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front diff ARB air locker install

Jon Wildsmith

Super Moderator
Feb 24, 2010
Country Flag
A not very well documented account of my front ARB diff install adventure

It was going to take a while to sort out a new R&P and all the other parts I'd need so I decided to remove the diff and then put the truck back together enough to use. I didn't photo the dissasembly but to remove the diff you first need to remove the drive shafts each side, goes something like this - with the wheel off, undo a couple of clamp bolts that hold the ABS sensor wire and brake hose and remove the ABS sensor, take the caliper off and zip tie it out of the way with the ABS sensor, undo the two bolts that hold the steering arm on and zip tie it out of the way, take the cap off the end of the hub and remove the snap ring, remove the split pin and loosen the nut on the upper arm ball joint and split the joint, same for lower arm ball joint, remove ball joint nuts and pull the whole hub / swivel assembly off the end of the drive shaft and put to one side, grab end of drive shaft and pull, the plunge joint and CV should act like a slide hammer and pop the drive shaft out With the drive shafts and prop shaft removed the diff itself is just a few mounting bolts more to undo to get it off.

Where the drive shafts go into the back of the hubs now had a big hole so I grabbed a bit of delrin that was handy and turned a plug for each side:


Then I put the hubs back together minus drive shafts and diff, locked the centre diff and drove around in rear wheel drive while I sorted this mess out:



In that last photo you can see my pinion bearing capture plate. I had no plans to reuse any of the old bearings because they were full of swarf but I did want the spacer from behind the big pinion bearing as a starter for the new pinion.

After a long wait and some complications all the bits were in place. The front diff carrier is shimmed and there are a lot of shims and two of each are needed, a big box full in fact!


I cut a new mounting plate for my diff frame:


Turned a solid spacer for the pinion and shimed it with pinion shims for a pre-load of about 12in lbs


Got a good pattern first time out with the origional pinion shim:


Torqued everything up to spec and bench tested for operation and air leaks before putting it back on the truck. Access to the front diff once installed on the truck is pretty limited so it's a good idea to fit the air line before lifting the diff up into place because it looks like it would be a PITA to get at afterwards.

While the front drive shafts were off the truck for this I also service those by stripping, cleaning, regreasing and re-clipping them but no pics
Hi Jon,

Great posts on your various mods. I'm a regular at and was pointed to you for some questions I had on installing an ARB in the front diff of a 100VX. Maybe you can help out:

1) The ARB instructions mention using a diff carrier spreader to insert the center portion under the correct pre-load. The workshop manual doesn't mention this so its seems like the preload can be achieved without one. Is a spreader really needed?

2) I will need to make a frame to hold the third member while I work on it. Do you have the dimensions or diagram showing the location of the cover bolts so I can fabricate something before hand?

3) Any pointers or info thats not covered in the instructions would be most useful.

Thanks so much,

for 1), you won't need a spreader, maybe the instructions are generic and that's for another makers diffs?

for 2), I just have my plate with a cutout in it for which I just used the diff cover as a rough template to work from, so it wouldn't be very accurate to pass on measurements from. What sort of thing were you looking for, x/y coords or a trace? For the rear diff and 80 series diffs I just use 2 pieces of flat bar one each side of the diff with a couple of holes in, much less fancy but just as functional really :)

for 3), crack the ring gear bolts while the carrier is still in the housing, trying to do it with the carrier out on the bench can be a challenge! Likewise, give them their final torqe onto the ARB with the carrier back in the housing. I insert a bar to the carrier to wedge against the casing and stop the carrier turning. Some ARB's go easy because the drive pattern is good and you can leave the pinion alone. Some require removing the pinion to change the pinion depth shim and then it's quite a bit more work finding the right size for the perfect pattern. Getting the inner pinion bearing off the pinion needs some sort of SST like the plates pictured above and a press. You may also need to adjust the carrier shims but that's quite easy to do you just need the right size shims. It's best not to be working to a deadline so you can take your time and do it right.
Hi Paul, looks like you beat me to it. I was just about to post a link to this from the SA site.

Welcome. There is some real knowledge on here. And Jon is the Diff Doctor!

Thanks Jon,

Think I'll use two pieces of angle iron with holes in as a diff holder. Good tip on removing the crown bolts early on. Hopefully I can put together a set of shims to match the existing backlash without playing with the pinion. The instructions say that the ARB kit (RD131) comes with a variety of shims to fit the carrier for adjusting the backlash - is this correct. I plan on doing the install over a weekend and cant exactly pop into Toyota if I need spares so I have to be well prepared. Worst case is I bugger up a bearing removing it but its a chance I'll have to take.
Howzit Paul,

Welcome - glad to see you made it here :thumbup: Hope you come right with the ARB!

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Paul Carter-Brown said:
The instructions say that the ARB kit (RD131) comes with a variety of shims to fit the carrier for adjusting the backlash - is this correct.
There are shims in the kit and they should do the job ok. I haven't actually used them because I have a set of OEM shims.

You should be able to get the carrier bearings off without damaging them. Also, I keep a small bottle of diff oil handy and dribble a bit of oil onto bearings when I'm putting everything back together because even used ones can get a bit dry during handling and make everything feel tighter/rougher than it really is / harder to judge if everything is ok. Put a bit of oil on the surface the air fitting slides onto as well to help make sure the viton seals stay in their slots when you push it on.