Reconditioning the Rear Diff

After testing the play in the rear pinion flange decided to re-build the rear diff.

 

 

Photo above is before and photo below show diff removed from the vehicle. Basically jack vehicle up, remove rear wheels, remove nuts holding axles, pull axles out and then unbolt diff centre and remove.

 

 

I stripped down the BJ42 diff and the HJ75 diffs that I had to salvage components.

 

 

 The ring gear and carrier were exactly the same even the same markings.

This is the ring gear from the 75 series diff, lots of pitting and ruting. It was also slightly warped out of tolerance. The runnout for the ring gear must be less than 0.1mm and this gear was slightly out. I think the pitting was from excess water in the diff oil, the diff had signs of water in the oil - who knows for how long it operated like this.

 

The ring gear below from the older 40 series diff was in much better condition so I reused it and the carrier.

 

Below are the side gears from both diffs. 

 

  The side gears below are from the original 40 series diff - they are trashed - I think this kind of damage occurs when one wheel is spinning due to no LSD and it then grabs onto something and the shock load causes damage to the gears. This would be more pronounced the greater the play in the gears due to wear.

Next are the two pinion gears which as you can see from the pic are different, both will fit the outer housing but require different bearings. The gear on the right is from the 75 series and uses a crush sleeve whilst the one on the left uses shims to set the bearing preload. I went with the crush sleeve method because the gear was in better condition, additionally the shim method will maintain the preload longer but it is much more of a pain in the ass to set. you have to build the diff, test the preload and if not in spec disassemble and put a shim in and rebuild and test again - continuing the process until the preload is set.

Getting the bearing off the pinion gear was a pain in the proverbial. I had to buy another gear puller and use a pipe and timber braces to belt it off. Dont panic fans I didnt apply force to the spline or the threading at the top of the gear - I am not that silly - made that mistake on the axle bolts after belting them with a hammer.

 

Broke a gear puller trying to get this bearing off. Hammer and chisel did the job in the end. Lucky Toyota has thought of Garage Gorillas like me and placed notches in the carrier to allow for such surgical removal methods,

 

Bearing was totally destroyed during removal.

Using gearpuller to remove bearing. You can see the bearing on the right has aleady been "removed" well partly, with the inner race remaining. I had to use a hammer and chisel and gradually wedge the inner race off.

Here I am in my 3rd world garage with my Malaysia safety boots on (as my mate constantly points out to me)

Diff above assembled and on makeshift stand. Below I am testing the preload with a luggage scale and wrench. As I didnt want to fork out $230 for a small Torque wrench that would be used once in a blue moon I used the same method that I used on the front hubs. Thus to calculate the Torque I used the age old Torque = Force x Length, calculation.

 

Using a dial guage and stand to measure the backlash which was required to be within .15 and .20mm. To make adjustments to the backlash requires moving the notched dial (shown in the centre bottom of the photo below). Again this required a tool which I could not find so I fabricated one from a shifter by drilling holes in it and using bolts.