Why is it that vehicles like Subaru need boots for their drive shafts.
My 4WD '91 Jeep doesn't and has no problems. My turn radius on my Jeep
is even better than that of my wife's Outback. What's the explanation?
Al
Al said:Why is it that vehicles like Subaru need boots for their drive shafts.
My 4WD '91 Jeep doesn't and has no problems. My turn radius on my Jeep
is even better than that of my wife's Outback. What's the explanation?
Why is it that vehicles like Subaru need boots for their drive shafts.
My 4WD '91 Jeep doesn't and has no problems. My turn radius on my Jeep
is even better than that of my wife's Outback. What's the explanation?
S said:Hi Al!
The Subaru half-shafts use an entirely different mechanism. The outer
end is a Bierfield (sp?) joint; uses steel balls closely fit into a
cup. The inner end (the CV; Constant Velocity) joint also uses steel
balls in a sliding spider. Both operate in a grease bath, and so
require a rubber boot to keep the lubricant in and the world out.
Your Jeep, on the other hand, uses conventional "U" joints; two U
shaped sections, joined by a cross shaped yoke with captive roller
bearings at the ends. Variations in the length of the drive shaft as
the suspension travels thru its stroke are accommodated by a sliding
spline arrangement on the connecting shaft. And yea, they probably do
operate thru a wider angle than the Bierfield; desirable in a vehicle
nominally intended for off-road use.
FWIW, the 4WD/AWD Subaru uses "U" joints on the drive shaft to the
rear differential.
Why the different technologies? Don't know, but I suspect it has to do
with long-term reliability. The Subaru half-shaft is basically
maintenance free unless (until) a boot fails. If modern Jeeps are
anything like the old Cherokee I used to have, you have to really keep
after the various "U" joints with a grease gun, or they get noisy and
fail. Sometimes they fail anyway, especially if you work them hard
off-road.
Jim Stewart said:A CV joint transmits torque smoother than a U-joint. The
U-joint alternately increases and decreases the output
shaft speed as the the input shaft turns at a constant
speed if it is flexed at an angle, which it almost always
is.
The CV joint, by design, does not alter the speed of the
input shaft.
S said:Hi Al!
The Subaru half-shafts use an entirely different mechanism. The outer
end is a Bierfield (sp?) joint; uses steel balls closely fit into a
cup. The inner end (the CV; Constant Velocity) joint also uses steel
balls in a sliding spider. Both operate in a grease bath, and so
require a rubber boot to keep the lubricant in and the world out.
Your Jeep, on the other hand, uses conventional "U" joints; two U
shaped sections, joined by a cross shaped yoke with captive roller
bearings at the ends. Variations in the length of the drive shaft as
the suspension travels thru its stroke are accommodated by a sliding
spline arrangement on the connecting shaft. And yea, they probably do
operate thru a wider angle than the Bierfield; desirable in a vehicle
nominally intended for off-road use.
FWIW, the 4WD/AWD Subaru uses "U" joints on the drive shaft to the
rear differential.
Why the different technologies? Don't know, but I suspect it has to do
with long-term reliability. The Subaru half-shaft is basically
maintenance free unless (until) a boot fails. If modern Jeeps are
anything like the old Cherokee I used to have, you have to really keep
after the various "U" joints with a grease gun, or they get noisy and
fail. Sometimes they fail anyway, especially if you work them hard
off-road.
ByeBye! S.
Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101
Al said:Why is it that vehicles like Subaru need boots for their drive shafts.
My 4WD '91 Jeep doesn't and has no problems. My turn radius on my Jeep
is even better than that of my wife's Outback. What's the explanation?
Al
bgd said:Excellent answers. I learned something..I wondered why tractor trailers
didn't have a jumbo version of cv joints.
The only driveline part I ever broke on a subaru was the u-joint . Broke to
the point of no return on the driveshaft, aftert being forced to listen to
the one error on one cap until it decided to fail- with no option to replace
quietly.
A tractor trailer has wheel bearings... A u-joint will break more than ten
times to one in chances, before the wheel bearings fail... food for
thought.All that turning and strain, unlike the relatively straight line job
as the driveshaft. Rather ridiculous to think u-joints are still mainstream,
with todays alloys and engineering. Maybe they'll go extinct with the 258
inline 6 and all the other monstrosities with no excuses anymore....
Frankly, I don't see the advantage of the Subaru version; I do read a
lot about failures of the booted linkage. Some say that it is needed due
nobody > said:You know that weird jerking of the steering wheel when you put in 4WD on
pavement? Subies don't do that. Those boots cover (and keep lubricated)
far more sophisticated constant-velocity joints on those driveshafts
under the Subie.
Turning radius is a function of wheelbase. Is your yeep a CJ/TJ/YJ? If
so, it's a hell of a lot shorter than the Outback.
I guess it depends on the Jeep model. Mine doesn't jerk!
Mine is the '91 Laredo, whatever that is in CJ/TJ/YJ.
Al
nobody > said:You know that weird jerking of the steering wheel when you put in 4WD on
pavement? Subies don't do that. Those boots cover (and keep lubricated)
far more sophisticated constant-velocity joints on those driveshafts
under the Subie.
Turning radius is a function of wheelbase. Is your yeep a CJ/TJ/YJ? If
so, it's a hell of a lot shorter than the Outback.
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