Speedo and Over Drive

[suza]

I spent the first half of Easter down the coast driving some tracks with friends and have developed a couple of little problems.
I drive a 92 Bighorn 3.1 Diesel with an Auto

1, The speedo no longer works
2, The over drive no longer works, its was a long way home without it

These 2 problems seem to be related as every now and then the speedo starts working and then so does the O/D my thought is that the O/D is hooked into the speedo and will only engage after a curtain speed.
The plan at this stage is to give the underside of the Bighorn a good water blast tomorrow and then check all the plugs attached to it and clean contacts and see if this fixes the problems.
Would be really good to here anyone else's ideas.

Also did the alternator up at the Denstent Mud hole but we rebuilt that during the night at Reefton.

[isuzumudman]

Overdrive won't work if speedo doesn't. I think trans goes into safe mode if speed pulse not present.
Speed sensor is on rear end of transfer case. 3 wires - ground, power and pulse. If electrics ok then check speedo drive inside transfer case. This is what happened to me.

[suza]

Cheers, I have cleaned the underside and am waiting for it to dry out, have also removed headlights, park/indicator lights cleaned the mud oout of them and have them drying. The radiator is out and soaking to get the mud out of the core so that it can do its job again so now I am off to check the sesor, I will let you know how I get on.

[suza]

I had to admit defeat so I dropped off at my local workshop for them to have a look at and also thought that while it was there they could give a warrant and service the auto as it was due. I got a call today from the owner who has found the problem the sender is stuffed and the replacement on that was sent out had a different plug and an extra wire. So another one is on its way.

[isuzumudman]

Bugger!

[teddy1970]

Hi does anyone know of a way to disconnect the speedo but still have overdrive?

[isuzumudman]

Now why would you want to do that?

The pulse signal comes from the speedo drive, then through the speedo and then to the TCM.

Difficult to change but possible.

[geeves]

I think he really wants to disconnect the odometer. If you do this you must make it easily switchable because sometimes mr plod checks the the odometer is working and that you are not cheating on your mileage tax. They check by noting the reading and getting you to drive a k up the road and check again. This test doesnt catch those that have big tyres causing a low reading but does catch those that have disconnected there speedo .