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01/25/07 – Transmission Modifications

First I added another brace to the cross member. This triangulates the subframe and I am convinced it is now strong enough. My welding leaves much to be desired1... I need to work on this much more...


Next, pulled the transmission back out of the car and unbolted the transfer case. I took everything out of it. This is what was left.

Then I went home.

Went to the shop after work. I taped off the bearings to avoid contamination2 and bolted the gutted transfer case back together. I then used the horizontal band saw and cut the output case off of the transfer case.

This step went remarkably smoothly3. The result:

Next I mounted the transfer case on the milling table I was only able to get 2 mounting points, one of which was a bit "shady" but I hit it with a rubber mallet after I bolted it down, and it didn't budge. The tool in the mill is not the tool I used (I used a 2.5 inch facing tool) I used a level and shims to get the case mounted correctly. The location of the face didn't need to be that precise, so a level was fine:

Next, I made pass after pass on the part, taking off about .100 per pass. About an hour later I had a flat surface, about an inch shorter than the above picture. (sorry, no pic)

At some point during this, the tape over the bearings gave way and a lot of aluminum chips made their way into the front bearing. I will try my best to get them out of there with a parts washer/ air gun, but I may need to suck it up and buy a new bearing.4 Meh, live and learn.  I should have taken it out first, instead of trying to take the easy way out and "cover" it.

Also at some point during this, I somehow managed to crush my hand between the work piece and the tooling. I had to pick bits of fingernail off the tooling. EW.

Now that the face was complete, I chucked up a drill and drilled (11) #21 holes X .9 deep along the perimeter of the face. Then using a hand tap, I tapped the holes to 10-32 thread. A hand tap was a bad idea; I should have used the mill to guide the tap, as one of the bolts went in slightly crooked, not a big deal, though. It is not terribly off. The hole that looks like it is "falling off" is intentionally placed there, as it was necessary to avoid an internal bolt.

All that was left was too make a cover. Since I had written down the X,Y locations of all the holes I had drilled in the case, it was relatively easy. I used a belt sander and the mill to make the outside perimeter, then after the holes and perimeter were complete, I made a few facing passes on the mating surface of the cover. Due to the fact that the cover was no longer in square, there was a tiny bit of chatter on the final face, but nothing that wont be sealed with RTV or hondabond.

The finished cover and assembly:

Total time = 6 or 7 hours.

Dollar amount saved (vs. buying rb25 transmission) = $1500

Weight difference = negligible

Now I just need to put it back together. Oh, I also plan on drilling a tapping a few holes on the cut-off portion of the transfer case, then using a torque wrench to find out at what torque the threads strip, this will allow me to get a torque value to tighten the hardware to.

I will leave you with this picture:


This was one of the cooler parts of the project to date, because something looked better/cooler than it did when I started.  A lot of the other parts of the project were unfinished/dirty/uninteresting.  Hopefully this holds up to the abuse!


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(1)   I’ve since become a much better welder…

(2)   Bad move

(3)   Even though I cut through the hardened steel race…

(4)   I was able to get the bearing fairly clean.