My Line Pressure is WAY OFF! Need advice!

[wjaholic]

I have been batteling a super soft shift in my 727 since I rebuilt it. I haven't driven it any considerable distance, just enough to test drive it up and down the road.

But I almost cant feel the 1st to 2nd shift and the 2nd to 3rd is too soft and smooth.

I have a 9 1/2" Dynamic Converter that is supposed to stall at 2800. But I really have to get the RPMs up to get it moving. Almost like it has a really bad slip in it or it was sticking in 2nd gear.

So I plugged a gauge in to the line pressure port on the passenger side of the transmission and the front servo.

I disconnected the throttle pressure lever (kick down linkage) at the carb. I brought the engine and transmission up to tempeture. I slipped it in to drive (on stands) and brought the rpm up to 1000.

The line pressure jumped up to 90 psi! The front servo didn't do anything, stayed at 0 until I bumped the gas and it shifted in to 3rd gear. Then the front servo pressure matched the line pressure.

When I moved the throttle pressure lever back, both the line pressure and front servo climed to 100psi where it down shifted, the front servo went to 0, but the line pressure continued to climb to 140 as I moved the throttle pressure lever all the way rearward.

I plugged the front servo and moved the gauge to the rear servo. I repeated the same steps as above except this time I shifted in to manual low. The line pressure stayed at 90psi but the rear servo didn't do anything. It stayed at 0 until I brough the RPM up to 1600. That raised the rear servo to 40 psi.

I stopped the rear tires and slowly worked my way up to reverse where the rear servo pressure jumped to 280 psi and jumped around! The throttle pressure lever was all the way forward!

When I rebuilt the transmission I installed the TransGo TF2 shift kit. We have a spare (unmodified) valve body that we are thinking about swapping in there when We pull the pan to inspect everything.

What do you guys think? Something is really off!

 

[wjaholic]

bump

 

[moparman9]

Did you adjust the pressure regulator?

 

[Max340]

the front servo port you were in sounds as though its the one that forces release of the front band, so the reading there could be correct. The fact that the rear servo did not show pressure in manual 1st is a bit bothersome. Do you have the FSM for the car? this would give you pressures that should be present.

 

[wjaholic]

Did you adjust the pressure regulator?

No I dont believe that we did, we followed the TransGo TF2 instructions.

the front servo port you were in sounds as though its the one that forces release of the front band, so the reading there could be correct. The fact that the rear servo did not show pressure in manual 1st is a bit bothersome. Do you have the FSM for the car? this would give you pressures that should be present.

It is a '73 big block 727 that we rebuilt a put in my '74 Duster. I have a couple of books on the 727s, a fsm and a rebuild book. Both of which say the pressure should be in the mid 50psi range.

But, the more that I learn about the TransGo kit is that it raises the pressure and has you measure the line pressure adjustment differently than the FSM does.

I am thinking that I should call up TransGo and ask them what kind of line pressure would be ideal. Because I have no idea what is too much or what even would be right.

 

[Max340]

Line pressure will be higher with the shift kit. Usually they send a small cardstock device that shows the proper dimension on the adjuster. All that you mention sounds normal except the lack of pressure at the rear servo when in manual low.