Toro LX 500. Loud vibration noise in F/R. Drive belt is real loose when peddle is not engaged. Is there a way to tighten tension?

SOURCE: Saturn Belt Tensioner...

You probably have a bad tensioner, you cannot tighten a bad tensioner because the bearrings inside have gone bad so your belt will just keep coming off. I had the same problem, don't wait to fix this because your car can over heat, you can lose power steering without proper belt tension. Pay the few dollars now(and I do mean few) and avoid problems later.

SOURCE: serpentine belt tensioner will not tighten

If the tensioner will not keep the belt tight then the tensioner is bad and will need to be replaced. The spring on the inside will loose it's tension over time.

SOURCE: primera 1990 P10 makes loud noise from belt when starting

i recently experienced the same issue. it can be your tensioner pulley or your water pump see the belts are connected to the pulleys and sometimes get worn out and need to be replaced. especially on a older car see a mecanic

SOURCE: 02 altima belt noise

OK, went through the exact same thing this week. Put on a new belt, checked for proper seating, etc, etc. and that wasn't it. Read all through this site and others and it comes down to one of two things, the tension pulley assembly or the compressor itself. Seeing as compressors ran about $300 or so and the pully assembly is less than $50 and takes about 45 min to an hour to replace, I did that first. And for me, that was it. Tip for replacing the pulley assembly? Have a wide variety of sockets (depth) and extensions.

SOURCE: drive belt not engaging. need more tension on

does the lever feel spongy when you try to engage it(not solid as it felt new)? usually this is caused by tightening the adjustment screw too far out.if so you brobally have a bad engagement lever on the transmission. the bad news is the lever is not avalible alone. you either have to bite the bullet and buy a transmission or find a junker that dosen't have the same problem.