How is the temperature sending unit grounded on these trucks?
When I got this truck, a ground wire was bolted from the firewall by the throttle linkage down to the transmission case (AOD). The firewall connection had a second wire that went to a connector that connected to a wire to the engine computer. There is another engine block-to-frame ground through the negative battery cable.
Does that sound right? Why is the transmission case grounded?
I just finished a Duraspark conversion on my 1984 F150 (302), and I noticed the older models had a single ground wire that connected from the firewall to the intake manifold. My truck doesn't have this ground at all. I am running an aluminum intake manifold, if that makes a difference.
The DSII box grounds through the black wire from the distributor, I think. If you've got the engine and transmission grounded separately then I would think that'd be enough. I'm running a C6 and I don't have it connected to ground, though I could see a grounded transmission case helping the starter out some (since it grounds through the engine and transmission).
I added an addition 4 gauge wire from battery negative to the front passenger side frame rail. Not necessary but some stuff grounds to the frame so I went ahead and did it.
I always prefer a ground directly to the engine block, so the starter has the best circuit it can.
Some of my vehicles I run a ground from the battery to the frame and from that bolt one to a starter bolt and a smaller gauge, #6 or so, from the battery to the body.
On my 460 I have a ground from the battery to the block at the front and from that bolt one going to the frame.
It doesn't matter, the engine and the tranny are bolted together as one. The intake and the engine are bolted together as one also.
The reason you have to run grounds to the engine/tranny is because the main heavy ground wire from the battery bolts to the engine block somewhere(usually on the front pass corner of the engine). But the engine/tranny are mounted in rubber motor mounts, as well as the rearend which is mounted to the springs which are mounted in rubber bushings.
So you need these little ground straps to ground the body. The factory also had a spot where they grounded the frame, but if the ground cable gets replaced you may have lost this part. But even when the frame is grounded, the body still won't be grounded. It's mounted in rubber body mounts, and the bolts do not touch the frame.
I use dielectric grease on all electrical connections (with a few exceptions) because it's not electrically conductive. For me it's easier to have just one grease for all electrical. But yeah, on a ground connection pretty much any grease is fine.