Joined
·
8,135 Posts
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....
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....
..but just in case it does, I'm subscribing. 
