About 5 years ago I bought a JDM B18C OBD I w/LSD swap from a reputable importer. Now I have a built motor and was going to use the tranny from that swap, but I wanted to put a Quaife LSD and take the stock one out. The stock one works fine, but I had heard they don't like higher horsepower and tend to give out. I thought that the diff would have (10) 14mm head bolts that are reverse fine thread holding it on, but this one has (14) 10mm normal coarse thread bolts. Obviously this gear will not work with my Quaife QDF6U that is supposed to be for GSR hydro trannys. So what do I do now? Do I need to buy the final drive gear from MFactory or what to get the Quaife to work? If I do need to get another gear what are the suggestions for a turbo setup making 500+hp for drag use.

 

That looks like a 66 tooth ring gear, which should be the stock 4.40:1 ratio. I have a stock differential and 4.40:1 ring gear from a 97 GSR sitting in my garage. (I used the ring gear that cam with the ITR LSD when I installed it.) I can look at the ring gear tonight.

 

Here is a stock GSR differential with a 4.40:1 ring gear and tapered bearings. It has the expected bolt pattern.

 

Op, is your pictured differential a viscous unit?

 

I talked to Dave @ synchrotech he told me what the deal was on this, and I think he did say it was a viscous, but I can't remember all the details on it. I was just wondering if this was an actual OEM diff or if the original owner had put an aftermarket LSD in it. I do have this diff for sale in the marketplace so I was just trying to find out all the info I could on it to provide to potential buyers, cause transmissions are not my specialty. This was the first time I've ever tore one down and I expected the ring gear to bolt on different than it did. Now I have found out that I just need a 66 tooth ring gear that bolts on with (10) 14mm head reverse fine thread bolts and it should match up with the gears on the main shaft to where I would not have to change it as well. If I'm wrong someone feel free to correct me on that.

 

I was surprised by the ring gear on your differential as well. I had only seen them assembled and didn't think about the different bolt pattern on the ring gear.

 

Yep, it's totally different the ring gear on this diff as you can see covers the entire top of the diff and has gears on the bottom side of it for the main part of the diff to turn in. It's not like most that have a big opening that slides over the diff for you to bolt it to the diff. It sucks I can't use the ring gear but, hopefully someone out there wants to get rid of their pegleg open diff and buy this for a lot cheaper than aftermarket.

 

You need to change the ring gear and countershaft as a pair. Gears develop a wear pattern, if you mix and match they'll whine.

 

I never had any issue when I swapped the CTR LSD (same as ITR) with the 4.40 FD into my GSR. (The differential that I showed is from my GSR.) With 15 teeth on the counter shaft and 66 on the ring gear, the same teeth do not always mesh, i.e. all permutations are possible.

 

That is an oem Viscous LSD that you have (it was a factory option on the SiR-G), so in order for you to use your new LSD, you will need to change the final drive to either one from a non-lsd B18C tranny, a type-r tranny or an aftermarket B18C fitment.

 

Dogginator sent me a ring gear and bolts that he had laying around(97 gsr if I remember right). I laid the ring gears side by side and matched up the gears they are exactly the same both 66 tooth and pitch match. I had been waiting on the shim for the diff bearing that had been backordered for a while, but as soon as I got the shim I put the tranny together with the ring gear and bolts that Dogginator gave me (which was awesome by the way I can't thank you enough!) everything works as it should tranny turns and shifts smooth as can be without any issues. So if someone stumbles on this later to make a long story short if you have a "viscous" LSD as I have pictured above and you want to put a different LSD in all you will need is the 66 tooth ring gear from another GSR (10) 14mm head reverse thread bolts, 91005-P80-E31 diff bearings (x2) and your correct shim to shim the bearings ( I used 41453-PL3-B00) By me doing this I would also assume that it would work in reverse that you could take this "viscous" LSD and put it into your peg leg GSR without any issues.