Of course there are lemons out there, but the most important thing is to maintain an automatic.
ATF breaks down, especially when it gets hot. You leave it in there for too many miles or after it has gotten hot or water mixed in and you are asking for trouble.
How many people do you know realize that 02 sensors need to be changed every 60K miles or so otherwise fuel will be dumped and the cat will be ruined. Nobody. They wait for the CEL to come on at 80-120K and then wonder whats an 02 sensor??
How many people do you know change their tranny fluid once a year religiously no matter what and check the condition of it periodically?? How many people even know a auto tranny even has fluid in it? hahahaha. You see where I am going?
An automatic trans has moving parts in it, they wear out and are designed to wear out. Unfoirtunatley for some reason when Ford added an OD unit to the C4 to make an A4LD they used aluminum OD components, etc. So the A4LD family is more prone to failure when steps are not taken to help it along.
Get a big trans cooler, get an inline trans filter, use Dacron filters in the pan, quality ATF, and keep up on your ATF level, color, and smell.
The best thing you can do for your truck is follow the manufacturers recommended service intervals at the very minimum. Personally I do about double when it comes to my 88 because of the 240K miles and the abuse she takes, alos I dont believe Ford when they say "rear gear fluid is good for life of vehicle and NEVER needs to be changed" (newer trucks) hahaha what if I use my Explorer to tow a 25' cabin cruiser all year long through the mountains. Do you think that super synthetic and friction modifier will last for 300K miles doing that? Do you think the limited slip will not wear out??
I have not dealt with Jasper transmissions. I would call Lynn at Performance Transmission here in Denver and ask him about rebuilding a A4LD. Then get on these boards and read through posts from people who have had A4LD's rebuilt. Dont talk to one transmission shop and shop by lowest cost. Talk to people, find somebody who wheels Rangers or what have you that builds them and has for a long time, that sort of stuff.....
I researched the A4LD for hours before I converted to one, of course I also read for hours about that flippin Mazda slush box......... If you dont like the A4LD you have options, a C4 can work (3 speed) and a WC T-5 can also be adap[ted to work without any $$$$ AA parts......
Oh and I am buying a larger boat, putting on bigger tires, not to mention the new locked front axle......we shall see how well the A4LD can do..........