3.5 revs would be a 3.55 gear, 3.9 would be 3.91, etc).  WIth that, and your rear tire height, you will know what speedo gear to buy.

[goldengladiator]

I must be counting my drive shaft revolutions wrong because I am getting 1.5ish? Is that right? I am pretty sure that ratio doesn't exist... Hm...

[ted]

if its a sure grip muiltiple times 2

[Chryco Psycho]

no if it is an open diff & only 1 tire is turning multiply by 2 , could be 2.9 ratio

[73EStroker]

Also I cannot see how you can disconnect the odometer and still have the speedo needle still indicating. That would require dismantling part of your speedo mechanism which starts you on the path to speedo destruction if you are not careful.

[73Chally]

Also I cannot see how you can disconnect the odometer and still have the speedo needle still indicating. That would require dismantling part of your speedo mechanism which starts you on the path to speedo destruction if you are not careful.

Mine was somehow "disconnected" on the rallye gauges I out in.  It turns out the previous owner had done something to screw up the drive gear that turns the numbers.

[73EStroker]

Then I would suggest you get it to the guys at RTE (one of the shops anyway) as they can make it like new. Of course budget comes t play here as well but at least you will end up with a like new unit and calibated like a cop car too.

[Changin Gears]

Mine was somehow "disconnected" on the rallye gauges I out in.  It turns out the previous owner had done something to screw up the drive gear that turns the numbers.

Sounds like somebody was trying to "adjust" the mileage.

[BIGSHCLUNK]

We have a great speedo shop in town here, does allot of resto work......