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It doesn't look very complicated... that's what I told myself everytime doing the work myself. It usually ends up taking much much much longer than just couple hours from a skilled technician, but it's a rewarding experience.
It will be really helpful if you could share the process in detail. I would like to swap LSD myself as the last project on my IS350.
A couple of points worthy of conversation when power levels go up.
1) Once he had the diff out, he never checked the rotational torque of the pinion nut and ring gear. If too low, it is an indicator that the crush sleeve may be loose and subsequent use of this diff could lead to ring and pinon damage as it allows the pinion to walk in and out. Mind you the OEM setup uses a crush sleeve to maintain pinion preload and it can fatigue and get loose. In short, torque the pinion nut to obtain the proper preload and this action crushes the crush sleeve to obtain the correct pinion bearing preload. At home we'll do 9ft/lb increments until new/used bearing spec is met. The pinion can not be moving end to end or deflecting side to side in there or the gear set dies. In our favor is I have not seen anyone blow up a diff so the Yoda crush sleeve must be a pretty good design compared to the past. Of course one can always replace it with solid spacers. It's cheap insurance.
2) He didn't check the backlash or ring gear preload to assess the health of the unit before tear down. Again, place an inch pound beam style wrench on the pinion nut with it assembled. Turn the wrench and measure the torque of the seals and bearings. Record number. Now place your dial indicator on the side of the ring gear and pry it sideways. Determine if the bearing has any deflection or lost preload. Record data. Measure backlash and record data.
3) As best possible remove all oil from both the R&P and apply Prussian Blue and check the heel and toe patterns for comparison when assembled again. Is it the same or have we changed it? Before/after data can be priceless!
4) [Video] We have no bearing caps so if the carrier bearings have much preload at all, the side snap rings (our application) are going to fight us getting them out and in. My plan is to make some custom tooling to compress at least one side or both using a long bolt or allthread so as to reduce preload and make it easier to get the snap-rings in/out. I know a picture would be worth a 1000 words but soon enough. The other option is a case spreader which is hard to justify for one time use.
5) Once the carrier was out he should have measured the pinion torque again and subtracted that from the previous assembled value. With the two numbers we know the individual values for pinion and carrier preload. Keep in mind these gears can't be moving around too much so they do run preload to minimize deflection. Too much preload promotes wear and heat, too little can lead to death and destruction. So lets say you don't touch the pinion, but just throw new bearings on the carrier. If we at least record the torque values, we can make an informed decision.
Granted, we have seen a handful of people just do it, get it done, and they got lucky as best we know. I can't afford to be a statistic and buy a bunch of parts all over again because I didn't take a few measurements to know the probability of this being successful.
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5) Prying the gears apart is a no no. There are better ways.
6) Assembly. Our options are to grind the case so the new diff drops in or settle the ring and diff into the case and torque them in place. If this is possible, there is no grinding the case. If not, it will be a long day.
7) Once assembled, verify those rotational torque values. Verify back lash. Verify run out. Verify the contact pattern using prussian blue compound. If all is well, seal it up and install it.
Removal and installation: Although our diff may come out of the vehicle without dropping the drive-shaft, I suspect the companion flange having a 20mm stub on it will prevent this. Maybe dropping the drive-shaft at the carrier bearing up in the tunnel is enough? My plan is to only drop one side of the rear suspension and lower the diff. Will our cars allow it to drop out without doing any of this, I don't think so but I might try it. It's just $32 a seal if you miss the stab and wreck the seal! haha!
EDIT: notice post 120 shows the torque spec for the NEW pinion nut is 360 ft/lbs or less. Mind you I think I read they want you to start checking pinion preload at 180 ft/lbs and go up in 9 ft/lb increments until you reach 13 to 14 in/lbsof rotational startup torque.
That's all I've go for now.
Last edited by 2013FSport; 12-17-19 at 07:54 PM.
Reason: Had to add more details? Seriously, I did! lol
I need some time to read through these. On the other hand, for my backup plan, my local shop gave me a quote on labor for installing LSD yesterday, but I am still eager to make this an DIY project. Greatly appreciated for the detail you are sharing!
With the weather being what it is here, I couldn't wait and have the opportunity to smoke up the rears with TCD installed as that's likely a month out or so. That said, new skins on the back. The old ones made it two years ~ 28,000 mi.
BFG G-Force Comp 2 A/S going back on. The RR was nearing the MayPop status....
$380, mounted, balanced, 2x discarded.
Had I started their life ar 31PSI like I'm doing here, I'm thinking they would have made it 35,000 mi.
Yes, 31 cold. At 36 its blowing the centers out. I do run around solo 99.5% of the time and nothing in the back. When pulled the rears were the opposites of the front. Tread on the edges, blown in the center.
Running 38 to 40 up front now to see if I van get the rest of the life from them. The edges are gone equally but 1/2 tread in the middle.
Granted, a bulk of the rears loss is from spinning but if the pressure is right, even then the edges go with it. This is why preach to adjust pressure to loading and style. The name plate values may work for some but not everyone.
FWIW - that 2 year run was the first set of new tires since buying it in 2017.
Add trans temp for good measures and maybe engine temp.
PS - Don't look at trans temp when at the track. You'll want to change your fluid more often or add a cooler that switches automatically... On my DD it takes 35min to hit 200°F. When thrashed on a bit, it climbs and stays for a while while engine temp hangs at 187-190°F pretty consistently.
I'm just saying that knowing what it does on a good day could be helpful on a bad day.
At a SCCA track night in America event at PBIR the trans temp on my isf was getting to 220-230, engine temp remained at 195-200. The sessions were about fifteen minutes
long and I was driving moderately hard but conservatively, I was trying not to thrash the brakes or tires...
Normal driving the trans temp stays around 175. What do you think about the 220-230 temp on the trans and fluid? The warning light did not come on, so can I assume
this is a safe operating temp? Do you know at what temp the warning light would come on? Any insight you could give would be appreciated.
At a SCCA track night in America event at PBIR the trans temp on my isf was getting to 220-230, engine temp remained at 195-200. The sessions were about fifteen minutes
long and I was driving moderately hard but conservatively, I was trying not to thrash the brakes or tires...
Normal driving the trans temp stays around 175. What do you think about the 220-230 temp on the trans and fluid? The warning light did not come on, so can I assume
this is a safe operating temp? Do you know at what temp the warning light would come on? Any insight you could give would be appreciated.
Those temps for occasional bursts should not harm anything. I could not find that information myself, I'd guess it 250/260F is the magic number but again (DTC pops up), just guessing. I would definitely consider a cooler if hitting 240 F and staying there. Tacoma's with a tow package have the A760 with the smart cooler that directs oil forward to an external cooler, but once I found them, they take a chunk of realestate outward that may hit our exhaust or underbody and not knowing the temps, I didn't move on it.
To this date, I have not pushed it while monitoring temps and seen how high it will go, but if you guys tracking on warm days see 220/230, that's not bad.
Merry Christmas to Lexi; OSG TCD came way early!!!
Yep, TCD came earlier than expected and I am far from ready for the install. I have a holding fixture to make, tools to buy, and tools to make. For now, it will have to wait until I get my act together. A couple of teaser photos.
Anyone else notice what I DIDN'T SEE HERE until it posted full screen? What???? Is that a SHARPIE over the HC making it an HA? WTF!!!! Gonna have to have a talk with all parties!
Which likely explains these being nearly identical. Errrrr..... I fear the HA is too harsh for DD but all I really have to go on is the carrier has US-SPEC on it. See 2nd picture on post 130. US SPEC TCD:
TY391-HC | Lexus IS-350 - GSE21 2GR-FSE V6 Ramps - 25/38 | Lock Timing - 336 | Total Plates - 14 | Preload - 12S
ORIGINAL LSD: 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.
EDIT #2
Adding to the confusion is the paperwork that came with the TCD lists just 8 clutch plates. Strange paying all that dough and receiving conflicting information. Perhaps I should open it and look & measure? Reads: LSD TCD 25/38-336-8-12S (14-D)
Anyone with information on the 350 HC, feel free to chime in.
Oh boy, that a cluster! I hope they are able to determine what you actually have there OR give you the chance to crack it open yourself without any issues with warranty (assuming there is one).
I clicked into this link to the webpage of HA version. It has "buy it now". It probably explain why you receive the purchase so much quicker than expected since they have "HA" version in stock.
The product label is so confusing with the sharpie ink.... I assume it's HA version, but it was mislabelled as "HC" so they corrected it with sharpie.
Oh boy, that a cluster! I hope they are able to determine what you actually have there OR give you the chance to crack it open yourself without any issues with warranty (assuming there is one).
More specifically it is a conversion. I wrote OS-GIKEN USA and they said when the order came in they had the HA unit in stock and opened it up, assembled the TCD with the HC plates. As for the plates being marked as 8, because these are not old school friction and steel setups, where one friction plate is bordered by two steel plates (like the clutch pack in our auto trans or a motorcycle wet clutch), the configuration is said to have 16 plates. These having no friction material per say which explains the longer life and minimal oil changes over the 30,000 mile period. All of that said, I think it should be fine. The diff is good for up to 600 HP.
Found these in a FS ad on BMR forum. Notice the deeper V of ramps. Not your standard 25/38. It is 45/20
Well, in the end, I hope you received what you paid for AND it is the perfect application for its usage. Odd that they just toss in different internals when needed and use a generic box causing all sorts of questions. But it sounds like they've been responsive and helpful.
12-17-19, 07:15 PM
challenge, but no trick, right? while doing some research, I wonder...... ummm....
I need some time to read through these. On the other hand, for my backup plan, my local shop gave me a quote on labor for installing LSD yesterday, but I am still eager to make this an DIY project. Greatly appreciated for the detail you are sharing! 
Merry Christmas to Lexi; OSG TCD came way early!!!
