RE: Drive Train Roughness in 4wd -Reply

From: JT McBride (James.McBride@GDEsystems.COM)
Date: Mon Dec 09 1996 - 19:39:40 EST


Scott -
        Sorry, Dave and I had discussed this a bit more off-line. Dave
had mentioned that he'd bought a new pair of tires, and that one end
of the vehicle thus had tires that were partly worn, the other brand
new. There is therefore a difference in tire diameter, and a difference
in the shaft speed to the differential front and rear -- or there would
be, if the Dakota had a viscous coupling or some other way to allow
slip between front and rear. Since there is no such provision in the
driveline, the only option is to squirm the tires a bit - felt as
vibration very similar to wheel imbalance.

        I think Dave did say he felt this only on clear roads. Obviously
on icy or snowy roads there's much more likely to be road imperfections
that would mask any vehicle vibrations. Also of course, the slip needed
would occur between slippery surface and tire...

        I thought of another solution besides tire inflation. Breaking
up the matched front/rear pairs so a new tire is at opposite corners, or
on one side would allow the slip to occur in the diffs front and rear.
Then both front and rear prop shafts would be turning at the highest
speed - that of the smallest diameter tires. There would not be enough
differential speed to engage the Sure-Grip, so this would work. Might
keep the pumpkins a little warmer than usual, but not likely a problem.
The tire inflation fix would avoid any funny handling that this fix
might introduce, and is still the preferable solution, IMNSHO.

Jim
 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
"The real voyage of discovery consists not in seeking new landscapes,
but in having new eyes." -- Proust
 



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