Slartibartfast

A bad crankshaft position sensor won't cause a click/no crank/no start. I would try the EL section of the FSM for that diode, but from what I've read it's more likely an issue with the starter switch being worn out. You could remove the clamshell, work out which wires on the ignition cylinder do what (EL section is your friend), turn the key to the run position, and basically hotwire it from there--if it starts you've ruled out everything but the switch. I prefer to test for power at the plugs. Insulation with a hole in it can trap water, corrode the copper inside until it won't conduct right, and still look fine from the outside when you try to track down the issue.

The MPG gain is only for the R50s, which come with drive plates (permanently locked hubs essentially). Auto hubs disengage the front drivetrain just as well as manual hubs do, provided they're working properly.

+1 on reading the codes, there's a service manual you can download here, and instructions in the AT section for how to read what's wrong with the trans through a flashing light on the power mode switch on the dashboard. The oldest manual there is '94 but '89 was the same trans AFAIK, so the instructions should still work. Sounds to me like either an electrical fault knocking out the trans computer or the torque converter packed it in. Hopefully it's the former or something simple along the same lines.

I was surprised when I had mine apart at how minty fresh they looked (apart from the black grease). With the noises they were making, I thought for sure I'd find some damage. It wasn't until I measured the clutch thickness against the FSM that I saw how shot they were. And no, there is no done, there's just better.

Might check the vacuum line to the fuel pressure regulator if you haven't yet. It's kind of a braille thing unfortunately, right at the back of the intake. Interesting that it ran fine once and then acted up the next time... that's gotta mean something. I kind of suspect the new fuel pump, given that it was pumping against a total clog (and possibly running while full of air, if there was nowhere for it to go), but I'm not sure how that would've worked the first time and then crapped out again.

It's in the distributor.

Sounds like the crank position sensor is sketchy. Warms up, gets erratic, that would explain the rough running and I'll bet it's what the tach gets signal from.

I've drained my battery dead flat by leaving the dome light on overnight, and I don't think the alarm went off. Then again, I've never actually tested mine to see if it works at all... and the siren from it is currently wired to a greeting card that plays the chicken dance. (I have my reasons.)

The extent of my knowledge of the alarm is that I unplugged mine and the truck still started. Apparently some have starter kills and others don't (or mine got hacked into at some point). I would probably try to just remove and bypass the blasted thing.

^+1, sounds like an alternator fault rather than an issue with the amperage being low. Good to hear it's fixed though!

You turn the ignition off and then the battery light comes on? +1 for checking the battery voltage with the engine off, but it seems like even if it was way high or way low it wouldn't put the light on when the ignition wasn't on. The fact that it's then staying on when you turn the ignition on again just makes it weirder. Hopefully there's just something weird with the alternator and the new one fixes it.

I was thinking more of the wiring on the outside of the transmission, if that's what you're talking about. The transmission computer is in the back of the truck, behind the passenger's side cargo area lower trim panel. It's in the way of removing the factory audio amps, so there are a few pictures of it here:

The switch grounds to the sheet metal of the door jamb IIRC, so I would start by checking that the bolt hole is clean. If that doesn't do it, jumper from the switch connector to body ground to rule out a problem with the switch itself. If neither of those do it, well, you're gonna have to pull the pillar trim and figure out where that wire's come loose.

I took one of my auto hubs apart last winter, cleaned and greased it, checked the clutch thickness vs the FSM spec (and found it was worn far past spec), reassembled with the old parts, and it made it worse. Binding up, coming unlocked while driving through town in 2x and making horrible ratcheting noises like the wheel was gonna fall off, fun stuff. Upgraded to manual hubs and haven't regretted it one bit. Knowing I can shift to 4x4 on the fly without having to think over my whole drive and try to remember whether any of it was done in reverse was totally worth the hassle of having to click the hubs on and off from time to time. Then there's the ability to engage the 4x in reverse. You don't think you need it until you unexpectedly run out of traction with the front end up against something. IIRC I found a rebuild kit somewhere online and discovered it wasn't that far from the manual hubs in price.

You can't buy a rear passenger door for an '87-'89. Other than that, the intake and fuel delivery is different (TBI vs MPFI).

Locking them at random times? Mine does that too, I think it's the contacts behind the key cylinders in the front doors, but whenever they're acting up it's cold enough outside that I can't be arsed to fix them. Worst case on the hatch trigger, you could just run a bit of wire from the switch on the dash to the alarm brain and tuck it under the console.

You might check on the wiring to the tranny before accepting that the solenoid is in fact shot. I imagine the TCU wouldn't know the difference between a busted solenoid and a corroded connector. Might be a long shot.

How does that even happen?

This doesn't sound like a cat to me--a clogged cat wouldn't be temperature related, right? Not liking higher revs would make sense, but only if it did it constantly--the fact that it's alright when it's cold says you're on the right track looking at bad sensors.

Did it just not start one morning, or was there something that happened prior to it crapping out? Might help to diagnose. +1 on checking the firing order.

I actually had a guy open the driver's door, flip the seat forward, and attempt to crawl past it. In his defense, it was dark out. Must be nice to finally have it back on the road!

I'm pretty sure the radio's on that circuit, too. Odd that it's affecting the starting system. Could be two separate issues. I would give the fuse links at the battery a look, though, make sure they're not corroded/smoked.

I never checked my stock tank, but judging by my gas mileage records and how much I put in to fill it, it was a 21 gallon tank. I checked the aftermarket tank with water, and it was 21 gallons more or less. Can't really recommend the brand though, it wasn't made that well.

Nevermind Manuel, he's from Barcelona. I'm looking at MT33, and it looks like the guts are indeed the same, but you'll have to swap over the back part of the casing with the shifter control housing on it from your old one so it'll bolt to the transfer case.

I had a lot of trouble getting my bumper back on, partially because the mounts are bent (that's actually why I had it off in the first place). I loosened the mounts from the bumper to get the brackets to line up, then tightened them again once the mounts were bolted up. Lots of people paint the factory Lego rims. I've got a set of generic black snow tire rims on mine now and IMO they actually suit it.