Spicer 20 spd

Lang I think John K is referring to the early Turner boxes, not the full synchro.
These were a 5-speed constant mesh and were on our two strokes as well as the first release sloper Perkins with the old bullnose cab.
Later two strokes and V8 petrols scored the 6-speed overdrive synchro box as did the Perkins when they finally got the later cab, albeit with only single headlights.

Jeffo

Thanks for that. The Perkins I had from new in 65 only had a 5 speed/2 speed axle as were all the others I ever saw. That is why I presumed my current 68 Commer had been retrofitted with the 6 speed but it seems it was a flash spec with overdrive and power steering (I would have killed for that back in 65 backing the trailer into tight loading bays in narrow streets)

Yes the Perkins 120hp had single lights and no external stacks while the mighty 135hp Knocker had twin headlights and intake stacks. Always wondered why I passed them until I realised they all were punished with bogie trailers while the Perkins blokes had single axle.

Lang

Yes, 63-64-65 would have been around the first release of the Perkins Commers.
Rootes Group must have hated the Perkins.
She had the old cab, vacuum/hydraulic brakes, no power steer with the smallest diameter steering wheel I'd seen on a truck. Think only a N0 3 Eaton down the back instead of the N0 4. (which the two strokes had) Engine cranked over to squeeze it in but I reckon they went really well, for the day.
A different truck by the time she scored the new look cab and of course by then the two stroke's output had increased to a massive 135hp with 10 stud wheels, air/mechanical brakes and so on.
A 6354 turbo would have given that old TS3 a fright though.

I think the Perkins were a winner, despite the snide remarks of many. they were the backbone of the truck, agricultural and marine fleet in many countries. Very reliable, easy to work on, good fuel consumption, parts available everywhere. A number of manufacturers Ford, Bedford, IH etc had their own equivalent power engine but also offered the Perkins for customer demand.


My 1965 VAAWE Perkins had full air (Tractor spec). The modern cab was a very good looking vehicle, easy to enter, almost flat floor but more importantly you stuck the gearstick in reverse between the seats, dropped in a cushion (which my mum made specially) and you had a very comfortable 6' 6" bed.

I reckon a Commer/Perkins/Turner 6 speed would be a beaut smooth drop-in box in Kwakatriple's bus.

Lang

Thanks John K. I have been looking for a higher diff ratio but cant find one. The bus chassis is narrower than truck chassis so I am finding it impossible to find one that fits. Hence looking for an overdrive gearbox to increase the final drive ratio. I have a six speed commer box but it is longer than the old 5 speed and puts the gear lever right in the middle of a cross member and the engineering to move a cross member is too much for me. Moving the engine forwards is a possibility but also a massive project I would prefer not to pursue.

Thanks again John K. Have to say with so many gearboxes being mentioned I do get a bit confused. The issue I am grappling with is that I have a 5.3 : 1 diff running 10.00 x 20 tyres and with the direct top gear in my 5 speed this equates to around 2200 rpm for 90 kph. The Perkins 180T would be much happier at 1800 to 1900 rpm so I need to change my final ratio. As I said bus diffs seem impossible to find and the 6 speed overdrive Commer box I have got just wont fit easily...

John K, sorry about multiple replies but I am slowly picking out the points you make. My current housing is a backyard modified one to take the Turner (as you rightly suspected) gearbox.
You mention rebuilding the Turner as an overdrive box. Is that just a gear swap so that you finish up with a 5 speed overdrive or is it an additional housing on the back of the box. If it results in a 5 speed overdrive does that make the step from 4th to 5th too big? I actually passed up a 5 speed overdrive box a while back because I thought it would be undriveable without a 2 speed diff but maybe I should go back and see if it is still there?
And finally, you seem to have a good handle on this era stuff, did any buses have 2 speed diffs? And if so, I wonder whether anyone on here knows where there might be one and what the high ratio might be?
Thanks for your indulgence

Think my years are a bit wrong, probably 61- 62 would have been the first Perkins Commers. (in the old cab)
Dad bought a new two stroke and another operator bought a new Perkins, both in 62 if memory serves correctly.
Ours had the 100hp TS3 (timing gears instead of the chain) and the new look cab but still the old 5-speed constant mesh box.
His had that old cab and the 5-speed constant mesh box. She lasted until 66 when he bought a Ts3 which by now boasted 135hp, 6-speed synchro box, etc.
That went a couple of years before she scored a 6V53 transplant.
As for the gearing problem in the bus, think I'd be looking for a fast 2-speed diff. if there's cross members etc to shift.

Here are the Turner 5 and 6 speed. Same box casing size, same gear stick position but extended (only by 20mm) add-on overdrive on the back of the 6 speed.

Lang

Just looked at the figures for the easiest fix - change tyre sizes from 10.00 to 11.00. Waste of time as it only drops you from around 2200rpm to around 2100rpm. Pity.

Starting to look like keeping your box and a diff change as Jeffo and John K suggested might be the quickest and easiest solution.

Lang