On Wednesday, May 05, 1999 9:10 PM, Pete & Aprille Chadwell
[SMTP:dynamic@transport.com] wrote:
>
> OK, now I'm noticing that in the Bentley manual on page 346 at the
bottom,
> item 29 reads as follows:
>
> "Carefully tighten the castellated nut checking the pinion bearing
> pre-load. Shim the bearing spacer as necessary to obtain a pinion torque
> of 15 to 18 lbf in when the castellated nut is tight to a torque loading
of
> 90 to 120 lbf in."
>
> Question 1.) How do I check the "pinion bearing pre-load?"
Pete :
The method to check the "pinion bearing pre-load" is mentioned in the item
you quote. The idea is that you gradually tighten the nut, and at each
stage you check how much force it takes to turn the pinion. When you get
to the nut's torque specification and it takes 15-18 in/lb to turn the
pinion, you've got the correct preload. If it takes less than 15-18, you
need to remove a shim. If it gets to 18 _before_ you've tightened the nut
to 120, you must stop and add a shim. Too much preload can immediately
damage the bearing, so you don't want to just throw it together and crank
it down.
I'm pretty sure the 90-120 figure for the pinion nut should be foot-pounds,
not inch-pounds.
> (or is this really critical? Should I just torque the nut to spec (INCH
> pounds, not FOOT pounds, thank you very much!) and forget about it?
IMO, if you're putting back the same pinion and shims you took out, the
preload is probably OK. However, since getting it badly wrong will ruin
the bearings (possibly more), I'd at least make a stab at checking it. You
can buy a 1/4" torque wrench from HF that will do, or even get a pretty
good guess by just hanging a 1/2" ratchet and socket on it. If you can
feel some resistance, but the ratchet handle will fall of it's own weight
from horizontal to vertical (while turning the nut), the pre-load is
reasonably close.
> Question 2.) Having learned my lesson with the pinion flange nut
> controversy, now I find I'm second-guessing the torque specs for the side
> flange nuts. Again, the Bentley manual shows 90 to 120 lbf.ft (notice
> that's FOOT pounds) However, page 339, (sec. 51.10.02) simply says:
>
> "Fit the plain washer and the nyloc nut to the shaft. Tighten the nut."
>
> Notice there's no torque spec given. Hmmm.
>
> NOW what do I do??
I'd use the torque spec you found. Judging by other similar things I've
worked on, it's pretty close. And, it's common practice in shop manuals to
not mention the torque in the procedure description.
>
> Pete "Quickly losing faith in the Bentley manual" Chadwell
> 1973 TR6
>
>
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