I have a 43re that drops out of overdrive when I hit a hard bump in the road. It will not go back in OD unless I stop, turn the ingition off and restart the engine, then it drives fine. It doesn't do it everytime a hard bump is encountered. Other than this problem it drives and shifts fine. I have checked all the wire and connectors everything looks good. Trans fluid is fresh ATF-4 and level is good. Could it be a lose connection internal to the trans or possibly a bad solinoid in the trans? I drove it on a 500 mile trip today and encountered this problem three times.

Sounds like it sets a code in the PCM when it does this which can be why it wont go into overdrive until you shut the ign off and start it again. I have run into that before that once the PCM has the right code in it related to the trans overdrive problem it wont let the overdrive work until you shut it off and then if its not a hard code and the PCM dont see it on restart it will let the overdrive work again. I would first see if it sets a trans related code in the PCM when it happens. What year and vehicle is it ? Ron

Ron, it's in my 52 Dodge truck. The PCM is an 01. I'm not sure the year or what vehicle the trans is out of. I'm getting a po500 code generic vss 3 signal. I still haven't had a chance to get the PCM flashed. The trans output vss is new. I'm thinking the vss 3 signal is abs related. The truck has no abs.

It can depend on the year. If your trans is a 42RE with an electronic gov then it will have a speed sensor in the tailhousing that is for the output shaft/driveshaft speed. The PCM uses that for the driveshaft speed so it knows where to set the gov pressure as gov pressure is related to driveshaft and trans output shaft speed. Then the PCM will duty cycle the gov solenoid to set the gov press and it will also look at the gov pressure sensor to be sure the gov pressure is where the PCM wants it. Course when a truck came into the dealer I would put the DRB scanner on it and see if that sensor is working. Did you use all the factory harness with the DRB scanner OBD connector where you can hook a scanner up ? If not that should be a two wire sensor that you can check with a low reading AC voltmeter as that will have a low AC voltage reading when turning. That sensor basically should work the same as the Mopar electronic dist two wire AC pick-up coil as it should be a two wire sensor and not the 3 wire Hall Effect sensor. Ron

Ron, I have a OBD scanner. I used the factory harness and can/have hooked up the scanner. I also kept the check engine lite. I can read and erase the code to turn off the check engine light. The VSS sensor on the tail shaft is the three wire Hall effect type. I replaced the tail shaft sensor with a new sensor. The diff ratio is 2.92. I'm basing this on the tag on the diff cover that has 2.9 stamped on it. I'm running 17 inch rims with a 235/75/17 tire. Tire diameter is 30.5 inch. I'm wondering if the trans out put speed is to slow and the PCM Is looking for a higher speed causing it to throw the PO500 code and kicking the OD out. I'm wondering if a lower diff ratio like 3.55 or 3.90 would fix this problem. I don't believe maw MOPAR ever put that tall of a tire on vehicle with 2.92 diff ratio.

Oh so it is a three wire hall effect type sensor as its been a while for me but I just remembered the two wire sensor on them. As long as thats the factory sensor and PCM then it should work good. The thing is many year trucks I remember used the ABS sensor in the rear diff for the speedo as that info was bussed to the cluster for it to work the speedo. That sensor info in the ABS module was set as we could set the gear ratio and tire size so it sent the right info to the speedo/cluster. We also had an option for Revs per mile if it had an odd size tire on it but the sensor in the trans tail housing had nothing to do with the speedo from what I remember it only was for the output shaft speed and gov press on the 42RE. But Mopar did use a hall effect sensor in some truck trans tail housings when they had fully hydraulic gov and they were for the speedo on earlier years without electronic gov. This is definetly the electronic gov in it right ? Also a taller tire wont matter as the gov pressure is related to driveshaft/trans output shaft speed as the tire size would only effect the speedo which this sensor should have nothing to do with if this is an electronic gov from all I remember as all electronic gov trucks use the RWAL ABS as standard and used the ABS sensor in the rear for the speedo.Ron

There should be electrical plug on the drivers side of the trans which points up and I would like to know how many wires are in that plug as that will tell us which trans it is. Most hydraulic trans had 3 wires in it as one was 12 volts and the other 2 wires were the grounds for the overdrive and lock-up solenoids ? If its an electronic gov it should have seven wires in that plug I believe. And its not the neutral safety switch plug as that is not the one I mean ? Ron

The plug on the left side just behind the shift lever has at least seven wires. The insulation on several of the wires was bad where they entered the plug. I'm told this is a common problem. I repaired the insulation. I have an after market speedo. It's not wired into the trans/PCM architecture. Based on my diff ratio /tire combo I'm wondering if my tail shaft out put speed is to low and the PCM is looking for a higher speed.

Ok it is a electronic gov then. From what I remember the factory PCM controlled all the electronic gov functions. But as I said that speed sensor in the tail housing has to work right to let the PCM control gov pressure so it will shift automatically. Are you using that sensor also wired to another controller for your speedo ? Ron

No

Fixed. The 2.92 rear end was to high a ratio for the 245/70/17 inch tires I have on the back so I installed a rear end with 3.55 years. This rear end has a VSS. I wired it into the PCM, problem gone. No more PO500 codes and dropping out of OD. The PCM was looking for a VSS signal.

Sorry I did not get back to you as I got sick for a few days. You are right as I seem to have forgot the PCM does need the vehicle speed sensor reading to turn on overdrive. It needs the tailshaft output speed sensor to set gov pressure for upshifts but it needs to know the vehicle speed by the speed sensor in the rear diff and eng rpm so it knows when its in third gear before it will turn overdrive on. It knows by eng rpm and vehicle speed when its in third gear. It also must reach a certain eng temp and the PCM needs the TPS and MAP readings also. Once it knows its in third and the other sensors are in parameters it will let overdrive turn on. Sorry I did not think to tell you this earlier as I have been away from the new cars for about 5 years now. Just glad you found the problem and got it working good. Ron