68rfe

[DEStewart]

Towing a12000lb trailer in heavy stop and go slow traffic. Trans would not shift past 4th gear. If you came to a stop it shifted to1 and then straight to 4th. Any ideas?? Had 139,000 on truck

 

[transe]

That means you have set a Gear Ratio Error fault (such as P0735, Gear Ratio Error in 5th, for example). Gear Ratio Error means the trans was slipping in that gear. So you likely have a weak / burned clutch (or a bad clutch piston seal) somewhere. Restarting the truck will clear the fault and give you normal shifting again.

Overheating the trans could be a factor, since you were pulling a trailer in stop-and-go traffic. Next time, shift to Neutral when you are stopped at a light. That will help reduce the amount of heat being generated in the trans.

Take it to a parts store and ask them to read the faults for you. If you have a 2010+ truck, they should find any trans faults. In 2007-2009 trucks, there is a separate ECM and TCM, and most parts store code readers will only read the ECM (which will show a P0700; this is just a flag code that means there is some other fault set in the TCM). In that case, have a dealer check the codes for you.

 

[RustyJC]

If it doesn't reset upon restarting the truck, I had a situation that had similar symptoms arise at about 15K miles accompanied by a MIL (check engine light). The problem was a failed output speed sensor on the 68RFE. It didn't want to shift cold or hot and wouldn't go beyond 4th gear.

Reading TransEngineer's comments above, I can understand how the behavior would be similar since, without the output speed signal, the transmission's "brains" would lose input-to-output speed rationality.

(TransEngineer, thanks again for participating on the TDR forum. Your informed input on issues such as this is invaluable and greatly appreciated!)

Rusty