they all come with 1" spindles, from the 990-998. just looked this up.
990s came with 3/4" spindles. It was a weak spot for them. The front end loader included a spindle upgrade.
from what i see the White GT-1855 was made in 1986, 87, 88, 92, 93, 94, & 95
so it could be a 992/995/996/998...............how confusing is that ? it all depends on the year it was produced.
From the available manuals on MTD's site:
992 = 20hp
994 = 16hp
995 = 16hp the first year only then 18hp after that
996 = 16hp
998 = 18hp
999 = 22hp
Here's a little chart I made up when I was first researching these and yes I had too much time on my hands then.
MTD tractors.pdf 44.11KB 86 downloads