Hey guys!

Thanks to Alan's generosity, I've connected a second sending unit to my trans temp gauge. I didn't like the factory port on the top of the Mag-Hytec cover so I just drilled and tapped where I thought it should be.

Items used:
Single Wire Sending Unit (Alan sent me his extra one)
SPDT Switch mounted on the dash
20+ feet of 18 gauge wire
Connectors (crimp style, but soldered)
11/32 Drill Bit
1/8" NPT Tap
Drill (I used my mill)

Now I can flip the switch on the fly and see what the rear diff temp is.

 

that's cool !! any more info on the sending unit ? just curious what it looks like, size, etc ?

 

Ummmm. Uhhhhh... Not quite sure other than it's a single wire and 1/8" NPT threads. Its about the size of a tube of chap stick I'd have to say. Maybe Alan remembers the original application. He had it extra since he had gone to a two wire setup.

 

That is a good idea how you ran it to a switch like that. I wish i had more ingenuity to think of things like that.

 

I wish it was my idea. It's been done many times on many different applications. Now I am kicking around the possibility of putting in a xfer case probe and a triple switch.


THE PMS NEVER ENDS, NOT EVEN AFTER 200,000 MILES.

 

any temps yet? daily driving? pulling? Just wondering as i have no idea of what temps they normally run

 

Nothing yet really. I drove 15 miles to work and verified that it actually sends a signal. I have no idea how hot it will get either. I'm planning on towing MAD MAX up the sierras sometime this summer so I will know FOR SURE what temp they get up to.

 

alright thanks.

 

I'm thinking that adding a braided ground strap somewhere to allow a "good" ground for the rear-end assembly wouldn't be a bad idea to insure reliable readings.

Think about it, the springs have rubber bushings in the shackles, the shocks are set in rubber, the brake line is rubber, and that only leaves the drive shaft, which is rotating through greased needle bearings, as the ground. All steel, but nonetheless, not a good ground.

I'm not sure how the VSS accomplishes this, but it's two-wire for a reason, and the ground may be floating for it.

Pop

 

I wondered about that too. Even thought about the VSS wiring. But, the thing works so I'm going with it for now. A good ground strap certainly wouldn't hurt.

 

I am willing to bet they approach 200* when really working it but I don't have one of those finned covers either. I'm going by hand sensor on stock cover in my truck. I had a rear diff gauge on my Challenger 440 but that was a DANA 60 and it never really got too hot, not like what I have now probably due to the weight of the rig.

 

The sending unit has to match the gauges that is is hooked with..The diff temp takes a good 20 minutes of highway driving before it comes up to about 250 degrees, it will be your hottest temp gauge you have. Once it gets warm the temp shoots right up. I haven't seen anymore then about 260 degrees.

I took my stock diff cover and tapped it and installed a sending unit and have it wired in..It is one of the last gauges I have installed on my truck, last count was 10 gauges..

 

I was wondering if you were going to get around to installing it, that was a sending unit from an autometer trans temp gauge.

Fat, maybe a piece of loom up and over the diff to protect that wire?

 

Cool idea. Not to rain on anybody's parade here, but I have to ask, are these sending units thermistors, or thermocouples? If it is a thermistor, you should be fine going through a switch, but if it is a thermocouple, there could be a problem.

Thermocouples work by measuring a voltage generated by two wires made of dissimilar materials coming into contact. Usually, the equipment they are connected to has terminals made of materials that either won't generate another voltage, or will generate an appropriate voltage that can be accounted for via the calibration of the meter. If you put some random switch in the line, without knowing what the terminals are made of, you can affect the calibration of the meter significantly. This is not a problem with thermistors, because they just change resistance with temperature, they don't actually generate a voltage like a thermocouple does.

I am not familiar specifically with the sensors you're using, but just wanted to bring this up as a general point that should be considered. Maybe someone here who is familiar with these gauges and also with thermocouples could address this. I hope it works out for you.

 

Kel, everyone I have spoke to when dealing with thermo's agree with you, but so far, with everything I play with, I dont think it is significant at the lower temps 450 and below, once i get up around 1450-2200* i start seeing 10-15* difference with the wrong conncectors. Even if using the wrong type wire, it normally doesnt read to far off at the lower temps..now, hook it up backwards, and you might be trying to figure out why your temp is dropping after driving for a while.