We have a john deere saber lawn mower 15.5 with a 42 inch deck. Need to replace belt and need a belt diagram to put the new one back on. Can't find any belt diagrams on here.

Hi,
I regularly post them. I also have them on the OPE by Crigby site listed below. Since Sabre is made by Deere, that is where to look.
Peace,
Clarke

How do you install the drive belt on a 15.5 Sabre riding lawn mower by John Deere?

Hi,
I will attach the JDAnswers document.
Peace,
Clarke

Must the deck be removed to re-install the belt? I have seen the pdf and diagrams (thanks Clarke) and the only impediment to re-threading the belt seems to be the (keeper?) tab on the small tensioner pulley (b. ). I am @ [email protected]

Thanks, Lanny

Hi,
You do not have to remove the deck to put it on; but you do need to loosen the nut to make the pullets allow it to pass.
Peace,
Clarke