I have a 2006 CTD with 4.10 gearing. It is a 4 speed automatic. I am pulling 1700 rpms at 55mph, 2000 rpm at 65mph and 2200 at 75 mph. does this seem about right? I am also wondering what is actually the ideal rpm to cruise at and what rpm might be bad for the engine.
Also( know alot of questions) does anyone know what rpm the truck should be shifting at. Seems like mine is around 2800-2900

Thanks

 

I have 4:10's and I get 60 mph @2000 rpms with a 4 spd auto I don't know if my speedo is off I have 285's for skins. Your speed @ rpm sounds right. From what I understand a stock engine is pretty safe at any reasonable rpm. I wouldn't redline it through the rockies. Tow mode will hold a gear and shift at a higher rpm. I keep my rpm's down for better mileage I think under 2400 will be about right. I just drive relaxed and take it easy on my truck I want a million miles out of it. If I want speed and cornering I drive the LHS!

 

I too have a 2006 with 4:10's - and my speed was just what Hiloram's was at 2000 rpms...before I put 35's on for the very reason of dropping those R's down. Now at 2000 I'm doing just a tad over 70 mph.
I have trouble stopping my old-school thinking that the higher R's aren't good for these CTD's - but in talking with some very knowledgeable Cummins tech reps, they tell me I can cruise all day at 2400 or 2600 and not wear the motor down any faster than at a lower R. BUT - the higher R's will drop your MPG logarithmically, so keeping them lower is better for the pocketbook.
As for the shift point, that's dependent upon how hard your accelerating - I tend to granny it a little so mine's shifting more at just a bit over two grand. (but when I decide to smoke someone it can shift all the way up very near redline)

 

Thanks for all the good info. The highest speed limit we have around here is 55mph and not many of those. I can now just sit back and enjoy it and start planning for those bigger tires.

 

putting on those bigger tires will also lower the actual speed you are traveling when you get your speed-o corrected.

but dont feel so bad, at 70 I'm pulling 2300RPM, NV5600 6 spd and 4.10's is a killer, but pulls like theres no tomorrow

 

I,m turning 2,000 RPM @ 70 MPH with 3.54 gears, stock tires. With the Gear Vendor in overdrive, the RPM drops to 1,500 @ 70. The Gear Vendor allows me to split gears when towing, so I am able to pull ok, but without it, the 3.54 gears would be a problem towing.

 

I do need an overdrive gear set. I dont want to swap axels, I like these 4.10's to much when it comes to pulling, just the unloaded part is what gets to me. but I cant quite come up with the funding for one right now. . .but I can fund a TST (hint hint)[sm=badbadbad.gif]

 

How can you verify what gearing you have? Dealers online add said that my truck had 4:10's but the guy told me it actuallt had 3:73's. At 75 I am hitting around 2100-2200 RPMS







Ken


2006 2500, QC, LB, 4X4
HO CTD
4 SPEED AUTO

 

ken, it sound like 4.10's. I believe with 3.73's at 75 with the 48RE you would be turning just shy of 2K.

 

Can somone tell me what all the gears are available for these trucks and also, the ups and downs of each.

Thanks.