The chunk for the rearend is cast iron at this point. I’m considering swapping to an aluminum carrier later when I decide on the final drive ratio. The gearset is an old 3.25 Ford brand set that I had. They are pretty worn and didn’t have really good pattern (even in the original stock setup from Ford). I set them up as close to the original pattern as I could get and set the backlash to what it was when I took them out. I'm not really happy with them and will definitely change them ASAP, but they will give me a starting point to judge what gears I want to run.
As it stands now, with the transmission ratios and 26” tires I’m running, the gear splits with the 3.25’s are almost exactly the same as the LS6 powered Z06 Corvette though 5th gear. I was originally planning to use an LS6 cam, so this made sense then. My gut tells me that the cam I’m actually using will probably be happier with more gear. I’m thinking that I will wind up with 3.50 – 3.73 gears.
Going by the dyno pulls I’ve seen for both my cam and the LS6 cam I may not be too far off with the 3.25’s, though. The cam I’m using doesn’t appear to give up much, it anything, in low end torque over the LS6 cam. My problem is the 2.97 first gear in my trans. If I go too high numbered on the rear gears, I risk making 1st gear too short to really be of any real use for ordinary driving. Luckily, the gearset in this transmission has a .64 6th instead of the more common .5 ratio, so my cruise RPM’s wont make as much of a drop. Because this is primarily a long distance cruiser, I don’t want to run any more rear gear than I need to keep the cam happy. Time will tell. For now, this gearset will get me by for engine break in.
I also swapped in an Eaton TRU-TRAC Torsen style limited slip differential. I’ve never ran one, but like the idea of how they work. One crazy issue I ran into was finding ring gear bolts that were the correct length. This is a 9” Ford, so that stuff should be easy to find, but not with this diff and ring gear combo. The flange on the Eaton diff was thicker than the Ford diff and I think the ring gear bolt holes were a little on the shallow side of Ford’s tolerance. I tried 4 different sets, from stock Ford large head bolts to ARP bolts. They were either too long and bottomed out or they didn’t have enough thread engagement to be safe (IMO). I wound up making a threaded collet to hold the too-long large head Ford bolts so that I could shorten them in the lathe. Even then, I had 3 holes that required lengths shorter than the rest. Crazy, but true.
I used an aluminum Daytona pinion carrier and solid crush sleeve (actually a solid sleeve and shims), too. The Daytona carrier pushes the yoke about .200 further forward on the pinion splines than the stock carrier. This means that you either have to run a thin pinion nut or machine the nut mating surface in the yoke deeper. I chose to cut the yoke deeper to use the stock pinion nut, so it took a ride in the mill.
I also got ambitious and built the handy, dandy carrier stand. In the past, I just rolled them around on the bench, which pretty much sucked. The stand sure makes things easier.