Oh! those slots. I don't think it would really matter whether they're toward the front or back. It's probably like a washing machine inside the u-joint ball when going down the road. Oil is going to get everywhere.

If you turned the cross (what you're calling a trunnion) around, then you moved the worn surface to the opposite side. That might have initiated the vibration.

Since you have it apart, a u-joint rebuild kit is a good idea.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.