From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Transmission jerks and crashes during gear changes.
| Identifier | Morton\M19\ img125 | |
| Date | 26th February 1931 | |
| - 2 - transmission jerks (and accompanying crash) invariably occur when this is attempted when the 1st. motion shaft is turning at any speed but the merest crawl, this appears to be unavoidable if the dogs are unaltered, and also emphasizes the necessity for a very quickly stopping clutch. (4) Changing down from top to 3rd. gear. by preselecting the gear and releasing the accelerator pedal. This can be accomplished easily and is accompanied by clicking of the dogs until synchronism is reached and by a slight transmission jerk if the engine speed is increasing rapidly when synchronism of the dogs is reached. (5) Transmission jerks when car is in motion. Unless the car is handled with thought as to what is happening inside the gearbox, terrific transmission jars and crashes can be produced, (in its present state the gear change requires more concentration than on standard box, otherwise apparently uncontrollable noises and crashes emanate from the transmission). These crashes can be produced as follows - (a) 3rd. gear, any time when engagement is attempted when the engine speed exceeds the car speed (1), by changing from 2nd. to third (using the clutch), it is not possible to feel the gear as on the normal change so that crashes occur readily (2), by changing from top to 3rd in traffic at slow speeds, either by preselection or by using clutch. When attempting to preselect under these conditions the load on the top gear dogs can be so slight that the dogs are disengaged by movement of the gear lever and without the driver being aware of it, the gear can be in neutral; if the throttle governer lever happens to be set to run the engine at a fairly fast speed (faster than the equivalent 3rd. gear road speed) crashing occurs immediately attempt is made to move the gearbox into 3rd. gear. The same effect is manifest if the clutch is used. (b) top gear, any time when engagement is attempted when the car speed exceeds the relative engine speed. This crashing however is not so frequently met with as 3rd. gear crashing which is always occurring unless one is very careful to remember what to do when changing gear particularly at slow speeds. On one occasion we thought we had caused crashing in 3rd. gear whilst trying to engage top gear when the engine speed was considerably in excess of the road speed, the impression was that the sliding dogs bounced off the top gear dog sufficiently far to come into contact with the third gear dog. However we have not been able to prove definitely what happened or to reproduce it again, a very big crash certainly did occur. | ||