yes, variable. vacuum increases with RPM. don't know if it's load specific though.

 

thats still SOMETHING to work with lol
ill have to find out more about this before i put my foot in my mouth, because it smells bad and would hate to taste it

 

Our vacuum pump pulls to about -25PSI. A stomp on the brake pedal will bring it down 10 PSI at a time but hold it constant with your foot held on the brake. So yah I guess that explains why if you pump the brake pedal a few times at idle you loost brake boost! (the '72 had a vacuum gauge already installed so I hooked it up out of curiosity.

 

Hey Archer, so even with a 47rh, your tranny still shifts up too early and still uses the tv cable?

 

humm.....need to figure something out... my trans still chirps 3rd and i want to keep it that way!

 

I think when i sled pull it might just finish this thing off... I'm hopin it does but I'm hopin it doesn't. Then it would make me put a 47rh in it, but yet i don't quite have the money and don't wanna be truckless.

 

Yes. And because of it I can't advantage of allowing it to shift though the gears locked. Driving in 3rd locked at 15 mph creates tons of smoke.

 

vacuum has no bearing on what a 518 618 dose or a 904 727 for that matter

 

I think Just ramit 91 was thinking that Vacuum could be used with a diaphram (similar to Cruise Control) to mechanically push and/or pull the Kick Down Cable. His question was how could it be regulated etc. to be used in this manner.

 

Txs A&A dose it for the line pressuse screw but its some thing that needs welding Ken

 

Yes, i'm looking for a better way to regulate the shifting of our transmissions. Seems like they are speed governed with a kick down cable keeping it in a lower gear.
Does anybody know about the governor weights in the trans. Maybe something out of a gas version would help because of the higher rpm shift points. This should let the trans shift more around 3k instead of 2000rpm.

Again any other ideas on how to makes a 727 shift better is welcomed

 

Here's what has worked well on my truck for two years.
I never had to mess with any of the settings inside the trans.

These transmissions must have proper linkage travel to shift right & not burn themselves up.
They use the TV cable to regulate throttle pressure and line pressure!!

Install the throttle ball in the inner hole on the injector pump arm.
Back out the high Idle screw half way.
Shim or bend the pedal inside so the throttle reaches full travel when floored.
This gives proper linkage travel to match the trans linkage.

Now: have a friend hold the pedal to the floor while you set the TV cable to full travel.
Both the throttle & TV should reach full travel at the same time.
This is how the old gassers were set up.
This will give proper travel to the linkage with the 3200 spring for properly synced shifting.

The trans will shift smooth & slow just off idle & will actually shift at around 2800 - 3000 wide open if i remember right. (I haven't driven the truck in a while)

Also, my gasser TPS mod works well with this setup since the gasser TPS has more travel than the Cummins one & does not readjust itself every time you floor the throttle.
I have found the truck will actually drop out of overdrive when floored in the 60 mph range set up this way.

 

Rampage sounds like you were the most sucessful at getting the auto tuned with the 3200 spring and the ball-on-inner-slot mod. Maybe some transmissions react differently to the KDC settings, but I know I barely got to 3/4 throttle before the KDC would bottom out when I set it to the proper shift settings on the '89. Additionally, of course full WOT romps will shift correctly but it is the around town stop and go at idle - half throttle where most of these mis-shifts are occurring.

 

I will play around with my tv cable and fuel cable to make sure they are set properly(rampage method).
Then i'll let you guys know if and how it works for me.

I also have limited travel with the tv cable and found that the wire shild came loose so i gluid it back in place and that stopped some problems i was having before with binding.