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What do you do to restore overdrive on third gear?
On an "overdrive on 3rd gear" survey form Kent Brown from Australia indicated his Factory MGBGTV8 did not have overdrive on 3rd gear but added that as he was used to his MGB Mk1 with OD on both third and fourth gears, it would be great on the V8 too. He asked "what needs to be done to make OD available on 3rd gear please?" The answer is an "engine out" so you can open up the gearbox and change the gearbox selector plate. (Aug 10)

When the MGBGTV8 was launched in 1973 it was fitted with the gearbox selector plate 22B386 already in use in the MGB 1800 which was also in production at Abingdon at that time. The selector plate in the remote gearchange activates the plunger isolation switch 22B406. When that switch is engaged it cuts off the electrical power feed to the overdrive solenoid in any gear other than third or fourth for the earlier cars. The plunger isolation switch was necessary to prevent the overdrive being left engaged for the lower gears and most important, to ensure it was not engaged whilst in reverse gear as the unidirectional clutch in the
overdrive will not take kindly to being driven in the wrong direction!

In the months following the launch of the MGBGTV8, the Factory at Abingdon received many reports that V8s were appearing at MG dealers with a damaged overdrive usually requiring a replacement unit under

Gearbox selector plate 22B386, later replaced by 22B726, is item 12 in this diagram. Item 18 is the remote control shaft which transmits the gear lever movements to the selector plate when you select gear. (Diagram from page 108-C44 Parts Catalogue AKM0039)

warranty. The high torque from the V8 engine in third gear was identified as the cause, so a production modification was introduced removing the overdrive option from third gear so the V8 model then had overdrive only on top gear. That change point was from gearbox A 1404 when the gearbox selector plate was replaced by part number 22B726 and the plunger isolation switch by 22B727.

See detailed note and V8NOTE368
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