727 line pressure question

[mderoy340]

I need to drop my tranny pan to fix the leak and decided to check the line pressure before removing the pan. Need opinions if I should reduce the pressure. 1-2 up shift seems to early. Adjusting throttle valve linkage doesn't change 1-2 shift much, it does extend 2-3 shift.
These are the line pressure readings I have.
Wheels blocked, e brake set, 1000 rpm
D/2/1 all the same readings
Throttle Valve FWD 85 psi (FSM says 60 psi)
Throttle Valve Back 105 psi (FSM says 96 psi)
FSM adjustment 1 turn = 1 2/3 psi change.

Thanks for any info

 

[AJ/FormS]

If the shifts are too early,And line pressure is up, And the tv doesnt respond, And the shifts are too early, Then something is not right.
More than likely the governor pressure has not been tweaked to keep up with the increased line pressure.
Do you know if a shift kit has been installed? Has the rear gear ratio been changed?
With no history, I would be tempted to turn the line pressure down to spec.Thats usually the quick fix.The other option is to modify the governor pressure.The governor is asking for a gearchange too early.This requires a lighter plug to start with and possibly a different spring.Its often a real trick to get it right.The shift kit has the parts and directions to do this. It also sounds like the wrong spring is in the 1-2 valve.Normally the outshift rpms are nearly the same between gear changes IF the throttle pressure remains unchanged;that means no gas pedal change.

What I have done in the past is to drill and tap a hole for an1/8pipe plug, right in line with the line pressure adjuster. Then you can mess with the line pressure without dropping the pan.To access the governor is more complicated. the rear extension housing has to come off.

 

[FredS]

change the 1/2 shift spring, and while you're at it, change the 2/3 also. Is your throttle valve full length still? Like AJ/FormS mentioned is there a kit in the VB?

 

[mderoy340]

Last time I adjusted bands I looked things over and I think the VB has a mild shift kit. The VB has the slot filed for the manual valve oiling in Park. Plug with the small orifice installed for the 2-3 shift overlap. The line pressure spring appears to be OEM.
Partial throttle kick down works fine. Shift is firm, does not bang. Same gears 3.23
I'll drive it today and write down shift points for light, medium, and WOT
Good tip on installing a plug. Hopefully my angle drill will be able to get there.

I assume I would need to get a shift kit for new shift springs?

 

[FredS]

Cope sells just the 1/2 spring. Is it just the WOT shifts that are early? How far off in RPM is the 1/2 and 2/3 shift? And what RPM are we talking about?

What motor/power are you at?

 

[KickDown]

You dont need a shift-kit for the new springs. A&A can help you out.
They have a split shift fix kit for $25. Part number is AASVS-1. IMO it would be wise to correct the line pressure before tearing into the VB.
Cheers. Gaz

 

[mderoy340]

Kickdown thanks for the part info.
9.5:1 73 340, TQ larger 1 1/2 primary, 270H cam/1 5/8 headers, 727/8 3/4 SG 3.23s. Assume 275-300 hp
I'll post MPH/RPM shifts later today
Thanks for the help.

 

[mderoy340]

Ran the car today and my shift points are better than I thought. I just got done rejetting the TQ and distributor so the car runs better than it ever has.

Light throttle
RPM 1800 1-2 15 mph, 2-3 35 mph

Normal driving throttle
RPM 2200 1-2 25 mph, 2-3 45 mph

WOT
RPM 4500 1-2 40 mph, 2-3 80 mph

If I lengthen the throttle valve adjustment any more I get the dreaded 2-3 bang shift at light throttle deceleration, as in 2 gear parking lot driving.