17_America_76
Junior Member
Hey guys, new here. I just did a valve body and solenoid swap on my 2018 Ram 2500HD 6.4L with the 66RFE transmission at 88,*** miles. I will post links to the things I purchased at the very end. Last Sunday, 2/22/25, on the way back from the store my truck went into 4th gear "limp mode" while doing about a 45 to 55 speed up. I noticed the truck did a strange hard shift went I bought it (around 57,*** miles) once in a blue moon, but never thought much of it. I got the P0871 error code when it happened this last time, which I did a ton of research into and came up with a valve body and/or solenoid issue.
Without getting into the real nitty gritty stuff, I will give a rough timeline of my solution for anyone out there that has this problem and would like to take the route I did. What research I did led me to replace both the valve body and solenoid without pin pointing which of the two items was the actual cause. I figured just because if you are going to replace one, it's a safe bet to upgrade and replace the other too. I went with the RevMax Billet Aluminum valve body with a new solenoid included. Since the truck's transmission fluid and filters had never been changed, I did go to a dealership and get a new sump filter, transmission filter, two 5 quart jugs and some Mopar RTV for the pan. I did the work in about 3 hours total, I did not use any lifts as the truck is tall enough, I had enough room to wiggle around underneath even being 6'4 and 270lbs. After I let the RTV set and cure for around 4 hours to ease my mind (I was told by a dealership tech and others that I did not need to let it cure at all), I filled the fluid up and started into the relearn process. I used the AlphaOBD app on my phone, which was a $49.99 purchase. Along with an OBDLink MX+ to pair to, a $139.95 purchase. 2018+ chrysler/dodge/ram's need a security gate bypass cable too, which I found out after I was trying to relearn the transmission, I picked one up for $15.99 that worked just fine.
After installing the bypass and syncing my MX+ to the AlphaOBD app, the relearn was a piece of cake. The process is rather simple once Bluetooth is connected, you choose your Make and Model, select Engine and choose your engine from the list of 10 or so options. Once selected you make sure to connect, which the app will show "connection status: (your vehicle name or engine)". I read my fault code and cleared it because I had read that the relearn will not complete if you have codes active in the ECU, you do that in the CHECK engine tab on the bottom right side of the app. After reading and clearing the codes you then select the tab with the car with an open hood (Active Diagnostics) and scroll through a long list and search for "Quicklearn RFE". The Quicklearn RFE option asks that you set your parking brake and hold your brake pedal down the entire time. It will have you shift into OD (Drive) and select OK, then shift into Neutral and select OK. It will then cycle the transmission and prompt you go into OD one more time, and then into Park. The relearn is then done and you get a completed screen.
After the relearn I drove around 35+ miles (25-30 is recommended from what I had read online) on back roads and in town doing some errands, just doing normal driving for the computer to adjust to the relearn. Don't just jam it on the highway because you can damage the new parts you just replaced. So far I have had no issues over the last 2 days driving, I even took the interstate this morning coming home from work with no issues. My 5th and 6th gears worked just the way they should. I will come back in a few weeks to a month and give an update on how the truck is doing for reference. Feel free to reach out if you have any questions, I will answer to the best of my ability.
ITEMS PURCHASED:
Without getting into the real nitty gritty stuff, I will give a rough timeline of my solution for anyone out there that has this problem and would like to take the route I did. What research I did led me to replace both the valve body and solenoid without pin pointing which of the two items was the actual cause. I figured just because if you are going to replace one, it's a safe bet to upgrade and replace the other too. I went with the RevMax Billet Aluminum valve body with a new solenoid included. Since the truck's transmission fluid and filters had never been changed, I did go to a dealership and get a new sump filter, transmission filter, two 5 quart jugs and some Mopar RTV for the pan. I did the work in about 3 hours total, I did not use any lifts as the truck is tall enough, I had enough room to wiggle around underneath even being 6'4 and 270lbs. After I let the RTV set and cure for around 4 hours to ease my mind (I was told by a dealership tech and others that I did not need to let it cure at all), I filled the fluid up and started into the relearn process. I used the AlphaOBD app on my phone, which was a $49.99 purchase. Along with an OBDLink MX+ to pair to, a $139.95 purchase. 2018+ chrysler/dodge/ram's need a security gate bypass cable too, which I found out after I was trying to relearn the transmission, I picked one up for $15.99 that worked just fine.
After installing the bypass and syncing my MX+ to the AlphaOBD app, the relearn was a piece of cake. The process is rather simple once Bluetooth is connected, you choose your Make and Model, select Engine and choose your engine from the list of 10 or so options. Once selected you make sure to connect, which the app will show "connection status: (your vehicle name or engine)". I read my fault code and cleared it because I had read that the relearn will not complete if you have codes active in the ECU, you do that in the CHECK engine tab on the bottom right side of the app. After reading and clearing the codes you then select the tab with the car with an open hood (Active Diagnostics) and scroll through a long list and search for "Quicklearn RFE". The Quicklearn RFE option asks that you set your parking brake and hold your brake pedal down the entire time. It will have you shift into OD (Drive) and select OK, then shift into Neutral and select OK. It will then cycle the transmission and prompt you go into OD one more time, and then into Park. The relearn is then done and you get a completed screen.
After the relearn I drove around 35+ miles (25-30 is recommended from what I had read online) on back roads and in town doing some errands, just doing normal driving for the computer to adjust to the relearn. Don't just jam it on the highway because you can damage the new parts you just replaced. So far I have had no issues over the last 2 days driving, I even took the interstate this morning coming home from work with no issues. My 5th and 6th gears worked just the way they should. I will come back in a few weeks to a month and give an update on how the truck is doing for reference. Feel free to reach out if you have any questions, I will answer to the best of my ability.
ITEMS PURCHASED:
Amazon.com: Security Gate Bypass OBD2 Cable - Compatible for Dodge Ram 1500 2018-2020 for Dodge Ram 2500 2018-2020 : Automotive
Buy Security Gate Bypass OBD2 Cable - Compatible for Dodge Ram 1500 2018-2020 for Dodge Ram 2500 2018-2020: Code Readers & Scan Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
Last edited:
