Have had a 09 Quad cab with 3.55 and 20" wheels for about a month now and have noticed that some times it will run 1700 rpms and other times it will run 1500 rpms at 60 mph. At both rpms it seems that the torque converter is locked up and it will go up hills without downshifting. If it is running 1700 with the cruise set I can push the gas down a bit and then let off and it will seem to shift again and will then run 1500 until I change my speed. Seemed odd to me that there are 2 gears that are that close together. Wondering what rpm other trucks are running at 60 or if something isn't right with mine.

 

mine does that too. i think its the truck running on 4 cylinders

 

I get the same thing that you do but cannot confirm whether or not the MDS has kicked in. It does make sense. I was just getting ready to post a topic on this. Since my was a pre-prod build it does not have the "fuel saver" mode displayed on the EVIC. I was hoping to confirm the RPM's with someone that has the "fuel saver" mode. When I am running at 65 mph my RPM's are at 1600. Can someone that has the "fuel saver" mode confirm this???

Thanks in advance!!!

 

lineguy

According to the math at 60 MPH in 5th gear you should be turning 1507.97 RPM and at 60 MPH in 4th gear you should be turning 1688.03 RPM. The gear ration for 4th gear is .750 and for 5th it is .670 so they are very close. Does it happen (the higher RPM's) when the engine is still cold or has it warmed up? Mine seems to run higher RPM's before it is warmed up but this is generallly due to the TCC not engaging until the temps are high enough. I am sure some of the techs here can add more informatiion.

I hope this helps.

Craig

 

I did some playing on the way home from work tonight. With a Good wind at my back it would shift all the way so it was running 1500rpm at 60. Then if I would move the shift lever so it said 5 on the dash it would jump up to 1700rpm, shift to 4 and it would show 2300 when the tcc locked up. Shifted it to 3 and it was at 3400 but the tcc wouldn't lock up. This was all at 60 mph with the cruise set. Seems that with Craig's ratios that if I shift manually I dont actually get 5th gear untill I shift it back to the automatic range. Is this normal. The dealer dosen't seem to know anything about it.

 

This is completely normal. What's happening is when you put it in manual mode so that your indicator says 5, you're actually in what we normally call 4th gear. When it says 4 you're actually in normal 3rd gear. The reason for this is that when you have it in manual mode, 2nd prime is selectable. That offsets all gears above normal second gear by +1. So yes, if you're wondering, normal 5th gear is not accessible in manual mode.

 

That Helps to explain alot. Still odd that it won't shift into 5th unless going down a hill or with a big wind at your back. Once it is there it dosen't shift down unless it is a big hill. Thanks for all the help.

 

Yes, you are correct. When the FS light goes out the rpms drop by a very slight amount. I would guess they want to decouple with additional TC slip while in FS. And fully couple (100% lock-up) while back in 8-cyl mode. My 05 Crossfire does something similar, except when the TC locks-up, it locks at something less than 100%, the book says this reduces driveline vibrations.

 

not to be off topic nice to see some other ky guys in here.