A follow up to document my adventures trying to remove the spider gear shaft roll pin from the differential carrier on my second transmission.
I had noted in my original post on removing this roll pin to replace the spider gear thrust washer (post #24) that this was the most challenging part of the rebuild. And, on transmission #2, that statement is still very, very true. On this transmission, the spider gear thrust washer was actually still completely intact, but it still had 420,000 miles on it, and I had already bought a new thrust washer and roll pin, so I dug in to replace it.
If you go to Matt-98AHU's video series on the hybrid 6-speed build (linked in post #1, dzelpwr on youtube), you'll find a short video he did on removing the roll pin using an air hammer. I tried that, and it didn't work for me. Once again, I sheared the end of the pin off without budging it. Now, it's very possible my technique was poor, so I'm not saying this isn't a viable method. Just didn't work the way I tried it.
So, I set out to drill and tap the pin as I had done with the first one, and things went sideways. I drilled it out with no issues with the 1/8 and 9/64 bits. On the 5/32 bit (3.97 mm), I only want to drill about half way through so the M4 tap has enough metal to bite into on the lower half of the pin. So, I drilled a bit with the 5/32 and got to work with the M4 tap. Once I hit the thicker section of the pin, the pin actually broke loose and started to turn. I had no way to hold the pin while tapping it, so I couldn't tap it all the way through. This obviously didn't happen with the first differential. So, I screwed the long M4 bolt into what had been tapped of the pin, and tried the slide hammer, but the bolt just yanked out of the pin without moving it at all. The upper half is drilled to 3.97 mm, and the M4 bolt is, of course, nominally 4 mm, so there's not enough thread to grip.
At that point, my not so bright idea was to use the tap as a pulling tool. I was hoping that the tip of the tap would get just enough bite on the thicker section of the pin to allow removal. So, I screwed the tap all the way down and decided to put a vice grip on the tap to give me something to pull on it with. I then started to use a regular hammer on the vice grip to knock the pin up and out. But, about 3 or 4 hits in, the tap snapped off inside the pin. Oops. Forgot that hardened steel is brittle.
Here's a shot of the broken off tap.
I thought I was dead in the water. I had a bolt extractor set that went down to small enough for an M4 bolt, but this was a hardened steel tap, and sure enough, the drill bit did nothing. If I pressed harder, I would just snap the bit. I had to walk away for a few hours, and let my blood pressure settle. I thought I'd be out the cost of a differential. Even used, it wouldn't be cheap. And, if I bought just a diff carrier, I'd have to go through the trouble of drilling out the rivets and transferring the ring gear. I came back, and a fresh thought came to mind. If I ground down a Dremel cut-off wheel, it would be small enough to work in the notch in the diff carrier without doing too much damage to the diff carrier, and maybe I could cut a slot in the tap and back it out with a screwdriver. And, it worked. At first, it didn't. The pin started to turn with the tap, but after almost a full revolution, the pin caught and the tap backed out. Whew, disaster averted. I was seriously thinking about just leaving it in and not changing the thrust washer. It was in OK shape by visual inspection. I figured with the solid tap lodged in there, the pin probably wouldn't go anywhere.
Here's the slotted tap with the screwdriver as I was removing it.
Now, I was back to the drawing board. I thought I wouldn't be able to drill it any more, thinking it would just start spinning again, but I tried it, and fortunately, I was wrong. Like with the tap, the pin would catch intermittently and allow it to be drilled out further with the 5/32 bit. So, I drilled deeper with the 5/32 to further weaken the pin. I then dug around my screw bin and found a long sheet metal screw that happened to be the perfect tight fit. I tried screwing that in with a couple of washers on it for the slide hammer to grab onto. Again, I thought the pin would just spin, but it didn't, and I was able to get the screw in pretty deep such that I figured I had a fighting chance of pulling it out... and success. It worked.
Here's the pin partially pulled, and a couple shots of the screw and pin removed.
One more useful note. I wrote earlier about some of the drill bits not lasting long working on the hardened steel of the pin. I found I could rig up my Dremel with a cut-off wheel as a drill sharpener for these small bits. I put it in the vice at an angle that was comfortable to rest my hand on the vice and hold the bit at roughly the proper angle to renew the cutting edge. It worked well to keep my 5/32 bit going. Obviously, I'm probably not getting the exact 118 degree angle that is optimum (I think that's the angle), but it was good enough.
So, once again, this part of the job ended up being a pain in the ass. My advice... avoid it and put in a limited slip differential. LOL.
Brett