Re: RE: Differential Modification - Hey Bob (Tom)

From: Bob Tom (tigers@bserv.com)
Date: Mon Aug 21 2000 - 17:25:03 EDT


Here's some information that I've been able to gather but do not know
how accurate or up-to-date it is.

The Kelsey-Hayes rear wheel antilock brake system is used on Dodge
applications
as well as on other makes. On trucks with 4WD, the antilock system only works
in the two-wheel drive mode.

The control module that regulates the operation of the ABS solenoid valves is
separate from the control valve, and is located on the passenger side cowl
panel
under the dash on Dodge trucks,.

The control module receives a speed signal from a single vehicle speed sensor.
On Dodge applications, the speed sensor is in the differential and the sensor
ring is on the ring gear, the driven gear (the pinion is the drive gear).
This jives with information given in previous posts.

Since this type of sensor typically picks up signal from between the teeth,
I would say that, unless the ring gear has a different number of teeth from
the one that it's replacing (gear ratio of a ring and pinion set is the
number of teeth on the ring gear divided by the number of teeth on the pinion
gear, no software recalibration is needed. That might explain the 3.55 to
4.10
example sent by Bernd (?).

I have no idea what type of calculations is being used for a gear ratio change
or a tire size change. For tire size changes, I would imagine that it
involves,
in part, calculating the circumference of the tire (taller tires move the
vehicle farther per tire revolution than shorter tires). I do know that,
for the '97 which uses a speedo pinion gear in the tranny, the smallest one
that you can get is for the 215/75x15 tire, and that there is none listed for
a 4.10 gear ratio.

As I said in my previous post, I'll speak with the parts person that I deal
with and see if he can confirm this or not, and if he can add any additional
info.

Bob



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