so like the title say i want to bye a OBS 7.3 and get out of my 6.0 not cause of problems its a great truck and i love it, its never given me a problem but i would like to sell it and bye a OBS and have no truck payment. I knew what to look for when buying my 6.0 but i dont know what to look at when it comes to OBS 7.3's please help me thanks
The number one thing that you need to look at is the air intake. I'd almost bet money it is either an open element K&N, or a k&n inside the stock airbox. These will let in dirt and dust your turbo. Pull the intake tube on the turbo and look at the wheel, if it looks sandblasted you should pass unless you get a screaming deal. Mine was a K&N and I got such a good deal and the guy drove 7 hours to bring it to me that I didn't even check anything, did the deal and walked. I figured if it made it 7 hours and didn't smoke or anything there were no major problems.
If you find a K&N remove it and replace it with Napa airfilter, 6637 which requires removing the stock airbox and then a 4 inch piece of ABS. It filters better as well as lets your motor breath better.
Second, Pull your oil cap and set it upside down over the fill hole. If it blows off the motor has a lot of blow by and I would likely pass.
Third, inspect the color of the oil to see if it has any milky color in it.
Ask about any additives for the truck coolant, they need scas. If they have no idea I'd probably pass unless they have mech or dealer receipts.
Ask about major repairs, injectors, turbo, trans, etc. Mine had no receipts for this but again I wanted an obs so badly and figured I got a good enough deal that I would deal with it.
I personally prefer a manual trans, if you are test driving it do a quick shift between 2nd and 3rd and 3rd and 4th if you have grinding the synchros are getting worn out from people power shifting it. My synchros did that alot but now that I double clutch and drive carefully the problem only rarely comes up. If it does grind it can be helped with synthetic mtf or atf, like amisol or redline.
Check for any clunking in 4x4, front ujoint is a bit expensive in double cardan. Check window and door lock function if power.
Look for fuel leaks in the valley it is a common condition, not something to walk away from but it does need fixed.
If possible when you go up to an obs open the hood and feel the turbo, if its warm they are trying to pull some kind of a stunt. You want it dead cold to see what kind of smoke it puts out. White, is likely glowplugs and mostly normal, blue or black means there is some bigger problem likely injector related.
Outside of that these trucks are beast and I love the heck out of mine. If you need any further detail or want to talk on the phone, send me an im I'll get you my phone number to try and answer any questions.
I am pretty new to the obs world, owned since 11/14/11, but I have done a hell of a lot of internet searching, reading the factory book, haynes books, writeups, as well as done my own writeups.