G'day

It has been stated on the GMCnet that the 3.21 to 1 planetary gear final drive acts like a LSD so I performed an experiment
yesterday to see if that was correct.

I clamped the final drive mounting flange in a vise and installed the axle extension in the passenger side of the final drive.

I had a mate hold the drive flange on the driver side and I turned the axle extension on the passenger side.

There was virtually NO resistance to me turning the axle extension.

As far as I'm concerned this demonstrates that the 3.21 planetary gear final drive doe not act like a LSD.

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426

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Bob,

OK, I'm going to need your and other members of the GMCnet help to understand how that happens as I can't figger out for the life of
me why it would act like a LSD.

I sent Bdub a copy of the Final Drive Manual for the 1966 and 1967 Toronados; here's a link to that document;

http://www.bdub.net/manuals/1967_Toronado_3.21_Planetary_Final_Drive.pdf

It is a 5 mb PDF file. You will have to download that document to follow along with the figures as noted in the General Description
Fig. 3EC-1 of the unit which I've copied and pasted below.

The final drive assembly, mounted and splined directly to the automatic transmission, consists of a pinion drive gear, a ring gear
and a planetary gear train. The planetary gear train consists of a planet pinion carrier with three pair of planet pinions, a sun
gear and an Internal gear and performs the same function as the side gears and pinion gears in a conventional differential.

Torque from the final drive is transmitted to a right and left output shaft which connect to drive axles. The right output shaft is
splined to the sun gear while the left output shaft is splined to the planet pinion carrier. gear and the planetary gear set rotate
in the same direction and at the same speed. The planetary gears are not moving. When the left wheel starts to turn faster than the
right wheel, Fig. 3EC- 2, torque from the transmission is transmitted to the drive pinion, then to the ring gear which is bolted to
the case. The case contains an integral internal gear which drives the three outer pinions which are in mesh with and drive the
three inner pinions. The three inner pinions being in mesh with the sun gear attempt to turn the sun gear at the same speed as the
left wheel, but are prevented from doing so due to the friction between the right tire and the ground. This forces the planet
pinions to walk around the sun gear, allowing the left wheel to rotate faster than the right wheel.

When the right wheel starts to turn faster than the left wheel, Fig. 3EC- 3, torque from the transmission is transmitted to the
drive pinion, then to the ring gear, which is bolted to the case. The case contains an integral internal gear which drives the three
outer pinions which are in mesh with and drive the three inner pinions. The three inner pinions being in mesh with the sun gear turn
the sun gear at wheel speed. The planet pinion carrier is prevented from turning at right wheel speed, due to friction between the
left tire and the ground. With the left wheel turning slower than the right wheel the planet pinion carrier The three walks around
the internal gear.

Regards,
Rob M.

-----Original Message-----
From: Bob de Kruyff

Rob. I think the issue may be while the drive is under considerable torque--it may react differently under those conditions.
--
Bob

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