5LM60, HM290, Getrag HELP
 

I've just recently purchased a 1989 GMC Sierra K2500 LB to replace my 1988 K1500 SB that started losing gears one by one. 2 months later, the tranny in the newer truck lost reverse. I can't afford to buy a 3rd truck so I have to repair it myself. Well, like most guys with these transmissions, I went thru hell trying to identify exactly which tranny I have. I'm 99% sure I have the 5LM60. My problem is that I've got the tranny almost fully taken apart, but I can't seem to remove the gear clusters out of the case and I can't find any info on it online to help me disassemble it. The diagrams for "Getrag 290" or "HM290" show slightly different internals so I'm stuck. Can someone please help me figure out how to pull the main shaft from the rear half of the case so i can replace the shattered syncro on the 5th gear/reverse rail? If someone could post photos of a few pages from a factory manual or similar, that would be awesome! Let me know if you need more info from me. Thank you in advance.