i am looking at a posi rear end. it is a TM code. the problem is that it will need rebuilt because it has sit with no oil in it for a long time. the inside is dry and has a little surface rust in it. i do not think anything is damaged but will need new barrings and all that. the other bigger problem is that someone cut off the brackets that attach the lower control arms and welded a leaf spring pad on it. the housing looks to not be pitted but has ben sandblasted primed and painted. the ring gear numbers are
12441 GM KD 325. i know that TM is a 3.42 but wondering if these numbers match for 3.42 i could not count the teeth at the time i looked at it and could not turn it to count the revolutions. he wants $475 for it. i think it is a little high but wondering what you all thought. also how hard will it be to have the correct mounting brackets welded back on. one other question is, what is the difference between the SH and the TM 3.42 rear end. i know that TM is for W-30 but other than that i am not sure.

 

Just a few thoughts here......first, if it's a posi in that "upper range" of numbers (i.e., 3.42 and up), $475 sounds like a pretty good price to me, even if it's just a core, so to speak (just an opinion!). Second, my book says that "TM" is exclusively for the W30. The W27 (aluminum rear axle carrier) uses code "SX" for the 3.42 posi rear end, and anything else "A" body uses "SH" for the 3.42 rear end. There should be a couple of numbers stamped into both the ring gear and the pinion gear near their respective part numbers that, if you divide one of the numbers into the other on the same gear, it will give you the gear ratio.

 

What year is it supposed to be?
Not quote following your numbers on the gear. 3.42 gears are 41 12, so that is probably just sloppy stamping of your 12441. The 325 *should* be the date code, but I can't make sense of that. But I've seen others that don't make sense either. That could conceivably be a Julian date code.
For 1970, I believe the SH was the standard rear with G80 Anti-Spin.
TM was the G88 Heavy Duty rear that included "heavy duty axle shafts" and I believe tapered roller axle bearings. Included with the G88 was Anti-Spin and a Heavy Duty radiator.
The TM rear was not exclusive to the W30, but was required with the W30.