Finishing the 3D printed TPU Shift Knob

[@The4Crawler]

I find the TPU material is an excellent replacement for the OEM rubber shift knob. It helps to dampen out any noise or vibration that comes up the shift lever while driving. I never appreciated that aspect of the original knob. In the Toyota W56 and other transmissions, the stick comes right out of the gear box where the end is in contact with the various shift gates.

[@cbh148]

For some reason, the factory rubber shift knob in my '88 Xtracab DLX 4x4 (22RE) turned sticky in the last year, but the one in my '87 4Runner DLX (22RE) didn't. It's like the rubber suddenly reached some critical point where it's sweating out stickiness or breaking down or something.

[@The4Crawler]

My old '85 knob never turned sticky. Instead, it started cracking and after a few repair attempts, it cracked into two pieces. But I have seen other rubber parts get that sticky surface. I'm sure there's a technical explanation of what's going on. I like to think of it as the plasticizers in the material working up to the surface to produce the sticky feeling. Or that material dries out and leaves the rubber hard and brittle. I've seen this with rubber body mount bushings. Some are dried out and cracked throughout while others are almost like jelly beans, soft and squishy inside with a harder surface. And then there will be some that look and feel like new.