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@adamzanThere are 2 bolts on the transmission that are about impossible to get to where the front pinion is at. I was able to remove them by fishing a wrench up there. I don't think I'll be able to get them back in without, at least, dropping it a little. One of the bolts on there was a non-standard bolt that was too short and stripped out of the bell housing. Something to investigate while it's out.... Maybe... while I'm at it... I could drop the oil pan and seal that back up... but it doesn't look like it's leaking at all from there.... Progress today; I cut the heads of the bolts off of the Y pipe and cut the pipe just in front of the catalytic converter. I had to fish the wire for the oxygen sensor out. I was able to unpin the connector and put the box end of a wrench around that. Took quite a bit of force to get it started, but it came out of the bung fairly easily once started. Dropped the transmission with just enough room to clear the extension housing on the fixed crossmember behind it. Sooo... that answers my question to being able to pull the transmission without chopping out the Y-pipe. That would be a NO, unless you take off the transfer case. Next: the rear main on the engine, end caps on the heads, front seal on the transmission and the intermediate seal between the transfer case and transmission.... Lots of stuff to do. New clutch, of course. A lot of work for a little bit of oil and piece of mind I guess...

87 and 87a both get power from 30 (which is wired to battery +), but through separate contacts inside the relay, which allows them to be switched opposite of each other. Switched power to the coil (from the headlight switch) turns off 87a, as it turns on 87. Removing switched power from the coil turns off 87, but turns on 87a. Here's another way to look at it. Imagine a standard household light switch. Switch up, light on. Switch down, light off. Now imagine two light switches, side by side. But one of them is upside down. If you flip both switches up, you've turned one on, and the other off. Flip them both down, and you've turned one off, and the other on. The right-side-up switch controls 87. The upside-down switch controls 87a. Both switches get power from 30. And both are controlled by the coil, which can only move them both together.

Either have to drop the front diff or remove the torsion bar crossmember. I'm older now, not struggling on my back anymore. Last time I put mine in, I used an engine crane through the passenger door.

Could be a wiring fault. Could be the bulb, I've heard of bulbs failing to where the filament sorta swings around and makes contact now and then. Worth noting that the illumination in these does not use a standard ground. The circuit gets positive from the headlight switch and ground from the dimmer (pulse width modulated, I assume). Should be pink/blue and pink/black wires. I would check for power across those at the plug (marker lights on, dimmer turned up) to rule out a harness issue.

The light for the HVAC head is not a standard bulb. I did a little search trying to find one by size, and there are a couple of sizes at the T-1.75 or 1.5 size that might squeeze into the socket. Cheap enough, might try it. There wasn't an LED option in that size... or at least from that website. Time permitting, I'll probably start tearing everything down this weekend and update. As far as them not lighting up, I really think there is a loose ground somewhere, because they will light up one day, and not the next. There isn't any consistency and I haven't located the ground for it. Probably just need better lighting for when I take it all apart...

Power to 30, headlight to 87, halo to 87a, 85 to ground, 86 to signal. If there's no signal, 30 and 87a connect, halo is on, headlight is not. If there is signal, 30 and 87 connect, headlight is on, halo is not. It only powers one pin at a time. If 87a does not disconnect from 30 when the coil is powered, then your relay is defective.

Great explanation.

87 and 87a are both switched, but they're switched opposite of each other. 87 is turned on by the coil. 87a is turned off by the coil. If you do better with pictures (I know I do), try this. As drawn, the coil is not energized (headlight switch off, in your case). Spring tension is holding common (30) against normally closed (87a), and away from normally open (87). When the coil is energized, its magnetic field pulls on the armature, which pushes that middle contact up, holding common (30) against normally open (87) and away from normally closed (87a). If it's still clear as mud, maybe this guy can explain better than I can. TL;DR, your relays have a feature that is not useful in this application. Ignore 87a and treat them like four-pin relays. While we're on the topic of relay harnesses, make sure yours is connected to the battery through a decent fuse. Mine's connected to an aux fusebox I added on for that and a few other circuits, but when I first set it up, I didn't know better, and I used something like this crap. Water got in, the weak little contacts corroded, the corroded contacts got hot under normal load, the plastic melted, and then my headlights quit working mid-corner in the dark on a rural highway. I replaced that garbage with a rubber fuse holder (this style, though I think I bought mine locally). Much better connections, takes the same fuses as the rest of the truck, never let me down, highly recommended. I only swapped that for the aux fusebox because I had three or four of those things bouncing around, and that bothered me.

There is power to 87a, but it works opposite to 87. If there's power to the coil, 30 and 87 connect. If there's no power to the coil, 30 and 87a connect. This is wasted in most circuits (which is why many relays only have four pins), but it can be useful in some applications. If you had halos or markers or something that you wanted on only when the headlights weren't, you'd wire those to 87a.