High miles
#1
#4
You can check for some basics of motor health by running an oil sample at Blackstone Labs: http://www.blackstone-labs.com/. It costs around $20. This will tell you if there's any fuel or coolant getting into the oil.
This can find serious problems that you might not be aware of otherwise. They once found a few percentage points of fuel dilution in the engine oil of one of my cars. This was causing excessive engine wear, but there was no outside indication of the problem-- no noticeable drop in fuel economy, no smell of fuel in the oil, no CEL. The problem turned out to be a leaky fuel injector. Replacing the injectors solved the problem.
I don't know if a trans fluid analysis is available for your trans-- is the fluid a nice clear red with no burnt smell? While not scientific, that will tell you a bit about how the previous owner cared for it.
This can find serious problems that you might not be aware of otherwise. They once found a few percentage points of fuel dilution in the engine oil of one of my cars. This was causing excessive engine wear, but there was no outside indication of the problem-- no noticeable drop in fuel economy, no smell of fuel in the oil, no CEL. The problem turned out to be a leaky fuel injector. Replacing the injectors solved the problem.
I don't know if a trans fluid analysis is available for your trans-- is the fluid a nice clear red with no burnt smell? While not scientific, that will tell you a bit about how the previous owner cared for it.
#5
It's yours. Drive it! There is no point doing anything else. It may be worth doing a plug change and a trans flush if you don't know when they were done last. While the plugs are out a leak down test can be done to see how well the rings still seal. If it still runs ok, I wouldn't mess with it. It is a used truck after all. FWIW my '97 F-150 has over 300,000K on the original engine and trans (4.6W and 4R70W).