Postal trucks are based on the Chevy/GM S-10 platform. I wonder what is unique about them, other than the body shell, right hand drive and smaller wheels.
The smaller wheels are what really does it for reliability. You can't really hurt anything when you can't get the drive-line loaded up with tons of torque because you just peel out.
The Chevy 10b rear axle in those S10s is a complete turd. It's like the Toyota pickup frame or Ford 6.0 of rear axles. But with small enough tires and deep gears it's impossible to hurt them before you break traction.
Everything else is just an S10. The front suspension is pretty meh. Compared to every other small pickup platform on the market in the US at the time there is nothing special to recommend it. It's basically an 80s GM car that's been narrwed (G body IIRC??). For sheer durability what you'd find in a 90s Ranger or 1st gen Explorer far eclipses it (doesn't handle as nice though) in basically every way. When you've got a maintenance department replacing the seriously worn stuff it doesn't matter that much. The S10 platform isn't perfect in this regard but it certainly gets the job done. It doesn't have to go get airborne. It just needs to handle bumping over curbs at 5-15mph.
The engine is pretty reliable. It doesn't make enough power to hurt anything and it can't move enough air to spin fast enough to hurt itself and doesn't have any Achilles heels to make it unreliable. Same story as basically ever other domestic iron block and iron head OHV engine of the era.
From the transmission's perspective being in the LLV is a really easy life. The engine doesn't make much power the rear is geared deep and the stop/start duty cycle doesn't allow for much heat buildup. Pretty much any trans is going to be highly reliable in that setting.
In retrospect a 1st gen Explorer (basically the Ranger with a couple upgrades) would hand have been the better platform as far as chassis/suspension/axles go. Seriously, I can't over-emphasize this. The S10 has nothing to recommend it and a few strikes against it when it comes to all the components from the frame down whereas the Explorer is the undisputed winner in terms of chassis/suspension/axles from that time period. I think the GM options for 4cyl engines and automatic transmissions were better from a long term reliability perspective.
GM basically set out to use their parts bin to build the most reliable S10 they could and they're not idiots so they succeeded. The performance goals and acceptable trade-offs are totally different from that of a consumer vehicle so they had a lot more room to make compromises and make the system more reliable.
If you lower and shorten an S-10, reduce the tire diameter by something like 40%, and stick an aluminum body on it, you've created a very unique driving experience in terms of acceleration and handling. I bet they're a lot of fun to drive.
I wouldn't bet on that. I owned a vehicle that had the same engine and was lighter, and it was a complete slug. Also, the tech underneath these is almost 40 years old, and was bad when new. These have no AC, so imagine driving one all day in 90F heat. I'm sure they all have a bazillion miles on them by now and are in poor repair.
GM was in a pretty bad spot for a long time. The car I had was in the junkyard by 80k miles, and it was well taken care of. I ended up in a same year Honda that never had a single malfunction in 120k + miles.
