68rfe problem

[LNaugle]

I have an 07. 5-6. 7L truck that when coming to a stop, it downshifts to 1st when completing the stop and it feels like it wants to power through the brakes for a split second then dies. Monitoring the trans it does not show TC lock up only that it is selecting 1st gear. When i drove the truck last it was doing all the same except dying. No codes, no other shift problems. Also, doesnt matter if you are getting off the highway or have been slowly driving down the street and come to a stop.

 

[DonFitzwater]

Search it. Sounds like a failed torque converter.

 

[JJPage]

LN, you could check the trans control plug if there is one? My 48re was behaving similar(I know it's a different animal and I know nothing about the 68), the front band adjustment stud was leaking and saturating the trans control electrical plug. It was causing a shorting situation between the pins, and doing exactly what you are stating when coming to a stop, it would only die because I had to stand on the brakes to get it to stop before I was able to get it out of gear. It was also shifting incorrectly which you state yours is not doing, just a suggestion of what you may look at.



By repairing the leaking stud and cleaning the connection all was resolved.

 

[cerberusiam]

I have an 07. 5-6. 7L truck that when coming to a stop, it downshifts to 1st when completing the stop and it feels like it wants to power through the brakes for a split second then dies.

It acts like a TC problem, except you should have problems taking off from a start. If the sprag clutch lets go it has no stall and it feels like a dead pedal until you get over 30-35 mph.

Does it do the same thing just starting it up and putting it in gear? How about reverse? IIRC, one of the weak links in the trans can cause a bind in gear. I though 3rd gear but possibly it can effect 1st?

It was causing a shorting situation between the pins, and doing exactly what you are stating when coming to a stop,

I cannot believe it would not throw a code in that situation. Evidently the short between the power and lockup solenoid was not complete but enough to apply the clutch. I HATE problems like that, they can make one bald in no time.

 

[JJPage]

I cannot believe it would not throw a code in that situation. Evidently the short between the power and lockup solenoid was not complete but enough to apply the clutch. I HATE problems like that, they can make one bald in no time.

It threw codes and put me in limp mode also. You cerb, helped me diagnose it at the time...

 

[cerberusiam]

It threw codes and put me in limp mode also. You cerb, helped me diagnose it at the time...

Ahhh, the thing I most regret loosing is my mind... ..... :-laf

 

[LNaugle]

It does take off fine, and we did find find a broken tab on the connector because it was previously shiffting wrong, didnt see any oil, I was leaning towards convertor but even exhaust braking feels good. I tell my customers with autos to set their pb and put the truck in neutral to warm it up, as do I before test drives, It doesnt do anything wrong reverse or forward when i do that. Maybe I should try warming in park and then putting it in gear to see what happens? I dont really see what that would change. Also, it doesnt do it in reverse, which makes me lean towards convertor failure in the sprag as Cerb was saying.

 

[cerberusiam]

The sprag spins the same way in reverse as it does forward. If you have a converter failure it will happen in forward or reverse.

For some reason, this transmission is ulta sensitive to charging the TC. If it does not charge correctly or pressures are low they have issues locking up or failing to release something. The fact you put it in neutral to warm up and charge the TC, and it doesn't have issues, makes me think there is an issue with the filters or the TC draining back.

 

[RustyJC]

Sounds like the opposite of the old 47RE torque converter drainback characteristic. The 47RE wouldn't move until the torque converter filled up after a long shutdown. The 68RFE appears not to unlock the TC lockup clutch until the converter fills up (although my truck is shut down for weeks at a time and has never exhibited this problem). How times have changed!!



Rusty

 

[LNaugle]

I appologize for that one sentence being misleading... When the truck is warmed up in neutral the truck initially doesnt do anything wrong forward or reverse, but once moving forward and upon completing the first stop, after shifting a few gears, thats when it seems to try and drive through the brakes... I thought I read in one of my books a failing sprag can cause different stall speeds forward and reverse? We also changed the filters and replaced the plastic adapter for the spin on with a billet one.

 

[cerberusiam]

I thought I read in one of my books a failing sprag can cause different stall speeds forward and reverse?

Yep, and surprisingly the stupid things will do it intermittently in some cases. Mine never do, they just break all at once and never get better.

About the only thing left to test is the pressures if you can, but, it sounds suspiciously like a TC problem.

 

[sag2]

It sounds more like the converter is trying to lock itself. Does it have any codes? If an RFE sucks air it will lock the converter. It happens quite often after a service and the snap in filter is leaking. Come to a hard stop, it sucks air (converter clutch is held off by pressure, applied by bleeding off the pressure from one side) and locks the converter, truck dies.

 

[LNaugle]

We have had that filter out twice, no extra seal, nothing visually wrong with the seal on it but could change it out to see... . It does feel like it is trying to lock the convertor and then unlocks usually before dying unless not warmed up. Will see. Thanks all!

 

[LNaugle]

It sounds more like the converter is trying to lock itself. Does it have any codes? If an RFE sucks air it will lock the converter. It happens quite often after a service and the snap in filter is leaking. Come to a hard stop, it sucks air (converter clutch is held off by pressure, applied by bleeding off the pressure from one side) and locks the converter, truck dies.

was thr filter... thanks sag2