This Hemi is driving me nuts!

I am having driveability issues at speeds above 55 mph.

The truck has a lot of pep and great driveability in 5 miles of city traffic I drive each day. But, the other 35 miles of highway driving is extremely frustrating. My commute (40 miles one way) is mostly 60-65 mph with rolling hills and light to medium traffic. Biggest problem is gear hunting (trans has commitment issues). When going up hills the trans will lock into OD and climb the hill like it is supposed to. However, considering it is turning 1,800 rpm the truck still feels weak compared my wife's Chevy 4.8L at 1,500 rpm. Down hill and flat driving is horrible. The truck constantly jumps from 1,800 rpms to 2,100 rpms. Up down, up down, up down for ever. It does this regardless of whether I am using the cruise control or foot pedal. I can distantly hear and feel the jump up and down. Every other truck I have ever owned would hold a gear and run a steady rpm. This up down up down is maddening. I have taken it to the dealer twice, each time I have been given the same answer, "Unable to duplicate, no codes, normal".

The only relief I get is if I engage the tow/haul mode. It then holds the gears correctly, but it is locked in 4th gear (no 5th in T/H) and my mileage drops.

Mileage on the commute is 14.5 mpg and 14.0 mpg in T/H.

Also, the constant gear hunting has to be damaging the transmission.

Any help?

 

Welcome to the world of MDS. You are actually shutting down four cyclinders when you see the tach hunting. This is normal. As for getting rid of it the only option I have heard is doing what you are doing, using the tow/haul feature. Like you said hurts fuel mileage. Actually might have been a rumor but have heard the diablo predator chip will be able to shut off MDS completely. Well good luck, oh and don't get an exhaust system because you will hear the exhaust drone of MDS.

 

Will the Superchips deactivate the MDS?

 

Yup that's MDS. It feels "weak" because it's running on 4 cylinders like RamSportBlue said...and it's not hunting for gears so don't worry about the tranny. Holding a steady speed in tow/haul and you will go into O/D...the only loss of mpg will be running on all 8.

 

4th is overdrive as well, but I don't think it will go into 5th.

cdhd, driving 5 mph faster might be a simple solution to your problem. you seem to be driving right on the border, and the hills are throwing you back and forth over the fence of MDS/No MDS.

 

Driving at 70 mph vs 65 mph does yield less MDS surge. But, the speed limit to work is 60 & 65 mph. I don't like speeding tickets.

Maybe this is why people with the 265/70 17 tires experience the surge less? (from a few other threads...) A 4% difference in speed would increase my 65 mph rpms to the same as 70 mph rpms.

Hmm...

After 4,300 miles I am not getting any closer to "not noticing" the surge. If anything, this is driving me crazier with each passing mile...

 

well, you could always drive slower too...

 

I suggest getting a programmer. Im not sure if it will cause your problem to stop all together but it a programmer will differently help make smoother and smarter shifts. I have one and it was the smartest investment I made.

 

Far as I know 4th is the only O/D...there's two 2nd gears which makes it a 5 speed. Count the gear changes in your truck...there will only be four.

 

I barely notice the change from mds to no mds. It certainly doesn't feel weak when driving at any speed.