68rfe 1-2 shift issues

[rmini]

Gents:

Have a 2008 6.7 with 68rfe at about 220k miles. Regular filters and fluid changes over its life. About 7k on the latest fluid/filter change. Pan and filters were clean last change. Now getting intermittent 1-2 shift hang in tow haul mode after driving several miles ie warmed up. Can hold 1st gear up to 2500 rpm at light throttle then harsh 1-2 shift. After that upshifts and OD for 4, 5 ,6 are normal. Scanned with no codes or recent recorded events. Truck has never beefed turned up or abused. Thoughts? Appreciate it!

 

[sag2]

I don't recall the symptoms, but some of the RFE transmissions sheared a couple of the valve body valve cover bolts off and allowed one or more of the shift valves to try and exit the valve body. If you drop the pan again you should be able to see it without pulling the valve body down. If you do a search you can probably find some photos of the concern.

 

[JR]

If you drop the pan make sure to give the accumulator plate a good look. It will be on the side of the valve body. The pressure from the accumulators push the screws out, bend the plate, etc. It is a common weak point of the 68. If your trans is tuned with higher line pressures it's an even more likely failure point.

 

[rmini]

If you drop the pan make sure to give the accumulator plate a good look. It will be on the side of the valve body. The pressure from the accumulators push the screws out, bend the plate, etc. It is a common weak point of the 68. If your trans is tuned with higher line pressures it's an even more likely failure point.

Gents:

Thanks! And good points! Will do that in the near future and report back. I am also cleaning all the grounds under the hood just in case. I have had the usual battery terminal/altenator connection maintenance issues from time to time with it so good follow-up. Again, appreciate the help from the group! More to follow. Ironically, hauled yesterday, no issues! Datalogs looked clean! Love intermittents!
Cheers
Rmini

 

[Ozymandias]

What did you use for "scanning"?
The 68 is quite sophisticated if it comes to diagnostic ability.
Means, if you have such a malfunction it would leave traces in the memory.

 

[rmini]

What did you use for "scanning"?
The 68 is quite sophisticated if it comes to diagnostic ability.
Means, if you have such a malfunction it would leave traces in the memory.

Ozymandias

I have an Autel Maxicom808. It can see most if not all of the tcm sensors, solenoid and associated integrated power module controls. There is only one event in memory and it’s several thousand cycles old. Nothing new or current. No codes either pending etc. I monitored the tcm controls, actions and events while someone else drove while hauling. It was flawless. And all shifting was nominal. It appears to intermittent. Only happens occasionally and have only experienced it while in tow/haul. I’ve disconnected after hauling and drove unloaded while in/out of tow/haul and leaning on it pretty hard. Flawless! With the miles on it, transmission performance including upper gears and OD and TC lock are normal.
Thanks

rmini

 

[Grumpy8811]

if I had the right diagnostic tools to enable doing a relearn, I would try doing a "relearn" on trans before going into anything else.

 

[rmini]

Grumpy,

Good thought! I can perform a relearn. Didn’t originally consider as the CVI’s appear smack in the middle of the limits. But it does have 220k on it!

Thanks!

 

[rmini]

Grumpy,

Good thought! I can perform a relearn. Didn’t originally consider as the CVI’s appear smack in the middle of the limits. But it does have 220k on it!

Thanks!

Folks

Wanted to give an update. Appreciated all the suggestions. Have done several trips with this thing in the week or so. Running with and without trailer and running Tow/Haul with and without exhaust brake engaged. The thing has not acted up once. I am just going to run it until I get a trackable failure. Again, appreciate the whole TDR community.

Rmini