I'm going to look at a used T5 (w/o shifter) and was wondering what the best way to check it out was without opening it up? Is there a way to put it every gear (one at a time) and spin the input shaft without a shifter?
You can try that, but it's pretty hard to turn the input shaft with just your hands when you're getting into the higher gears. Besides, you won't be able to feel much of anything unless it's a catastrophic gear failure.
The usual things to go on the T5's are the synchro's, making them difficult to shift at RPM, and causing them to fall out of gear when driving. Even bolted to the car, low speed/no load testing doesn't always find problems with synchro's. Missing gear teeth is another thing you won't always feel/hear when trying to spin the trany by hand.
The only real way to know about the condition of things is to take them apart and look inside, and that's not a simple process. Unless you want to go to all that trouble, your best bet is to find out as much as you can about the car it was in and what kind of driving it may have been subject to. and make sure you can row the trans through all 5 gears. Even then, there's no guarantee. After all, you are buying used.
You want to run away from units built for 4 cylinder cars, even turbo cars as they have the wrong gearing and a different input shaft. You cannot use a T-5 (t-45) from a car with a 4.6 liter V8.
Be advised that if you have a rear end with gears numerically higher than 3.25, the 3.35 first gear in most T-5's is nearly useless
I bought a used T-5 that turned out to need a substantial rebuild. I advertised it as such and sold it on Ehay for $300 or so. If you are only paying $200 you should be safe. If you are paying $500, you should be worried.
The Main Shaft (or output shaft) go bad a lot right at the front where the roller bearings ride. Be sure to check this if you get it apart also INSIDE the imput shaft where the roller bearings also ride.