Fitting a Limited Slip Differential into a Rod Change gearboxThe factory Rod Change gearbox requires some modifications to allow fitting of a C-AJJ3387 LSD. Not only is the body of the differential itself much beefier than stock, the bolts that hold the ring gear to the diff will also run into the case.
The stock case we started with in this instance was the DAM5627 - but not that all Rod Change gearbox casing will require the same modifications. The process to do this very fundamental first step requires a lot of hand grinding and trail and measure fitting of the diff into the housing.
The first step is to mount the ring gear to the differential. The prescribed bolt is a BTA370. This is the same bolt as used to mount the drive flange on front hub of bakes with 8.4" rotors. While these are the exact bolt for the brakes, the use of them to mount the ring gear will require the first grinding. After installing the ring gear a trail fitment into the case will easily show that the head of the bolts protrude out from the ring gear way to far and even after grinding on the transmission case for some time the bolts will still interfere with rotation. we typically with do the finish torque on bolts, then wrap all the openings on the differential with tape or shrink wrap and then with a hand grinder take the head of the bolt down by 1/2. Remember not only do you need to retain the strength but also may need to remove them one day and thus the socket still have to have enough engagement to loosen, etc. It is a compromise as to how much you take off the head of the bolt vs how much grinding you do on the alloy transmission case.
The stock case has a fair amount of material that can and must be removed but in no ways has affected the needed strength even in the most severe racing application.