Hit a stumbling block in what I thought was a simple steel-to-aluminum driveshaft swap. The driveshaft came with a slip yoke, but it was looking crusty, so I figured I could use the one off my steel driveshaft. Ordered up U-Joints and found that the Moog 369C doesn't match up with the slip yoke that is currently in the car with the steel driveshaft. However, the 396C DOES match the original aluminum slip yoke, so I change course and beginning cleaning up that yoke. Looks like it had been left outside for awhile as the shaft both inside and out is covered in a very light covering of rust. After getting it to look much better - starting with 220 grit sandpaper on the outside, going up to 2000 for a nice, smooth finish and running a steel brush through the splines several times, I try a test fit onto the output shaft.

Not happening... Can barely get it seated and it stops. I'm guessing the splines need cleaned better, so will put it in my blast cabinet tomorrow and hit it with some glass beads. Hoping that will help.

I've measured everything I can think of with a set of calipers and the numbers appear to match between the two slip yokes. I'm stumped.

Couple of questions, just so I'm not going down the wrong path:
1) Output shafts are universal, correct? I have a T5 in my 85, and no idea what trans was mated to the driveshaft, but guessing an automatic. Looking on Rock Auto, there is only type of slip yoke offered (two suppliers, but no callout for manual or automatic transmission).
2) If this fails, does anyone know the correct U-Joint to mate the aluminum driveshaft to a steel slip yoke? When I try and pair up anything, the room starts spinning and I lose consciousness. I never imagined the complexity behind U-Joints until this project!

As always, any help would be greatly appreciated!

Aluminum yoke on the left, T5/steel driveshaft yoke on the right

 

1) Everything thirdgen except firehawk is 27 spline, yeah. If you have nothing for rust-removal sitting around, you could try naval jelly, or evaporust. A light abrasive like (some types) anti-sieze and a toothbrush might get you there.
2) Same answer as mine here: https://www.thirdgen.org/forums/tran...l-u-joint.html
There are moog and other mfg PNs but they all cross to the basic reference sizes.

 

Thanks for the idea of naval jelly! Hadn't thought of that, so went out to the garage and found my 12+ year old bottle hiding on the shelf. Will try that in the morning.

 

Now soaking the splines in naval jelly, which seems to be helping. On its second soak now.

Naval jelly getting more difficult to find. Neither Lowes nor Home Depot carry it any longer. Must cause cancer if swallowed. Going to go out and buy up a bunch more after this project.

Related question: the u-joints that I ordered are both supposed to have the galvanized coating to prevent electrolysis reaction between the aluminum driveshaft and steel slip yoke and pinion flange. The front joint certainly shows the coating, but looking for opinions on the rear. Not the same, dark color.

Rear U-Joint. Moog 372C

Front U-Joint. Moog 369C

 

The soaking in naval jelly did the trick. After a couple of soaks, I ran a small file down each spline to clean it up. I'll create a new thread on this with additional detail, in case anyone also falls into this trap.


Success!

on the u-joints, I'm going to swap two of the coated caps on the front joint onto the rear. Put those two caps on the front where they mate with the yoke.

Good times. Little projects sometimes grow bigger than planned!