I have a husqvarna LTH 126 ride on mower ,do i have to check oil in gearbox and is there more than four grease nipples

Go to bing.com search husqvarna Lth 130 and you should come up with a 50 page manual on the mower that might help with problem.

21 hp briggs big motor

if not a drive belt or gearbox issue

is the Governor set properly
rider mower serviced regularly
carby jets adjusted
no stale fuel clean fuel filter
valve clearance to spec
newish plug
not burning oil

The best way is to remove the deck from the mower. At this time you should grease the pulleys and spindles. there are four post that hold it. two on either side and one in the front. they are held by cotter pins. lower your deck level down makes it easier. you will have one engagement cable that just pops out it has a spring on it. then slide it out from the easiest side or pick the mower up and pull deck out . at this point it will be apparent where the belt goes and do your your other maintenance of cleaning and lube. factory says lube spindles every 8 hours of use.Then put it back under and re attach.

10-30

Look in your manual. If need one, go Goggle husqvarna lth 130 manual.

you should be able to get online from husqvarna

It depends on where the leak is.

husqvarna lth 130 with kohler 13 hp": have fuze any on it

my husqvarna lth 120 will not move backwards or forwards

Here is a diagram I have found for you.