ARB air locker install - shim question

[UKTJ]

As part of my regear I am installing an ARB Air Locker and have a question on shim stacks, any guidance much appreciated.

When I pulled my old carrier I romved the bearings and measured the shims so I had a starting point when I installed the new locker and gears. The shims in the old set up measured 58 thousandths on the ring gear side and 38 thousandths on the non ring gear side. I understand as part of the ARB set up I need to use the ARB master shims included with the lockers, however, I have just opened one of the master shims included with the locker and it measures 97 thousandths. Is the master shim in addition to the shim stacks I should use?

In addition, to the master shim I have 8 shims in the ARB pack, two x 0.031, one x 0.013, one x 0.12, two x 0.006 and two x 0.004. With these shims I can make close to the 0.058" or 0.038" shim stacks. But only if I do not count the thickness of the master shims.

 

[hosejockey61]

You need to start from scratch or you will drive yourself crazy. ARB carrier bearings are a different thickness than the stock bearings. On the seal housing side, the ARB master shim goes between the seal housing and the bearing race. On the other side, it goes to the outside of the shim stack.

If your axle didn't have any thick master OEM shims, then you will have to make up the difference with what you have. That makes it a tougher (but doable) job. The difficult part is, you can only add so many shims between the seal housing and bearing race. If you add too many, the airhole will fall outside of the rubber O ring and the locker will not operate properly. That means if you need more shims than what can fit properly between the seal housing and ARB master shim, you'll have to put them to the outside of the seal housing between the seal housing and diff housing. This is where a case spreader can really help. You can still get it in without one, it just makes it tougher to do so.

What I do to start in this case, is I add shims to both sides to figure out what me preload needs are first. I don't care about backlash or anything else until I know the locker is hard to get in and hard to get out. I will add more shims to the right side though to ensure the gears aren't forced into each other (meaning I want way too much backlash rather than none or negative so they don't bind). This can be any number of shims and will not match what you took out. That number doesn't matter anymore. Once your locker is hard to get in and out, yet you can do it, then you know what your overall shim stack will be. Now is the time to start moving shims from right to left in order to tighten up your backlash to spec.

ARB's are tough to install if you've never done it before. This video is queued up....

 

[UKTJ]

Thank you for your help.

You need to start from scratch or you will drive yourself crazy. ARB carrier bearings are a different thickness than the stock bearings. On the seal housing side, the ARB master shim goes between the seal housing and the bearing race. On the other side, it goes to the outside of the shim stack.

If your axle didn't have any thick master OEM shims, then you will have to make up the difference with what you have. That makes it a tougher (but doable) job.

How thick would a master OEM shim be? I had a shim on each side that is 0.030", is that thick enough to count as a master shim?

The difficult part is, you can only add so many shims between the seal housing and bearing race. If you add too many, the airhole will fall outside of the rubber O ring and the locker will not operate properly. That means if you need more shims than what can fit properly between the seal housing and ARB master shim, you'll have to put them to the outside of the seal housing between the seal housing and diff housing. This is where a case spreader can really help. You can still get it in without one, it just makes it tougher to do so.

I have bought a case spreader, so hopefully that will help. I am very much in "all the gear, no idea" territory, as you can no doubt tell!

What I do to start in this case, is I add shims to both sides to figure out what me preload needs are first. I don't care about backlash or anything else until I know the locker is hard to get in and hard to get out. I will add more shims to the right side though to ensure the gears aren't forced into each other (meaning I want way too much backlash rather than none or negative so they don't bind). This can be any number of shims and will not match what you took out. That number doesn't matter anymore. Once your locker is hard to get in and out, yet you can do it, then you know what your overall shim stack will be. Now is the time to start moving shims from right to left in order to tighten up your backlash to spec.

OK, I guess lack of experience is the tough thing here, not knowing how hard it needs to be to get the locker in and out. In some ways having a case spreader makes me feel that is even more difficult as the case spreader helps get the carrier in.

ARB's are tough to install if you've never done it before. This video is queued up....

I think this is the definitive 'how to' for a Dana 30 ARB install, trust me I have watched it at least a dozen times. Yet still, when it comes to doing it myself I am still left with questions.

Many thanks again for the time you have taken to give such a helpful answer. It is very much appreciated.

 

[hosejockey61]

How thick would a master OEM shim be? I had a shim on each side that is 0.030", is that thick enough to count as a master shim?

They can vary in size. I have stacks of them of all different sizes. For high production in the factory, they don't mix and match shims like we do, they just grab one of the right thickness and go from there. Usually master shims are around 100 thou or greater. They can be slightly less. I wouldn't classify a .030 as a master shim. It is thick enough though that it can go outside of the seal housing if needed. When building shims stacks, keep in mind that you want to sandwich the thinner shims between thicker shims to keep them in place and keep them from bending.

I have bought a case spreader, so hopefully that will help. I am very much in "all the gear, no idea" territory, as you can no doubt tell!

OK, I guess lack of experience is the tough thing here, not knowing how hard it needs to be to get the locker in and out. In some ways having a case spreader makes me feel that is even more difficult as the case spreader helps get the carrier in.

Having a case spreader will certainly help if it's a good one. Trying to determine spreading it to .015 thou (MAX) takes time and effort. You have to place your dial indicator in a way that will show that. I prefer to do it by hand because I like to "feel" what is going on. You might start by trying to do it by hand to ensure you have enough shims for good preload and then use the spreader from there. By doing it by hand, you won't overspread the case like you can with a spreader. Once you have determined the overall shim stack, just adjust until backlash is in spec. You can use the spreader at that point just to make it wide enough to drop the locker in with a little bit of snugness. You don't even have to measure how far you are opening it. Just adjust a little at a time until the locker starts to go in and then seat it with a deadblow hammer.

As far as knowing whether you have enough preload or not is relatively simple. Keep adding shims until the locker can not be put in or taken out by hand. There is no magic number or tool that will measure it. If it comes out really easy (even if not by hand), then add some shims until it is what I would call firm to go in and out. If you add too many shims, it is REALLY hard to go in or out. Don't force it. Take a couple thou out and try again. You will feel the difference and see what I'm talking about.

 

[UKTJ]

Having a case spreader will certainly help if it's a good one. Trying to determine spreading it to .015 thou (MAX) takes time and effort. You have to place your dial indicator in a way that will show that. I prefer to do it by hand because I like to "feel" what is going on. You might start by trying to do it by hand to ensure you have enough shims for good preload and then use the spreader from there. By doing it by hand, you won't overspread the case like you can with a spreader. Once you have determined the overall shim stack, just adjust until backlash is in spec. You can use the spreader at that point just to make it wide enough to drop the locker in with a little bit of snugness. You don't even have to measure how far you are opening it. Just adjust a little at a time until the locker starts to go in and then seat it with a deadblow hammer.

As far as knowing whether you have enough preload or not is relatively simple. Keep adding shims until the locker can not be put in or taken out by hand. There is no magic number or tool that will measure it. If it comes out really easy (even if not by hand), then add some shims until it is what I would call firm to go in and out. If you add too many shims, it is REALLY hard to go in or out. Don't force it. Take a couple thou out and try again. You will feel the difference and see what I'm talking about.

Any thoughts on a sensible starting point for total of shims on both sides? The two master shims are 0.097" each so that gets me to 0.194" without any other shims, but if anyone has a suggestion for typical amount in addition to that as a start point it woud be appreciated.

 

[hosejockey61]

Any thoughts on a sensible starting point for total of shims on both sides? The two master shims are 0.097" each so that gets me to 0.194" without any other shims, but if anyone has a suggestion for typical amount in addition to that as a start point it woud be appreciated.

There's no magic number. Just start adding shims until it starts to get snug.

 

[LJGreg]

I used the “two screwdrivers” approach mentioned in this write up. It got me within a few thousand right from the start.

http://www.billavista.com/tech/Articles/Gear_Setup_Bible/index.html