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A couple months back I decided that I wanted to regear to 4.56 as well as add an ARB locker. I came across a complete front and rear nitro gear setup along with an ARB locker that another member was selling so I jumped on it. I had never set up gears before, but I figured how hard can it be? Well, it turned out to actually be fairly difficult to get right. There was also very little information available on setting up the 8" IFS clamshell, so I figured I would share what I learned in the hopes that it will make it that much easier on anyone else wishing to do this themselves. This is by no means a complete tutorial or guide, just a collection of pictures and information from my installation.

First up, tools! I ended up buying as well as making a number of tools to accomplish this installation. I am kind of anal, so many of the specialized tools could likely be substituted or improvised.

In terms of precision tools, I used the following:
  • Accurate beam or dial style inlb torque wrench with a range of 0-30 inlbs at least
  • Micrometer
  • Dial Indicator with magnetic base and long extension arm
  • 100 ftlb and 250+ftlb torque wrenches
  • Feeler gauges



As far as heavy tools and fixtures:

  • Heavy bearing splitter
  • 2 jaw puller
  • 12T Press
  • Press blocks to get bearings in and out
  • Brass drift



I wanted to take my time in setting this all up, which meant I needed to get another housing that I could just swap when done, minimizing downtime. The bare Toyota housing complicated things since there were no existing shims to use a starting point for the various preloads, pattern and backlash. More on that later though.

I started off by mounting the ring gear and pressing the bearings onto the ARB housing. The ring gear and ARB carrier housing mounting surfaces were first lightly stoned to ensure that there were no dings or irregularities that would prevent the ring gear from sitting flat. The ring gear was heated to about 200 degrees in the oven to help it go on the carrier. It was a very tight fit. BE SURE THAT THE BOLT HOLES ARE LINED UP BEFORE YOU ATTEMPT TO DRIVE THE RING GEAR DOWN. Seems obvious but I nearly missed that myself. You will not be able to rotate the ring gear once it is seated. Also, it is important to not use the bolts to draw the ring gear down as that will likely distort the flange.

A little red loctite and 70 ftlbs or so of torque in a star pattern and you are done. You will not be able to hold the ring gear and carrier by hand to torque the bolts, so either pop it in the press and apply moderate pressure to the carrier to hold it, or use wood blocks in a vice to grab the ring gear during torquing.




Next up I installed the carrier bearings. I actually used setup bearings initially, which are just new bearings with the ID and OD increased and reduced so that they can be mounted and unmounted by hand. Since I had a bare housing with no shims, I needed to do many iterations on the shims. That process would have been very difficult if the bearings had to be pressed in and out constantly. Below is a shot of the actual bearings being pressed on:



Now that the carrier is complete, it is time to move on to the housing. I used a solid pinion spacer vs. a crush sleeve, so rather than remove the oil retainer ring as the spacer instructions called for, I decided to bore it out to maintain the same clearance as the crush sleeve. I figured that Toyota put it there for a reason.






Next up was drilling and tapping the airline bulkhead hole. I decided to make a fixture for this so that the fitting would be straight, true and tapped properly:




Once the housings were finished, I gave them a good wash with brake cleaner and moved on to installing the bearing shells. The pinion bearing cups do not have shims behind them, so they can go right in. Again, I used setup bearings initially, but here are shots of the real bearings going in. It is CRITICAL that the front pinion bearing cup be perfectly concentric when it is pressed into the housing. I tried to do this by tapping initially and it was clear that it was not going to happen. I fabricated a tool to align the cup as well as press it into the bore:






The rear cup can be tapped into place. I used the same tool to put it in nice and straight:



Next up its time to press in the carrier bearing cups. These have shims behind them that are responsible for setting bearing preload as well as backlash. Since I had a new housing, I needed to establish the total shim thickness to achieve the correct bearing preload. After a number of iterations that number turned out to be 0.100, split between the shallow and deep carrier halves. This value is the total amount needed to preload the carrier bearings to an approximate 6inlbs starting torque as measured at the pinion. The end float or gap between the clamshell halves to achieve this preload was around 0.008". I initially started with 0.0895" on the deep side and 0.0105" on the shallow side under the ARB seal housing. Here is a shot of the bearing being pressed in. The deep side was the same:




For the pinion, I started with 0.078" of shim since it was in the middle of the shims available from Toyota. Shim pack gets pressed in behind the front bearing:





Next, the pinion is assembled into the carrier and the flange tightened until approximately 10 inlbs pinion preload is measured:




Now the carrier can be assembled:


 

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Discussion Starter #2


Once assembled, the backlash can be inspected. This is accomplished with a dial indicator, magnetic base and long extension arm:





The backlash with these shims was tight at 0.004". I added 0.0025 of shim to the deep side and subtracted the same from the shallow side. This

put the backlash right at 0.006". At this point we can run a pattern:



Pinion is too deep. I subtracted 0.010 off the pinion shim, reset the backlash to 0.006 and ran this pattern, which is too shallow:



I then split the difference and after another iteration or two ended up with a 0.074" pinion shim, and this pattern, which is acceptable:




I used my drill press (unplugged) to apply resistance to the ARB carrier, by cutting a slot to engage the spider gear pin in an appropriate sized

socket. I then held the chuck and turned the pinion flange to make the paint patterns.



At this point I was ready to swap out the setup bearings for the real deal as shown in previous steps. After the swap, I ended up with 0.019" of

shim on the shallow side under the ARB seal housing, 0.081" of shim on the deep side and 0.074" of shim under the pinion bearing. This gave me

0.007" backlash and the following pattern:





At this point everything looked good. The pattern was acceptable, backlash was 0.007" which is well in spec for the Nitro Gear range of 0.006"-

0.009". Pinion preload (including seal) was tight but in spec at 13 inlbs, and total carrier preload tight but in spec at 20 inlbs. This was with

a torque on the pinion nut of 200 ftlbs. I wanted it to be higher, but I wasn't going to take everything apart again and with the solid spacer I

figured I will be fine. I staked the nut really well and applied loctite. The solid pinion spacer is in my opinion very difficult to set up. Even

0.0005" in shim makes a real difference on the pinion preload. I would go with a crush sleeve if I was to do it again.

For final assembly it was time to install the ARB air line bulkhead fitting:




And finally, apply FIPG to shallow carrier half and torque the bolts to 37 ftlbs in a star pattern. I used blue loctite on the bolts as well.




And finally, the deep side CV joint seal in pressed in:



Obviously there were many steps, busted knuckles and curse words uttered that were not included in this write up, but overall this is the

procedure that I followed. I will fine tune this in the coming weeks, as well as provide feedback on how everything is holding up. I wanted to

get it written up while everything is fresh.

:cheers:
 

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Very nice write up thanks!
 

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Great write up! Your patterns look real good too. Good advice using a solid spacer as crushing a new sleeve is very hard to do. When I installed my 4:56's and ARB I couldn't find a solid spacer so I used a new crush sleeve. For those that are going to attempt this gear change and have a new crush sleeve you can save yourself a lot of grief by pre crushing the sleeve in a press to get the sleeve close before installing it. Another tip, don't waste money on expensive synthetic oil to break in the front differential. I used regular 70/90 gear oil and found a nice fire road to gently break in the gears. Make sure you do this because if there are problems you want to find them quickly and close to home; not out on a lonely trail.

Good job! :cheers:
 

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Great write up can`t wait to hear about the results. :)
 

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Thanks guys!

Good advice on the inexpensive gear oil for break in. I will probably do it a couple of times in the first 1000 miles or so, then switch to synthetic. I still need to do the rear re-grear, but I am hoping that is going to be significantly easier. We will see though..
 

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I have a question if your anyone can answer. I have a 2008 Fj manual. So full time 4x4. Can I use a part time front differential and just swap over the axle extension? I looking at buying an extra set of diffs for spares. Also my front diff needs a rebuild soon as it is noisey on deceleration
 

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I have a question if your anyone can answer. I have a 2008 Fj manual. So full time 4x4. Can I use a part time front differential and just swap over the axle extension? I looking at buying an extra set of diffs for spares. Also my front diff needs a rebuild soon as it is noisey on deceleration
The manual trans and automatic trans vehicles have different gear ratios in the diffs. So no.
 
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