95 Hard Shifting When Hot

[Nathan Plemons]

Recently I have noticed that at times my truck doesn't want to shift smoothly, especially when trying to go into first or reverse from a dead stop. My first thought was that the slave cylinder was going out again. When it went out the first time, however, I could easily put the truck into first gear by shifting into fourth, and then going into first. This time, that trick doesn't work.

I started paying close attention to it and I've figured out that it is only hard to shift when the engine is really hot. What I mean by this is that if I'm driving normally and the engine is at it's "normal" operating temperature, it shifts fine. However, if I sit in stop and go traffic for a while, or even a drive thru line for any length of time and the temps start creeping up, it starts acting up.

Likewise I can drive somewhere at "normal" temperature and park it. If I come back maybe 5-10 minutes later it won't easily go into any gear, it will want to grind. It behaves like I don't have the clutch all the way down, but I most certainly do.

What is really odd is that it can be hot enough to cause a problem, yet I can drive less than a quarter of a mile at a reasonable speed to cool the engine down and it will immediately shift better. It is completely repeatable and seemingly only dependent on engine temperature, ambient temperature has little effect.

If memory serves, the clutch system consists merely of the master cylinder, the slave cylinder, and the hose in between. On the 300 six cylinder none of this comes particularly close to the engine. I can't imagine any part of it being in such close proximity to the engine that it could heat up or cool down as quickly as the engine does.

Short of the cheap plastic slave cylinder going bad, the only thing I can think of is that the fluid in the clutch has drawn too much moisture and is boiling at high temperature. The air bubbles then collapse when I depress the pedal, preventing the slave cylinder from working completely. The only thing that bugs me about this theory is that I don't notice any difference in pedal feel.

Thoughts? The slave cylinder is cheap enough, I'm just really not big on the idea of pulling the transmission to swap it if I can't definitively prove that this is the problem.

Second question.. If I do have no choice but to replace the slave cylinder / throwout bearing combo again, does anybody know of a metal version that might last instead of the cheap plastic ones?

Thanks!