jaw0001

The guy who had my 68 firebird before me had the converter lockup wired wrong, now I am trying to fix it. I understand the function of each item in the 4th gear pressure switch, brake switch and vacuum switch setup, and was wondering three things I haven't seen explicitly answered:

1) Is anything more than the 4th gear switch really necessary? Seems to me the lockup will let go in time in anything less than an all out panic stop.

2) Is the brake switch necessary when a vacuum switch is used? Seems like it's a split second between hitting the brake and high vacuum.

3) Was wondering if I could substitute the unattractive GM firewall mounted vacuum switch with a honeywell component- http://content.honeywell.com/sensing...scorp/P3_6.pdf
(last page) I think I would need a normally closed unit, but what would be a good psi (I have a vortec headed 406, dual plane, 262EH cam - hi vac at idle). This switch would be obscurely screw directly to the plenum port behind the carburetor.

Thanks

8a8mfh

iTrader: (3)

I never used a vacuum switch, never wanted to or found it necessary.
I always wired a three position toggle switch along with the fourth gear pressure switch.
One position would be manual lock up in any gear (except first), one position would be no lock up, one would be lock up automatically in fourth.

If you insist on a vacuum switch i think some experimentation may get you the right setting, actually I think thats the only way to get the right setting. All I know is I cannot stand driving in moderate traffic, having to be on and off the gas and having the tcc lock and unlock over and over due to high and low vacuum.
I know some people like it to be fully automatic, but I'd just switch mine to off in situations like that. Plus I had the governor set to switch out of fourth with little throttle to prevent lugging.

jaw0001

I'll just do the 4th gear switch only (and maybe the toggle) and drive it, see how it feels. Thanks for the response. Top quality forum here.