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Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
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Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
Cusco RS Rear LSD 1.5 Way (R160) (Part Number: )
Cusco RS Rear LSD 1.5 Way (R160)
Subaru WRX 2002-2014
Read 5 Reviews | 16 Q&As
Part # LSD 183 L15
msrp: $1,400.00

Product will ship from manufacturer

Features & Product Details

Cusco is one of the pioneering companies based out of Japan that has invested countless hours of research, design, and engineering to develop quality suspension and performance products that will improve your driving experience. Some of the fasted cars around the world who compete in time attack, time trials, and other racing avenues will more than likely have a Cusco product on their car.

On this page, you are viewing the Cusco RS 1.5 Way Rear Limited Slip Differential. 

Featuring high tension chrome molybdenum steel housing and gears the Cusco LSD is up for the task of serious competition. With large oil windows for increased flow and Cusco's original groove cut technology for improved efficiency on the clutch plates, stability and longevity are promoted. The 1.5-way Type RS utilizes coil springs located between the pressure rings to develop initial torque and features full engagement during acceleration and partially under deceleration. The use of coil springs rather than cone plates helps promote faster, smoother engagement, along with higher durability. This LSD can be converted to a 2 way LSD as well.

The LSD is completely customizable with different clutch pack order and spring tension preset, allows them to be set up to an exact preference of the end user. This particular unit can also be changed into a 2 way by rotating the center spline to engage on acceleration and deceleration.


Brand: Cusco
Adjustable: Yes
LSD Function: 1.5 Way / 2 Way
Location: Rear
Mfgr. Warranty: No Warranty
Condition: New Product
Return Policy:

RallySport Guarantee - 30 Days

Items that are covered under the RallySport Guarantee offer a 30 day no questions asked return policy.

RallySport Guarantee items may be returned within 30 days of the original invoice date and must include all the original parts and contents for a refund.

The RallySport Guarantee does not apply to products that have been modified, damaged, misused or abused. All returns require an RMA (Return Merchandise Authorization) Number, and freight charges are strictly non-refundable. For more information regarding our freight refund policy, please refer to our return policy page found HERE.
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5 Reviews
5 out of 5 Stars
5 Stars
4 Stars
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1 Stars
Customer Photos and Videos
Cusco RS Rear LSD 1.5 Way (R160) ( Part Number: LSD 183 L15)
Cusco RS Rear LSD 1.5 Way (R160) ( Part Number: LSD 183 L15)
Cusco RS Rear LSD 1.5 Way (R160) ( Part Number: LSD 183 L15)
Cusco RS Rear LSD 1.5 Way (R160) ( Part Number: LSD 183 L15)
5 of 5 people found the following review helpful
One of my favorite upgrades 1 year ago
5out of 5stars

Most recent WRXs (GR onwards) have come with open rear diffs, which even at stock power levels allow the inside rear tire to spin when applying a lot of power in tight turns. You have the option of leaving traction control on and having it cut engine power or trying to drive around the tire spin. I figured when I bought this that the worst case scenario (provided I did the install right) would be that I wouldn't notice any difference with this part installed. That worry immediately vanished on my first drive with the diff. The diff (depending on the settings you use, to some degree) locks up tight when power is applied. I don't even bother turning traction control off most of the time anymore because it rarely detects slip now, even when driving the car hard. It helps the car rocket out of corners, and makes driving in snow a lot more fun as the car has a more tail-happy character. Snow donuts and oversteer were always disappointingly lacking in my WRX until I installed this diff - but not anymore. I actually bought an extra stock diff housing and diff from eBay to install this into to reduce the risk of being left with an undriveable car and to give me plenty of time to do the install right. Install went something like (omitting the obvious diff housing removal/install from the rear of the car): 1. Remove diff housing rear cover 2. Remove diff housing side plates (keep track of the shims and sideplates and don't get them mixed up) 3. Pull the original open diff 4. Stick the original diff in a vise and remove the ring gear 5. Press new bearings onto the Cusco diff 6. Press new axle seals onto the sideplates (not required, but you don't want to have to fix a leak once this is installed back in the car) 7. Setup the Cusco diff with your desired settings then bolt it together 8. Install the ring gear on the Cusco diff 9. Grind down the two small nubs inside the housing that prevent the Cusco diff from sliding into the housing then clean out the housing. 10. Install the Cusco diff into the housing with the sideplates and shims 11. Get out the dial indicator and prussian blue to measure backlash, preload, and pinion to ring gear engagement. Install & remove shims on the sideplates as needed. (lather, rinse, repeat until the measurements are within spec). This is the only part that requires much skill - just take your time. 12. Bolt up the housing rear cover and new gasket. Started the diff on Redline 75w-90 GL5 with friction modifier. Added even more Redline friction modifier to ease the break-in process. The diff was extremely stiff during break-in, nearly how I would imagine a welded diff to feel. After this it settled to a very nice state where it's only noticeable when you want the diff to be working. When I initially set up the Cusco diff, I installed all the coil springs for 100% preload. I didn't really understand this setting until driving it the first time. The preload is how much the diff locks without any accel or decel being applied. What I noticed with full preload was that the car was noticeably resistant to initial turn-in (I had always liked how eager the car was to turn-in). After the 1000 miles break-in, when it was time for the first fluid change I pulled the diff entirely and changed the preload to 1/3. This is actually less than Cusco recommends (minimum 1/2), but this is the least you can reasonably get away with with the design of the diff. I reinstalled the diff and the turn-in was back without any noticeable sacrifice to lock-up under power! My settings: 1.5way 80% lockup (4/5 clutches engaged) 1/3 preload (4/12 coil springs installed) These work pretty well for a daily driven / auto-x car.
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6 of 7 people found the following review helpful
LSD Cusco.  3 years ago
5out of 5stars

I bought this part after my stock differential decided that the spider gears were going to grind down to almost nothing. I ordered this part and had it next shipped to the transmission shop that my car was at. I have a 2009 Subaru WRX, which requires the shop to make two small alterations to the housing in order for the differential to fit in. It was nothing extensive. It took about two minutes for them to grind down the two dimples that where stopping it from going in. It did not compromise the integrity of the housing at all by doing this. After that it went right in and the shop finished putting everything back together. Rallysportdirects customer service was amazing when I ran into this issue and even contacted Cusco directly. I will continue to purchase parts from here. Always great products and a reasonable cost.
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2 of 2 people found the following review helpful
NVH 3 years ago
5out of 5stars

Had it professionally installed by a transmission shop for about, so I can't attest to the ease of installation, but there were no reported issues. Just finished the break-in and performed the first differential oil change, using Cusco LSD Oil (80W-140) both times. Noise is minimal after break-in, and only occurs when performing low speed turns (think parking lot speed). I don't daily my 03 WRX, but I certainly don't mind it, though I guess it could briefly startle a passenger or pedestrian. Overall, I'd say the harshness of this unit is over-stated, and probably mitigated by the use of Cusco LSD Oil. While I haven't flogged it too hard, just a little city driving and a short canyon romp, I can definitely tell there's a lot more grip coming from the rear. Throttle input will have much more effect on how the car turns after you install this unit, and it'll take a lot more throttle input to fully break traction; more torque than a Cobb Stage 2 kit like mine could provide. Haven't tested the locking torque under deceleration yet, but I'll give it a nice pull of the handbrake soon. Price is much cheaper than the Torsen Diffs on the market, which seems to be the only other game in town when it comes to Bugeye Rear LSDs. Though I haven't tested it out much, and I can't attest to how long it'll last, I'm pretty happy with my purchase.
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Wow what a difference in the way the car drives 4 years ago
5out of 5stars

I bought this to replace my broken stock diff. I initially broke it in with some Lucas Gear oil and friction modifier. The diff was loud and popped a bunch. I searched around and found others talking about how loud it is. After 500 miles I drained the fluid and replaced it with the Cusco LSD oil. Noise and popping is gone and the wife is a happy camper now. The car powers through corners much better now. If your going to buy this I defiantly recommend the Cusco LSD oil. 2003 WRX wagon 4EAT Stage 2
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6 of 6 people found the following review helpful
More grip=more speed. 6 years ago
5out of 5stars

This diff has definitely helped me with getting the power to the ground. My car has a tendency to lift the inside wheel during sharp corners. Rather than tune my suspension to compensate for this, I decided to add this diff to the rear of my 2002 WRX. The difference was absolutely astonishing. I was able to keep the balance of the car while completely eliminating any power loss due to having a wheel off the ground. I went with an 80% locking setup with 8 initial pressure springs and it seems perfect. Not too noisy after break in, and definitely not too aggressive for daily driving. The car hooks up much better coming out of corners and the rear end stays planted during high speed sweepers. I can apply power earlier, and no longer have to worry about pushing wide from getting on the throttle to soon. I broke the diff in using non synthetic 75/90, figure 8's in a parking lot at 5mph for 30 minutes. After I got sick from going in circles, I drove with the diff at a local autocross, drained the fluid and switched to a non synthetic 85/140. The diff is now quiet and seamless in its operation. Lifting mid corner, then reapplying the throttle gives the car the ability to rotate easily. Then getting back on the power firmly allows the car to remain at the desired angle through the rest of the turn. I would highly recommend this diff to anyone who wants to be able to make use of their AWD system to the fullest extent! However, one thing that should be noted is that many WRX differentials will need to have 2 small tabs ground or filed off inside the differential housing before the Cusco diff will drop in. Not a big deal, but just be prepared to have to do a bit of housing removal. Overall, 5 stars. I just wish that I had installed this diff sooner!
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  • Q: Front diff  TRJ2.5GT1 month ago

    Just wondering why you guys dont offer the Cusco front diff also. I know they make them I have seen them on other sites. Also they make center diff. Just wondering why you guys dont offer them.
    • 0 of 0 people found the following answer helpful

      A:  We do not carry them in stock at this time, however we can special order them if needed

      Devan M. @ RallySport Direct 1 month ago  
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  • Q: Stock settings from factory  Alexwrx053 months ago

    Which are the stock settings of lsd about % of block,100 ,80 or 60 ? I had also a quife torsen on front. Which would be the best settings for it 100 80 or 60. My use is street and sometimes mountain and track Many thanks
  • Q: 2010 Subaru Forester XT   fozroamer1 year ago

    Curious if this would work for my Subaru Forester XT R160 4.44 ratio. I would like to use this LSD for more offroad use what adjustment setting would you guys recommend to have this LSD benefit slower offroad speeds?
    • 0 of 0 people found the following answer helpful

      A:  This would most likely work just fine. Unfortunately, we only have this confirmed for the 02-14 WRX's. If you are using this for offroading, technically speaking, you would want this to engage right away.

      Tyler G.
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  • Q: Is this all that's needed?  Chikubi2 years ago

    So, based on the reviews/QA's that I have been reading. Is this all I need if I wanted to install this into my '13 WRX rear diff? (other than the minor dimple alteration) Do I need any other spare parts that need to be replaced when installing this diff? All of the existing OEM hardware can be reused?
  • Q: Fitment issues ?  rotaxmax33 years ago

    Hi I have been researching a bit, and on another site selling this diff I saw this "(1) There may be fitment issues with 3.9 and taller final drive ratios where the pinion contacts the LSD case. Modification may be required." I have a 4.111 rear diff, and wondered if this is true? If so, what would one have to modify?"
    • 0 of 0 people found the following answer helpful

      A:  We have not had any issues reported about the pinion clearance, and if your car is in the Confirmed Applications list, then there should be nothing to worry about.

      Zach G. @ RallySport Direct 3 years ago  
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    • 0 of 0 people found the following answer helpful

      A:  Just a little update from me. I contacted rallispec and he told me that a taller ratio would be 3.545. I got myself one of these and installed it myself. The hardest part of the install was fitting the diff unit back on the car. Running Motul Gear 75W-140 oil and having no issues with noise and harshness even with the diff set up at 100% everything

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