[Fot] Differential Pre-load

[Bob Kramer]

I think the main reason a specified amount of  preload is required is that
it sets it up so that the bearings roll under mild tension. To tight and
the components slide over each other.  Too loose and they cock in place.
Without rolling, bearings will soon fail the same way a lifter that doesn't
spin fails.

Bob Kramer


On Wed, Jan 29, 2020 at 8:15 AM fubog1 via Fot <fot at autox.team.net> wrote:

>
> Does someone know why that preload is necessary?
>
> Yes it's basically because things want to move around a lot & the pinion
> wants to stretch.with torque on/off loads.
> Over time as the bearings wear, the preload will be lost, and any further
> wear will cause the gears to be out of mesh and the pattern will be lost
> and then they'll wear.
> Glen
>
>
> -----Original Message-----
> From: van.mulders.marcel--- via Fot <fot at autox.team.net>
> To: Bill Tobin <william.tobin31 at verizon.net>
> Cc: fot <fot at autox.team.net>
> Sent: Wed, Jan 29, 2020 8:14 am
> Subject: Re: [Fot] Differential Pre-load
>
> Does someone know why that preload is necessary? When I check a
> differential before using it and I notice there is almost no preload at
> all, I tend to be lazy, assuming no preload means less friction loss.
> Marcel.
>
> ------------------------------
> *Van: *"fot" <fot at autox.team.net>
> *Aan: *"fot" <fot at autox.team.net>
> *Verzonden: *Woensdag 29 januari 2020 04:06:57
> *Onderwerp: *Re: [Fot] Differential Pre-load
>
> Hi Scott I think that's the torque required to turn the pinion. Put a
> socket to fit the pinion nut on a?? inch pound torque wrench; measure how
> much torque it takes to turn the pinion. Get it turning and read the torque
> wrench while turning it. 12 to 15 inch pounds sounds ok. With shims either
> add or remove shims to get the correct preload. Thicker to lessen and
> thinner to increase I think.
> With a collapsible spacer it's easier. Keep?? tightening the nut and
> measuring the preload until it's right. Small increments. If you over
> tighten you take it apart and start over with a new spacer. (Ask me how I
> know this!)
> Also a "clicker" torque wrench isn't the ticket for this. Use an older
> beam type.
> Hope this helps.
> Cheers Bill
> On 1/28/2020 4:34 PM, Scott Janzen via Fot wrote:
>
> I???m rebuilding my differential. ??The manual says the pinion bearings
> should be assembled with spacers to yield a??
> *12-16 lb/inch pre-load,* using a bar affixed to the input flange and a
> sliding weight. ??Of course there is a churchhill tool for that!
>
> Either I???m not grasping the concept, or 12 lbs *per* inch doesn???t
> seem right. ??I???m guessing this is supposed to be 12 inch-pounds,
> which I think means a one pound weight at the end of a 12??? lever. ??All
> testing is performed with the seal removed.
>
> Even if I am correct, I???ve got it set up with about a 1/2 lb pre-load
> right now, and that feels pretty stiff already.
>
> Anyone have any experience with this? ??This is a GT6 diff, but I???m
> guessing the instructions don???t vary much.
>
> Thanks,
> Scott
>
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