I know this thread is old, but I just finished my A518 install and thought it would fit best here. First of all I’d like to thank Alan for his write-up and support. Also Rory Fontana for the crossmember and installation tips. I’d also like to thank Paul G on the Charger site for the ideas of controlling the OD and LU shifting. The car is a 71 Challenger with a 93 360 magnum. The trans is a 93 46RH. Converter is a lockup with heavy duty clutches, 2500 stall.
I modified the trans as per Alan’s instructions, except I cut off an additional boss on the right rear. I also dented the trans tunnel on the right and left sides This allowed me to get the trans a little higher up in to the tunnel. I used Rory’s crossmember with the three 1/8” shims, plus I added an additional 1/2” shim. Clearance to the slapstick linkage is less than 1/8”, and less than 1/4” to the upper tunnel crossmember frame. The tailshaft still sits 1” lower than the old 727 tranny.
I wanted it to shift automatically, but because of my 3.91 gears and low manifold vacuum, I didn’t want to use the PATC setup. I bought two adjustable 60 psi pressure switches for $30 each, so I could set the mph the OD and LU come in. I ran a 5/16” line from the governor pressure port to the upper bellhousing mounting bolt. This puts the switches between the motor and the firewall, and I don’t have to climb under the car to adjust them. These work really well, presently I have the OD coming in at 42 mph and LU at 52 mph.
PATC has a deluxe control setup for the A518 for $375. If you look at it closely, it uses a B&M TH400 kickdown switch and a relay. I bought the kickdown switch and a relay from Summit for around $50. It is set so if you push the throttle down about 1” it cuts off the power to the OD and LU solenoids and you’re back in drive. Let up and it shifts back into OD and LU. Works well.
I have a second high beam dimmer switch mounted on the floor as an on/off switch for racing, etc. I’m also using the Bouchillon kickdown cable and bracket. Great products.
The driveshaft was shortened 2.5”. If you notice in the pic, the grease fitting is in the cap, so I can actually grease my u-joints. These are Spicer 7260 joints, p/n 5-1306-1X.
Thanks for this great site and all the info I got here.