Running an auto at about 80kph (50mph) on unsealed roads. The gearbox seems to be changing to third, then bach to 4th all the time. If I run at about
85kph it seems to stay in 4th gear. Can the gearbox be 'fixed' to stay in 4th gear. (RR 300Tdi, ZF, standard wheels) Michael T, Aussie RR
Are you sure it's changing between 3rd and 4th, not 4th locked and unlocked? There's a hydraulically controlled clutch within the torque convertor that locks above a certain roadspeed - around 53mph! - to provide a direct drive for "economy" reasons. If it's hunting between 4th unlocked and locked and you wish to alter the roadspeed that this occurs at, then the answer is to remove the sump pan from the 'box, drop the hydromechanical control valve block assembly off and invert it to gain access to the 'convertor lock valve' and either soften the control spring to reduce lock-up speed or stiffen to increase. The effect of altering the spring pressure is purely trial and error to reach something you are happy with, but it doesn't need a lot of change, I'd imagine grinding 2mm off the free length would do what you require. Badger.
...and Badger spake unto the tribes of Usenet, saying...
I love these simple "plug 'n' play" solutions.
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