Cummins12V98 wrote:
To say a trans failed because someone did not use TH is simply a farce. Locked is Locked in TH or not. EB will be almost useless without TH still nothing to do with trans failure.
Someone please correct me, I think my 15 once plugged into a trailer the TH is automatically ON.
This could happen depending on the condition of the overdrive clutches. T/H does two things, increase max line pressure threshold and causes the trans to shift later. Both of these are done to help the trans clutches last longer. If T/H is off and the valve body is not injecting enough line pressure to keep the overdrive clutches together and it shifts into overdrive at a really low speed, then you are asking for a slippage or some kind of clutch wear. It is better for the trans to shift at higher rpms above 1,600 when towing and for the line pressure as high as possible to make a firm shift with as little clutch slippage or wear as possible.
One issue that the 68RFE has been plagued with is a weak valve body that cannot hold more than 170 psi of line pressure because the valve body plate is very flimsy and will start flexing at higher pressure causing pressure to bleed through. Couple this with very flimsy overdrive clutches and you have a recipe for disaster if not tuned right by an after market tuner.
Also, the 2019+ 68RFE is not the exactly the same as the 2007.5-2018 68RFE. There are extra valves that control torque converter lockup and reverse that allow the pressure to be ramped up during engagement for a smoother transition. The older trucks were all tied to the main valve for a rougher TC locker up and reverse because it did not have the ability to ramp up pressure during engagement. It had to use whatever pressure the main valve was pumping out at the time since it did not have its own valve.
