After 21 years it is likely due for a major overhaul. I had several early Dodges. The 360 is a tough engine with decent torque for towing. The 727 Torqueflite automatic and NP standards are absolutely bullet proof. Big issues were rust although Fords and GM's of that era had their issues too. Body and trim parts are getting hard to find, took two months to find enough pieces to build a tailgate after mine was stolen and that was over ten years ago.
I have an '89 b250 with a 318. I have rebuilt everything on it at 202,000. Everything.
The tranny at 130,000
The engine at 172,000
The rear axle at 197,000
The whole front suspension last month
The whole cooling system, this week, maybe.
That said, I always had plenty of warning, I've never been stranded, and the engine and rear axle could have gone much longer before overhaul were absolutely necessary. The tranny too if I did not care about having overdrive. The front end only needed upper ball joints, but I did everything at once, myself.
But now I have a completely reliable vehicle that I know how to work on, that costs very little to register and insure. I do have a fiberglass roof, but not the super tall camper one. Mine was a people mover before I converted it
That said, I'd much rather have an '89 Dodge than an '89 Chevy or '89 Ford.
If it were not for the roof gutter rust...... Dang salt air.
The '89's have a hydraulic roller camshaft. The 318 is rated at 170 HP @ 4000 rpm and 260 lb/ft torque at 2000, the 360 is 185hp @ 4000 and 283lb/ft @1600 rpm. Not impressive numbers I know, but mine has no problems getting out of it's way. Mopar guys say the 360 is one of the best motors to build up, even better that a SB chevy, though I will make no such claims.
They either have a 3 speed tranny, or a 4 speed A-500 overdrive transmission with lock up torque converter. 1t gear with the A-500 is very low with a lot of torque. The weak link is the overdrive unit. If you do not tow in overdrive, do not climb hills in overdrive(which the engine can do) and have an additional tranny cooler, you are good to go as long as you use ATF +4 fluid.
The A 518 has a more robust overdrive unit. but supposedly yields slightly poorer MPG.
I get 9 to 11mpg Hilly, stop sign traffic light rich city, and 14.5 to 18 mpg highway averaging in the high 16's as long as I keep it under 68mph. The rear axle is a 3.55 to 1 ratio. It came with a 8 3/8 axle(10 diff cover bolts). I now have a 9.25 axle(12 diff cover bolts)
They both have throttle body injection. The '88 360 still had a carb.
Sniff the tranny fluid
Check for oil leaks, diff leaks, coolant leaks
Ask for documentation for all work done, especially if they claim a rebuilt transmission.
Check steering wheel slop
The negative cable was most likely removed to keep small parasitic loads from draining the house batteries. It is strange that everything still works. They must be getting the ground and all their power from the engine battery. This means the isolator or soleniod is not working as designed, or has been bypassed for whatever reason. As it is you can be stranded by the engine battery being drained by your house electrical accessories.
Get a digital voltmeter. ~7 dollars at harbor freight, ~20 dollars an autoparts store or Home center.
Test the engine battery voltage
Test the house battery voltage
Return the ground cable on the house battery
Check voltages again with engine running
The house battery, if it has been disconnected for a long time could be dead. Either charge it before hooking up the ground cable and starting the engine, or if it tests over 12 volts just hook it up.
Run the above voltage tests post the results, and we can help you further.
Your model year has a carburetor, not fuel injection, probably does not have a roller camshaft, and has slightly lower HP and torque numbers.
This Manual will discuss only the dodge chassis systems for your specific model year, not the explorer camper conversion stuff. You should look for that manual on line. Perhaps someone here can help you out on that matter.
The Haynes or chilton manuals cover a dozen or more years and are not nearly as helpful.
This info was helpful for me also as I just picked up an '87 Dodge B-250 w/ 360 (Xplorer). Does anyone know if the negative cable on the 2nd battery (the acc. battery) is supposed to be hooked up on these? Mine only has a cable hooked to the positive post and everything seems to run. The other (starter) battery has the standard ground and positive cables on it.