68rfe gurus

[The motor guy]

So on my dodge ram truck, anytime the trans temp gets above 150 degrees it typically goes into limp mode where it where shift out of 1st gear until I hit 20mph and then it skips to 4th and then I can get up to 45-50mph but the torque converter doesn't lock up which makes the temp go up very quickly. Anyone know why? If it's going to do it typically it will be when I slow down to about 20mph then get back on the throttle and it downshifts back into what I believe is 4th gear then it won't lock up or shift any higher after that. It's also a rough shift into 4th when it happens. The last couple years this was something that would happen maybe once a year now this has happened numerous times this year and I have to pull over and restart the truck to get it to go back to normal, but it will typically happen again if the trans is above 150 degrees. The truck has 160,000 miles of city driving. I've heard it's a worn SSV bore in the valve body if i'm saying that right. Apparantly the 07 models didn't have an anodized coating and wore out quickly. Although I don't think I can complain about 160,000 miles of city driving. I've also heard it could just be an electrical connection. Opinions?

 

[mattd]

There should be a DTC stored in the TCM. That give you a clue

 

[The motor guy]

It said P0700 but I think that's just a generic code

 

[mattd]

That stores in the ECM. That’s only telling you there are codes stored in the TCM. You need to retrieve the ones in the TCM

 

[The motor guy]

Don't I need a starscan for that?

 

[Skippy722]

Don't I need a starscan for that?

Something like the Autel HT200 from Walmart might be able too, I’ll plug it in and let you know for sure later if you want.

 

[mattd]

What do you have to read codes right now?

 

[The motor guy]

The truck reads its own codes by cycling the key on and off 3 times.

 

[mattd]

That won’t do it. You need some kind of diagnostic software with a scan tool or Forscan

 

[The motor guy]

Yeah I don't have one of those. I don't want to take it to the dealer either. Just need to find an independent shop I guess.

 

[BigRich954]

maybe i missed what year trans ? how much work you willing to do ?

 

[The motor guy]

I'd probably be willing to put a valve body in it. 07

 

[The motor guy]

I have a buddy who thinks that it just needs the the fluid and filters changed. Not sure how much logic their is to that. He claims when the fluid gets hot it doesn't have as much pressure going through the clogged filters.

 

[BigRich954]

I know a decent amount about the 680 RFE most likely you’re having slippage in the overdrive clutches that is causing it to go into limp mode where fourth gear activates overdrive and underdrive clutches used together.
Is the truck tuned is it a diesel?

 

[BigRich954]

Also one of the filters screw in stubs is made out of plastic and is known to crack causing a loss of pressure .

if you can find the line pressure that will get you in a Direction . the ECM reads line pressure.

max stock line psi will be 170 under a load

 

[The motor guy]

It's usually when it downshift. Say it was in 6th gear then I coast down to 20mph and get back on it the trans will shift into 4th gear then the torque converter won't lock up or go in a higher gear until I restart the truck

 

[The motor guy]

Runs fine just don't let it get up to 150 degrees in the pan. Gonna need to get this fixed cause it's going to get warmer out.

 

[The motor guy]

Probably should just throw a new transmission on do a quick learn and be done with it.

 

[The motor guy]

Also one of the filters screw in stubs is made out of plastic and is known to crack causing a loss of pressure .

if you can find the line pressure that will get you in a Direction . the ECM reads line pressure.

max stock line psi will be 170 under a load

Should I pay someone with a starscan to drive the truck around?

 

[MattPersman]

Would have a dealer check it out or a actual transmission place that deals with these not just a general one. They will all claim “no problem” bring it in.

call a couple diesel shops in your area and ask if they have any recommendations on a transmission shop for a 68
It’s going into limp mode based off the 4th and no shifting when you turn it off it restarts it and thinks it’s ok. It should be setting a DTC when it’s going into limp mode and that can be a direction to look. Solenoid. Gear ratio error. Line pressure etc

yes the valve bodies are an issue with them. Doesn’t matter the year they wear the bores. I put a new one in on any of them I rebuild

with no DTC can’t really even guess what it could be