2021 2500 Limp Mode (transmission?)

[rfullen280]

Cruising down the highway empty at 70 miles an hour the cruise control kicked off a check engine light came up and the truck would not shift higher than fourth gear this is on a 68RFE.

Hooked up Alpha OBD and I got an error that said shift solenoid B fault.

Truck has 32,000 miles, about 10,000 of which is towing. Any ideas? I'm gonna clear the code and continue going home and see what happens. Will let you know.

 

[GPurcell01]

Just went through this on my father's truck. At minimum you need to replace the solenoid pack. Since we were in there, it got a built valve body and some other goodies.

 

[rfullen280]

Just went through this on my father's truck. At minimum you need to replace the solenoid pack. Since we were in there, it got a built valve body and some other goodies.

Good news - it didn't come back in 50 miles. When I got home, the dipstick had worked it's way out an inch, the rubber was stuck in the tube, and the little metal washer had slid down. So... that was a pain in the rear.

Fluid a little low/below the Hot Dots... Will add some.

Where did you get the solenoid pack and valve body from?

 

[GPurcell01]

ATS Diesel. Got it as an entire kit. We cleared his code too at first and it came back within a few hundred miles.

 

[GPurcell01]

https://www.atsdiesel.com/ats-bille...-pack-68rfe-with-blue-electrical-connector-20

 

[flan]

How’s the shifting with the new valve body? Firm them up any? Sorry to go OT.

 

[H3LZSN1P3R]

Next time it comes up leave it and let the dealer replace the solenoid pack for free

 

[GPurcell01]

How’s the shifting with the new valve body? Firm them up any? Sorry to go OT.

Apparently it puts the power down a little better. Shifting is smooth and crisp.

Did this more for longevity than changing shifting.

 

[rfullen280]

Good news - it didn't come back in 50 miles. When I got home, the dipstick had worked it's way out an inch, the rubber was stuck in the tube, and the little metal washer had slid down. So... that was a pain in the rear.

Fluid a little low/below the Hot Dots... Will add some.

Next time it comes up leave it and let the dealer replace the solenoid pack for free

Yeah that is definitely in my plan I was just 50 miles from home. And stuck in fourth gear on the highway. Just glad I was able to reset it and get the drive home, at 75 vs 55.

 

[rfullen280]

Okay, so, can someone tell me where the TCU is?

 

[H3LZSN1P3R]

Okay, so, can someone tell me where the TCU is?

Built in to the PCM its not a stand alone unit

 

[rfullen280]

Built in to the PCM its not a stand alone unit

Going some searching on this fault code I can't where I saw it but it said that that this code is in electrical only code and there's possibilities of either having a bad or poor connection at either the PCM or the transmission itself. I don't know how likely that is but I used to work on aircraft electrical connectors and they be perfectly fine until they weren't.

 

[GPurcell01]

Going some searching on this fault code I can't where I saw it but it said that that this code is in electrical only code and there's possibilities of either having a bad or poor connection at either the PCM or the transmission itself. I don't know how likely that is but I used to work on aircraft electrical connectors and they be perfectly fine until they weren't.

That is universal for the specific code. (P0765, P0755, or similar) We thought the same thing. It is the shift solenoid pack itself though.

 

[rfullen280]

That is universal for the specific code. (P0765 or similar) We thought the same thing. It is the shift solenoid pack itself though.

Gotcha. I would've expected Ram to have the better shift solenoids with the number of years they've been running the same transmission, but of course ask if the people who had their block heater solid-state relay catch fire.

Does the pan have to come off and change the solenoids?

 

[GPurcell01]

Gotcha. I would've expected Ram to have the better shift solenoids with the number of years they've been running the same transmission, but of course ask if the people who had their block heater solid-state relay catch fire.

Does the pan have to come off and change the solenoids?

Yes. Transmission pan and valve body both have to come off/out.

 

[rfullen280]

Yes. Transmission pan and valve body both have to come off/out.

I saw this thing - https://www.cumminsforum.com/threads/2014-srw-3500-68rfe-p0755-code.2350737/ that made me think electrical.

 

[GPurcell01]

I saw this thing - https://www.cumminsforum.com/threads/2014-srw-3500-68rfe-p0755-code.2350737/ that made me think electrical.

Always could be - albeit very rare for that

 

[Firebird]

https://www.atsdiesel.com/ats-bille...-pack-68rfe-with-blue-electrical-connector-20

Wow, they are proud of that valve body!

 

[garretgetsit99]

I went through a similar scenario with my 2014 RAM 2500 Cummins at about 115k miles. Not sure if you're going through something different or not but it ended up being such an expensive fix for me that it was easier to order a remanufactured replacement than fool around with the old one. Got the replacement a couple of years ago from these guys https://reman-transmission.com/transmission-codes/?code=68RFE. Still one of the cheapest rebuilt 68rfes out there probably

 

[Will_T]

Next time it comes up leave it and let the dealer replace the solenoid pack for free

These days our dealer would be 2-3 month wait to look at it and confirm you have a problem. Then who knows how much longer to get the parts.