Transmission / Overdrive: Update...Funny symptoms : Overdrive (1953 2R6)

[jackb]

In another post, I concluded a successful adjustment to my OD cable - to - lever adjustment. I decided to take the truck on a 100 mile run, on the highway, to confirm operation. [ Note: There was some light drizzle while driving home that night. ] Driving along, without a hitch in operation, I felt the engine surge, or rev up and it felt like I'd lost power to the rear wheels. This happened 3 times while at the end of my last 5+ miles home. The first 2 times were almost immediately together, the 3rd was a few minutes later. Lasted maybe 1-2 seconds and "IN" overdrive. There were no other symptoms. No problem with OD operation in all functions up til then. I'm denying that the rear wheel(s) lost contact on the wet surface because there was no tail spin or wheel hop. No other noises at all. I got off the highway and finished the last few miles in conventional 3 speed w/o issue. Free wheeling issue ???

[jclary]

I think I can help you here. Now that you've solved your mechanical OD cable problem...time to check your little "kick-down" switch on your throttle linkage. You'll notice that that switch is screwed into a bracket and held in place by a jamb nut. There's a little paddle "doohickey" (my technical term) that contacts the switch plunger. The switch needs to be adjusted (screwed into the bracket) so that the paddle only pushes it in at near "full throttle." It does not take a lot of turning on the switch to make a big difference in sensitivity. Make sure you mark your wires good so you can correctly reconnect them after turning the switch.

Our trucks are sprung much stiffer than the cars. They tend to bounce around a lot. What happens is that as you are bouncing down the road, that part of the bracket that contacts the switch plunger, will kick your overdrive out merely from vibration. Since you are happily motoring down the road without intentionally flooring the accelerator...the sudden kickdown will startle you as the engine rpm speeds up without acceleration. Also, since you are not jamming your foot to the floor, it does kinda freewheel as you are neither decelerating or accelerating. However, if you're like me, you almost panic and lift you foot off the accelerator pedal. As soon as you do that...the overdrive re-engages and the vehicle resumes "normal" operation.

Once I experienced that a couple of times, I realized that my kick-down switch was adjusted too sensitive and needed to be backed off a thread or two. Check that out and let us know what you find.

[RadioRoy]

The overdrive free wheels when it is below overdrive speeds, but not when the overdrive is actually engaged.

Could your surges have happened at lower speeds, typically below 25-30 MPH?

Or, could it have dropped out of overdrive electrically from something like a loose wire or dirty governor contacts?

[jackb]

Roy 1st: These happened while driving around 60-65 mph. Since it went back into good operation, I'm unsure about wires, but will check in the AM. Now John..... you really got me thinking. When I adjusted the kickdown switch, I made sure that there was no possibility of the plunger not activating the switch. Might be too close to the plunger.....Again, will check.