Correct me if I'm wrong, but within a given gear, engine RPM and vehicle speed should be linear, right?

I've owned a 2006 SCab XLT for a little over a month, and notice that while in 3rd gear, when I'm accelerating slowly, the engine either remains at a constant speed or sometimes even slowly creeps backward on RPMs. When I give it more throttle, RPM jumps up and puts out more juice and I accelerate faster. I mean everything feels and sounds good, but the math doesn't make sense.

Is this normal? This is probably a NEWB question, but couldn't find it through the notorious search function.

It's a 5.4L, 4R75E xmsn

BTW, hi!

 

umm hi... i dunno what you are asking really.... but 3 gear on these trans is Direct drive...

 

are you sure its not just shifting into and out of OD?

 

that or its in overdrive .. and the lockup torque converter is locking and un locking

 

this^^

i have an edge tuner and i have it so it displays what gear im in and when the TC is locked and ive noticed certain times that the TC locks up in 3rd gear. it does mostly while towing with OD off but ive also noticed it while the OD is turned on just driving normal.

 

hmm. it's probably in OD when that happens then. So, in OD, since the torque converter is constantly locking and unlocking, this is normal? I'll kick OD off and see if it's doing it in 3rd.

Thanks for the replies!

 

actually, ive noticed this with my truck as well. in about 3rd gear, my speed is increasing, but my rpms are staying the same or decreasing. but like doverboy says, its at low throttle. maybe the pcm programming?

 

I don't know for sure. But I know that with a STANDARD transmission, each MPH gained or lost is linear to the respective RPMs. But with an AUTOMATIC, each MPH gained or lost isn't linear after a certain gear (usually 3-4-OD). Ex: you can increase from 30-35 MPH with light throttle and not really have the RPMs move up near as much as you would with the standard trans.

 

Yes, it is OD that it's unlocked in. Is the TC ever supposed to lock while in OD? Any maneuvering of the throttle results in greatly varying RPM (not gear shift unless I really punch it). It's almost as if I'm driving a stick while slipping the clutch.

I got into this truck coming out of an m3 with a standard xmsn. Slipping clutch = no bueno. No TC lock in OD = bueno?