Been meaning to post something about my axle conversion. I got carried away and spent a bag of cash, and though there was upside there was also downside. So where to start?
In brief, I decided I wanted a 3.9 ratio diff in R180 size in order to accept SR20 turbo. I advertised looking for a diff but didn't realize datsun never built such a beast, however subaru did but only for two years, and only on the rear of the STI. I sourced a diff and it included the factory subaru clutch style lsd - great! Now I just had to find stub axles and Dave at Futofab had them.
Something lingering in the back of my mind was chassis vibration due to lowering and discrepancies of half shalft U-joint angles. I built my car using 16" wheels mostly because they were what I had on hand, and then for certain reasons my tire choice was a little tall which required added lowering and this accentuated the problems with half shaft angles. I felt now was the time to address this having discovered a facebook post where a guy bought direct fit Subaru stubs machined for CVs along with the entire axle assemblies. The company is called The Driveshaft Shop.
I placed my order and had to wait a couple weeks for production but then they arrived in short order. In an earlier post within this thread we discussed CV joint and axle weights respecting unsprung weight. Well, the driveshaft shop builds equipment designed to maintain their reputation by NOT breaking. As a result these axles are built as though the car will be used for drag racing, not lending to light weight as would be liked for a road course car. So, I now own a really nice pair of super heavy duty axles which I positively will never, ever, break in my lifetime, well perhaps as long as I don't go V8, which I have done before, some 33 years ago - I was as a teenager gimme a break. Bigger is better right! Heh.
After buying the subaru 3.9 diff which is somewhat rare, then the axles, then covering shipping, duty, brokerage, and Canadian dollar exchange, my rear end has become the one single most expensive aspect of my 510 project. Bleeding $1000 bills. Heck, just a few "aviation units" my airplane friends tell me! Lol.
One concern identified by some other posters was axle splines cut slightly small which resulted in driveline backlash. I can say with certainty this is not the case with the Driveshaft Shop equipment. Further, these splines are rolled, not cut. I was surprised to see this but then driveline is their business and it appears they don't mess around.
Not much else to add but these are 108mm CVs used on the rear of 930 turbos. The axle shafts are, well, BIG. The diff stub and the outer adaptor pucks are said to be 4340 (a very tough alloy commonly used for these sorts of applications). Honestly, 100mm CVs (common to non-tubo porsches) would have been perfectly suitable for our light little cars, without drag slicks I suppose. Whatever, I'm not worked up over this and my car is street rod, not a refined track machine. Chassis vibration has gone down though I still need to deal with a driveshaft issue. Look forward to driveshaft 2.0 the CV version. This time however I might take to building something myself as my funds have nearly dried up.
I sandblasted the diff then painted it. The blue paint was my alternate color choice for my car, but in the end red won. I still have the can of blue sample paint which matches some late volvo suv. Oddly, this is almost an identical blue I painted the R180 diff in my last 510 in 1988.
Used a breaker bar to R&R the input flange as the subaru flange does not mate to a 510 driveshaft.
Cleaned off the wheel flanges with a small file to remove any surface imperfections then bolted on the outboard CV adaptors.
The subaru stubs slip directly into the diff and have spring circlip that snaps into place, unlike the typical datsun flanges which are through-bolt. Then simply torque up the CV bolts and it's ready to go.
Notice the drip tray under my diff in the last picture? My last differential puked oil, this diff pukes oil, and this diff even has a steel shim gasket which covers the vent tube so as to avoid direct splash. Am I over filling? I filled to the bottom of the top NPT hole, the one seen with the temp sender. The rear of my car was up on axle stands but front wheels on the floor so there was a bit of angle. opinions?
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