[sscanrun]

I'm using the one on the metering block

[sscanrun]

Cobalt327- I hook it up and does the same thing

[cobalt327]

"Same thing" = shifting too quick?

What is the rear gear ratio? If you're talking about part throttle, low throttle shifts, they do tend to be very quick if there's no load on the engine. The best way around this is to shift it manually. It will always shift through the gears quick if left in Drive, under low load, light throttle settings.

[sscanrun]

468 bbc ,th400 trans, cam has a 640 lift and rpm range 2500-6500 , single plane intake ,2600-2800 stall , gear 3:90

[cobalt327]

Yeah, w/those 3.90 gears it's gonna shift through the gears quick under light throttle/light load conditions. It's normal for it to do that. Holding the gears manually is about the only way around it.

[496CHEVY3100]

You can drill and tap a port at rear for vacumn connection ,be shure you have Heavy grease on drill bit to catch alumimum shavings ,i would also remove carb and duct tape on inside where you will be drilling. or you can buy an aluminum spacer plate to go under carb with vucumn port already in it ,I have one but do not know how to put pictures on this sight ,if you cant find one i will posy picture in my picture albumn Also do you have the elactric kick down connected if not it will shift to early part throttle or WOT

[MARTINSR]

Are we talking normal shifting or full throttle shifting?

Brian

[ducrider123]

I had the same problem multiple times. This is what i did.

I checked out the tag on the trans to see what it originally came from. IE bigger car usually ment lower rear gears, and earlier shifts for comfort.

Then made sure i had a new red line (adjustable) vacuum modulator. I drove my car and checked the vacuum while the car was at cruising speed. I set my modulator to start pulling in at this measurement. that way when the car is under light throttle it shifts smooth and a lil early but then under heavy throttle it's a lot more firm and a little later.

Normally running anything over 3.42 you have to do governor work. Buy a governor recalibration kit. and start playing with springs and weights. I use a scale and weigh all the weights and compare them to the ones that are original. I also make a graph to record my findings on each combination. also you can remove weight off the outer weight which will help raise your shift points under light loads. inner weight under heavy loads, and the springs separate the shifts.

I went from a 55g outer weight to a 44g. 14g inner weight to a 9g. and 2 step heavier spring. on a 67 firebird 400 th400 3.42 rears. heavy load 1-2 shift 5500, 2-3 shift 5200 rpm.

Also a thing to note is instead of picking 5500 rpm to shift at, you should choose a shift point that correlates with your engine peak torque and hp rpms.