What rpm are you guys with auto ctd's seeing at around 70-75 mph? Test drove a 99 4wd with 4.10 gears and it was turning around 24-2500. It seemed like it just wouldn't shift into OD? Even when cruising on a flat interstate--not lugging it or anything. The only thing I could think of is when I pulled onto the interstate I turned the OD off, then back on after a minute. Then it just seemed ot stay in drive.
Any clues as to what this might mean? Anything else to look for in the transmission?

my 00 CTD with 3.54's and 315 tires does 70-75 MPH around 1700-1800 RPM...I'm not sure on your setup but you would probably be tach-ing at least 2000 RPM, maybe more.

My rig cruises great, and once it's in OD with the lock-up, life is good!!!

my 99 CTD 24v auto runs at 2K @ 70. Can't remember what gearing I have.

2000 rpm on my 98 is ~72-73mph. 4.10 gears and 35" tires.

my 97 spins about 2400 rpm @ 70mph

4.10's, 235 tires, 5 spd manual

my 06 i think with 3.73 spins around 2000 to 2150 rpms at that speed

my 2000 with 285/75R16 runs about 2100 rpm at 70-75

What rpm are you guys with auto ctd's seeing at around 70-75 mph? Test drove a 99 4wd with 4.10 gears and it was turning around 24-2500. It seemed like it just wouldn't shift into OD? Even when cruising on a flat interstate--not lugging it or anything. The only thing I could think of is when I pulled onto the interstate I turned the OD off, then back on after a minute. Then it just seemed ot stay in drive.
Any clues as to what this might mean? Anything else to look for in the transmission?

It was in overdrive.

With 4.10 gears and stock size tires I will be at 2500 rpm in 3rd gear at about 55-60 mph. Cruising with OD on I will be at about 2300ish rpm at 75mph.

I have a set of 285's that I really want/need to get on the truck. Hopefully it will lower cruise rpm down to a reasonable level with the 4.10s in it. If not, I guess I'll be looking for a set of 35" tires.

My 97 with 4.10's and 265/75/16's is at 2050 at 65, 23 or 2200 at 70. The 4.10's really make it scream on the highway. I didn't realize my truck had them when I bought it or I would have seriously reconsidered the purchase to find a 3.54 axled one. I drive the truck empty most of the time and it only gets 15-16 mpg with mixed driving - not the 20+ that everyone seems to claim on the web!

my 06 i think with 3.73 spins around 2000 to 2150 rpms at that speed

same

My 97 with 4.10's and 265/75/16's is at 2100 at 65, 23 or 2400 at 70. The 4.10's really make it scream on the highway. I didn't realize my truck had them when I bought it or I would have seriously reconsidered the purchase to find a 3.54 axled one. I drive the truck empty most of the time and it only gets 15-16 mpg with mixed driving - not the 20+ that everyone seems to claim on the web!

i have one for sale but i am in so cal

'01, 285's, 3.55's - cruises at about 1750rpm at 70mph in OD and locked up.

'01 6spd, 4.10's, 315's. i turn about 2200 at 70mph.

my 3500 drw 4wd 6spd with 410s runs around 2500or so rpms while running 70-75
i need to up size my tires when its time to replace the tires.

payton

01 auto,245/75/16's/3.55's 70mph,1800rpm's/ in od.

'05 2500 4x4 3.73 stock tires 68mph is about 1800, fuel milage starts to fall off at 75.

'01, 285's, 3.55's - cruises at about 1750rpm at 70mph in OD and locked up.

I will add that I used to have 265's with the above setup and just recently went to 285's. I like the way it was geared with the 265's better than the current setup. If it didn't cost so damn much, I'd regear the axles to 3.73's.

If you have the 4.10s, I'd suggest upsizing the tires to a 315/75/16. They fit with a leveling kit on the 2nd gens and they look like a normal sized tire for the truck. The stock tires make the truck look like it's rolling around on donuts :laughing:

When I had 3.55s in the diffs, it was nice when the truck was empty, about 1700rpm at 70-75, but it sucked towing.