My OS Giken finally shipped after being backordered for months. Anyone install one of these and have feedback? The installation seems straight forward. I just remove the stock torsen unit from inside the diff and bolt in the OS Giken into it's spot? Let me know if im missing anything as the OS Giken site didn't provide instructions.

 

You are going to want to have a differential specialist do this job.

Not for the diff's sake, but for the pinion and ring gear's sake.

Get rid of the stock crush sleeve pinion spacer and purchase the solid pinion spacer kit so once your specialist sets up the gear mesh you can service the diff without getting a new crush sleeve and re-setting the mesh pattern all over again.

The solid spacer makes the diff more durable as well, as it cant crush back under the shock loading of a hard launch or wheel hop and mess up the gear mesh.

Use the OS GIKEN diff oil for it. I had some Motul in it cause thats what came with it, bit Teamrx8 obliquely pointed out how superior the high temp viscosity of the OS GIKEN fluid is.

And the proper OS GIKEN fluid really helped the lock up characteristics of the diff.

 

BTW, you will love it.
You will be amazed how much earlier you can get on gas in a turn. So predictable you can gas before the apex.

I just went to sell my stock 60,000mile torsen and found I couldnt cause it was missing a bunch of the little helix gears on the torque biasing mechanism. Autox car on stockish power. Never realized how weak torsen is.

 

Thanks for the advice. Based on another thread, looks like you got the solid pinion spacer kit from Spence at Weir?

 

This is a great read. https://www.rx7club.com/3rd-generati...riteup-897359/ The fms covers this as well.

I’ve recently installed a kaaz 1.5 way. But have put a few positive traction units in. I definitely agree you need a specialist if it’s your first time. It takes a little finesse to set pinion depth, backlash, and gear pattern to get them right. A few special tools as well. I don’t see a ton of track time, launches or abuse other than canyon carving. I’ve used the standard crush sleeve with great success. I’ve never had to disassemble one once it was set up correctly from it walking around as blue describes. I’m sure with all the things he described though they definitely could. If I ever needed to take it apart, crush sleeves are pretty cheap.
I recently spoke with Ray when I did the 1.5 and he suggested using Torco rgo 85-140 gear oil with one bottle of the torco type “f” friction modifier. I have the differential set up for 60% lock up and it’s great lockup with no clunk. I definitely prefer a positive traction unit over the factory torsen, it seems to be more mannered but even the oem unit does have its place.


~ GW

 

That is correct.
Spence at Weir for the solid pinion spacer.

 

Did you by chance go with the Greddy high capacity differential cover while you were doing the install? Curious if you think it's worth it.

 

I didnt change the rear cover.

I have heard the greddy cover often has casting porosity that lets oil out. If you use it, paint the inside with glyptic to seal the porosity.

Others have used the RX8 case with its little cooling addition.

Whatever cover you use make sure it fits with your diff brace.

 

Found some info about the RX8 cover. Glad I asked you, seems like a good option.

 

What do you mean by painting the interior with glyptic? Is that a particular type of sealant?

 

I believe it was originally a winding paint. Typically used for internal engine coating particularly on cast iron blocks. Trying to use conventional paint in that application, you end up with large peels onto your oil strainer......and bad things happen! Glyptal is probably the brand meant.

Internal casting quality of recent edition greddy covers seem pretty good to me, no shrink crazes like the stock item.

 

I'm in the same boat as @Net Seven ; backordered OSG diff recently shipped.

Love the info here, thanks all. Regarding the solid pinion spacer kit - Weirs' website lists a Miata kit that is RX7 72-85 compatible. Is that the one to buy?

 

Based on another thread, you have to contact him and he can make ones for an FD. I emailed him a few days ago and haven't heard back yet tho.

 

FYI to all:
I called and spoke to Spence. Pinion kit for the FD isn't listed on the site since they hardly sell them. He said he can make them still but his production schedule is slammed. He put me on a list to try and get one produced around early August.

 

PM'd you on the spacer.

I've found that 4x4 shops are experts at diff installs and you can typically find them anywhere. Those guys are constantly messing with diffs and gear ratios. It's all the same technique to do, there's nothing special about our diff.

Dale

 

^^
exactly.
I had mine done at Ed' Custom 4x4

He does all the trucks, circle track cars, etc "around my parts"

Ed didn't want to do the job unless I got the solid pinion spacer.

 

I just send them an email about same and once they confirm the price that I’ll need 2 or 3 kits. So maybe it will help motivate them some.
.

 

Did this ever happen? I'm about to get mine in the car

 

they never responded and it slipped off my radar

honestly though, I’ve yet to hear of it ever being an issue in any high power RX8 differential to date (my application), not sure if the FD3 diff flexure is influencing it or if possibly overkill or not necessary. Because the pinion is locked between two opposing angle-seat bearings with the crush spacer only filling the space between them. The idea seems a bit questionable maybe … 🤔
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