Dedman
Forum Member
- Joined
- Dec 3, 2012
- Messages
- 766
- Location
- Perth Western Australia
- Car Year
- 1999
- Car Model
- Forester
- Transmission
- 5MT
After having tested my KAAZ rear LSD on and off road for close to 20,000km I thought I would write a bit of a summary of my experiences with the diff for anyone thinking of buying them.
I will start by saying the below review is very harsh pointing out all of the issues/concerns I have with the diff. This is not because I believe it is a bad product, they are just issues that for the most part most reviews/discussing seem to not consider so I thought I would share my experience with others giving my opinion of the full picture. Despite the following issues this diff has significantly increased my vehicles off road ability with the right techniques and even knowing all off this I would still recommend it for off road Subarus and would buy it again.
My vehicle: Lifted 1999 SF, lift, custom winch bar, stock N/A EJ20, custom gearbox with front helical LSD, DCCD, 1.59:1 L-series low range, 4.44:1 diff ratio. I drive some of the harshest off road terrains achievable with a Subaru and often keep up with modified real 4wds (Lifted patrols on 35s). Have a look on my YouTube channel if you are interested in the terrain I drive, more recent videos are generally more extreme.
https://www.youtube.com/channel/UC_uIq1hkQuQUavV1ovSLQhw
I will start this critical review by saying that my rear KAAZ is setup to 100% lock configuration. It is a common misconception that this means it is 100% locked, thus pretty much a locked diff. What it actually means is that it is set up so that it will bind the left and right axles together as best it possibly can). Off-road this is great or at least heaps better than pretty much any other form of LSD however it is nowhere near as good as real locked diff.
Many people will claim that even with a wheel in the air a KAAZ diff will move you forwards almost like a locked diff however I have not found this to be the case. These diff are load dependant meaning that the higher the load on them the better they bind the axles together. What this means is that if you are powering hard (meaning the diff is binding well) before a wheel leaves the ground the diff will provide traction to the wheel on the ground quite well (basically as a locked diff would). However if you are stopped with a wheel in the air or are crawling along with low throttle when a wheel lifts the diff will slip and act largely as an open diff. The way to overcome this is to apply the hand brake with a moderate amount of force so that there is always load on both wheels which works very well however it wears the hand brake and means you need to rev more to overcome the extra load being applied by the hand brake which is a noticeable amount if this method is actually going to work. When the diff was new the preload in the clutch plates was very good meaning that this was less of an issue (but still and issue) however after 15,000km I can jack up a rear wheel and turn it by hand, it requires more force than an open diff but still doable. As far as I am aware the only way to get the stock preload back is to buy new clutch plates (as there is no adjustment in the diff) which would be an expensive operation to do every 10-15,000km. The other maintenance issue is that the OEM recommends diff oil be change every 3,000km which in itself is a pain.
Now for on road down sides. I correctly followed the OEM bed in instructions to the letter for the diff when it was purchased using the oil supplied with the diff. Others have said that after the diff beds in a bit that on road they are not too bad. I found that there was a small improvement compared to new however the I have always found that you notice the diff binding and releasing when making tight turns in 1st gear (at intersections or in parking lots etc). Given that it is such an aggressive LSD you would expect this as these are higher load situations with large left right speed differences on high tractive surfaces. When the diff is hot after a long drive I have found this binding becomes far more noticeable with the diff banging and popping but can be reduced somewhat with different types of oil (The KAAZ supplied oil was one of the worst for this). I don’t really mind any of this and on all other types of on road circumstances it is not really noticeable, with the exception of the car being a bit more tail happy in almost all circumstance. What I don’t like though is how harsh this on road binding is on your rear axles which will cause them to fatigue over time and then they will fail under high load situations off road, typically in the most incontinent locations. As a result I now carry a spare rear axle at all times as well as tools to replace it.
The final aspect of these diffs that I did not fully understand before buying them is just how violent the transition from unlocked to locked can be under the wrong circumstances. The case of a lifted wheel spinning violently then coming down onto the ground can be far more harsh on the drive train than with an open diff. I have broken 4 rear axles this way, 3 of the failures were as a result of fatigued axles being placed in high than usual load and the other a complete overload failure which I did not think was possible from a gutless ej20 even with the extra gearing from my custom drive train. The risk of this happening is virtually zero if you use the hand brake trick listed above as the diff will always be binding however still likely to happen. The below link is a video of my testing the effectiveness of applying the brakes to start moving again when wheels are lifted. Car was not moving, 1st low and engine at 3000rpm, brakes gradually applied until car started moving forwards. Once the load on the rear diff reached a high enough threshold the diff went from pretty much fully unlocked to fully locked in an instant meaning all of the kinetic energy from the drive train and the spinning wheel was transferred to the wheel on the ground (which had most of the weight of the vehicle on it) shattering the axle instantly…
[ame="https://www.youtube.com/watch?v=-wu81J8RLgM"]Subaru axle snapped in two places caught on camera - YouTube[/ame]
In conclusion, diff is great off road and despite its draw backs I would buy again. However if these CAPSLocker people end up releasing a rear locker for the Subaru I will be upgrading and would not consider the KAAZ diff even if it was a quarter of the price of the locker.
These are all my opinions and experiences and I would love to hear if others disagree or feel differently about this.
I will start by saying the below review is very harsh pointing out all of the issues/concerns I have with the diff. This is not because I believe it is a bad product, they are just issues that for the most part most reviews/discussing seem to not consider so I thought I would share my experience with others giving my opinion of the full picture. Despite the following issues this diff has significantly increased my vehicles off road ability with the right techniques and even knowing all off this I would still recommend it for off road Subarus and would buy it again.
My vehicle: Lifted 1999 SF, lift, custom winch bar, stock N/A EJ20, custom gearbox with front helical LSD, DCCD, 1.59:1 L-series low range, 4.44:1 diff ratio. I drive some of the harshest off road terrains achievable with a Subaru and often keep up with modified real 4wds (Lifted patrols on 35s). Have a look on my YouTube channel if you are interested in the terrain I drive, more recent videos are generally more extreme.
https://www.youtube.com/channel/UC_uIq1hkQuQUavV1ovSLQhw
I will start this critical review by saying that my rear KAAZ is setup to 100% lock configuration. It is a common misconception that this means it is 100% locked, thus pretty much a locked diff. What it actually means is that it is set up so that it will bind the left and right axles together as best it possibly can). Off-road this is great or at least heaps better than pretty much any other form of LSD however it is nowhere near as good as real locked diff.
Many people will claim that even with a wheel in the air a KAAZ diff will move you forwards almost like a locked diff however I have not found this to be the case. These diff are load dependant meaning that the higher the load on them the better they bind the axles together. What this means is that if you are powering hard (meaning the diff is binding well) before a wheel leaves the ground the diff will provide traction to the wheel on the ground quite well (basically as a locked diff would). However if you are stopped with a wheel in the air or are crawling along with low throttle when a wheel lifts the diff will slip and act largely as an open diff. The way to overcome this is to apply the hand brake with a moderate amount of force so that there is always load on both wheels which works very well however it wears the hand brake and means you need to rev more to overcome the extra load being applied by the hand brake which is a noticeable amount if this method is actually going to work. When the diff was new the preload in the clutch plates was very good meaning that this was less of an issue (but still and issue) however after 15,000km I can jack up a rear wheel and turn it by hand, it requires more force than an open diff but still doable. As far as I am aware the only way to get the stock preload back is to buy new clutch plates (as there is no adjustment in the diff) which would be an expensive operation to do every 10-15,000km. The other maintenance issue is that the OEM recommends diff oil be change every 3,000km which in itself is a pain.
Now for on road down sides. I correctly followed the OEM bed in instructions to the letter for the diff when it was purchased using the oil supplied with the diff. Others have said that after the diff beds in a bit that on road they are not too bad. I found that there was a small improvement compared to new however the I have always found that you notice the diff binding and releasing when making tight turns in 1st gear (at intersections or in parking lots etc). Given that it is such an aggressive LSD you would expect this as these are higher load situations with large left right speed differences on high tractive surfaces. When the diff is hot after a long drive I have found this binding becomes far more noticeable with the diff banging and popping but can be reduced somewhat with different types of oil (The KAAZ supplied oil was one of the worst for this). I don’t really mind any of this and on all other types of on road circumstances it is not really noticeable, with the exception of the car being a bit more tail happy in almost all circumstance. What I don’t like though is how harsh this on road binding is on your rear axles which will cause them to fatigue over time and then they will fail under high load situations off road, typically in the most incontinent locations. As a result I now carry a spare rear axle at all times as well as tools to replace it.
The final aspect of these diffs that I did not fully understand before buying them is just how violent the transition from unlocked to locked can be under the wrong circumstances. The case of a lifted wheel spinning violently then coming down onto the ground can be far more harsh on the drive train than with an open diff. I have broken 4 rear axles this way, 3 of the failures were as a result of fatigued axles being placed in high than usual load and the other a complete overload failure which I did not think was possible from a gutless ej20 even with the extra gearing from my custom drive train. The risk of this happening is virtually zero if you use the hand brake trick listed above as the diff will always be binding however still likely to happen. The below link is a video of my testing the effectiveness of applying the brakes to start moving again when wheels are lifted. Car was not moving, 1st low and engine at 3000rpm, brakes gradually applied until car started moving forwards. Once the load on the rear diff reached a high enough threshold the diff went from pretty much fully unlocked to fully locked in an instant meaning all of the kinetic energy from the drive train and the spinning wheel was transferred to the wheel on the ground (which had most of the weight of the vehicle on it) shattering the axle instantly…
[ame="https://www.youtube.com/watch?v=-wu81J8RLgM"]Subaru axle snapped in two places caught on camera - YouTube[/ame]
In conclusion, diff is great off road and despite its draw backs I would buy again. However if these CAPSLocker people end up releasing a rear locker for the Subaru I will be upgrading and would not consider the KAAZ diff even if it was a quarter of the price of the locker.
These are all my opinions and experiences and I would love to hear if others disagree or feel differently about this.
:iconwink: :lol:.
