1-2 Shift Hesitation

Hey guys, I have a shift hesitation on my 1-2 shift at WOT. This is in 4wd, TCC permanently grounded. I don't notice it in 2wd probably because I cant load it enough without the tires spinning. My 2-3 shift seems to be fine. I tried to tighten the front band and it didn't seem to make a difference, maybe made it slightly worse. When I initially set the band I did 72in/lb then backed off 1-7/8 turns.

47rh. Single disc billet converter from Revmax. Transgo TFOD-Diesel shift kit. Line pressure in 8 turns, last time I checked was when it was in 7 turns which was about 135 at idle. If its pertinent, Ill check again what my pressure reads now. Kickdown stop is in almost all the way. Maybe 4 threads showing. Endplay and clutch packs were all within tolerance, on the tighter side. Billet no leak accumulator. Upgraded Oringed front servo cover. 3.8 apply lever, strut, and anchor from goerend.

I appreciate any help I can get in tuning this out. It has to be adding at least 2 tenths to my time.

Running 70% Hygard Low Viscosity, 30% cheap Oreillys Dex/Merc. The fluid is maybe a quart to quart and a half over full. I checked after running it hard to see if it looked aerated at all, it looked fine so I didn't bother pumping the excess out.

No ideas? Is it possible that the fluid is sloshing back and starving the pump?

So I just put a gauge in the accumulator port. It says 125 at idle and maxes out at 150 in overdrive.... :huh::

Something not right with the valve body? You should be about 90psi at idle.

rockjeep73 said:

You should be about 90psi at idle.

Click to expand...

You saying pressure should jump from 90 at idle up to my Goal of 180 max in overdrive at 2500rpm?...

Or are you saying that overall my pressures are high? Because that for sure isn't the case, the transmission wouldn't last a week behind this motor if I was running lower line pressures...

So I pulled the pan and valve body. I had a few theories and ideas.

I turned my line pressure in to a total of 10 turns. Which seems like ALOT. There wasn't even any threads showing out the other end of the spring perch piece. My line pressure is now about 140 at idle and 170 max in overdrive.

I replaced the spring in the part-throttle valve body with the white one that came in the Transgo shift kit. It was recommended for gas and 24v use... I'm guessing that it is to raise up shift and downshift points? I figured with using this spring it would allow me to lower the tv hard stop to make the lower throttle shifts bang less.

I also added the restricted orifice plug into the accumulator port in the case. I know that they say this is not needed since it is in the new seperator plate, but my thought was now the restriction orifice is closer to the accumulator. From my understanding, this helps keep the accumulator partially charged and ready for shifting?...

So now my part throttle shifts seem to be smoother and about 300rpm later even with the tv hard stop turned out about 2 turns. My overdrive still kicks in almost right after 3rd, but I believe I need to adjust the TPS to change that... My WOT 1-2 seems to be doing a lot better but I haven't got to really run it HARD.

rockjeep73 said:

Something not right with the valve body? You should be about 90psi at idle.

Click to expand...

After doing more reading, I think you are saying that with my max WOT pressure only being 150, my idle pressure should be lower.... So it sounds like something isnt right? But I don't know where to start looking?

I think I found a possibility as to why I might only be seeing this problem when I am at WOT. After studying the Hydraulic diagram I think it is highly probable that what is happening is my governor pressure is pushing on one side of the 1-2 governor plug and trying to force the shift to 2nd (and perhaps a little early) all while the kickdown passage is filled on the opposing side of the 1-2 governor plug. It would make sense to me that with the high line pressures I am running and with a leaky governor that is causing early shifts (read higher than normal governor pressure), the kickdown pressure and governor pressure are fighting with eachother causing the 1-2 Shift Valve to momentarily pause between spools.

What say you?

Redrider2911 said:

You saying pressure should jump from 90 at idle up to my Goal of 180 max in overdrive at 2500rpm?...

Or are you saying that overall my pressures are high? Because that for sure isn't the case, the transmission wouldn't last a week behind this motor if I was running lower line pressures...

Click to expand...

Yes 90 to 180 is possible, but what I overlooked is how far you have your tv stop ran in, that explains the much higher than 80-90 base pressure that you will typically see with the tfod diesel kit.

Well I'm going to check pressures tomorrow to make sure the governor is operating properly. If it is, I'm going to look into either drilling a hole and bleeding off the governor pressure more to raise my shift points, or put stiffer springs in the 1-2 and 2-3 shift valves. Then I can lower the TV stop to lighten up the shifts between park, drive, and reverse. I might look for an even stiffer TV valve spring too so the throttle pressure will ramp up quicker. Another thing I hope I can accomplish is modifying the drains between the pressure regulator and boost valve so the jump in pressure when locked will be closer to the 48re.

Checked governor pressure. I am literally double the MPH throughout the whole range. Didn't witness any sticking or pressure drops, ect. It would make sense to me that when a governor fails, it would constanly be low on pressure. What would cause it go proportionally higher than MPH? At first I was thinking that it could be because my line pressure is doubled; but that doesnt make sense to me as governor pressure is controlled off a spring; not a restrictor orifice correct? So line pressure shouldnt have much of an effect on governor pressure...