What is this light?

[CG]

I bought this rebuilt gauge cluster from a board member ages ago and never used it. I put it in my k20 a few months back. Today for the first time I noticed this light flashes on for a second as I start the truck up...not very attentive am I? Im guessing he got this gauge off a larger size truck...Curious what a tandem lock is.

[t&tkennels]

On a tandem axle truck , only one axle pulls in normal mode like for highway use. But when us but when using off road like in a slick or muddy situation you can lock both axles in so they both pull. Its usaully found on dump trucks or road tractors & activate by air , on older trucks maybe they were electric or work by some kind of linkage.

[Boog]

It sounds like a power divider for a tandem axle truck. Locks in both axles to pull in slippery conditions.

[mvfd70]

Usually on a larger truck with tandem axles (two rear axles) only the more forward of the rear axles has power to it. If you look at the Diff. housing on that axle it has an output shaft and then a short drive shaft going to the most rear axle. When the "Tandem Lock" is engaged, power is given to both rear axles making both of them drive axles. It aids in getting traction since 8 tires spin instead of 4.

[stllookn]

How cool is that? I love it!

[ChevLoRay]

So, it's a guage cluster from a big truck, probably at least a C-60.

I drove a '74 C-65 tri-axle dump that had locking twin screw differentials. When the going got rough, as t and t said, you could lock the diffs and all eight rear tires would pull together. It was only for straight pulling, with no differential action in turns. If you needed it, you were lucky to have it.

I broke the yoke on the front twin screw, while loaded with nearly 20 tons of hot mix asphalt....on a hill. Ever hear of "fail-safe brakes"? With air brakes, the LACK of air pressure is what makes them work. When you are rolling backwards, with a curve at the bottom of the hill and you have no engine and no air and no brakes......let's just say, "Life is good!"

The asphalt that I had in the bed that day? It's still in the ravine where I dumped it. That was in '75....July 2, to be exact.

[CG]

Thanks for the info guys. I can pretend Im driving a bigger rig. Wonder if Ill have to get my CDL now? =)

[special-K]

Maybe you won`t get stuck when the light comes on.

[Longhorn Man]

since no one mentioned it, that is the brake warning bulb, with the wrong lens due to the fuel guage being out of a c/40 or bigger.

[special-K]

Maybe you won`t stop when the light comes on.

[CG]

Could there be any particular problems running this large truck gauge panel on my truck? I had an original tach dash in it before I put this one in. Everything on it worked perfectly...it was just kind of old looking so I put this one in that I bought for a project I let go. The speedometer doesnt work correctly, the odometer barely works, the temp gauge pegged as soon as I started the truck first time after I installed it. The tach works, but sometimes reads way higher than it should be (Sometimes at 60mph it will almost be pegged, sometimes its normal). I haven't hooked up the oil or vac gauge yet. Do you think any of the weirdness is because of the style truck it came off of? Doesnt seem like it would make a difference to me.

The problem is I purchased it at least a couple of years ago and it had just been sitting in the top of my closet, so any kind of warranty the builder may have given would be way passed...and the other part of the problem is...I dont remember who I purchased it from...Crazy I know.

[Longhorn Man]

the only things you'll notice, is the wrong lens on the light, and the oilpressure guage is a n 80 ppound guage instead of a 60 pound guage... so you'll be at mid guage @ 40 PSI instead of 3.4-ish guage @ 40 PSI... the guage will look like the oil pressure is lower than it is.
Those are the only things you'll notice, and quite possibly, all that there is at all. (been a while since I messed with the big truck guages)

[special-K]

Maybe there`s a short in the printed circuit?I know the temp gauge pegs when it`s grounded out and with the warning like lighting makes me suspect something.

[Longhorn Man]

it's supposed to come on when the key is in the crank position.