lockup converters

[Boog]

Hey guys, my 85 k5 blazer, 305/700R4, all stock. At about 45 mph, the overdrive kicks in and the torque conv. locks up ok but around that speed and beyond, it jumps in and out. A real nuisance you know. Do you think the vacumn switch on the firewall is bad? I can't find any vacumm leaks. Boog.

[Fast68Chevy]

Does it do that on flat level ground, or on hills ?

[Boog]

Well, mostly on flat ground, around 45 mph on up. I know engine load will make it unlock for passing or up hills,etc. I'm playing with the TV cable now to see if that has any effect on it. It seems to be very intermittent. I remember when the lockup convs. first came out in trucks, many people put toggle switches on them to stop that constant in and out irritance. I don't want to go that route though. Yesterday I loosened up the TV cable a notch or two. Softened up the shifts just a bit but I couldn't tell if the lockup was that much better or not. I do like the firmer shifts in my vehicles though. I'll experiment some more. I just put on some taller tires, so the shift points will occur at a different speed on the speedo too. I also shortened the vaccumn line to the switch on the firewall for the conv. This may also make a difference in how it reacts. Thanks, Boog out.