Digital to Analog

[pmac33]

Trying to change the speed sensor output in my truck back to analog ; so the speedometer will work. I replaced the trans in my 98 ford with a 02 trans. the later model trans does not support the analog sensor. So I need to change the digital over to analog . Please Help !!

[reloadron]

You don't mention the specific model and engine? Not to deter from the N&V forums but you would likely fare much better in The Ford Truck Enthusiast Forums. Unless of course someone here has run into a similar situation.

Ron

[pmac33]

I hav looked everywhere. The model is 98 F350 AT/2WD . 5.4L engine.

[haklesup]

You could always get a portable GPS device and use the speed display. It may not be as accurate under certain circumstances but at least you'll know when your speeding on the highway. The other drawback is they don't get an initial fix on the satelites very fast if you are moving so you might have to idle in the driveway for a few minutes at the beginning of each trip to wait for it to boot and find itself (or leave it turned on all day).

Another apporach would be to build some sort of digital speed display but that's a much more technical fix. I'm sure someone has done this as a project before. If you search "Digital Speedometer" you can find some aftermarket solutions.

What you probably need is an integrator circuit to add up all those pulses and output a DC signal. I don't have any details on that either at this point. I don't know if its even possible to change out a speed sensor thats an integril component of the transmission.

[MrAl]

Hello there,


I would go with the replacement digital display because doing a digital to
analog might be tricky getting the calibration right especially if there is a
built in curve to the analog or digital part you already have.
You might not like the GPS speedometers either because they drop out
sometimes and you are left with a reading of 0000. They certainly
are a quick fix however and can be purchased as a full unit all ready
to go.

Here is a link to an interesting digital speedometer circuit:
http://www.edn.com/article/CA529384.html

You'll have to read up on it if you want to use it, or you could build one
yourself. Wouldnt be especially hard to do but would take some time to
get all the parts and maybe make a board, etc.

Another idea would be to build your own frequency to voltage circuit,
which may not be that hard to do with a decent frequency to voltage
ic chip made just for that, but again there may be some calibration issues
to deal with if the digital or analog part has any curve to it.

[CeaSaR]

Found a possible explanation of how that sensor works here.

A possible solution may be found here.

That's just a small sampling of what was listed at Comcast's search (Ask.com).

Hope someone can come up with something for you.

CeaSaR

[Bob Scott]

.... the later model trans does not support the analog sensor. So I need to change the digital over to analog . Please Help !!

Did you check with a Ford parts dealer? I was thinking that there might be a way to change out the digital sensor and/or a housing of several parts to downgrade the transmission to analog, but you said that you checked this. I'd find out exactly which parts are not compatible and see if you can transplant some of the old parts from the old transmission, including any housings and shafts etc.

Ask a local transmission rebuilder/jobber how they would handle this situation. I don't mean your local AAMCO, I mean a wholesale rebuilder if you can find one. Show up in person.

[jimmy101]

Can you find a junked 02? Perhaps it's as easy as removing the speedo from the dash of the 02 and installing in the dash of the 98?

[pmac33]

Thanks 4 your time an concern guys. I got a good heads up now. Hope I can help you some time real soon.