I am in the process of rebuilding a 95' A518, 46RH transmission with Lock-up converter. All is going very well following the instructions of the Transmission Bench videos. Very detailed. My fears have turned into pleasure as it goes together one piece at a time. Check him out on You-Tube.
Truck in question is my 68' D100, 3.91 rear diff and 265-70/15 rear tires ( same diameter as the front 235-75/15) speedometer is spot on right.
Here is my question: PATC has the kit with oil pressure switches controlling the Overdrive (44 or 50 PSI) and Lock-up (50 or 52 PSI)? What has been the result of this on your trucks? Should I pay for the adjustable switches? Kind of leaning that way right now. PATC suggestion is 44 and 52 PSI running stock rear end and tires. I still need to call them in person and talk to their tech guy. Anybody have a source for cheaper pressure switches?
i can talk to my trans rebuilder friend
but would think it just has to do with feel higher pressure with just give a harsher engagement
lower pressure softer shift
I opted to spend the extra money for the adjustable switches and am very glad I did. Unlike being stuck with whatever the fixed switches give you, you have adjustability and even if you go to a different advance curve, readjust the carburetor, change tire size, axle ratio, or any number of other parameters, it doesn't matter, you set overdrive engagement and lockup where you want. Overdrive and lockup solenoids simply engage when called upon and have nothing to do with shift quality or harshness. Even adding an extra friction and steel to one of the clutch packs and installing a shift kit did not result in overly harshness of any shift change and I started with the heavy duty RH47. In my case, a 5 turn adjustment of the stock 727 TV linkage gave me light throttle upshifts of 16-18 MPH out of first and 24-26 MPH out of second. I currently have the overdrive engagement set around 38 MPH and lockup set about 44 MPH.
I also used a 3 foot long hose (braided stainless) to connect to the transmission port that allowed me to place the switches in a box (I made it from scrap aluminum and the lid out of scrap sheet ABS) in the engine compartment on the right fender apron. The brass manifold for the pressure switches was made with fittings obtained at relatively low cost from Harbor Freight as were the grommets mounting it in the aluminum. This enabled me to tweak the engagement speeds as I drove the truck, stopping and adjusting them without crawling underneath the truck, until I got them where I wanted them. Even in the rain it was a relatively painless procedure, taking literally about 30 seconds to stop, pop the hood, adjust a pressure switch, drop the hood, and jump back in. It only took a few times per switch, and after a few miles, I had the overdrive shift and convertor lockup where I wanted. That was a year and a half ago.
The other thing I did different from the PATC diagram is running two toggle switches. One in each of the wires from the transmission connector to the pressure switches (end pins on the transmission connector) as opposed to the suggested single toggle in the B+ wire (center pin of the transmission connector) from the voltage source. The vacuum switch is still in this B+ circuit (to the center pin) to kill the voltage to the transmission dropping it out of overdrive and lockup under full throttle. This allows me to individually engage or lockout the overdrive or convertor lockup, even though I'm at a speed higher than the pressure switch engagement settings. One benefit is to have them set to engage at relatively low surface street speeds, but still be able to manually disengage them to keep from lugging the motor on grades. I also fused and used relays for the control circuits, mounting everything in the underhood box. The GM 4 pin HEI module (mounted to the heat sink) and Mustang coil visible in one of the pictures were added along with a Mopar mag pulse distributor at the same time (along with bypassing the ballast resistor) to give me electronic HEI ignition in place of the points.
I adjusted the pressure switches by road speed and never bothered mounting a line pressure gauge, even though I made sure I could add one to the brass manifold I have the switches mounted on.
