68rfe valve body solenoid problems

[Markhef05]

Hello,

My 08 2500 6.7 auto, 4x4 laramie was lunging when put into first gear or when shifting down when coming to a stop. It was showing codes P0868 and P0871. I replaced the valve body and rebuilt the solenoid pack. After that it would reverse and go from first to 4th. So I completely replaced the solenoid pack with a new one. Now it goes straight to limp mode (4th gear only) its making a buzzing sound in P and N. And throwing code P0750. Im tired of bathing in transmission fluid and looking for some direction. Is there something I could have missed? I'm going to replace the preassure sensor which looking back i wish i would've done first.... thanks in advance for any advice.

Mark

 

[transe]

P0750 is an LR Solenoid Circuit fault. That is causing full limp-in (4th gear only). The buzzing noise is the main regulator valve in the pump, due to line pressure being uncontrolled (maxed out) when in limp-in. So ignore the buzzing, it will go away when you fix the P0750 problem.

P0750 indicates an open circuit in the LR solenoid. Could be the new solenoid is bad (broken LR solenoid coil wire), or a bad wiring connection.

Step 1: Go to rambodybuilder.com and get the wiring diagrams and connector pinouts for the solenoid and the TCM. I would look at the info for 2009 MY. I think the 2007-2008 info may be incorrect.

Step 2: Disconnect the C4 connector on the TCM (it has only two connectors, C1 and C4. C4 should have a green stripe or marking by it). Check the resistance between the pin in the harness that connects to pin 2 (the LR solenoid) at the transmission, and one of the pins in the harness that connects to pin 10 at the transmission. I believe this should be pins 10 (which connects to pin 2 at the trans) and pin 19, 28, or 38 (which all connect to pin 10 at the trans). You will then be checking the resistance of the entire circuit (the power feed going to the trans, the LR solenoid coil itself, and the grounding circuit back from the LR solenoid). The resistance should be about 1.8 ohms. If you find an open circuit (no continuity), then you have confirmed the cause of the P0750 (wiring, or the solenoid coil).

Step 3: Assuming you find an open circuit, disconnect the harness at the transmission, and inspect both the harness terminals and the pins in the solenoid connector (hard to do in the vehicle, but use a mirror). Check for corrosion or any bent pins. Also check for one of the terminals in the harness being pushed partway out of the connector (the terminals should all be at the same height). If you find one, push on that wire to reseat and lock the terminal so that it's fully inserted into the connector.

Step 4: If the wiring all looks OK, see if you can check the resistance between pins 2 and 10 on the solenoid (again, very hard to do in the vehicle). If open circuit between those pins, the solenoid is bad. If you can't check the solenoid, I would simply reconnect everything and see if the P0750 still sets. Sometimes just disconnecting and reconnecting the harnesses can clean up the connections and "fix" it.

Step 5: If wiring was OK and P0750 still sets, repost here and I'll explain how to do a "wire swap" to confirm whether the root cause is the wiring, the solenoid, or the TCM.

 

[Markhef05]

Hello
Thanks for all of the information. I ended up finding out that the "rebuilt" solenoid pack I purchased was bad. The truck wouldn't even recognize that it was there. I reinstalled the original one that I had rebuilt (new o-rings, springs and spacer plate. I also replaced the trans pressure sensor. For the most part things are ok. Occasionally it down shifts from 5-6 into 4th. When I come to a stop it shifts to first. From then until I turn the truck off and restart it I only have 1st and 4th gear. Once I restart it runs fine... until it does it again. Probably happened 4 times. It also occasionally fails to engage the torque converter in 4th, 5th, 6th. Usually after I slow down and it shifts down through the gears, it will engage the next time I come up to speed. Things are far from perfect but im hoping to get 6 months out of it and save up to buy a built aftermarket trans. Any info on the above issues is greatly appreciated I've learned a lot through this experience. Mainly that transmissions are crazy complicated and I'm tired of transmission fluid! haha.

Thanks,
Mark

 

[transe]

Hello
Thanks for all of the information. I ended up finding out that the "rebuilt" solenoid pack I purchased was bad. The truck wouldn't even recognize that it was there. I reinstalled the original one that I had rebuilt (new o-rings, springs and spacer plate. I also replaced the trans pressure sensor. For the most part things are ok. Occasionally it down shifts from 5-6 into 4th. When I come to a stop it shifts to first. From then until I turn the truck off and restart it I only have 1st and 4th gear. Once I restart it runs fine... until it does it again. Probably happened 4 times. It also occasionally fails to engage the torque converter in 4th, 5th, 6th. Usually after I slow down and it shifts down through the gears, it will engage the next time I come up to speed. Things are far from perfect but im hoping to get 6 months out of it and save up to buy a built aftermarket trans. Any info on the above issues is greatly appreciated I've learned a lot through this experience. Mainly that transmissions are crazy complicated and I'm tired of transmission fluid! haha.

Thanks,
Mark

The 1st-and-4th behavior is the result of setting a Gear Ratio Error (meaning your trans is slipping). Sounds like it slips in 5th or 6th gear (which then bumps you into 4th with no TCC engagement). That means your OD clutch is probably weak (and slipping when the input torque gets over a certain level). Be forewarned that once a clutch starts slipping, it can often go RAPIDLY downhill. If you want to eke a few more months out of it:
• Drive VERY GENTLY when you are in 4th gear or above.
• Before climbing a hill, or before accelerating at highway speeds, tap it down manually to at least "4", and "3" if possible.
• Personally, I would run it in "4" all the time (and still being gentle on the throttle), and only tap it up to "5" or "6" when you are cruising gently on a flat road.

The OD clutch carries 100% of the input torque in 5th and 6th gear, so that is where it is most likely to slip. But it also carries about 70% of the input torque in 4th (direct) gear, so you can also slip it in 4th gear if you get too deep into the throttle.

 

[6.7ferrell]

I have a 2008 3500 6.7 stock 68rfe when I start it up in the mornings to go to work and the transmisson is cold when I put it into gear it wants to lunge forward and then starts shifting crazy feels like the TC is locking in and out by its self but once it warms up it shifts fine. Curious to know if you think it's TC issue or syilinoid pack issue? Also if I get on it hard sometimes it like shudders.
Thanks!

 

[transe]

I have a 2008 3500 6.7 stock 68rfe when I start it up in the mornings to go to work and the transmisson is cold when I put it into gear it wants to lunge forward and then starts shifting crazy feels like the TC is locking in and out by its self but once it warms up it shifts fine. Curious to know if you think it's TC issue or syilinoid pack issue? Also if I get on it hard sometimes it like shudders.
Thanks!

If the truck wants to lunge forward at a stop (forcing you to mash the brake pedal), that is caused by the Torque Converter Clutch (TCC) dragging (partially applying). The TCC drag could be caused by a bad converter (failed TCC or a cut seal), but if that were the case I would expect it to exhibit the problem at all temperatures, not just when cold. Could also be due to a sticking TCC control valve (in the pump). But the most likely cause is a momentary drop in line pressure. Pressure is fed into the front side of the converter to keep the TCC released. If your line pressure suddenly disappears, that pressure feed to the converter goes away, and then the TCC drags.

So I think it most likely that you are getting dips in line pressure. THAT, in turn, can be caused by several things: Low fluid level, loose or bad spin-on filter, or a loose, cracked, split, or misinstalled main sump filter (the flat filter). Since your problem only happens cold, I suspect it is either related to the fluid level (which is lowest when the trans is cold), or to converter drainback. Drainback is when some of the fluid in the converter drains back into the trans sump when the engine is shut off overnight. Then, when you start it up, the converter is half full of air. Since air does not transmit torque to the transmission very well (a gross understatement!), it feels like the transmission is slipping when you first put it in gear, and then feels like the transmission slowly "oozes" into gear (as the converter slowly refills and the torque level slowly rises). That slug of air that was in the converter gets pushed out through the cooler system, and when it comes back into the trans, it goes into the pump suction passage, which then causes you to suddenly lose line pressure (and get TCC drag). So if this sounds like your situation, I'd suggest you change the spin-on filter (which is inside the trans pan). That filter has an internal diaphragm that is supposed to prevent converter drainback. If you're getting drainback, then either that diaphragm is defective, or it has a piece of debris lodged underneath it (holding it open). So changing the spin-on filter will usually fix it.

If you don't have drainback (but do have TCC drag), then I'd first confirm that the fluid level is correct. If it is, then I'd drop the pan and check both filters. Make sure neither one is loose. The spin-on filter should be snug (but not too tight, or you can crack the threaded plastic snout that screws into the case). Just tighten it BY HAND like you would a spin-on engine oil filter. The flat filter's snout should be pushed up THROUGH the seal in the pump housing (not just resting against it). Check the flat filter for being split open along the side seam, or for cracks at the base of the snout.

If the filters are all OK, and the fluid level is correct, yet you still have TCC drag, then I would pull the trans and replace both the converter and the pump assy. If you do this, READ THE INSTRUCTION SHEET that comes with the new pump (and follow it)!! You MUST check the input shaft end play (after replacing the pump) to confirm that one of the thrust bearings in the input clutch assy (the next big chunk of parts behind the pump) didn't fall out of position while you had the pump out.

 

[Yazzie19]

2007 Dodge 3500 6.7L - 68RFE.... Transmission has been completely been rebuilt, when taken for a test drive everything shifted smoothly and about a mile down the road transmission went into limp mode. The most noticeable symptom is putting the transmission in reverse, the transmission will shift and feel it shift in reverse. But when you release the brakes and try to accelerate the truck won't reverse as if something locking up, it will intermittenly release and reverse, but well lock again where you can see the wheels drag a bit. The only codes I pulled were P0740-TCC Out of Range (Pending) and P0875-Underdrive Hydraulic Pressure Test (Pending). After clearing these codes no other DTC's has been set. Need help with direction to go from here, this truck is driving me nuts.

 

[transe]

2007 Dodge 3500 6.7L - 68RFE.... Transmission has been completely been rebuilt, when taken for a test drive everything shifted smoothly and about a mile down the road transmission went into limp mode. The most noticeable symptom is putting the transmission in reverse, the transmission will shift and feel it shift in reverse. But when you release the brakes and try to accelerate the truck won't reverse as if something locking up, it will intermittenly release and reverse, but well lock again where you can see the wheels drag a bit. The only codes I pulled were P0740-TCC Out of Range (Pending) and P0875-Underdrive Hydraulic Pressure Test (Pending). After clearing these codes no other DTC's has been set. Need help with direction to go from here, this truck is driving me nuts.

So now no active codes, but still won't go in Reverse?

Can you tell whether the TRANS is locked up (in Reverse), or whether the WHEELS are locked up? I've seen cases where the parking brake lining came off of one of the shoes in the rear axle, and it would intermittently jam up in reverse (and stop the wheel from turning). Can you push the truck backwards by hand when it's in Neutral? Also, with engine running in Neutral, does it want to move forward?

 

[Yazzie19]

Okay I had the truck towed backwards in neutral and rolled freely. We took for another test drive shifted well up until 5th to 6th it jerked and put the transmission in limp mode. Weh reversing the truck, I let it roll backwards in reverse and it did, but when i applied acceleration it sounded like the RPM's raised without engaging reverse. Not sure if being understandable. But I pulled these codes after a test drive P0740-TCC Out of Range, P0736-Gear Ratio Error in Reverse and P0875-Underdrive Hydraulic Test Pending. I am beginning to point in the direction of the Solenoid Pack, I'm lost in all test procedures. After the road test the truck only shifts to 4th, no 1,2,and 3... I winder if feasible to have a deeper discussion

 

[transe]

Okay I had the truck towed backwards in neutral and rolled freely. We took for another test drive shifted well up until 5th to 6th it jerked and put the transmission in limp mode. Weh reversing the truck, I let it roll backwards in reverse and it did, but when i applied acceleration it sounded like the RPM's raised without engaging reverse. Not sure if being understandable. But I pulled these codes after a test drive P0740-TCC Out of Range, P0736-Gear Ratio Error in Reverse and P0875-Underdrive Hydraulic Test Pending. I am beginning to point in the direction of the Solenoid Pack, I'm lost in all test procedures. After the road test the truck only shifts to 4th, no 1,2,and 3... I winder if feasible to have a deeper discussion

Sounds like you have multiple issues going on. P0736 says it is definitely slipping in Reverse. P0740 says (most likely) that the Torque Converter Clutch (TCC) isn't engaging. P0875 is pretty rare; that says the UD pressure did not respond when it was tested, yet apparently that switch was working OK in 1st thru 4th gears (when UD would be applied), so that's a little baffling.

If you start it up fresh, shift to Drive, tap it to "4", and then drive, does it work OK (all gears 1-4 OK) with no faults? How about if you try it in "5"? Will it drive OK in 5th gear (and 1st thru 4th) without setting faults?

I don't know of any single problem (solenoid or otherwise) that would cause all 3 of your faults.