Spicer 20 spd

Hi John, I might be interested in your Spicer if it is still available. Could you do a measurement on it for me first tho? Can you measure from the bellhousing face to the gear lever? This is a critical factor for me as I have a chassis cross member to work around. Oh and what part of the country are you in? Thanks

Silver 892-1420 3b spicer,perfect combination.i had one with 4:11 diffs.mine had a switch on the bottom of the stick for lo/lo, then 5 in the normal position,all were splittable wich gave you your 20.similar to todays 18's, just with an extra stick position.but that crawler was very low,perfect for backing into docks.

Just on those 20 speed Spicers, popularity may have had something to do with that they (compared to Fuller R/R's) were hellaciously expensive to do up.
Worked for a tanker mob who had a Transtar with one behind a 525 Crummins set up for double work, also had a similar set up with the 525 but with an 18 speed R/R. The Transtar/Spicer did a transmission in, possibly because a lot of blokes didn't really know how to drive them, (not that I was any sort of expert!). I remember the workshop manager got a quote to do the Spicer up and after picking himself up off the floor, commented if it wouldn't have both been cheaper and more practicable to drop a Fuller 18 in. fair bit off dicking around, though. They may have even have traded it is as is, fair while ago now.
Have a feeling in the back of my mind that Rockwell also came out with something similar, albeit in a lighter version.
Dave

I like changing gears
Tell me about your 6 speed box. What is it? Is it an overdrive box? I am looking for something to go behind the Perkins 180T I have just put in my Bedford bus. I want to replace the 5 speed that was behind the old 6354. I need an overdrive to capitalise on the extra power I now have and bring the engine revs down a bit.
Thanks

I think this has been mentioned before but for your application for ease of fitting and price it would be hard to go past the very smooth 6 speed Turner overdrive box fitted to Commers and others. Will fit both Knocker and Perkins. Exactly the same as the 5 speed but just an extra bit bolted on to give you overdrive. Mounts, gear stick etc no change.

Lang

A Commer box will fit a Perk,IF (big if) it comes off a Perk.The same box off a knocker wont,unless you find the big ally one piece housing.I would assume your Bedford has a Turner 5sp,but on what kind of housing.Perkins housings can of course be bought new,but thats only the flywheel housing.You also need a bellhousing for the gearbox.All of the onepiece housings were made by truck makers.There are Inter onepiece (from the AS180.suits only Fuller 5A330 box ...rare),Dodge onepiece from the AT4/D5N, suits only NP540 box,and Commer onepiece..suits Commer 5/6 sp box.You can buy ,from Perkins,the round 2 piece housings ,in SAE 2 and SAE 3. Costly.....Next point ...is a Commer box a Turner?Not as I remember. Turners were licence built US Clarks.And not as good as the US built box ,by a long shot.Turner was bought by Dana/Spicer in the 70s and the Clarks discontinued,but as Volvo took over Clark,parts were available from VME Construction Equipt.

Kwakatriple,
I don't believe it is an overdrive box, the 7 speed I replaced it with it seems is a slight overdrive
6v92T is doing about 1900 at 100 kph if thats any good to you, don't know what the diff ratio is but could find out if interested, maybe someone on here would know what sort of diff ratios they ran in highway coaches in early eighties. (tourmasterwith rockwell gear)
One extra gear though makes a whole world of difference, totally different in driveability

Can tell what Denning ran,cause Ive replaced them...3.7 with Silver 6/92 T.....early 6/71 single axle 4.8 about the slowest from memory,with 5sp TC.Incidentally,all of the Turner boxes were available as overdrives,might be easier to rebuild your existing box with O/D gears ,seeing as Clark gears are the same.And could be available from the US.I have seen a few OD Turners over the years,from bedford SB5 buses,maybe.Secondhand OD boxes are highly likely to be knackered,cause the OD always failed first.Personally ,Id be looking at a higher axle ratio.If you want to save fuel,you must eliminate drive going thru multiple gears,ODs just slow engine revs ,dont save fuel.

John

I can not see what difference the gear ratio between the engine and the wheels is if it happens at the gearbox, a joey box, an overdrive or at the axle. To my simple mind the only thing that is ever in play is the relationship between the engine and wheels ie the final drive ratio.

Assuming the same engine sweet spot power/torque RPM for the speed you want a low speed diff requires a higher gear to achieve than a high speed diff. You mention having to go through extra gears, if it is bolt on unit maybe more wear etc but if it is just a bigger wheel on the cluster no extra gears? Taller tyres will give you the same result as higher ratio diff - final drive again.

Maybe I need a lesson in gearing but I have always found a two speed axle is just another gear the same as a remote overdrive/joey box. Without touching them you can use the gear stick to achieve about the same (gearing might not be to the tooth) result except at the top or bottom of the range where you run out of equivalents by another method. As I said, it matters not where the gear changes are in the system, final drive is the only measurement.

Can you put me straight.

Lang

Just had a look at my Commer parts book. The Perkins Turner box is exactly the same as the Knocker Turner box. Perkins uses SAE3 Bell Housing the TS-3 uses SAE2. The 6th gear overdrive off the TS-3 gearbox can be put on the 5 speed Perkins box. The overdrive box was available in UK for Perkins trucks according to the parts manual, don't know if this was offered in Australia.

My 1968 Perkins Commer has a 6 speed overdrive box.

Just found another Parts Manual and according to this every version of the Perkins Commer was offered with either 5 or 6 speed. Maybe my truck was 6 speed from new? If so there should be a few of these around.





Lang