For all models. Here's a modern guide with some explanations, but please also refer to your Instruction/Owner's Manual too. This page still under construction...
TRANSMISSIONS, ROLLERS, IDLERS, FINAL DRIVES, and MAINSPRINGS
Mark my words — the most damaging thing you can do to rollers and idlers is use grease instead of oil — and it's a very common mistake!
For all of the above parts, the specified oil is a 90wt or 80/90wt API-designated GL1 gear oil.
GL1 means that it is benign to brass/brass components — in this case, that means your bushings and brake band linings are safe.
An alternative, in the transmission only, would be SAE 50w. non-detergent engine oil.
Here's a list of known gear oil products: Warren 90W, NAPA 90wt (not available in Canada), Shell Dentax 80w90 (what I use), Esso Marvelube 80w90, Castrol sell a straight 90wt GL1 — some of the above are available in 20lt.[5gals] & and 60lt.[15gals] sizes (see your local dealer for availability).
Note: there is ONE and only one grease that will work for idlers and rollers — JD Cornhead Grease.