Quote:
Originally Posted by Runnin'Rich
TLDR:
The potential easiest/cheapest way to make a part would be:
1) anneal (remove the hardening) the original RWD pinion
2) Shorten the pinion length by cutting off the original gear form to the same length as AWD pinion.
3) Cut a new gear form at a slightly increased angle to match AWD housing angle
4) Harden the pinion once again.
The unknowns that an expert could answer:
a) is the meshing depth of the RWD and the AWD gear sets the same? is the centreline of the rack and the centreline of the pinion the same offset for both the RWD & AWD housings. I've done some basic measurements and they appear to match, but would need to confirm.
b) can annealing allow a used pinion to be re-machined and then hardened for a second time?
c) What size gear hob do we need to cut the gear. Does it need to be custom made? The machine shop I spoke to thought is was metric 17 Module. Having measured the rack yesterday I calculated it to 1.7Module using a formula I found. Whichever is correct, they are both non-typical sizes that would potentially need a custom gear hob specially manufactured. Big $$$.
d) Is the change in gear cut angle a nominal size? As in the AWD is 18 degrees and the RWD is 15 degrees. The difference needs to be accurately measured.
e) How do you polish the fresh cut gear before hardening?
The M3 rack could be advantageous if the gear module is more normal and we could buy an off the shelf gear hob. Will definitely need to retrofit Servotronic when using such a fast ratio.
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I'm a metallurgist actually, so I can answer the heat treating questions. The answer is, "it depends"
. Really, the particular alloy and the current heat treatment are going to dictate whether you can anneal and re-harden the parts. My guess is that this is a fairly "normal" steel like a 1045 though, so I'd venture to guess that you'll be okay. With that said, one thing I'd be a little concerned about would be distortion. When you anneal a hardened part, you're taking it from martensite to austenite when its at temperature, and then back down to ferrite/pearlite at room temp. Martensite/austenite/ferrite/pearlite are all just different ways that the atoms can be arranged; temperature and temp changes alter the way that the atoms want to sit next to each other. So with all the atoms moving around, there are slight volume changes that can occur and with a non-uniform part the result can be distortion.
At the axle plant I worked at, we would do a rough turn, finish turn, heat treat, THEN grind the bearing diameters and thread the ends of the fixed joints. I suspect that some kind of finish grind might be required on your pinion gear and I'm not super familiar with the equipment that would be used to do that. We had specialized grinding wheels made for each family of part numbers but there's got to be an easier way to do it for small volume production.