Bogie drive two speed diffs

I remember doing a used truck appraisal on an ex logging truck brought to Brisbane from the Sydney branch of Collins & Davey back in 88/9.
It was a C500 Kenworth with 2 speed Eaton Bogies, which I thought were rare at the time, seen plenty of singles, overhauled the diffs of quite a few Accos with lazies and 2 speed gear munchers, even dropped one on me foot, but i never thought there was a 3 speed!

The C500 had a 15 speed and either a 3 or 4 speed joey, (memory not that grate any more) how many ratios was that then?
Even i couldn't get em all drivin it, and i was known for puttin it in every hole.

I remember that Beddy of Horton Bidwells too Mike
Hell that was a long time ago

Malfunction

The type of bogie 2 speed diffs you mention were mostly 44DT Eatons. Which were fairly common in Transtars (for example) in the late 60's but also were still used for heavy work into the 1980's (and after - I think something similar is still avail today).

All due to the avail (then) of lower HP engines to what we know today. Usually - either 2 speed diffs or a joey box - were common - but your monster with a 15 spd RR + Joey + 2 spd Diffs wasnt very common.

I seem to recall Rockwell also having a 44,000lb 2 speed avail for a while too. But the Eaton was the most common type I saw.

Quite often - they were fitted without 2 speed change motors - and were simply locked in low range. Once taken off heavy worrk - the lock plate was turned upside down - a big screw driver thru the hole to change the dog clutch into high - and they became a highway truck.

Back to the ones used as '3 speeds' - this was usually matched with a 5 speed gear box. Not RR's or anything with Joey boxes - and the ones I vaguly recall were only 30,000/34,000lb light duty diffs.

While we know it happened - it was (I think) unusual for the 44DT's to be used in a 3 spd mode - and even the 2 speed change was not an 'on the run' change.

Like - stop - engage both diffs in low range and engange the power divider only after moving off and making sure (as best as one could) that both diffs had changed down. Other wise - there was a 'big bang' and an exploded power divider housing.

Them were the days!!

Oldfulla

I have a hendrickson setup bogie drive Eaton air change 2 speed 38DT diffs with diff lock that I plan to put under one of my old trucks when fixed,

but the only setup that was the same as the thread asked "to split the diffs separately so as to gain 3 different diff ratios", was at the Menangle Steam Preservation rally a few years ago. It was a 6 wheeler Acco about 1970 model and it would only driive 1 diff at a time with different ratios in the front and the back. the owner was describing it to me but I didn't see under it or look at the stick to see how it changed.
In theory it could have diff lock in one of those 3 ratios if the ratio was the same on both diffs, then not use it on the ratio that was different on each diff, but having these things engage at the wrong time would be upsetting to owner, driver and truck.