68 REF transmission question.

[DFerverda]

My 2008 2500 68ref 6.7, The last couple weeks the truck will kick out of lockup, in 5th and 6th, if you pull a small hill or move the throttle more then a hundred rpm.
Checked the fluid was down maybe 1/2 quart, topped off and still same.
About 30k ago had code and looked here and decided needed a new VB so went to mopar parts and bought a new , not rebuilt one with the solenoids, complete. Put it in and has been perfect since, till now.

The fluid is good, not burnt and am getting ready for new filters and fluid, but only want to open this up ONCE. What solenoid should i replace or what should i be looking for at this point.
Just finished a hundred mile trip, and it did great except for the lockup thing. Will be pulling a heavy 5th wheel toy hauler in the next month and don't want any trouble.
Thanks Dirk

 

[transe]

Do you have a check engine light? Any fault codes? I presume the trans still shifts OK 1-2-3-4-5-6 (no limp-in)?
Once it kicks out of lockup, will it re-lock again later? Or does it stay unlocked forever (until you restart it)?

 

[DFerverda]

No check engine light no fault codes with flippen the key 3 times, shifts awesome except for the lock up. When i touch the peddle and push it any, it will unlock and then will lock up again. It acts just like it used to but when i pulled a overpass or small hill it will unlock and lock and maybe do it another time or 2 and when the pressure is off it will lock up and act like usual.
It just seems to be unlocking awful easy for some reason. I think it will be a problem when i am pulling the 5th wheel.

Thanks Dirk

 

[transe]

The lockup schedule depends on throttle opening. Might you have some kind of engine performance issue, so that you have to step into the throttle deeper (than usual) to maintain the same speed or to accelerate? Has your fuel economy been worse lately?

 

[DFerverda]

It's running fine fuel economy right at 18 checked it this morning when i filled up. I don't know if this truck has a tps or apps like my second gen did. I checked the cables and grounds, but will go over them all again and load test batteries, just to be sure.

So your saying the big solenoid in the valve body that wire harness plugs into does not control lockup?

When this started happening, i thought it may be the tps because that is kinda the way my old truck acted before i got the dead pedal when it died. And once i found a bad ground that caused the 2nd gen to shift in and out of lockup.

 

[transe]

...So your saying the big solenoid in the valve body that wire harness plugs into does not control lockup?

Well, the solenoid module does control the Torque Converter Clutch (TCC) function. But the TCM is what turns the solenoid on and off.

If the TCM commanded lockup, and the TCC didn't lock, that could be due to a bad solenoid. But that would set a P0740 fault and light the CEL. Since you don't have the fault or the CEL, then apparently the TCM is indeed commanding the TCC to unlock / relock as you're describing. So the question is: Why is the TCM commanding this? My first guess would be a throttle signal that is either too high, or flaky (jumping back and forth, erratic). You could have a shop monitor the throttle reading (with a scan tool) as they slowly open and close the throttle (key on, engine off) to see if the readings look smooth / reasonable or if something is wacky.

 

[DFerverda]

After watching like a hawk, i have come to the conclusion the TCM or as mopar calls it PEDAL-ACCELERATOR is amiss. It only hunts in and out of lockup at 50 to 60 mph. Above 60 it is locked up pretty good. I had 2400 lbs of coal on this afternoon and most of the hunting was in that range. Ordered the pedal today and will let you know if it is the cure. Thanks

 

[DFerverda]

Well sorry to state it is not the apps, new one does same thing. I don't know if maybe it is not locking and unlocking, but rather maybe it is shifting from 6th to 5th and hunting to get back to 6th. I reran the scanner on it and came up with nothing. I tried a cheap one and got a code of P0004, and I don't see such a code, and a u3fff code. I think it is just a cheap scanner. I will go ahead and pull the pan later this week when we get back to warmer weather,(not -17) maybe Sunday. Any ideas what to look at other then if the pan and magnet is clean? Thanks Dirk

 

[transe]

Well sorry to state it is not the apps, new one does same thing. I don't know if maybe it is not locking and unlocking, but rather maybe it is shifting from 6th to 5th and hunting to get back to 6th. I reran the scanner on it and came up with nothing. I tried a cheap one and got a code of P0004, and I don't see such a code, and a u3fff code. I think it is just a cheap scanner. I will go ahead and pull the pan later this week when we get back to warmer weather,(not -17) maybe Sunday. Any ideas what to look at other then if the pan and magnet is clean? Thanks Dirk

I don't think I'd bother pulling the pan on it (especially in the sub-zero weather!). See if you can get a better scanner that will display Current Gear, Target Gear, and TCC Status. That way you can see for sure what's going on (or at least, what the TCM is commanding).

 

[DFerverda]

Took the truck to the transmission shop today they tested it and read it with the scanner it is kicking out of 6 gear lock up and hunting they don't know why, may be a weak pump but they haven't got a clue. I asked him what he suggested and they don't know I guess it's either the dealer or try another transmission shop anybody got any suggestions

Edit. He did say he thought maybe TPS but I have already put the new one in so it's not it

 

[transe]

Took the truck to the transmission shop today they tested it and read it with the scanner it is kicking out of 6 gear lock up and hunting they don't know why, may be a weak pump but they haven't got a clue. I asked him what he suggested and they don't know I guess it's either the dealer or try another transmission shop anybody got any suggestions

Edit. He did say he thought maybe TPS but I have already put the new one in so it's not it

So it sounds like the TCM is commanding this behavior. Typically, hunting and dropping out of 6th is a sign of a weak OD clutch, but if the trans (OD clutch) is slipping, it ought to be setting a Gear Ratio Error fault and lighting the CEL. If there's no fault, then the TCM should be responding to the TPS signal, so I'd still suspect a bad TPS. Can they monitor the TPS reading, and see if (at a certain output speed) the downshifts from 6th are happening when you exceed a certain throttle opening? And then also see if the TPS reading is holding constant when the throttle is being held constant.

 

[JR]

TransEngineer, your time is most appreciated on this forum. Love hearing from you and your knowledge every time a transmission problem is posted!

 

[DFerverda]

Ok i will find a shop to look at the tps. This morning i pulled the pan and changed the oil and filters. Mostly looking for something that should not be in the pan, NOTTA nothing a little fuzz on the magnets but clean and not burnt. I had my old VB that i replaced last year with a NEW one from mopar. The old one worked ok untill i pulled the trailer then it would mess up and set a CEL. The new one fixed that issue. SOOO in it went, (the old one) buttoned it up and still doing the same thing.
Besides the TPS could anything else be causing this? I would really hate to have this thing rebuilt and find out i have the same thing going on..Thanks for the help, Dirk

 

[DFerverda]

Well while i was still wet, changed the VB back to the new one. Getting pretty good at that......Will start the hunt for a shop that has good equipment and knows how to use it.. A shame, I live within 20 miles of the biggest travel trailer industry, hundreds of trucks a day pulling out of Goshen Elkhart area with travel trailers galore and a pot full of trucks, and no real good places to get stuff fixed. Dirk

 

[DFerverda]

Ok couple of guys told me about a place in
Angola In. Says they can re set pram's in ecm kinda like a Mad Ecm, but adjustable. Don't know if they will be able to figure this out or not, but the guys are telling me it's worth a shot. With the warmer temp's today the truck seems to be behaving better, not right but better then when it was cold.. Had the guys at the salvage yard put their Genisys scanner on it and looked at the TPS It is smooth and seems real stable, took it for a ride and it would kick out at any where from 47% throttle to 24% depending where it was in shift pattern, it would stay locked up untill you pushed the throttle and then would re lock, but the peddle % would stay steady where ever you held it. When key on, engine off it would go from 0 to 100% and stop anywhere in between and not fluctuate if you didn't move peddle . All specs on the thing looked good but it will not read TCC status or target or any thing like that. Well see what happens Tomorrow at the shop...... Thanks for all your help. Dirk

 

[DFerverda]

Got to shop, bad snow ice. They did the programing but could not test drive. The truck never made it over 45 going or coming home due to ice, so don't know much. Didn't get to play with new tune, guess will call the dealership and have them schedule time with mechanic, don't know if Warsaw or Goshen or maybe should go to Fort Wayne or South Bend Will do some research who has a tech that KNOWS these trucks......

Edit, Anybody use a Dealership service in Northern Indiana that they trust to work on their truck?????

 

[DFerverda]

Sorry so long. Took to dodge in Goshen, they said internal transmission fail 5-6 clutch. Bought new transmission and it is now working fine.