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Discussion Starter #1 (Edited)
This is a guide designed to take the mystery out of rear differential upgrades for the FJC. Never forget the date, 11-19-2016 is when I broke the ring and pinion out of my '07's 8" rear diff. If you've had that happen you'll never forget the sound and you'll never wheel the same afterwards. It will always be in the back of your mind as if you are driving on glass until you upgrade. Adding weight and larger tires increases the stresses on the rear end and increases the likelihood of it breaking. One bad hop is sometimes all it takes. With some of our FJ's getting older the gaps between the teeth of the gears will start increasing as things wear out which means the diffs will get weaker over time. More and more are breaking their ring and pinions so I thought it would be a good time to introduce this thread.

Let me preface this guide with saying that before I broke the rear end in mine, I literally had no knowledge about any of these options or even what a Dana 60 was. (for shame....) If you are like me at that point, this guide will be a perfect place to start considering options. It will be up to you to choose based on your particular needs. I'm not going to say one is "the best" because there isn't one. They all have trade-offs. I will try to explain it as simply as possible. If anyone has suggestions or thinks changes should be made feel free to contact me and I will add them. I'm far from an expert on this stuff!! I've just researched quite a bit the past few months and thought it would be beneficial to create a thread to save people time. You can continue to fill in the knowledge gaps through YouTube or Google.

Definitions:
It will behoove you to know these basic terms in order to follow the rest of this thread: (there will be a test at the end) ;)

Third member: Basically the ring and pinion (R&P) gearsets. This term is most commonly used when the gears are combined together in a carrier like what can be found only in Ford 9" or Toyota diffs. Be glad Toyota chose this design as it makes replacing gears very easy and quick! This type of diff allows a professional to set the ring and pinion spacing and ship to you ready-to-go as a single bolt-in unit. It makes it a DIY deal (couple hours if heaven forbid you get good at it), and can even be done out on the trail if you have a replacement on-hand. Also loosely called center section or pumpkin.

Regular: In contrast to the drop out third member type, the other type of differential I'll just call regular because I honestly don't know what they are called if they even have a name. :lol: These include the Dana's and feature a large cover at the rear which usually needs to be removed in order to service the oil and for sure to remove the gears if they break. The gears in this type are not able to be removed as a single unit! This means in order to replace the gears someone with knowledge and tools required to set ring and pinion depth must be on-site. This means if you break out in the middle of nowhere you are at the mercy of the shop you find to set the gears back up. The other school of thought is that the Dana 60 is such a strong unit the likelihood of breakage is minimal. If you are unsure about tackling this I found an excellent video to further explain.

Axle Shaft: The shafts that transmit power from the differential to the wheels. Their diameter is directly related to their spline count. Stock FJC 8.0 and 8.2 is 30 spline. Chromoly (41xx steel) shafts can be an upgrade but Toyota shafts are considered very stout already. There are many other shaft materials out there with different load handling characteristics.

Housing: Obviously the exterior case that holds the gears and shafts together. Can be cast or fabricated with plates and needs to be strong to stop flex.

Semi Float (SF): Describing how the wheel hubs interact with the axle shafts. In this type, the weight of the vehicle rests on the shafts which introduces a constant, increased force on the shaft. Stock FJC is SF where the wheel bearings are pressed onto the axle shafts. All current available diff replacement options that retain OE wheel speed sensors (necessary for ABS, A-Trac etc...) are SF!

Full Float (FF): Commonly found on HD trucks etc. In the full float configuration the axle shaft does not support the weight of the vehicle. Only the hubs and bearings do. This means a FF axle shaft is always comparatively stronger than the same-sized SF axle shaft. As far as I know Front Range Offroad AKA Diamond Axle is currently the only manufacturer of a full float option for our late model Toyotas compatible with wheel speed sensors that retain ABS etc... Another huge benefit of FF is the ability to pull the axle shafts from the housing with the tires still on the ground. This makes the FF a popular choice for competition vehicles and serious crawlers. Another benefit is the FF bearings are not pressed onto the shaft! They are easily accessed from the outside of the housing which makes a wheel bearing change so easy compared to the usual semi float.

High Pinion (HP): Describing the orientation of the gears. Google some pics of this. A high-pinion axle positions the pinion above the centerline of the axle. This allows for more ground clearance from the rear driveshaft but is comparatively weaker (approx 20%) than a low pinion in the rear because the gears are essentially formed to run one direction and HP rear runs them on their weaker "coast" side. Due to the direction the driveshaft spins, a HP is actually stronger as a front differential than a LP.

Low Pinion (LP): A low-pinion axle positions the pinion below the centerline of the axle. This is the strongest for the rear diff and is how the factory Toyota diff is orientated, but offers less driveshaft ground clearance than a HP.


Why?
If you are reading this hopefully you didn't just break the ring and pinion in your FJC. If you did, you have a few choices depending on build and budget:

1) Upgrade now to a larger housing and gears. ($2k+)
2) Regear to a new ratio front and rear. (consider locking the front too)
3) Buy just the gears ($300) and use a couple hundred dollars in tools to set them up yourself. (wouldn't recommend)
4) Replace just the rear with the same ratio third member ready to bolt in from a place like ECGS. ($800)

The good news is even if you are only replacing the rear 3rd member with ECGS setup gears you are still getting an amazing 5 year warranty (35" tires and under) and new, freshly setup gears that are likely stronger than the 10 year old set you just broke. Review these threads on how to replace the rear third yourself (option 4): http://www.fjcruiserforums.com/forums/maintenance-tech/135359-diy-3rd-member-swap.html, Step by step removal and installation of e-locker 3rd member

The other set of people more likely to be reading this are those of you who are considering an upgrade to be preventative since you often wheel a far distance from home and need the strength.


"The List"
What you've all been reading for, here are some of the common options and companies, approximately and subjectively listed as strongest first. All retain factory brakes, wheel sensors, and possible of making a like-factory replacement diff for your FJ. There is no "one size fits all" IMO, by that I mean everyone's setup and needs are different. For example the 10.5 is a diff I would only consider running on 37" tires. Its more diff than most people need and will hang down low. The D60 I would want to be running at least 35" tires. And I will preface this by saying if you wheel with 33" tires you most likely will not break the stock diff in your FJC. Once you get into the 34-35" tire size range and start doing true rock crawling type wheeling then IMO breakage is almost inevitable on the stock 8.0 diff.

Tundra 10.5: Offered in both SF and FF from Diamond, this BA differential is reaching 14 bolt diff strength territory! Equipped with 36 spline axle shafts you're almost guaranteed to never break this under a street driven FJC. Housing hangs down 1/2" lower than the 9.5 but the pinion angle does not appear to be too bad. Will require a new driveshaft. Only gear options avail are 4.30 and 4.88. One of the most expensive options but strongest and heaviest. IMO not a great match for most FJC builds but very cool nonetheless. Just more diff than most people need.

ECGS D60 aka "FJ60": Using the same 9.75" ring gears as the Dana 60, this is a newer product developed by ECGS that actually comes in at an attractive price considering what all you get. Pre-assembled with 35 spline axle shafts. Least ground clearance out of the bunch and requires the driveshaft to be shortened. Tons of locker options. Read more about it here: http://www.fjcruiserforums.com/foru...tion-aids/653178-fj-cruiser-dana-60-ecgs.html Possibly the best strength for your buck I have seen.

Currie Ford 9": The F9 sees a lot of use in the desert race crowd due to strong design, drop out third (for quick ratio changes) and LP is fine for the desert as rock crawling type clearance isn't needed. Notoriously low driveshaft angle and requires the driveshaft to be shortened. Less ground clearance than stock housing but a little better than D60. Surprisingly not many selectable locker options exist for the F9, ARB air is pretty much it and the F9 ARB airlocker parts are basically the same size as Toyota 8" airlocker parts so not an increase in strength.

9.5" Diamond FF: Full float version of the 9.5 housing built by Diamond Axle (see SF below). Every LC ever sold in the U.S. has had a 9.5" rear end, but as you can imagine there were many changes and upgrades throughout the years to keep it relative and is even used today in the 380hp Toyota 200 series. The FF housing is a very new product and offers all the benefits of a FF setup. Since they are made with new FF chromoly shafts by RCV they can go 32 spline, use 100 series gears which offer more tooth contact, and also use larger bearings. Downside is the significant cost increase compared to SF. I would say this option is approx equivalent in strength to the Ford 9" listed above.

Currie RockJock 60: One of Currie's offering for the FJC is a HP D60 with a strong AR400 skid at the bottom of the pumpkin. Requires the driveshaft to be shortened and backing plates to be pressed out of your stock axle shafts which requires quite a bit of wrenching.

9.5" Diamond: The 9.5 uses Toyota gears found in some Land Cruisers and early model Tundras. Diamond fabricates the housings for these to be darn-near bolt-on for FJC's. Drop out style third member setup. Supposedly higher ground clearance than the factory FJC housings. Retains sway bar, factory driveshaft and axle shafts.

8.2": Used in 2010 and later FJC's and 4runners. Few people have broken these, I would like to receive feedback on those who have. It's the cheapest option at around $2k and a pretty easy swap.

8": Originally found in old Toyota mini-trucks, Toyota used the same for the 07-09 FJC, 2nd gen E-locker Tacoma, and 4th gen 4runner. IMO this diff is way too small to use in our heavier and higher powered trucks. Apparently Toyota did too because they upgraded the later models to the aforementioned 8.2. R&P's are the weak points on these. Don't think many people have snapped a shaft.


Hope you learned something! :bigthumb: To be updated and continued....
 

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Discussion Starter #2 (Edited)
Other considerations

Selectable Lockers:

Factory Toyota Electric: Only available for the 8.0 and 8.2. Takes a few seconds to engage as your tires must be rolling but that "negative" is offset by nearly 100% reliability. Push the button before you get to the obstacle.

ARB:The most popular aftermarket selectable locker. Requires an air compressor or CO2 tank to actuate. Not a problem for those who already have on-board air but increases the complexity of the system. Locks as soon as you flip the switch. Available for all of our differential options above.

Eaton/Harrop Electric:
The relatively new Harrop is identical to the Eaton, just sold in different regions for different vehicle applications. Available for the Dana's and Toyota axles.

Ox:
Available for the Dana's, they are made in the USA with air, manual, and electric locking mechanisms.

Yukon Zip Locker
Cheaper version of ARB air.

Installation:
Installation of some of these axles varies. Some are very nearly bolt-on while others require a little work. They can pretty much all be built more complete if you supply more $$ so you don't have to use any of your old parts. The options are endless. The Diamond 9.5 SF like what can be purchased from JustDiffs will only require you to pull the axle shafts out of the stock housing and then re-insert them into the Diamond housing which is quite easy, unless you want new wheel bearings. Then you have to do quite a bit of disassembly and use a shop press or get the company building it to complete it for you with new axle shafts and wheel bearings. The ECGS D60 is pretty much bolt-on since you get new beefy 35 spline axles ready to go with new bearings. The diff options from Currie will require some work unless you purchase $500 worth of backing plates and have them complete the diff before shipping.

Width: Now is the time to ask big picture questions while doing this upgrade. If you decide in the future to install front long travel, you can either run wheel spacers on the rear to compensate for the wider front, or order the axle to be wider. You won't be able to run the stock axle shafts like the Diamond SF allows you to do however. The benefit to running a wider axle will come into play if you ever want to go custom 3 or 4 link in the future. Having more tube length gives you more options for shock and bump stop placement and the rear needs to be wide when stuffing a tire to help with rubbing from shock hoops if you go that route too. The benefit of custom 3 link is to have additional suspension travel and you can probably hop further down the rabbit hole and tuck the gas tank up a few inches depending on if you have a body lift or not. But that's for another thread. ;)

Hopefully that gives you something to think about before spending your hard earned $$!
 

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could you include options for lockers?

I have the E locker in the FJ, does any of the option above allow to retain that? Is that for the front? (super noob)



Sent from my LG-H910 using Tapatalk
 

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Discussion Starter #5
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could you include options for lockers?

I have the E locker in the FJ, does any of the option above allow to retain that? Is that for the front? (super noob)

Sent from my LG-H910 using Tapatalk
FJC is locked in the rear. Yes I was planning to talk about that. Only the 8.2 allows you to retain a factory type e-locker. Another option is the Harrop e-locker (Identical to Eaton e-locker but for Toyota diffs) for the 9.5 LC. Of course they are all available with ARB air lockers but as ubiquitous as they are I still have some reservations on running those.

I think Diamond can do a fabricated 8" housing that retains the factory e-locker but its not much of an upgrade.
 

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@Iconic This is a fantastic, well-written contribution!!! :clap: It was your diff blow-up that triggered my getting serious about finding and installing the '13 8.2 last January, so once again your experience is serving as a positive change agent for others....you rock! :rocker:
 

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Looking forward to updates , good job, thanks for doing this.
 
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Nice write up, thanks for spending the time on this.

Pretty good video too. One of these days I'd like to try my hand at setting up gears. He missed checking his work with the setup paste or I skipped that part.

Will the pinion depth not change ever so slightly with pinion bearing pre-load? Or if you are affecting PD have you torqued the nut too much? Is that what the solid spacers and shims are for? So you can't over tighten the pinion nut while keeping the correct bearing pre-load.
Case spreaders?? I thought these were needed to insert the carrier and ring. I kinda wish he would have need to adjust the lash too so I had a visual.
How many times is it safe to press the pinion bearing off and on without trashing it? One of the comments mentioned emery cloth to make it easier to shim out the pinion without a press and bearing separatorr. Is that not advisable?
 

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Nice write up, thanks for spending the time on this.

Pretty good video too. One of these days I'd like to try my hand at setting up gears. He missed checking his work with the setup paste or I skipped that part.
No he doesn't, he just measures it.
 

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Discussion Starter #15
It would be quite useful if some people could measure the ground clearance on their diffs by first measuring from the approximate center of the axle tube to the ground, then from the lowest part of the center section to the ground, and subtracting the two. I can't believe there isn't really any measurements out there for this. I guess its because there are so many different options and makes that it varies. If we could come up with an FJC specific list of measurements it would be pretty awesome. I'll add it to one of the first posts. Let me know what you come up with.

Stock 8.0 I measured to be about 15.75 - 10.75 = 5" down from axle centerline.
 

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Will the pinion depth not change ever so slightly with pinion bearing pre-load? Or if you are affecting PD have you torqued the nut too much? Is that what the solid spacers and shims are for? So you can't over tighten the pinion nut while keeping the correct bearing pre-load.
Case spreaders?? I thought these were needed to insert the carrier and ring. I kinda wish he would have need to adjust the lash too so I had a visual.
How many times is it safe to press the pinion bearing off and on without trashing it? One of the comments mentioned emery cloth to make it easier to shim out the pinion without a press and bearing separatorr. Is that not advisable?


I'm actually in the process of setting up my rear diff for the first time because my pinion seal went out, so I'll share what I learned. It's actually pretty easy with the right tools. I'd be done already, but I just learned you won't get a good gear mesh pattern (with paint) on used gears. (I tore it apart and reassembled it probably 15 times already)

FJ pinion depth does not really change with pinion bearing preload, the depth is changed by shims between the pinion gear and rear pinion bearing, unless preload is zero or the pinion nut comes loose and allows the pinion to walk deeper into the ring gear

The FJ comes with a crush sleeve spacer between the two pinion bearings that sets the pinion bearing preload. It crushes as you torque the pinion nut. Over torqueing the pinion nut will crush the spacer too much and give you too much bearing preload and will burn up the bearings. If it's over torqued, you have to tear it all apart, replace the crush sleeve, and try again.

Solid pinion spacer replaces the crush sleeve and preload is adjusted with shims. You can still over torque a solid spacer, but you can just back the nut off and re-tighten (assuming you have the right shims installed). The main reason for going to a solid spacer, is durability and ease of service. Crush sleeves can crush farther if the diff takes a hard hit on the pinion, which will throw off the preload and lead to bearing failure

The main reason for solid spacers, is durability and ease of service. The factory crush sleeve can actually crush further if the diff takes a hard hit to the pinion. (Toyota put solid spacers in factory in some early 80s axles). You can also change a pinion seal without tearing apart the diff or replacing the spacer

FJ diff does not require a case spreader. The case bolts together and can be separated by a soft hammer after removing the bolts.

Backlash is easily adjusted by turning the adjusting nuts, though they do require a special spanner to tighten properly, (no shimming here, like on dana60)

Depending on what tools you're using to remove the pinion bearing, will determine how many times you can take it on/off before the bearing needs replaced. With the press/bearing separator method, I probably wouldn't take it off/on more than 3 times, but I could be overly cautious. Yukon gear makes a special tool that makes it real easy, but it's $400, or $100 to rent it from ECGS (knockoff sells for $230 on ebay). In my case, I used my old bearings as setup bearings and buffed the center out so they go on with a tap

I wouldn't use emery cloth on the pinion or bearing, except to clean up burs or pitting/corrosion, but if the bearing doesn't need pressed on or goes on too easy, it will wear out real fast, because the inner race will spin on the pinion and burn up, can also damage the pinion when the race spins.

If you're going to try it yourself, the special tools you'll need are:
- press (10ton min.)
- bearing separator/puller (or Yukon gear tool)
- spanner wrenches or sockets (for adjusting backlash, elocker has 2 different sizes, for the small and large carrier bearings)
- dial indicator
- seal puller
- bearing race installer
- "dial" or "beam" style inch pound torque wrench
- torque wrench that goes to 273 ft/lbs (for crush sleeve) or about 190ft/lbs (for solid spacer)
- 30mm socket
- fixture to hold the diff while working on it (I cut out a steel plate that bolts to the diff housing, and fits in my vise or bolts to my engine stand)


Hope this helps
 

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トヨタ Master
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What size tires (or more importantly, the actual inflated diameter) are used for the differential clearance measurements?
 

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Discussion Starter #18
What size tires (or more importantly, the actual inflated diameter) are used for the differential clearance measurements?
When measuring from the axle shaft centerline to the lowest part of the diff, it takes the tire size out of the equation.

In my case I measured from the centerline to the ground, then from the lowest part of the diff to the ground and subtracted the two to achieve the same measurement. Hope that makes sense.
 

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トヨタ Master
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When measuring from the axle shaft centerline to the lowest part of the diff, it takes the tire size out of the equation.

In my case I measured from the centerline to the ground, then from the lowest part of the diff to the ground and subtracted the two to achieve the same measurement. Hope that makes sense.
You're still measuring from something to the ground, be it the lowest part or axle centerline subtracting the lowest point. The axle centerline is still affected by the radius (half the diameter) of the tire. The taller the tire, the more you are raising that centerline. Are you picking up what I'm laying down? :browsmiley:
 
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