Geordielad:
AEC introduced the Leyland Pneumo-Cyclic gearbox into their Mandators in 1969 as an option along with the 10 speed constant mesh splitter box (simply a 5 speed box with the 6th overdrive replaced by an air operated split on each main gear). The semi-auto box also had ten ratios with a splitter on each main ratio and was the same box as fitted to the Leyland Two Pedal Beaver. These boxes gave the same top speed as the normal 6 speed boxes but enabled more flexibility on climbs etc. These boxes were also used on the V8 Mandators but because of problems the semi-auto box was discontinued and withdrawn in 1971. AEC also produced their own 10 speed range change box and this was offered in replacement of the auto box in Mandators, not that many had been sold with that box originally. Again though by 1974 the AEC range change box was replaced by a bought in Fuller Roadranger range change box which was more cost effective. As for the Mammoth Major Eight I donât believe the semi-auto box came as an option, as in 1971 two boxes were introduced both being 10 speed constant mesh splitter and range change gearboxes. Possibly the auto box in the video was one from a Mandator and not the original driveline. The semi-auto boxes werenât as much a success in lorries as in buses (being the same box), the demands in road haulage being much more excessive, quite often the gearbox fluid temperatures would become extremely hot and damage would occur. Franky.
Cheers Franky, youâre never too old to learn.
One question: wouldnât gearbox fluid temps also get excessively hot in stop-start/ short/ slow urban work (i.e. bus routes)?
ParkRoyal 2100 wrote;
Cheers Franky, youâre never too old to learn.
One question: wouldnât gearbox fluid temps also get excessively hot in stop-start/ short/ slow urban work (i.e. bus routes)?
It didnât seem so although those on here that know more on buses may answer that, I do know Fire Appliances with the Allison auto boxes had a rad with a fan mounted on it which cut in at the required temp to cool the oil passing through. This worked well even when the vehicle was stood at an incident with the main water pump operating and the engine revs on high. However Iâm unsure but donât believe AEC or Leyland had this sort of cooling system fitted which would have helped. Franky.
Geordielad:
ParkRoyal 2100 wrote;
Cheers Franky, youâre never too old to learn.
One question: wouldnât gearbox fluid temps also get excessively hot in stop-start/ short/ slow urban work (i.e. bus routes)?
It didnât seem so although those on here that know more on buses may answer that, I do know Fire Appliances with the Allison auto boxes had a rad with a fan mounted on it which cut in at the required temp to cool the oil passing through. This worked well even when the vehicle was stood at an incident with the main water pump operating and the engine revs on high. However Iâm unsure but donât believe AEC or Leyland had this sort of cooling system fitted which would have helped. Franky.
I can only speak for Dennis buses here but they have a variety of temp switches that bring on the fan connected to the rad. Those fitted to the coach chassis (Dennis Javelin) came on at 89 deg whilst the buses (Dart SLFâs) were higher, originally set at 101 deg on the Euro 2 engined bus and 103 deg on the Euro 3 one. The temp switch has 3 terminals, two wires controlling the fan motor and the third terminal that took a wire to the fuel pump. This would switch off the pump if the temp went too high.
Geordielad:
ParkRoyal 2100 wrote;
Cheers Franky, youâre never too old to learn.
One question: wouldnât gearbox fluid temps also get excessively hot in stop-start/ short/ slow urban work (i.e. bus routes)?
It didnât seem so although those on here that know more on buses may answer that, I do know Fire Appliances with the Allison auto boxes had a rad with a fan mounted on it which cut in at the required temp to cool the oil passing through. This worked well even when the vehicle was stood at an incident with the main water pump operating and the engine revs on high. However Iâm unsure but donât believe AEC or Leyland had this sort of cooling system fitted which would have helped. Franky.
Good point: all the Isuzu (15T gross) rigids in our depot with Allison 6-spd auto boxes have an entire cooling system of their own.
ParkRoyal2100:
Good point: all the Isuzu (15T gross) rigids in our depot with Allison 6-spd auto boxes have an entire cooling system of their own.
Not talking about wagons, but a much loved car I owned in the UK was a Granada auto. When I got it I had a lot of trouble with the gearbox. Eventually it was discovered that the pipe with the fluid in the box was fed forward to pass through the radiator and back again. Apparently a previous owner, possibly because he thought it was leaking, had by-passed the rad altogether, which meant the fluid just got hotter and hotter till it decided enough was enough.
Thanks to essexpete, Buzzer, Punchy Dan, robthedog, Dennis Javelin and lurpak for the photos also ParkRoyal2100 for the links
Oily
All credit to SCP for the photos.
