07.5 stuck in fourth gear - Dodge Cummins Diesel Forum
07.5 - 09 3rd Gen 6.7L Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine, Transmission, etc...NO ADVERTISING

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post #1 of 41 (permalink) Old 09-26-2012, 11:20 PM Thread Starter
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07.5 stuck in fourth gear

Today my 07.5 megacab 3500 diesel with a 68rfe shifted up to fourth gear and then stayed would not shift up or down. Pulled codes with scanner and got p0700 (which I believe is just to turn on the CEL) and p1776 Solenoid switch valve latched in the LR position. I drove the truck home parked it cleared the codes and tried again, the truck shifted up to fourth and then stayed will not shift up or down either automatically or manually.
I stopped by the local trans shop and they had never worked on a 68rfe so they said they would have to get pretty invasive and that they did not have any idea until they tore into it.
I decided to stop by the dealer then and they really did not know at all and suggested replacing the solenoid switch but did not have a part number the service guy said just get my vin and talk to parts, I did so and they said to replace the solenoid pack($355) not sure if this is the part that needs replacing or not so I figured that I would post here for any help in the troubleshooting of the problem with my truck. I have read alot of posts here and just not seeing the exact same thing anywhere. I have seen that valve bodies have been an issue and replacing them fixes some of the problem also just not sure. Any help is greatly appreciated. Thanks. Brad


07.5 megacab 3500: Mini Maxx, with trans tune; 5" diamond eye exhaust; deletes....
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post #2 of 41 (permalink) Old 09-27-2012, 12:49 AM
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Contact Transengineer on here. He's the head honcho on these trannies.

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post #3 of 41 (permalink) Old 09-28-2012, 08:21 AM
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The Solenoid Switch Valve (SSV) is actually in the main valve body. It is not part of the solenoid module, so replacing the solenoid will not fix it. The solenoid module is also part of the main valve body assy.

P1776 indicates that the SSV is stuck in one position. It could just be due to a piece of debris that has jammed the valve, and if that's the case, then you can just drop the pan, pull the VB assy out, disassemble it, clean the valve, and bolt it all back together. But while you're at it, you should check the diameter of the outer end of the SSV bore. It is very common for this bore to get worn oversize, and if that's the case then you should replace the entire VB assy with a new one from Mopar.

On top of the valve body is a sliding code plate (that moves when you run the shift lever back and forth). Inside the center “chunk” of the valve body, underneath this sliding plate, are two valves - the manual valve (which has a pin that engages the slot in the code plate - this is the valve that moves when you move the shift lever) and the SSV. The SSV is retained by a rectangular plastic retainer, and it has three (3) barrel-shaped plugs at the outer end of its bore. You want to check the size of the four (4) outer lands in this bore (where the plugs slide). The diameter should be 11.544 mm (0.454 inch) max. If any of the lands are worn oversize, replace the entire VB assy with a new Mopar VB. The diesel (68RFE) VB is RL033980AC ($510 list).

The new Mopar VBs are all anodized to resist the SSV wear, so your new VB should last much longer than the original one. All 2010 MY (and later) RFE transmissions already have an anodized VB. Note that Mopar uses a "reman" part number for the diesel VB. This is so we can get the old VB back for core. But the service VBs are all new (anodized) units now.

Make SURE when you reinstall the VB that the slot on the code plate's vertical arm lines up with the pin on the manual lever (the one inside the case, that rotates when you move the shift lever). Leave the shift lever in Park when you pull the VB, and then make sure the code plate is slid to the Park position (fully rearward, with detent roller up against the code plate's vertical arm) before you bolt it in. If it's not lined up correctly, you will break off the pin on the lever, and then you have to pull the trans and tear it down completely in order to replace the lever! Good luck!
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post #4 of 41 (permalink) Old 09-28-2012, 11:49 AM
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This is great information. ") good for all of us to know so we don't break something in the future!

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post #5 of 41 (permalink) Old 09-28-2012, 05:16 PM
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Valve body

This is the same thing that happend to mine. First they changed the one valve and tested it in town and it worked fine, I picked it up, headed for home out on the highway and it was skipping 5th, so the next dayit was back in and they brought a valve body in from Origon and fixed by that night but they told me the new anodized one would not fit in the early ones. So as far as I know I have the older type valve body that I only got 40,000 k on the first one. I hope you have better luck with yours.
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post #6 of 41 (permalink) Old 09-28-2012, 05:26 PM
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Valve body

This is the same thing that happend to mine. First they changed the one valve and tested it in town and it worked fine, I picked it up, headed for home out on the highway and it was skipping 5th, so the next dayit was back in and they brought a valve body in from Origon and fixed by that night but they told me the new anodized one would not fit in the early ones. So as far as I know I have the older type valve body that I only got 40,000 k on the first one. I hope you have better luck with yours.
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post #7 of 41 (permalink) Old 09-29-2012, 02:45 AM Thread Starter
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Went into dealer today to get diagnostics ran on it. They said that it needs a solenoid pack. Iam going to pull the vb and check it out. If its out of tolerance then replace it. And replace the solenoid pack. Does this sound right?
Thanks for the info trans engineer. Should i just replace both at the same time ? Thanks again for the help.

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post #8 of 41 (permalink) Old 10-01-2012, 09:16 AM
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Jawboneus,

A new VB assy will already include a new solenoid, so if you replace the whole VB assy you will also have a new solenoid.

Unfortunately, many dealer "techs" simply read the fault code and then shoot from the hip (make an educated, or in some cases uneducated, guess) about how to fix it. We publish a complete diagnostic procedure (it has 23 steps) that tells them how to pinpoint the actual problem, but many techs never bother to consult it. They make more money replacing parts than diagnosing problems, and if they guess wrong, well, they make more money "fixing" it again.

Hordos,

For the 68RFE, there is only one service VB assy (as far as I know) and it will be the anodized one. Even for gas engine trucks, where we do have multiple VB assys for various years (we've made changes to some of the orifices, so old and new are not necessarily interchangeable), the service VBs should all be built with anodized housings, even if they're being built for older vehicles.

If you get a chance to looks at them, you can tell by the color. Unanodized VBs are a grayish silver (aluminum) color. The anodized VBs have a dark brownish gray color. Note that only the main VB housing is anodized. The solenoid housing (aluminum casting that's the main chunk of the solenoid module) and the transfer plate (the "bottom half" of the VB assy) are both unanodized, so they will still be a bare aluminum color.
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post #9 of 41 (permalink) Old 10-08-2012, 06:56 PM
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Transengineer,
I was told the reason the 68RFE would only shift from 1st to 4th only is because it has a "limp" mode to prevent further damage. Is this true?? They replaced a solenoid, then a pressure valve, but nothing worked. So they dropped it, didn't find any glitter in the pan and found that it needed a new clutch pack. What would make me need a new clutch pack at 50k miles?? Driving style, towing, or a fluke??
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post #10 of 41 (permalink) Old 10-09-2012, 07:53 AM
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Quote:
Originally Posted by $.99 TACOS View Post
I was told the reason the 68RFE would only shift from 1st to 4th only is because it has a "limp" mode to prevent further damage. Is this true?? They replaced a solenoid, then a pressure valve, but nothing worked. So they dropped it, didn't find any glitter in the pan and found that it needed a new clutch pack. What would make me need a new clutch pack at 50k miles?? Driving style, towing, or a fluke??
The RFE transmission has two different limp-in modes. The first, which we call "orderly shut down" (or OSD), commands the trans relay to open (disconnecting the normal 12V feed to the solenoid module). This causes the trans to run in 4th gear (with converter unlocked) whenever you're in Drive. The truck will feel really sluggish on a launch from a stop. This is the response for most faults (which result in limp-in).

The second kind of limp-in is what's called "logical limp-in." In this mode, the trans relay continues to power the solenoid module, but the TCM commands the trans to use 1st and 4th gears only (when in Drive), again with the TCC unlocked all the time. So if your trans launches normally (using 1st gear) but then shifts directly into 4th gear (and stays there until you come to a stop), you are in logical limp-in. Logical limp-in is the normal response to a gear ratio fault.

So you can tell (a little bit) by your truck's behavior what the problem might be. Many of the "normal" faults (which cause OSD) are electrical faults, caused by a broken wire, bad solenoid coil, bad sensor, etc. So these can often be fixed relatively cheaply, without pulling the trans (although that's not always the case). But at least there is hope...

On the other hand, if you're experiencing Logical Limp-In (1st and 4th gears), then you probably have a burned clutch inside the trans (for the 68RFE, probably the OD clutch, which is the typical weak link).

50K miles is unusually low for a clutch failure. Often, clutch failures are caused by a blown piston seal (which the tech should find when he tears it down). They can also be caused by driving habits (making repeated shifts back and forth between the same two gears). Or, debris in the solenoid module or a leaky valve in the main valve body can contribute to clutch failure. Line pressure problems (such as a sticky main regulator valve in the pump) can also lead to a fried clutch. So there are lots of possibilities.
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post #11 of 41 (permalink) Old 10-09-2012, 11:27 AM
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Quote:
Originally Posted by TransEngineer View Post
The RFE transmission has two different limp-in modes. The first, which we call "orderly shut down" (or OSD), commands the trans relay to open (disconnecting the normal 12V feed to the solenoid module). This causes the trans to run in 4th gear (with converter unlocked) whenever you're in Drive. The truck will feel really sluggish on a launch from a stop. This is the response for most faults (which result in limp-in).

The second kind of limp-in is what's called "logical limp-in." In this mode, the trans relay continues to power the solenoid module, but the TCM commands the trans to use 1st and 4th gears only (when in Drive), again with the TCC unlocked all the time. So if your trans launches normally (using 1st gear) but then shifts directly into 4th gear (and stays there until you come to a stop), you are in logical limp-in. Logical limp-in is the normal response to a gear ratio fault.

So you can tell (a little bit) by your truck's behavior what the problem might be. Many of the "normal" faults (which cause OSD) are electrical faults, caused by a broken wire, bad solenoid coil, bad sensor, etc. So these can often be fixed relatively cheaply, without pulling the trans (although that's not always the case). But at least there is hope...

On the other hand, if you're experiencing Logical Limp-In (1st and 4th gears), then you probably have a burned clutch inside the trans (for the 68RFE, probably the OD clutch, which is the typical weak link).

50K miles is unusually low for a clutch failure. Often, clutch failures are caused by a blown piston seal (which the tech should find when he tears it down). They can also be caused by driving habits (making repeated shifts back and forth between the same two gears). Or, debris in the solenoid module or a leaky valve in the main valve body can contribute to clutch failure. Line pressure problems (such as a sticky main regulator valve in the pump) can also lead to a fried clutch. So there are lots of possibilities.
On a goat trail with trailer in tow transmission got to 275 F and then went into some sort of limp mode where it had only first gear. I am guessing that if it had been possible to go faster it would have shifted into fourth?. Whenever the transmission got to 275 (seven times in all) it went into first only (maybe with some speed fourth) mode. Eventually got the 1 to 4 shift on a freeway ramp and that is when the ATS transmission went in.

Have never had it heat up at all with a proper torque converter and internals that handle the torque.

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post #12 of 41 (permalink) Old 10-09-2012, 02:40 PM
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Great information...Thanks! Now that it's fixed, the truck, when in a slight incline, tends to have a minor jerking feel when a constant pressure is applied on the accelerator or in cruse control at low rpm. i hit the accelerator and it goes away. Is that tranny related now after being repaired or is it engine from low rpm on an incline? Hope I make sense.
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