[pjmoreland]

I redid my TCC harness today according to the schematic in post #33 above. It works just the same as my previous harness, except now the internal transmission over-temperature switch should be active. I have no good way to test the temp switch, but I suppose I might find out if it works someday if my transmission overheats and the TCC locks in 4th regardless of what the vacuum switches and relay are trying to do.

One minor issue I've noticed is that if I'm cruising along in 4th with the TCC locked and I coast down to a very low speed, the transmission stays in 4th and the locked TCC really lugs my engine and causes it to stutter a bit. I noticed this in stop-and-go traffic the other day. Connecting both of the vacuum switches to the carb timed vacuum port would solve this issue by unlocking the TCC whenever I'm coasting. I don't like this solution as I mentioned in a previous post because it makes for an unnatural driving experience when coasting and reapplying the accelerator at higher speeds. A partial solution to this issue is to connect only the high vacuum switch to timed vacuum. This will prevent the TCC from re-locking after tapping the brakes to coast down to a low speed. At the same time though, this will not unlock the TCC at higher speeds when coasting periodically because the high vacuum switch is ignored by the circuit once the TCC is locked.

The ideal solution for the low-speed lugging issue would be to install a B&M 70244 speed-based TCC controller, and use its output signal to power my harness instead of tapping into the 12V from the Tail Stop fuse. This way the TCC could be prevented from locking altogether under, say, 35mph, but the vacuum switches and delay relay could still function as I have them functioning at higher speeds. I doubt I'll go this route though because the B&M controller is $242.

*EDIT* - The internal switch in the transmission is the 4th gear switch, not the 3-4 switch as it says on the schematic below