I need a source or a list of tri-five rearend numbers so I can go look at one tomorrow and be able to decipher them. Please help!
Dont Know about numbers Tri fives Have different shaped tags that identify gear ratios. Posi units have a large P cast on the differental. You can Find more info on Tri Five .com OldWolf
Here's your tags. If it's all together I think the only numbers you'll find is the date code, something along the lines of 1 A 57, -- 1st day, January, 1957. I think there may be other more specific numbers on the ring gear. And hope for a 'P', for a posi! Well, there are other numbers, not sure how to decode those though. The top one is the date code I described above.
My rear came out of a 59 full size car, and has the very common 3:36 gears, with the tag still on the pumpkin. I believe the tags from that picture were used from 55 - 64, but I may be off on the dates. Unless the rear end had never been messed with I would guess the tags were lost or removed pretty often.
look for the P, and get good at counting turns of the pinion and axles.....most of these old cars have had the rearend swapped out a time or two already.