[trx9]

Hey guys and girls,

I have a 1964 chevy C-10 stepside, stock 350 V8, 3:73 gear, backed up by a freshly rebuilt 1985 700r4 ( yeah i know, should of went wit 87 or up) with heavy duty parts according to a local reputable builder.

It shifts find but when you are merging onto the highway between 50-60 mph at half throttle it will shuffle between 3rd and 4th gear several times (annoying and bad on the transmission I've been told). My 84 700r4 that was supposebly replaced with the 85 did the same thing.

TV cable has been adjusted correctly and I have the geometry kit from Chevy Bowtie transmission web site for my eldebrock 600 carb.

Also, I've noticed if your at a constant 30 mph, it will shift into 4th. Half throttle shift are 1-2(15-20), 2-3 (25-30), 3-4 (40-45).

[C-10]

If the truck has a lock-up controller and L/U TC, the shifting you describe could actually be the TC lock-up cycling on/off repeatedly.

Something to check, anyway.

Maybe the local reputable builder could help further?

[fast68]

mine in my 91 s-10 does this at around 40 or 45 just cruising along, like it doesnt know if it should be shifting up yet or not.

very reliable though.

i just live with it because its a 196k miles and still going strong

resetting the cable didnt do anything of course

probably is the TCC engagement yeah.

[trx9]

C-10, you were correct.

A light bulb went off and I realized it was the TC lock up feature. It seems to engage in third and fourth at a steady cruise.

I went and hooked up a lighted toggle switch between the TC wiring and the power source at the fuse box. I leave it on for normal driving and then just flick the switch off (shuts off TC lock up) when heading to the highway, perfect.

Once I'm on the highway I just turn it back on and the TC works properly.