2013 & up transmission lock up and behavior

[LocoPilot750]

I'm definitely stuck in the 90's. I'm still driving my old '97 2500 which I bought new. I can tell a lot has happened since it was was a pup. Back then the remedy for the transmission was a triple disc, low stall converter with a "mystery switch". You could manually lock up the TC in 3rd, or in "OD". That is still working like new at nearly 400k, but I'm thinking about a new 2014 now. Tell me how the new six speed auto trannys function, and how lockup is treated on the new 2500's. Hopefully, the TC has been upgraded over the years with something besides a friction ring. Oh, I'm also going 4-wd on this one too. I'm sure all the shift events are going to feel different to me compared to what I'm used to.

 

[PC12Driver]

It's a different way of thinking now. You just drive it. I'm not sure how different the '14s behave, but my '12 locks the TC in 4th normally and in 3rd with tow/haul on. The transmission can hold whatever the stock engine puts out and manages it quite well (right gear at the right time). Pulling the 10k lbs fifth wheel at 60 mph the engine is around 1,500 rpm and the transmission temps hang out around 160*. In the rolling hills I'll click it down to 5th (still an overdrive) and that'll stop almost all of the downshifting on the uphills (it'll still downshift and engage the exhaust brake automatically as needed to maintain speed on the downhills). No extra mods or switches needed - it just works.

I'm not a fan of slushboxes, but I can live with this one.

 

[cerberusiam]

Little has changed around the size of the components in the transmission or their inability to hold power once the safeties are removed. If anything, they are probably a little weaker in some areas. What has changed dramatically is the transmission controls, the trans is now full electronic control and integrated with the engine controller.



TC is somewhat larger and better but still under clutched as are the rest of the gears. What makes it work better and live longer is the TQ management. Engine is defueled in high stress situations to save the parts then ramped back up. Shifts points are the same, it won't shift under full power and generally will not allow the engine or the driver to hurt the drive train. It can still be done if one is not careful but for the most part it works quite well.



Along with that electronic control comes some peculiarities that take getting used to. The 2014's have even more than the earlier trucks as the power ratings have gone up and the engineers have not quite worked out all the bugs. Over all they are impressive performance and once you get used to them they are definitely a lot better than the older units.

 

[Gonzo 1066]

I have 8000 towing miles on my 2013 now, it took some getting used to but now I am very happy with how well the engine, trans,truck works in hard towing situations. There is a bit of RPM flare in the 4-5 and 5-6 shifts and this is normal. The TC unlocks pre shift,trans shifts then the TC locks. On a hard pull there will be a 100-200 RPM flare in these upshifts. At first I thought the trans was slipping but it is the TC. . Tows great for me.

 

[LocoPilot750]

Thanks for the replys, looks like I'm going to learn this one all over again. I was already trying to figure out who to see about an upgraded TC and how to control lock up. But it sounds like they took care of all that for me, all I have to do now is buy the truck. Are pyro & boost gauges necessary, or is that just part of the display now?

 

[PC12Driver]

I'd probably just get one of the Edge monitors that'll show all the data being piped along the bus. Whole bunch of information to be seen. Provided they come out with one for the '14, that is.

 

[Gonzo 1066]

I have little interest in adding the extra gauges to my stock truck. Figure the EGTs will be just fine as long as the truck is STOCK. Maybe someone can prove me wrong.

 

[Cummins12V98]

Leave them stock and enjoy the ride! No gauges needed it can't hurt it's self.

 

[transe]

There was one important difference in the Torque Converter Clutch (TCC) between the 48RE (5. 9L) and 68RFE (6. 7L). The 48RE used a single-surface TCC, whereas the 68RFE uses a double-surface TCC. So the 68RFE has significantly more TCC capacity than the 48RE did.

 

[PC12Driver]

Just one?

I like the change where hydraulic pressure releases the TCC, so a potential low rpm/pressure situation won't cause the TC to slip. It'll pull itself back up to speed from 1,100 rpm in sixth and never break lock.

 

[transe]

Actually, both the 48RE and 68RFE actuate (and release) the TCC in the same manner. Pressure is fed to the front side of the piston to release the TCC, and pressure is fed to the rear side of the piston to apply the TCC (for both models).



A dip in line pressure will cause a corresponding dip in TCC apply pressure (in both models). But I would guess that the 68RFE (with double-sided TCC disc) still has enough capacity (to maintain full lockup) under some low-pressure conditions (where the 48RE would exhibit TCC slippage).

 

[PC12Driver]

Huh, I was thinking there was some new mechanics going on there.

On one hand, I kind of wish I new more about what is going on with slushboxes. But on the other hand, with the 68RFE, I don't need to. It's nice to finally have a transmission that matches the Cummins and its intended service.