Alright, here goes.
I have an 01 Ram 1500 2WD. I just had the tranny rebuilt about a month ago. Seems my TC went and pushed metal throughout. Well, it still seems as if my truck is lacking power. I changed all my oil, air filter,plugs, wires, cap and rotor. I also did a compression check. The compression came out like this:
#1 - 171psi
#2 - 170 psi
#3 - 179 psi
#4 - 173 psi
#5 - 171 psi
#6 - 170 psi
#7 - 169 psi
#8 - 171 psi
So, it seems to me that my compression is good. I took it out for a test run and noticed (thought it was happening before I did the work) that my truck seemed to lunge in 3rd gear, 41 mph,at about 1800 RPMs. I took it out and as I went over a bridge, it seemed to do it, but worse, in 4th gear, 51mph,at 1500 rpms. I did some research and found a forumn that stated to change the TSP. I did that, it idles a lot smoother but I still have the lunge problem. I took it out ona longer trip and noticed that it is worse on hills. I have pinpointed when it happens:
3rd gear, 41-42 mph, 1800 rpm
3rd gear, 49-50 mph, 2100 rpm
4th gear, 51 mph, 1500 rpm
4th gear, 61-65 mph, 1900
It is hard to tell if it is slipping. When it lunges, it goes up about 200 rpms and back down about once or twice every second. It almost seems as if I am pushing on the gas and back off, but I am not. I hope that I have been descriptive enough. I am just hoping that it may be a simple fix. Maybe a fuel delivery problem. Or am I going to have to take it back to the tranny shop? Any help/info would be greatly appreciated!

 

could it be torque converter locking and unlocking. thats about a 300 rpm change at around 45-55 mph.

 

^^^agreed

Torque converter locks up just after 3rd to OD (4th gear,) and as acceleration continues it lets go and the truck feels like it's finally gone into overdrive. RPM's drop and you feel like you've got your power back.If your really into the pedal, it'll take off on youa little bit;that might be your lunge. It's a little weird when you first start to notice it, but it's always been there.

 

there was a wiring issue in the tranny that someone found to cause the same exact problem... check the info threads at the top...

 

Thanks to all of you for the info. The lunge itself is more like a pulse. It will do it 2-5 times at the noted speed/rpms/gear. It is alomost as if I am pushing down and then letting up on the gas pedal over and over. However, it doesn't switch to the next gear after that. Once above a certain rpm, it smooths out. It is pretty strong. My wife and kids noticed it and asked me if there was anything wrong with the truck. I will take it back to the tranny shop and have them check it over again. I will also asked them to check the wire as described in the other thread. Thanks again for the info!