speedometer questions

[Wintermute]

Okay, so say I get all of my stuff done (differential gear changes, new transmission, np205 transfer case, etc...), I take it that at this point, my speedometer isn't going to read anywhere near the actual speed the truck is moving at. Is there a way around this? Are the speedometers adjustable for changes in things like tire size? Is there an alternate option for a speedometer that I could use that would allow me to adjust it appropriately for these changes?

Thanks guys

--Wintermute

[LONGHORN]

You can just change the speedo gear in your 205.

[brute4c]

There are also little ratio boxes that bolt to the outside of the case, on the fitting the speedo cable mounts to...that allow for changing the ratio to corrct your speedo...might find one on ebay...

Heres a link to anothe site with some pics showing one:

http://coloradok5.com/forums/showthread.php?t=269149


You can also get one of the new speedos that allow you o push a button on the speedo, drive 1 mile, then push it again and it calibrates itself from that.

[compexp]

When I finish the current truck I am building, I will use an electronic speedo, as Jon referenced. push button, drive mile, push button, done.

Currently, my speedo is 20% slow, give or take. The upside is that I don't put many miles on my truck!

The downside is my mileage sucks even worse!

[Wintermute]

any links to the electric speedo's with the pushbutton? Are they 24v?

Ohh, and are they reading from the existing speedo cable but with an automatic adjustment with the pushbutton? or are they reading from something like an alternator waveform?

--Wintermute

[randyscycle]

Autometer makes one of the speedometers that is electronic and it uses a small AC generator that screws onto the existing speedometer drive on your trans or transfer case. Not sure if they offer a 24V version though, but they do have a good website with info on all their instruments: http://www.autometer.com/default.aspx

Once installed you just calibrate it according to their instructions.

The only instrument I've seen that works off the alternator is a diesel tachometer.

[compexp]

http://www.sw-performance.com/produc...uxeElecSpeedos

http://www.autometer.com/cat_gaugede...id=3928&sid=75

any links to the electric speedo's with the pushbutton? Are they 24v?

Ohh, and are they reading from the existing speedo cable but with an automatic adjustment with the pushbutton? or are they reading from something like an alternator waveform?

--Wintermute

[Wintermute]

Thanks for the links guys. I used some of the information from the autometer manuals to figure out what I'm looking for. Apparently VDO makes a programmable 24v speedometer...a bit more spendy than the autometer ones, but it uses a hall effect sender as well and I won't have to use a step down transformer to run it

http://www.egauges.com/vdo_mult.asp?...Vision&Units=E

--Wintermute

[Roy]

I have had the Autometer version in use for 12 years now. Had to replace the sending unit/signal generator once.
Several years ago I configured a portable, GPS-derived speedo to check vehicle speedos for accuracy and other functions.
Several companies now offer them for street rods and such. I think Autometer, VDO, and Stewart Warner.

[wolf.dose]

Since there are digital instruments used in trucks and passenger cars, it is difficult to find a shop which still maintains the mechanical little boxes, which are crimped into the speedemeter drive cable. They contain a number of gears which are chosen according the rate fond on a roller bench.
Here in Germany you must be qualified according § 57 B StVZO to do these changes for there are specific requirements for accuracy. The easier way is to use an electronic replacement with the cappability to calibrate it by yourself. There are versions available which are driven by the classic speedo cable but with the wrong diameter for the instrument cluster. As far as I know, they are f.ex. made by Motometer, a German brand.
Wolf