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Don't want to jack this thread but I was also considering a OS Giken LSD and I saw that there are 2 models for the IS350. Do you know what the difference between the 2 are? The part numbers are TY391-HD and TY391-HC. There is a huge price difference between the 2 so if the cheaper one is doable I might be able to justify the cost.
Don't want to jack this thread but I was also considering a OS Giken LSD and I saw that there are 2 models for the IS350. Do you know what the difference between the 2 are? The part numbers are TY391-HD and TY391-HC. There is a huge price difference between the 2 so if the cheaper one is doable I might be able to justify the cost.
There are 3 generations of the OS Giken LSD, the original Super Lock (-HA), the Neo model (-HD), and the newest generation called the TCD (-HC). Unfortunately, the Neo model (-HD) is no longer sold by OS Giken in the US market, only the original and TCD models. Racing teams in Japan felt that the Neo model was inconsistent with its progressive lockup so improvements were made to the disc design which led to the TCD model. OS Giken will now only sell the Neo model to vehicles in Japan that need a LSD but will not see any high performance track usage.
There are 3 generations of the OS Giken LSD, the original Super Lock (-HA), the Neo model (-HD), and the newest generation called the TCD (-HC). Unfortunately, the Neo model (-HD) is no longer sold by OS Giken in the US market, only the original and TCD models. Racing teams in Japan felt that the Neo model was inconsistent with its progressive lockup so improvements were made to the disc design which led to the TCD model. OS Giken will now only sell the Neo model to vehicles in Japan that need a LSD but will not see any high performance track usage.
Nothing like a 5 year thread bump....
C, it seems you have the most answers on this stuff. As of 2019-11, OS Giken lists TY391-HA while pretty much every other site lists the TY391-HC. And I still have the same question from 2 years ago as the what is the difference between the IS-F and 350 application. Why the $600 price difference?
If I had to guess the 350 version is less tuneable or perhaps not tuneable in stock trim without buying parts. But who wants to pull the thing for tuning. That said, I have yet to find out if our 350 version is set as a 1 way or 1.5 way. Details are hard to come by and I've been writing and calling people since Monday and no one has called or emailed back.
Redspencer: do you have any notes from your 1.5 way OS unit? I'm trying to confirm the angle and lock timing OS uses out of the box for the ISF/is350 1.5way.
The numbers on the 2-way we have are 55/55-224-8-16S
The 2-way OS unit is an extreme drift spec or standard "Super Lock" unit with a 55/55 angle. The lock timing is 224 which is said to be set for an aggressive and snappy response.
OS comments were that the unit will basically be a spool that briefly unlocks when the gas is neutral, only very briefly though.
In speaking with the original owner/user he was kind enough to provide his impressions of the unit on both street and track. While usage was limited he indicated that he would try the 2way on daily driving before modifying it to a 1.5way. It seems most of the concern is around aggressive decel into a tight curve. Talking with Dan we made the point "most of our harsh braking and decel is done in a straight line." The lockup wouldn't really be a factor in this scenario. However, with the use of my s/c I do often come in hot to a curve with rapid decel needed. I would need to be more cautious and become familiar with the 2way or risk demise of my car into a wall. Lol
Perhaps by definition, the 1.5 way is decoded right in the spec?
TY391-HA Ramps - 25/38 Lock Timing - 336 Total Plates - 16 Preload - 12S
I'm surprised to see the -HA models (1st Gen OS Giken Super Lock LSD) finally available for the ISF and IS350 (or maybe it was a business decision as the -HC unit (3rd Gen TCD model) is typically priced $700-$1000 higher than the -HA version).
From looking at the revised website, it looks like the difference in price for the ISF and IS350 Super Lock LSD (-HA model) is only $60. The OS TCD versions of the ISF and IS350 differentials (-HC) has a price delta of $600 and is very likely due to low sales for the IS350 TCD (as I paid $2500 for my TCD back in 2013).
From the old email conversations I had with OS Giken USA reps many years back, there are no mechanical differences between the ISF and IS350 TCD units. As the ISF makes 100+ more horsepower than the IS350, the ISF unit is tuned slightly differently (lock timing, preload, etc). The Lexus ISF and IS350 LSDs are also sold as 1.5 way by default (unless you special order a 2-way for certain circumstances like drift competitions like the one GVille350 acquired years back).
As the price difference for the IS350 -HA and -HC unit is currently very minimal ($200 difference), I would highly recommend going with the much improved TCD (-HC) version as the TCD spec disks will provide "increased oil cooling and even smoother operation" per their website. Here is how OS Giken describes the locking rate between the two units:
One thing I'm surprised to read on their revised website is that the ISF and IS350 units only have 16 clutch plates as I was previously told by OS Giken USA that both the ISF and IS350 diffs had the max capacity of 28 plates. I'll have to ping one of the reps to verify this.
Yes, I was a little surprised by that too. That said, when steals and clutches are too thin they can overheat and deform. Notice the 2way unit only has 8 clutches. Perhaps for the Instant On effect?
Even in the picture Gville posted, there is a shortage of round things....
Thanks for you're input. I'm trying to get this deal sealed and get it shipping. Fingers crossed!
From my research when I had the 2-way OSG looking to convert it to 1.5-way, the differing "ramps" have to do the angle those "pins" are cut at, which in-turn tune when the plates activate. The preload affects this as well, which are simply concaved washers.
I couldn't tell you what the "lock timing" is; this never came up in conversation with those "in the know".
The cusco hybrid LCD TCD looks pretty similar to the OSG unit. This link has a lot more details than OSG guys publish. What I didn't see was OCI and rebuild intervals. But it seems they designed it to be street friendly.
Historically speaking, Cusco clutch LSDs create more noise/chatter, usually require a break-in period (figure 8 driving on a parking lot), require more frequent gear oil changes and require a teardown and rebuild. OS Giken units tend to have more available clutch plates, no break-in procedures, longer gear oil change intervals, and no required rebuilds. OSG diffs also have the reputation of being the better/best performing LSDs.
I can't speak about the Cusco Hybrid Diff and if any of these traditional clutch LSD quirks have been resolved compared to their previous models.
07-29-14, 05:20 PM
2019 bump OS Giken TCD TY391-HA vs HC
