Over 30 years ago, back in the day when I was being taught the ins and outs of rebuilding, I was working for my brother Ken “Racer” Brown at Brown’s Transmission.
His head builder, Bobby Phelps, was keeping a close eye on me. I was building an A540E and had everything on my bench clean and ready to go back together… or so I thought!
Bobby came over to my bench and asked to see my direct clutch plates. I pointed them out to him and he proceeded to pick them up, stack them together, center them on the edge of my bench and put his body weight on them just enough to bend them a little.
I freaked out and asked him what he was doing. Bobby told me to get the old clutch plates out of the box and let me show you. I looked at those clutch plates carefully and noticed they all had a wave to them. He then told me if I had put the ones without a wave in them that I would have experienced harsh reverse and a harsh/firm 2-3 shift concerns. It was a great lesson to learn!
From time to time we see the A540 with the harsh reverse and firm 2-3 shifts. It seems that the same problem has popped up again with another Toyota transmission, but this time it’s a 2007 Toyota Tundra 5.7L 4WD with an AB60F.
This vehicle came in with two codes, a P2714 and a P0766. Code P2714 is a Pressure Control Solenoid “D” Performance code (Shift Solenoid Valve SLT). The linear solenoid valve (SLT) controls the transmission line pressure for smooth transmission operation based on signals from the throttle position sensor and the vehicle speed sensor.
Code P0766 is a Shift Solenoid “D” Performance code (Shift Solenoid Valve S4) S4 stuck OFF malfunction or brake control valve malfunction shifting to 5th and 6th gears is impossible.
The codes were cleared and the vehicle was taken on a road test. During the road test it was discovered there was no 5th and 6th gears. When we got back to the shop we checked the fluid, it was dark and smelled burnt!
During the disassembly we found the C-2 clutch burnt. A complete rebuild was done and both the SLT and S4 solenoids were replaced. (figure 1).
There was a very harsh, chirpy 2-3 shift at 20% throttle (enough to chirp tires on corners) and a firm reverse. Light throttle upshifts, all kick downs and coast downs felt normal.
The shift problem was only on the 2-3 shift and shifting into reverse. The first thing the builder thought was there must have been an accumulator spring in the wrong location (figure 2). The valve body and accumulators were removed, only to find that everything was in the right locations.
Next step now is to air check the clutch (figure 3). Primarily the C-3 clutch that is applied for the 2-3 Shift. It has a good air check with 30 psi, what could be the problem?
The only thing that hadn’t been checked at this time was line pressure and rise. But, you would think if it was a line pressure problem we would have other shift concern. But we need to know before pulling the unit back out.
So with the valve body put back on and the transmission filled with fluid, it’s time to check pressure (figure 4). Line pressure at idle in drive should be 50-60 psi and stall should be 180-195 psi in reverse at idle should be 70-80 psi and stall should be 210-235 psi.
What I want to know is what the pressure does on the 2-3 shift. Is it spiking the pressure? The pressure looked the same on all of the shifts, no spikes in pressure.
At this point I recalled the lesson about clutch plates. Looking at a clutch apply chart (figure 5) you’ll see the C-3 clutch is coming on for 3rd and reverse. We need to remove the unit to inspect the C-3 clutch plates.
Going straight to the C-3 clutch it has five frictions and five steel plates. Stacking the C-3 clutch up on the bench, the clutch plates supplied in the kit had a free standing height of .291” no wave to the plate.
After checking with parts supplier, we were able to find a clutch plate that has a wave to it, Raybestos part # R560480. Stacking these clutch plates up on the bench we now have a free standing height of .313” and a compressed stack height of .291” partial waffling on friction surface.
So the free standing height had a difference of .022”, that’s .022” of cushion so that will make all difference on the 2-3 shift and reverse engagement. The real test is to put the transmission back in and take it for a test drive. After a long test drive the transmission worked perfectly!
So, builders beware and keep a close eye on the parts you take out and the parts you put in… that’s not just smart THAT’S STREET SMART!