overdrive automatic

Conductorblg · Post by **Conductorblg** » Fri Feb 18, 2022 1:17 am

Just finishing up the install of a 2005 47RH behind the 383 in my 68 Camper Special. I managed to take some photos as we were doing it. Understandably, it wasn't exactly a straight bolt in and we had to deal with a few issues along the way. I can explain what changes were made to bolt the diesel transmission behind the 383 and in the truck. Also we made changes to the governor and added a shift kit to make it compatible with the RPM and torque characteristics of the gas motor.
Would anyone here be interested in a writeup and a few pictures detailing the process?

BigBlockTrucks · Post by **BigBlockTrucks** » Fri Feb 18, 2022 8:44 am

I’m sure many of us would be interested to see how it was done. There aren’t a lot of options for overdrive behind a 383.

my5thmopar · Post by **my5thmopar** » Fri Feb 18, 2022 9:35 am

Watching!

Conductorblg · Post by **Conductorblg** » Fri Feb 18, 2022 1:37 pm

I thought this might be interesting to a few of you. It may take a few days to do a proper writeup and I'm still figuring out how to resize my pictures small enough to post them, but I'll get on it.

Kaegi · Post by **Kaegi** » Fri Feb 18, 2022 5:44 pm

looking forward to it. i use postimage.org

Conductorblg · Post by **Conductorblg** » Mon Feb 21, 2022 4:48 am

Following up on my 727 to 47RH conversion in a 68 Camper Special:

This may take me a while, so I'm going to start out with an overview of the process, then later add photos with captions to make it clearer.

The Transmission: This transmission is simply a lockup 727 with an overdrive section added in the tailshaft extension housing and controlled by two electric solenoids (the smaller 42RH is simply an overdrive version of the 904-998-999). Automatic control of the transmission can be managed by two pressure switches and a vacuum switch replacing the factory computer. The vacuum switch could be replaced by a mechanical switch mounted to the accelerator linkage for motors with poor vacuum if needed. Later versions (RE) control all shifts by solenoid and would require a factory harness and PCM, or a stand alone computer to control.

If your truck has a small block, the 46RH bolts directly to the block, making it the most logical choice, but I went with the internally beefer diesel/V10 transmission because my truck has a 383, and I would be converting the case using an Ultra Bell anyway.

An additional friction and steel was added to one of the clutch packs, but it wasn't necessary to modify the other. We added a larger aftermarket servo and a 5 to 1 lever. An aftermarket shift kit was used and the governor weights were changed out using weights for a 904 because they were on hand.

The case was initially cut apart using a Saws All with a 14 tooth blade installed if I remember right. It was then taken down with a 4 1/2" angle grinder mounting an 80 grit disc, finally finishing up with a three inch 120 grit disc on a pneumatic die grinder, constantly checking the fit of the Ultra Bell with feeler gauges to get clearance without taking off too much. The Ultra Bell is designed for a late style starter and the nose of the original starter would not allow it to seat. Rather than going to the expense of replacing the starter, it was simple enough to machine the starter nose recess in the Ultra Bell a little deeper with an end mill allowing the original starter to seat into the bell. I also took down areas in the starter pocket slightly where I thought it might not clear the starter drive with the 3" disc on the die grinder, but I don't think it was really necessary. We did break through a little with the end mill, but it doesn't affect anything structurally, and the later style starter will still fit. A small rubber plug could be glued over the area on the outside of the Ultra Bell with RTV, but I haven't even finished adapting the original dust shield to the bottom of the bell yet, so it's redundant at this point.

The Ultra Bell is a certified race piece and has no bosses to mount linkage, so I made up templates from left over packaging cardboard for a bolt on bracket. I made up the bracket from some scrap 3/16" plate I found at the local steel salvage yard. That bracket bolts to the backside of the engine mounting flange on the Ultra Bell using two of the mounting bolts. My welds look like crap, but it's hell for stout, and the stock shifter cable bracket lines up perfectly. I wasn't going to give up my dash mounted shifter, no way, no how!

An 11" convertor is the largest that can fit in the Ultra Bell. I wanted a high stall (stock for a 340 or HP383) and it took a couple of weeks for our rebuilder to source the components. The 727 (Loadflite in Chrysler speak) from the truck has a 12" convertor and it takes a larger flex plate than the 11" convertor needed for the Ultra Bell, requiring us to change it out for a smaller one. We initially though the convertor would require a larger hub for the 47RH, but this turned out not to be the case. Apparently this hub was enlarged on the 48RE, but the 47RH or RE uses the same converter hub as the 518 and 46RH or RE.

The original speedometer drive from the 727 bolted right in with no adapting or modification, and the cable length was spot on too.

The neutral safety switch was a bolt in too.

The stock 727 throttle valve linkage was already adapted to the Edelbrock Performer and Street Demon carburetor by my friend Bob when he changed it out from the two barrel for me right after the truck followed me home almost five years ago. My friend Don (Transmission and Brake Center, Salem Oregon) bolted it right to the 47RH. Adjustment consisted of screwing in the adjustment rod 5 turns. Under light or no throttle, it shifts out of first at 16 MPH, and out of second at 22 to 25 MPH.

The cooler hard lines for the lockup transmissions are bigger than the 5/16" lines used on 727 transmissions, so I adapted the 3/8" lines out of a 90 3/4 ton, carefully adjusting (bending) them over the leaf spring crossmember and around other components including the 383 oil pan. Aluminum brackets were constructed and attached to long oil pan bolts with spacers to place those brackets below the oil pan flange. The cooler hard lines then run through rubber insulated Adel clamps attached to the brackets to retain them. I elected to run a large (11" X 11" X 1 1/2") external plate style cooler bypassing the in tank radiator cooler with it's smaller fittings. I stepped up to AN fittings and braided stainless steel lines off the hard lines, through the core support, to the cooler hung in front of the radiator. Plugs were placed in the radiator transmission cooler openings. This cooler keeps the transmission cool without the need for additional shrouding or fans.

Crossmembers:

Truck is hell for stout, there are three crossmembers in the area of the transmission alone.

The transmission clears the underside of the truck easily, the crossmembers not so much. Farthest forward of the three is a crossmember tying together the rear perches of the front leaf springs. It runs just under the transmission oil pan and has a drop out center section with end sections riveted to the frame rails. Because the 47RH has a pan roughly 1 1/2" deeper than a 727, the crossmember center must be dropped to clear. I planned to build a new center section out of square tube, but found that cutting the original center section midway between the end sections and the transmission oil pan allowed me to drop it enough to clear using 3" X 3" plates made from the same 3/16" plate used for the shifter bracket. I bolted the cut off ends of the center section up and welded the plates to them, I then kept grinding and fitting on the center until I could just slip it in place and have it stay before welding it solid. I have about 1/2" clearance on the 47RH transmission pan.

Next crossmember back (middle of the three) held the trans mount for the 727. Because it was tight to the 47RH extension housing and would have required cantilevering a bracket off the back side for a mount, and I didn't have the mount plate that bolts to the three bosses on the bottom of the transmission extension housing, I elected not to use it.

Third crossmember back almost lines up with the boss right at the rear of the 47RH extension housing that would normally mount a vibration balance weight in some instances. Because this boss on the extension housing is a flat pad already drilled and tapped for bolts (3/8-16), I chose to put the mount here and use this crossmember.
The distance from the centerline of the output shaft to the floor of the cab was 4 3/4". Using a 1" thick piece of steel 3 3/4" X 6" from the scrap yard allowed using a generic Camaro/Mustang style biscuit mount. Holes were drilled and counterbored in this plate to attach it to the extension housing with hidden Allen head bolts. Holes were drilled and tapped in the plate to attach the mount, centering it front to rear where it bolts onto the crossmember. Because this crossmember rises sharply on the right side to clear the exhaust, the mount appears not to be on the level part of the crossmember, but it is. Distance from the centerline of the output shaft to the floor of the cab is 4 5/8", although replacement of the front motor mounts with the new ones already on hand will likely restore this dimension back to what it was.

Driveline:

Measuring from the back of the transmission case to the end of the output shaft, we found the 47RH is 2 3/4" longer than the 727 requiring the driveline to be cut. I had it cut 3" to be safe, but 2 3/4" would have been just fine.

Controls:

Two hydraulic and one vacuum switch are required to control the transmission without a computer, these switches were sourced from PATC in Louisiana (looking for information of this swap, I found them online). They were possibly the first shop to adapt the Chrysler OD transmissions in place of the earlier transmissions and have a really thorough writeup on their website.

Because of all the adjustable switch gear, I mounted these switches in a box I built and mounted the box on the fender apron in the engine compartment, rather than somewhere less accessible under the truck. The hydraulic line to run the switches comes off the #4 test port at the upper right rear of the main transmission case. This did require a 3' long hydraulic line to reach the control box.

PATC instructions online recommend a 1 to 6 inch vacuum switch. They sent me a 7 to 22 inch vacuum switch, so I called and ordered a 1 to 6 inch vacuum switch, but after consulting with the tech at PATC, I've decided to use the 7 to 22 inch switch, initially setting it at 8 inches with a Mityvac. The power brake hose fitting on the power booster was replaced with one having a second small nipple and a vacuum hose was run from there across the firewall behind the engine air cleaner, behind the right hood hinge, and down the fender to the vacuum switch in the control box.

I stepped up (at almost twice the money) and purchased adjustable pressure switches, because I felt (and the PATC people agreed) the larger tires of the truck would change the OD and lockup points obtainable with the lesser expensive fixed switches. I wanted to be able to use the OD and lockup at less than highway speeds and be able to fine tune the setting points to suit my driving area and style.

Not having a stock Chrysler 3 pin wiring harness plug socket, I ordered a plug from PATC. The WeatherPac type plug they sent goes on the pins, it doesn't fit the electrical socket on the transmission properly, allowing moisture and whatever else access. Unless I can find a suitable substitute or a stock Chrysler plug, I'll have to address sealing it up in some way eventually.

I modified the schematic given on the PATC website to include two dash mounted rocker switches enabling me to lock the transmission out of overdrive, but engage the lockup feature of the convertor. Running with the convertor locked up with the transmission not in overdrive might prove to be quite advantageous for a truck that's not just a toy. I also decided not to depend on the 50+ year old wiring from the ignition switch for power, using it to only run relays. Power is taken from the starter relay and a ground is run direct to the engine block. My wiring diagram also shows the wiring for changing out to a GM HEI 4 pin module, Mustang E coil, and a new genuine Chrysler mag-pulse distributor for the ignition. I also added a Sun tachometer I had laying around into the mix (mainly to help adjust the overdrive and lockup points, but mounted to the steering column it fits the era of the truck and does kind of look cool. I'll include my wiring diagram when I add the pictures.

PwrWgnDrvr · Post by **PwrWgnDrvr** » Mon Feb 21, 2022 5:31 pm

The stock HD gauge set includes a nice, matching tach. The same setup can also be upgraded with modern round gauges that look very similar in shape.
https://www.dolphingauges.com/
Much nicer than the aftermarket column mount tach and still very much era style correct.

Conductorblg · Post by **Conductorblg** » Sat Sep 10, 2022 2:03 pm

I wanted to include these photos back in february, but being a luddite had no idea how to resize them at the time

Conductorblg · Post by **Conductorblg** » Sat Sep 10, 2022 2:11 pm

more photos

Conductorblg · Post by **Conductorblg** » Sat Sep 10, 2022 2:20 pm

yet more pictures

Conductorblg · Post by **Conductorblg** » Sat Sep 10, 2022 3:29 pm

While I had hoped for more, the fuel mileage increased only about 2 MPG initially, but I've since changed the metering rods in the Street Demon and it may have improved slightly from that. Perhaps playing with ignition advance curves to optimize the timing for RPM and load and using an O2 sensor to help with tuning will give me the 5 MPG increase I was expecting. On the other hand, the RPM has dropped from 2600 @ 65MPH to 1800 @ 70, reducing the noise and vibration at speed enough that cruising on the highway at normal freeway speeds is enjoyable now.