OD alpiners.
The Laycock overdrive uses an overruning clutch to ensure that the
input shaft will spin at no less than 1/1 with respect to the output
shaft.
This means that the pump, spins ALL the time that the rear wheels are
spinning.
The OD will not go low on oil pressure unless the vehicle speed gets
too low.
The OD operates in third or fourth only because the electrics isolate
the solenoid to function only when the trans is in 3rd or 4th.
As far as the lurching is concerned, the same ocurrs on any
planetary gearbox as it downshifts without load. The engine
loads down the trans, and the reverse torque, and ratio reduction
causes the car to decelerate. The overruning clutch takes up
the majority of the load after the OD downshift, so even the faces
of the cone, dont see too much abuse.
However, using the clutch to prevent the lurch will not damage
the OD, so dont worry.
Whatever you think is right (clutch or no-clutch) is fine.
Somebody mentioned that failure to use the clutch to disengage the
OD can cause twisted tailshafts,
As far as twisted OD tailshafts are concerned, this is caused
by popping the clutch in first or second, as there is about 3 or 4 times
more torque on the shaft in these gears than from 4thOD to 3rdOD,
not including the additional torque from the flywheel inertia.
The Laycock OD should be able to handle continuous loads of
300 to 500 lb ft of torque at the tailshaft, so the 90 or 100 lb ft
it sees in top gear, or the -120 to 150 it sees on a 4thOD to 3rdOD
downshift, should be of little consequence.
Jarrid Gross
----------
From: Heuer, Paul
To: alpines(at)autox.team.net; Rootes2(at)aol.com
Subject: Re: Engaging overdrive
Date: Wednesday, April 30, 1997 4:06PM
Jon Arzt wrote:
<<snip>>
And by the way, I do not use the clutch for upshift, and find that I
seldom
need to downshift to 4th - usually I need to slow down more than that,
so I
use the clutch, and move out of the 3-4 gate to deactivate the OD.
<<snip>>
Jon,
Let's see if I understand this statement. The OD operates in third and
fourth gear, correct? Are you saying that by pressing the clutch, moving
the
gear lever out of fourth and over to the neutral position between first
and
second, that the overdrive will disengage, and stay disengaged when you
shift into third gear?
Can you explain why you feel it is OK risk loss of lubrication at this
time,
but not during engagement (when you don't use the clutch). Is it because
the
oil is only pumped around the overdrive while it is operational, or that
there is less stress on the OD during disengagement that when it is
engaged?
Please bear with me, I'm very new to all this. The variety of answers is
also very interesting; as always lots of ways to skin the same cat.
Thanks for taking the time to respond.
Cheers,
Paul.
------------------------------
This archive was generated by hypermail 2b30 : Tue Sep 05 2000 - 09:41:00 CDT