jzr

Hi guys,
Still relatively new here, got a couple quick questions, highlighting my unfamiliarity with the Cummins motor.

1 - Driving fast. My truck has the 4.10's and the 48re. 65mph is 2000rpm, but at 85, a speed at which I regularly drive when unloaded, the motor is up over 2700. I always take it easy until she's warmed up, but assuming good warm-up and maintenance is done, is this bad for the Cummins?

2 - Lugging. Couple weekends ago towed my race car to Nor. Cal and back. With the open trailer the load is between 4 and 5k. Coming back, southbound over the Grapevine (big steep hill, 6+% grade for several miles) I went into Tow/Haul mode (mine's an '05, no OD lockout). I got slowed down by traffic from 70 to 63-64mph, so I went to full throttle to try and speed back up. The truck wouldn't downshift out of 4th, climbed to about 65, and just sat there. I was at full throttle for a couple miles, with the engine only spinning 2000rpm. Is this considered lugging the Cummins? I don't have any guages but was worried about EGTs, and it was pretty warm out, almost 100. The temp guage moved from half a needle's width to the left of 200, to half a needle's width to the right, very little.

In my old truck ('99 F150 w/5.4 V8 3.55 rear) and the same load, I'd start the climb with the O/D locked out, and a little ways up my speed would drop below 66 at which point it would downshift to second - but from there it would at least accelerate up to 75 before going back into third. I guess I just didn't like the feeling that with all the power in the new truck, I would have been beaten up the hill by my old one? I would have liked to be able to select third gear to get some extra oomph going...

Oh well...any ideas besides "shoulda got a manual"? My truck duties are split 50/50 mile-wise between towing and commuting, but time-wise that means more of it's commuting, hence the auto.

DSLRammin

1- unloaded and 85mph at 2700rpm, won't hurt anything but your wallet,
You'll pass everything but a fuel station.
2- IMO, 2000 isn't lugging while towing, but a little more rpm wouldn't hurt for that length of grade.

stock you shouldn't worry to much about egt's, but it's nice to know what's going on with her while towing, stock or other wise.

hammerjammer

When towing in tow haul mode and the tranny don't shift from od to third to keep the rpm's up,double click the tow -haul button and it will down-shift to third.