Neil -
There is a definite reason for the famous "Clunk" when the rear wheel drive
cars are put into Reverse. It is designed in. I'll try to condense this and
if you can't follow it all, let me know. When put into Reverse, an entire
different hydraulic circuitry is used and the line pressure will flow to a
different part of the Regulator Valve which causes the line pressure to
rise. This line pressure is directed to the Low / Reverse Servo and the
Front Clutch. The need for higher pressures is due to the design features of
each clutch assembly. Both clutches are applied by hydraulic force and the
Rear clutch utilizes a Bellville Spring, which multiplies this force. This
multiplied, higher force pushes against eight mechanical levers to assure a
firm application of the band without slippage. Rear Clutch pressure here
can rise to 270 psi - they deem necessary to prevent slippage. The other,
forward circuit design does not have this pressure range to control those
shift points. The front cluch, in this circuit does not require this higher
pressure because it is used only in the upshift to Drive, and since the car
is already under way, there is no likelihood that there will be any slippage
here. Chrysler tried to reduce this shock somewhat, but they didn't want to
revise the whole thing. If you look at a cross section of the Low / Reverse
Servo, you'll see the spring cushoning the piston travel as it applies the
band; This lever has the Low / Reverse Band adjustment on its' end. If you
loosen the adjustment to reduce the shock, the shock will become more harsh,
this adjustment is not recommended. There is one aid a Chrysler dealer
recommended to me, he said that they modified the circuit flow rate by
adding a small Cotter Pin into the hole for this circuit in the valve body.
What this did was to delay the pressure build-up , not eliminate it, but
build it up slowly, and they had many happy owners with no more complaints.
Later, I remember a Dodge truck that had a terrible chatter in reverse gear
while on an incline - I found out the the factory tried to modify the harsh
engagement and it was a failure. Several Service Bulletins are still
available on this subject, but I don't think they ever really eliminated it.
Bob Harris
From: "Neil Thorpe" <nt014b6628@xxxxxxxxxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
> I was thinking of changing the transmission oil
> and filter on my 82 imp, while doing this i will
> maybe adjust the bands especially the low
> reverse band due to the usual harsh
> engagement when selecting reverse.
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