[TR] high engine rpm

[Michael Porter]

Joe Curry wrote:
> Mark,
> I am pretty sure that if you do not secure one wheel, one will spin backward
> relative to the other with an open diff.  Don't ask me to explain it but
> that is what I have noticed when I tried it.
>
> I am going to have the Red Mk1 off the ground this week to adjust the rear
> shocks and when I have it in the air, I am going to give it a try to see if
> I remember it correctly or if I am actually going crazy.
>
> I will report back to reveal if I am beaming with success or have egg on my
> face.
>
>
>   
Okay, I have just done what I should have done when this brouhaha 
began.  I went out into my generally unnavigable, overstuffed garage, 
dragged the GT6 diff out from under the bench (the one with the cracked 
rear mount), which I know to be a 3.27:1, and applied vise grips to the 
right-hand axle flange, rotated the pinion input until the right-hand 
flange was well-fixed and immobile. Took up the lash, made witness marks 
on input, left flange and case.  One rotation of the left flange made a 
little less than 1.7 turns of the input flange.

Now, releasing the right flange and allowing it to turn with the same 
resistance as the left flange, each flange turns at the rate determined 
by ring and pinion ratio, which makes sense given that the spider shaft 
rotates at the same rate as the carrier, so the spider gears are static 
relative to the rate of rotation of the side gears, if the resistance to 
torque on both sides is equal.

Sorry, Joe. A full floating diff makes twice the revs of a locked diff 
with one wheel fixed.  I made the same mistake-brainfart when I advised 
the original poster privately.  The simple fix, of course, is to jack up 
one side and count two revs of the wheel, or, jack up both sides and 
count one rev.

The reason for it becomes obvious when one figures in both rotation of 
the spiders and the rotation of the carrier/spider shaft assembly. With 
one side gear fixed, the free side gear is being turned by the spiders 
rotating around the fixed side gear and the spiders rotating with the 
spider shaft as the spider shaft rotates with the carrier, so the rate 
of rotation of the free side gear has to be double the rate of carrier 
rotation alone. Easy to visualize when one compares both wheels turning 
to one wheel turning. When both side gears are free to move, the spiders 
don't rotate--one tooth set on each side engages the side gear and the 
spiders, side gears, spider shaft and carrier move as one unit.  Lock up 
one side gear and the spider begins to rotate around the fixed side gear 
_and_ is turning with the spider shaft and carrier. 


Cheers.

-- 
Michael D. Porter
Roswell, NM

Never let anyone drive you crazy when you know it's within walking distance....