I'll back up a little because I forgot to mention a step I took when removing and installing both transmissions...
I used the drivers side of the car to remove and install the transmission. I removed the exhaust pipe and muffler/tailpipe sections. I did this to make it easier and to have more clearance, I disconnected the exhaust/header flange and removed the muffler and tail pipe section. Not difficult to do. I also purchased and installed new engine exhaust manifold and header tube/flange gaskets when I installed them.
Back to the transmission swap...
The new transmission cross member I purchased from US Car Tool is very nice. It stated in the instructions that the customer may have to modify it to make it work for their car. I had to slightly modify a small section of the cross member to make room for the speedometer cable connection to the transmission. I asked a friend with a plasma cutter to square up one of the corners to allow additional room for the speedometer cable connection. It worked well and has a nice finished look. The instructions require that you use a GM transmission mount. I purchased an Energy Suspension Performance Polyurethane transmission mount for RWD cars and 2WD trucks. The part number is 3.1108G. "Transmission Mount for GM". The transmission cross member comes with a 90 degree bracket that is not attached. Basically you install the cross member and mock up the transmission height. When you determine the transmission mount height, you C-clamp the 90 degree bracket to the cross member. Remove the cross member and weld the 90 degree bracket to the transmission cross member. I had the same friend Mig weld the bracket and the job turned out perfect. Afterwards I painted the cross member to prevent corrosion.
Attaching the speedometer cable to the transmission. What a pain!!! There is barely enough room to do this due to the upper torsion bar support. I took 360Fish advice and had to grind town the corners of the speedometer cable hex nut. What I found out by accident is that the speedometer gear/attachment on the transmission is an eccentric. I removed the hold down clamp and removed the section completely. I inspected the O-ring and it was good. Lube the O-ring with transmission fluid and install back into the transmission while carefully mating the gears. I was then able to turn the speedometer connection towards the back of the transmission. I installed the hold down clamp while aligning the notches in the transmission speedometer connection. It worked! I had just enough room and didn't have to (or want to) grind the upper torsion bar support. Next, install the transmission cross member and attach it to base of the transmission. Torque all of the bolts.
I want to mention that my 70 Challenger has the steering column gear shifter. I did not have to go into the process of modifying any hardware as 360Fish did for a floor shifter car. The only thing I did was exchange the transmission gear shifter lever and kick down lever from the 727 to the A518.
Electrical, this is where things got a little confusing. The 727 and A518 both have a three prong neutral safety switch plug on the transmission. The first wire is black. This is your 12 volt DC power wire. The second (or middle wire) is brown with a yellow stripe. This goes to your starter relay in the engine compartment next to the battery. The third wire is black with a white stripe. This is for your reverse lights. The A518 has a yellow connector with a two or three wire connection. My A518 only has overdrive. My connector only has two wires. You have a locking torque converter and overdrive. Your connector will have three wires. As 360Fish explained in his write up, connect a wire from your black wire 12 volt DC on the neutral safety switch and attach it to the center wire that connects to the yellow plug. Refer to 360Fish wiring diagram to complete the circuits for a locking torque converter A518 transmission. Also, the PATC transmission webpage has good information and products to support a locking torque convertor A518 transmission and control it automatically without the use of toggle switches.
For my overdrive only transmission, I connected the 12 volt DC power wire on my neutral safety switch to a blue wire on the A518 transmission yellow connection port. The remaining wire was orange. This is the overdrive transmission relay ground wire. I ran this wire to a toggle switch under the dash board near the steering column for easy access. I connected the other side of the toggle switch to a good ground connection. I used a steering column mount. Basically when flipping the toggle switch, you are connecting the ground on the coil of the overdrive unit inside the transmission. When the coil energizes, the transmission will shift into fourth gear (overdrive).
Measuring the drive shaft length...
With help I used a tape measure and measured from the transmission spline gear face to the center U-joint opening on the pinion of the rear end. I highly recommend taking pictures of the measurements and giving copies of these measurements to the drive shaft shop to avoid miscommunication. Your car MUST be level and at ride height for a correct drive shaft measurement. I had the rear jack stands on the rear axle housing for ride height. I used a small bubble level on the tops of the doors to indicate being level (or very close to).
Other information...
I needed to change the transmission filter, oil pan, and gasket. The original pan was wet and was somewhat rusty. The transmission filter was no problem. I bought this at my local auto parts shop. Breakout your wallet! The oil pan and gasket are a dealer only parts. The gasket is a special reusable type molded plastic material with rubber gasket material weaved into it. The oil pan was deeper than the original. The transmission system including torque converter will hold 10 quarts of oil. The transmission oil pan and gasket cost me $182.00.
I took 360Fish advise and added a transmission cooler. I purchased some bulk straight steel 5/16" tubing and bent my own lines to connect the transmission cooler. I also installed new pre-bent transmission lines from In-Line Tube. I purchased the transmission cooler from Rock Auto. I matched the cooler size with the original year make and model truck the transmission came out of. Note when connecting rubber transmission hoses to steel lines, you CANNOT use fuel line. Transmission oil runs hotter and under more pressure than rubber fuel lines. You MUST use rubber hose made for transmissions. Also, when connecting transmission rubber hoses to steel lines, double flare the steel lines. Use fuel injector clamps to secure. I personally used two fuel injector clamps per connection.
I installed the muffler/exhaust pipe, starter, and made sure my shifting and kickdown linkages all worked without binding. I also installed high temperature muffler wrap around exhaust pipes I thought were a little close to the transmission and cooler lines.
Well I think that about covers it. I'm waiting for my 2 degree axle shims to arrive so I can install and test drive. If I think of anything else, I'll be sure to continue this thread. Best of luck with the engine/transmission install.
Regards,
Tirekickertoo
