My guess is that when you brake it sends a signal (using the feed to the brake lights) to the gearbox to say "get ready to change gear but not until the brakes come off"; when you release the brakes the gearbox changes down to the appropriate gear (if you're still travelling at high speed there'll be no change). With a blown fuse, the gearbox doesn't get the signal, so changes down (to a lower gear) whilst you're still braking. Normally, with a working brake light, you don't notice the gear change because it coincides with you releasing the brakes. To test this hypothesis, try rolling to a stop (using an upwards incline or the handbrake to get a similar retardation to using the brakes) without using the foot brake.
How convincing does that sound?
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PUSHKIN wrote:I have a Vanden Plas 1300 Auto with no electronic trickery
Wow! That takes me back! The Automotive Products (AP) 4-speed automatic gearbox was a remarkable design from the mid-sixties for several reasons:
- four ratios (plus reverse) was unusual for smaller cars when most automatic gearboxes had only three. I seem to recall that four were thought necessary because the small torque converter couldn't be designed to generate enough torque multiplication to mask the differences between the ratios. Plus each gear could be manually selected as well as just leaving it in 'drive'.
- it incorporated sets of bevel gears in an arrangement similar to a rear-axle differential, rather than sun-planetary gears which were tied-up in a range of US patents for use in automatic gearboxes.
- the whole gearbox package fitted even into a (slightly enlarged) Mini850 sump casing, with the torque convertor inside the clutch housing.
- and what I still find astonishing is that it worked using the hot and filthy engine oil for the hydraulic operation of the internal brake bands & clutches as well as filling the torque convertor, rather than the highly-crafted ATF which has to be kept pristine in today's modern designs. (Though I understand the oil filtration was uprated, I wonder what the service life was for those AP gearboxes.)
For all it’s faults the car always brings a smile to your face and in case any of you guys feel tempted the ADO16 club is amazing
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