1975 Atkinson restoration

The early Rockwells like that one have a pivoted fork engaging the lockout..........so the cylinder has to push back.....To me it looks like the lock has been immobilized,common on fleet trucks to stop drivers fiddling and wrecking tyres and diffs...........To engage the dog clutch teeth on the PD,air pressure would be let into the front chamber of the cylinder,where the breather is now.The units Ive seen with a spring had a diaphragm chamber ,and a spring to push back similar to a plain brake booster.....If you are in doubt,just take the unit off the gearcase,its easy to remove and replace.........you can clearly see inside to the clutching teeth....Just be sure the fork is properly engaged when you refit the unit.........probably a good idea to replace all the seals in the air cylinder,a leak on the rod will cause a air leak into the diff,and maybe moisture/sludge with the air.

JOHN.K. wrote: To me it looks like the lock has been immobilized,common on fleet trucks to stop drivers fiddling and wrecking tyres and diffs.........If you are in doubt,just take the unit off the gearcase,its easy to remove and replace.........

John, I tried the diff lock when I bought the truck (got it bogged) and the DIFF LOCK light comes on and it works, so it hasn't been immobilised. Also, I did pull it apart as a bought 4.11 diffs and I transferred it from my old diff, which is how I worked out how it seems to work. I guess when I get it all back together again I will know if there is a problem. Hopefully there isn't, but was just a bit interested in how this type works. Couldn't find anything on the internet. By the way, the new 4.11 diff had the type you mentioned with a brake type booster which pushes the fork to engage the lock.

On Facebook, might be good for some spares?

It needs air to engage it, the spring behind the diaphragm disengages it. (Diff Lock actuator). If you aren't sure, just undo the 4 bolts that hold it on, it'll come off easy. The fork will come off with the housing. Might pay to check the diaphragm, though if you put air into it and nothing leaks out I wouldn't get too worried about it. Sometimes it easier to get the through shaft back in the spline if you take it off too.

jeffo wrote: On Facebook, might be good for some spares?

I know that truck as I bought my first truck from MJ and Bob (Bob has since passed away) about 4 years ago (the Yellow MKII Atkinson with a sleeper).

I have been pretty lazy over the winter, just too cold in the shed and can't paint anyway. Over the weekend a neighbour with a forklift dropped the motor back in so I can get on and do a few more jobs. Need to get the gearbox back in and then I can measure up and get the tailshaft made.

Great stuff there
Can be hard to stay enthused if you cant feel your fingers


Paul

Well I got the gearbox back in and had the tailshaft shortened. Fitted the air tanks and some plumbing. Started fitting the air chambers to the wheels and can then make the new hoses up. The wheels have all been sand blasted and just off to prime them. Any one have any great ideas on how to manage wheels so I can top coat them. Too heavy to hang so looking for others ideas. Thinking I may have to paint the inside (covered by the tyre) first and then paint the outside after it has dried.

Well I got the wheels painted this weekend. Have only just noticed I have 9 that are 7.5" and 1 each of 7" and 8". I don't think anyone would notice an 8" rim on the front or inside rear, but I might get another 7.5" sandblasted.

The 8" ones are the rarer ones. Mack used to put 7.5" on the drive and 8" on the steer.
When I did my Diamond Reo up I kept looking at all the wreckers and managed to find 4 of the 8" ones which I put on the outside of the drive.