Tony Rhodes wrote:
>
> I have 2 transmissions apart and
> they BOTH have had layshaft failure by delamination of the hardened surface
> at the rear bearing near the 1st laygear.
>
> It would appear that the hardness of the surface or the depth of the hardening
> is not adequate for the force the needle rollers apply.
>
> I want to get my new layshaft hardened better (more?) (deeper?). Before
> I make a lot of phone calls, is this something most machine shops can do?
> If not, then whom?
>
> Also, for those of you with tranny experience, is my impression correct that
>this
> area is a high failure rate area? This and the top hat bushing?
FWIW, the layshaft on my GT6 was a total loss when I opened the box up.
I bought a replacement from Rimmer-- it was included in their
"reconditioning kit"-- but have decided not to use it.
Rimmer's replacement wasn't finished to quite as high a standard as the
original part, although it looked to be "good enough" and certainly fit
well.
The problem is that it's too soft. A layshaft ought to be "file
hard." In other words, when you stroke a file across the part, it ought
to skate along without digging in. My file bit right into Rimmer's
part.
I took the shaft to a local machinst who was recommended to me by a
colleague at work, who is timekeeper for one of the local Busch light
teams. The shop was unable to harden it, because they couldn't identify
the material used.
I ended up buying a properly hardened shaft from Quantum Mechanics
(Monroe, CT)
with whom I've dealt with before (and highly recommend).
For future refrence, Rimmer's faxed me their specs for the shaft. I
quote, without fully understanding:
material ... BS.970:part3:212A42
heat treat ... case harden 60-62 HRC, depth .75mm (pre-grinding)
finish grind ... 4-6u c.l.a (that's 'u' for 'micro')
tolerance (dia) ... 85 somethings
max runout OAL ... .0015in
If anyone can identify the US equivalent of that BS number, I'd
appreciate it!
--
Douglas Frank Compaq Computer Corp. Friendship, n.
ZKO 110 Spit Brook Rd. A ship big enough to carry two in
603-884-0501 Nashua, NH USA 03062 fair weather, but only one in
foul.
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