1988 Mazda b2000 vibration in 5th gear

Hey all!! i'm thinking about buying an 88 b2000, i took it for a test drive but it makes a loud vibration when in 5th gear, i really like this car and i'm hoping its not too much of a problem...any help as to what is causing this would be appreciated, thanks!!!

Loud Vibration? Loud noise? Strong Vibration? All of the above?

Does it seem to come from the front more than the rear? Or vice versa?

Could be any number of things. Is it completely smooth prior to 5th? I would leave it in 4th and take up to the same speed you hear/feel vibration in 5th gear, just to make sure it's not happening at that speed that you hit in 5th gear instead of 5th gear itself. If you can hit the same speed in 4th (60 mph? 70?) and it smooth, then you've definitely isolated it to the transmission - 5th gear. Maybe you are already 100% sure it's 5th gear and not happening a certain speed.

If it does turn out to be a function of speed instead of gear, then you might look at U-joints, tire/wheel balance, alignment.

its a strong vibration and it happens at any speed, it feels like its coming from more of the front than the rear. doesnt make any grinding noise or anything, just a loud humming noise and the car vibrates, hope this helps.

and yes, it only happens once you put it in 5th, the rest of the gears feel smooth.

Sounds like you've got a bad transmission then. If you really want to buy it then you should get a least a few hundred dollars knocked off the price so you can get it repaired or rebuilt. It's really hard to say how much it might cost. You can also look for a replacement from junkyards or salvage parts places.

thats what i suspected....ive already have a replacement lined up from a local salvage yard for 150$ so not bad...haha, thank you very much!!!