Cleaning the Differential 1923 Hudson

rhurst

When I "drained" the differential on my 1923 Super 6 the oil came out in globs. I know it is a 600 wt oil but I really want to clean it out before I refill.  I heard from a friend to use a light wt oil and hand turn the wheels an let it sit for a few days before draining.  He cautioned that using kerosene or diesel might clean parts of the gears that would loose their oil film.

Any suggestions?

Robert

Geoff

Diesel would be fine, as this leaves an oily residue, unlike kerosene. Personally I think 600 is too heavy.    250 would be more suitable.  

barrysweet52

I was thinking recently that I would be stripping the diff, giving it a good clean and checking clearances before doing the oil change. When was the last time it was done? The following may be of interest. I have discussed diffs with Geoff Clark and he has confirmed and provided some info for this article. Hopefully he will correct if there are any mistakes. 

There is a set of 3 felt seals on the axle in the centre of the diff to stop oil moving towards the outer end of the axle where the brakes are. Then 2 more felt seals for the same purpose. Finally, a felt seal in the big nut to control excess bearing grease – this is the big nut that screws in to give 5 to 10 thou clearance between the axles. Screw in both LH and RH nuts equally into diff housing.

The backlash between crown wheel and pinion is 6 to 8 thou clearance. The pinion bearing clearance is approx 5 thou. Clearances came from several Hudson books and seem to be a little generous compared to today’s standards. Clearances can be measured with a dial indicator. Good luck with this.

Welding a diff housing is possible using common mild steel rods or MIG.

The axle button can be welded with Hardcraft arc welding electrode and faced

I had to make a heavy-duty C spanner to undo the pinion cage from the pinion body.  Because my diff was nearly 100 years old and the lock bolt had been overtightened, I had to carefully drive a blunt chisel into the slot to slightly open the housing. This should not have been necessary. The cage is screwed in to get the correct pinion alignment with the crown wheel. I also had trouble removing the pinion driveshaft flange. Be careful not to distort this flange. A 2-leg puller and heat finally popped off the flange. A very similar process to removing brake drums.

I found a grease nipple on the pinion body for the pinion bearings – one has a taper bore. I don’t know why it has to be greased as the bearings run in the thick diff oil.

There is a grease nipple on top of the diff by the backing plate. I don’t know why as the best way to grease the bearing is to pack it 100% during an overhaul. Using this nipple to pump grease will do nothing except eventually getting grease past the felt seal and stopping brakes from going rusty ?

Last thing to do is find some steam cylinder oil 600W, or a modern equivalent, and fill up the diff.

rhurst

Thanks for all the info Barry. Differentials are a black art for sure.  I'll keep to just filling and draining. Hope I never have to get into it.

Robert