David Brown 990 Clutch

Been searching the internet for some info on the 990 I am trying to put a clutch in here in Nova Scotia. I am unsure of the exact year (serial number is covered by loader mounting plate) but Im gonna say mid 70's. The manual I have says the clutch can be replaced by opening the transmission and removing a section of the input shaft. This isn't so and the shaft is one piece in this tractor. Also Im not sure what the transmission is. It has a very low range, low range, hi range and another range (shifter all the way ahead) which is the same as one of the previous ranges (low i believe). Havn't drove it in quite some time so my memorys a little fuzzy. Each range has 3 forward gears resulting in 9 different forward speeds. Strange huh? The transmission and clutch diagrams in my manual dont match my tractor. I suppose I got the odd ball... Anybody wanna help me figure this one out? Thanks for any help, its much needed!

Jay