Ever since I have owned my 1986 Spider, the differential has slowly leaked gear oil; the bottom becoming covered with a gummy substance made up of oil/dirt/sand/bugs - something like almost-hardened Jell-O. Over the years, the leak has slowly but steadily increased in volume. I was topping it off twice a year, which is way too much for me. Last summer I decided it was time that I fix this pesky problem.
At a recent tech session a friendly Alfa mechanic pointed out the problem areas on the underbelly of a late model Spider. I asked about rear end leaks. He said that 99.99% of them originated at the seal where the drive shaft is bolted to the rear end. He said that it is usually caused by worn U-joints which cause an oscillation of the drive shaft and distort the seal. I had already replaced these U-joints, but I think that the previous owner allowed worn U-joints to remain in service a bit too long. I asked how hard it was to replace the seal. He said it was EASY (a four letter word!); unbolt the drive shaft, remove the pinion nut and flange, pull out the seal, replace with a new seal, replace the flange, and torque down the pinion nut. He said that it would be even EASIER (there it is again) to remove the pinion nut with an air wrench; and I had a new one - just waiting to be tried out.
I ordered a seal, bought some Mobil 1 gear oil and on a warm spring day, I drove the rear wheels up on ramps and started to work. I unbolted the drive shaft from the differential and had a look at what was underneath the flange. What kind of strange nut was this? The sides were smooth without flats, instead there were notches cut out (see Figure 1). I could see why; there just wasn't enough space to get a regular socket in. I discovered that the strange nut was called a ring nut. I looked it up in my manual and saw that there was a special Alfa tool needed to remove the nut; I assumed that it was just a socket of a certain size that I could buy at Sears or an auto repair store.
I began my Hunt (another four letter word) for the Elusive Ring Nut Socket. I knew that I couldn't rent this tool anywhere, so I inquired on the Italian-cars-digest on the Internet, if anyone had such a tool. No one did, but one guy said that he had made one from a large, castellated nut; he ground down the castellations until they fit. I bought a replacement ring nut (bloody expensive) to use as a template and scoured the hardware stores for such a castellated nut. I never found one of the correct size, they were all too small.
Then I decided I might as well buy the socket. I called a local Alfa dealer and placed an order for one. A week or so later I received a call from them saying that Alfa no longer sells that tool! Then I called some other dealers on the Eastern Seaboard to see if they might have one in stock, but to no avail; they all came back to say that Alfa no longer sold it. I called a few mail order places, but they never carried the socket in the first place. One guy said that maybe I'd get lucky and find a mechanic who was willing to sell it me...on his deathbed maybe!
Next, I canvassed several people about the socket and only found one person who had one and he had made it himself. He said that I was welcome to borrow, but I decided that I'd like to emulate our Neanderthal ancestors and make the tool. Finally, I was able to borrow a genuine Alfa tool to use as a template from Julio at Milano Motors. Julio told me that there are several pinion ring nuts based on model and the only difference is the spacing of the notches. Healso told me I'd have to leave town if I broke or lost the tool.
I measured the diameter of Julio's socket and then went to Trak Auto with my trusty calipers. It turned out that a $6, 30 mm, 1/2" drive, chrome socket was the right size (well, just a bit smaller). I placed the two sockets together, opening to opening, and transferred the location of each "tooth" as well as its' height. To ensure that each tooth had enough thickness, I made sure that each tooth was located on the center of one of the socket's flats. I could have used the ring nut as a template, but it was easier doing it this way (see Figure 2 for an illustration of the tool and the critical dimensions).
Using a 4", right angle grinder, I removed the waste between each tooth. I thought that I'd be grinding away for a while, but it went pretty quickly. The grinder wasn't able to get into the corners, so I used a metal file to square up the sides and bottom of each tooth, as well as the gap between each tooth. The socket wall thickness was greater than the depth of the ring nut's notches, so I chucked a small grinding cylinder in my drill press and ground away the extra thickness from the inside of the socket (the original socket appeared to have been done the same way). I then trial-fitted the ring nut to the socket, using the file on the teeth until a smooth fit was obtained. I spent about 3 hours total making the socket.
The next nice weekend, the car was again up on ramps. And with the ring nut exposed, I was ready to put my new tool to the test. I attached it to my air wrench and the old ring nut came off as nice as you please. After replacing the seal (and getting coated with dripping gear oil), I torqued the new pinion nut into place (58-101 ft. lbs.). Now my Spider's rear end is clean and dry - as it should be. I returned Julio's socket and mine is resting in my tool case, ready to be called to service in the future. It is nice working with a tool that you made; it makes me feel more like a mechanic and less like a part-replacer.
Note from Carson Damm, Ft. McMurray, AB, Canada:
If you're replacing the differential pinion seal on a model 115 Alfa and need a Speedi-sleeve to repair the shaft sealing surface, the CR (Chicago Rawhide) number is 99177 (1.769"-1.775").
For more information on Speedi-sleeves visit http://www.chicago-rawhide.com/auto/speedi/speedi.htm.
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