This weekend I started work on swapping the open diff in my 2007 WRX trans for a Quaife QDH3Y. The box with the new diff did not have the QDH3Y number on it but did have a number of 93.309.170.With the help of Hindsight's excellent pictorial and instructions, there were no surprises on what to expect. Inside, the trans look very good, no rough, damaged, or missing teeth, the sychros look in good shape, and the shift forks still looked like they had a lot of life left.

As recommended by Hindsight, I purchased and installed new output shaft bearings confirming bot were fully seated on the Quaife. Confirmed the bearing parts numbers were the same as the original bearings. So far, so good.

I started the process (after thorough cleaning of the entire trans). I noticed that the old diff had the output shafts about .250 above the bearings; the Quaife out shafts had only about .060 above the bearings. I double checked that the bearings were fully seated. You will see what I mean in the pictures. I did not dimensionally check the Quaife thinking there may be other differences which make the bearings sit 'higher' on the shafts ( in Hindsight's picture it appears the bearing sit lower). I continued with the install.

I was able to get zero backlash set, preloaded the bearings per the process, and then obtain the final backlash of .0058, within limits. The problem is on the left side, where the adjuster for the bearing depth is about .020" higher than the outside of the case; you barely see the o-ring. And on the right hand side, the adjuster is about .150" higher than the case and the o-ring groove would not be below the case; oil would leak out readily as there is no sealing surface for the o-ring to seat to.

I had the trans apart three times to verify everything was in order. The transmission spins smoothly and shifts easily when the case is torqued and the backlash is set, but the adjusters are higher than the case, the right side much higher than the left as noted above.

I have sent an e-mail to Quaife US support yesterday and not heard from them as of this afternoon. My impression was the diff was not machined correctly on the shafts to allow the bearings to rest lower like the stock diff. Other than the fact adjusters do not seat deep enough in the case, it looks good.

If Quaife does not respond, or just says tough luck, I am going to machine the adjusters to reduce their overall height which would allow them to seat below the case surface, the o-rings would seal correctly, adjusters would seat against the bearing cups correctly, and still obtain the proper backlash. Other than the hassle and expense of machining, I do not see any downside to this repair other than these adjusters are tied to this diff. Ideally, I could have the output shaft bearing seat area machined to allow the bearing to seat lower but I do not think I want to modify this high load area.

Any thoughts? IMG_1335[1].JPG IMG_1340[2].jpg