[Mgs] Overdrive Noise/Shifting Problem

[Max Heim]

You seem to be describing a separate "reverse lockout" and "3-4 lockout"
switch. I don't believe this to be the case.

The two switches (on either side of the transmission) are the OD "lockout"
switch, and the reverse lamp switch.

The OD lockout switch cuts the OD circuit if the lever is not in the 3rd or
4th gear position (or just 4th gear on late cars).

The reverse lamp switch completes the reverse lamp circuit when the
transmission is in reverse (naturally).

These happen to be the identical model of switch, just in different
locations.

There is no "reverse lockout" switch, as such.

BTW, these switches used to be mislabeled in the Moss catalog exploded view
-- I don't know if they still are.

--

Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the primer red one with chrome wires


on 1/29/08 11:43 AM, Dodd, Kelvin at doddk at mossmotors.com wrote:

> Mark:
> 
> It is easy to check the reverse lock out switch. With the ignition on,
> actuate the OD switch.
> 
> Check for power at the OD solenoid lead under the transmission. Have
> someone put the gearshift in reverse and make sure that there is no
> power to the solenoid when the shif lever is wobbled around in the
> reverse detent.
> 
> While you are there, check the 3-4 lockout switch too.
> 
> It would be a good idea to pull the coil feed wire, just to make sure
> there is no way the motor can start while you are under the car
> checking.
> 
> Unfortunately this problem sounds more like a slipping planetary clutch
> though.
> 
> 
> 
> Kelvin Dodd
> 
> 
>> -----Original Message-----
>> From: mgs-bounces+doddk=mossmotors.com at autox.team.net
>> [mailto:mgs-bounces+doddk=mossmotors.com at autox.team.net] On
>> Behalf Of mark.jones at exxonmobil.com
>> Sent: Tuesday, January 29, 2008 11:37 AM
>> To: mgs at autox.team.net
>> Subject: Re: [Mgs] Overdrive Noise/Shifting Problem
>> 
>> I have the exact same thing happen to my car.  The loud whine
>> in reverse is due to the reverse overdrive lock out
>> switch/circuit not working and allowing the overdrive to be
>> "engaged" while in reverse.  You really should check the
>> circuit and check the lockout switch, probably the lockout
>> switch needs replacing.  Unfortunately it is on top of the
>> tranny and very hard to get to with the tranny in the car,
>> although not impossible.  If the overdrive continues to
>> operate while in reverse you may do damage to the overdrive clutch.
>> 
>> Mark
>> 73 MGB GT