Included with the roller block I picked up a couple months ago was an aluminum driveshaft. Needing a project, I decided to polish it up and install it into the car. Things went smoothly until I discovered the slip yoke on my steel driveshaft wouldn't mate up with the aluminum driveshaft with the U-Joint that I had ordered (Moog 369C). That left me with two options - use the slip yoke that came with the aluminum driveshaft, or try and figure out the correct U-Joint to order. I opted for the first option and began working on the worst slip yoke I have ever seen. Details below:


Here is the driveshaft after picking it up. Must have been left outside for awhile. Yoke was all rusted and the aluminum surface was extremely dull.

First thing I did was polish up the aluminum. Started with 150 grit, working up to 2000. Then polishing to a shine.
The polishing part was a lot of fun, something I enjoy doing. The driveshaft is nice because it starts with a good, smooth surface. Polishing up a TPI system or wheels takes a lot of work to remove casting marks (TPI) and machining marks (wheels). With the shaft, you could just get into the light sanding and working it into the polishing stage. I did a more in-depth write-up of the polishing process in another thread. HERE

After polishing, I placed the order from Rock Auto for the correct U-Joints. My car has the 9 bolt rear end, here is what fit perfectly. Found these part numbers after searching extensively here on TGO:
Front: Moog 369C (details on that below)
Rear: Moog 372C

First surprise came when I found that there was no way I could use the slip yoke that I'd taken off the steel driveshaft. It slid on and off the T5 output shaft so smoothly. So, now to tackle the POS slip yoke that came with the driveshaft and looked like it had been at the bottom of the lake.

Nasty on the outside, no better on the inside. Splines had the same coating of surface rust.
Couldn't get a good picture of the inner splines, but they were not pretty.

Aluminum yoke on the left, steel yoke on the right. This is after I worked the aluminum one over with a wire wheel brush and multiple grits of sandpaper. Had also made passes on the inner splines.

After getting the yoke into presentable condition, I wanted to test fit it onto the output shaft before going further. It wouldn't even get onto the shaft. I pulled it out and worked it over hard with a steel wire brush, sandpaper, anything I could think of. On second attempt, it would barely slide on, and that took lots of effort. I was getting ready to throw in the towel. Big thanks to a member here, jmd, for making the suggestion of naval jelly. I had a really old bottle on the shelf and got to work. First, I tried brushing it on and working it into the splines, letting it sit for 10 minutes, rinsing and repeating. That made a bit of an improvement, but not good enough to work.

Realizing that I could just pour the contents into the yoke and let the chemicals to their thing, I set the yoke upright in an old machinist vice.

Jaws on vice tightened only enough to keep the yoke from falling out. Two of these treatments did the trick!
I left the jelly sitting in the yoke until the bubbling action started to slow down. I bet it was 30 minutes or so the first time, then 1-2 hours the second. I kept removing jelly from the top as it reached the edge and was ready to spill over.


After rinsing, I ran a needle file down each spline to clean up the edges, and also lightly along the top of each spline.


SUCCESS!!

Now time to get it painted and keep future rust away. Wiped everything down with mineral spirits and added the car for flavor.

Finished and ready for U-Joints and installation.

 

Installed the driveshaft and took it for a test ride this afternoon. Smooth as silk, no vibrations. I thought I had taken a picture of it actually in the car, but somehow managed to mess it up and not save the shot. Next time it is up on my QuickJacks, I'll hopefully remember to shoot a pic and post it.

Final thoughts - If I had known the issues I was going to fall into with the different slip yokes between steel and aluminum driveshafts, not sure I would have gone forward with the swap. Was fortunate that the aluminum shaft still had the yoke attached, or I would have been up **** creek with no paddle. I am comfortable solving complex issues, but trying to decipher which U-Joint would actually work between the aluminum driveshaft and steel slip yoke was forcing me to the edge of consciousness. Bringing life back into the rusty slip yoke ended up working and - looking back - rewarding, but it was a whole day working on it.

Also, something for people to be aware of when ordering U-Joints for aluminum driveshafts - they must be the coated version (the "C" suffix on the end of the pat number). Otherwise, the dissimilar metals between the aluminum driveshaft and the steel slip yoke and rear pinion flange will cause a chemical reaction and the U-Joint caps will essentially become fused to the steel housings. At least, that is my understanding.

Here is what the caps should - and should not - look like:

Moog 372C - I believe I was shipped a regular 372 part in a 372C box. Notice the shiny silver cap.

Moog 369C - Four nice, dark caps showing the coating. I swapped the two free caps in this picture with the two silver caps on the rear.

On second thought, I'm glad I did it. Have something shiny under the car that nobody will ever see. Several pounds lighter too. Could really tell the difference when I was pressing out U-Joints from the steel and aluminum shafts.