View Full Version : OS Giken Super Lock Review

08-26-2014, 06:14 PM
On Thursday I installed an OS Giken Super Lock LSD in the car. I’ve driven on OS Giken differentials in the past and I was pretty impressed with them. That being said, I had never driven a car before and after the differential. I had no idea how much of a difference it would make.

It came nicely packaged, very well protected for shipping. Unboxing it was like a little Christmas present. I anticipated having to re-shim the differential so I ordered some shims for the FR-S in preparation. Lucky for me though, after installing new carrier bearings and races to the OS Giken the gear contact, backlash and bearing preload were right on the money! With the help of Rick Reichenbach I had already had the bearings on the differential before having the car so from the time that the FR-S got on the lift to the time it was back on the ground was about an hour and a half.

Saturday I was fortunate enough to join the Boeing Employees Autosport Club for a practice event at Sanderson Field in Shelton to get some testing done on the new diff. Right from the start I could tell the car made much better grip out of the corner. It was amazing how stable the car was. That, however, made for a little difficulty. My driving style is to use the throttle to turn the car (something I learned from racing in a CP Mustang) but the new diff was putting down so much grip I was having a hard time getting the car to do what I wanted. Instead of rotating the rear end of the car just stuck! Even with that, I was able to get the fastest time of day on Saturday. With one day of racing on the OS Giken I concluded that I needed a little more rotation from the back of the car and when I got home I increased the rear stiffness of the rear swaybar one position in preparation for an event the next day.

On Sunday I came out to Sanderson once again. This time it was for the Western Washington Sports Car Counsel Enduro Lite event to see if the increase in rear stiffness allowed me to drive the car more intuitively. Oh boy did it change the balance of the car. Before the diff the FR-S seemed to transition from mid-corner understeer to mild on-throttle oversteer. On Saturday there was no real understeer but no oversteer or rotation either. After the increase in rear bar I was able to get nice off throttle rotation and mild oversteer with liberal application of the throttle. The car felt amazing on a very fun, very fast course.
With just a week left before Matt and I race in Lincoln, Nebraska for the SCCA Solo National Championships we took a big gamble by making a big change to the car. That said, I think we made the right choice and the car is faster than it has ever been. Here is hoping that we are able to drive to the potential of the car in Lincoln and keep up with a crowd of very fast, and very fun, competitors in the largest class at the National Championships.


08-27-2014, 03:25 AM
Good review, I'm a bit surprised there's THAT much difference between the stock and the OSGiken, though!

The Captain
08-27-2014, 04:13 AM
The man really knows the feel of his rear end. It grips.

08-27-2014, 08:08 AM
Hmmm... dunno why I can't embed youtube videos anymore...

08-28-2014, 11:35 AM
You didn't use the right tags.

That looks fun, does the Scionubaru not come with a factory posi, or this the aftermarket one make that much difference?

08-28-2014, 12:19 PM
Yeah it comes with a torsen/helical from the factory and YES, the OS Giken does make that much of a difference. Compared with the factory diff the OS Giken (which is tuned for this car in this class of racing) is far more modular in the torque application and puts down power amazingly. It allows me to really be able to let the car slide into the corner and hook up hard out of the corner. My in car video didn't turn out as well as I had hoped (washed out due to the bright day) but it showed how well I was able to get the car to do exactly what I wanted it to do.

08-28-2014, 04:43 PM
The OS Giken is a clutch type diff isn't Joey?

08-29-2014, 04:58 PM
Yeah, Salisbury clutch type.

08-30-2014, 04:55 PM
good review. and good luck this weekend!

and say hi to spaceball one.

09-08-2014, 05:26 AM
Damn I didn't get to say hi to Danny for ya. We chatted a bit but didn't really get to talk much. Mostly I was elbow deep in a GT-R replacing the front diff for a while then getting my own shit squared away. Didn't drive as well as I had hoped but made it in the top 20 (0.026 seconds from trophies) of the largest class at nationals ever (tied with Super Stock in 2010) in a car that we put together in 5 months with only one other concrete event before.

Realizations were, we need more camber for concrete. Our setup, while awesome on asphalt, is really not extreme enough for the extra grip we get on concrete. We were seeing higher g forces than we had in the past (over 1.4g on static turns). Looks like next time we hit concrete we'll be adding another -.5* of camber all the way around and adding more rear bar. Hopefully we'll get more chances to fine tune the setup next year since we won't have to be throwing so many parts on the car come next season.

Looking forward to the 2015.