When I'm on the freeway in my 01 Z28 (4L60E) at around 55 - 60 mph I go from around 1700 rpm to 2100 (roughly) and then back down to 1700. It only lasts for a second or so, so not long at all. Also, I've noticed when I'm in higher gears and I go to pass aggressively that it will just spin the engine to the sky 5000+ rpm while not putting any of it to the rear wheels.

I'm thinking the torque converter isn't locking up or losing its lock. Either that or the transmission is slipping.

Thoughts? Any way to test it?

 

If you floor the pedal and the engine revs up, but the car speed does not follow, it is not the TCC. The TCC automatically disengages when you floor the pedal. However, the transmission could be slipping under load. Go to a good transmission shop and get the transmission diagnosed.

 

Well, I just went out in the car for a quick one around the block. I'm not 100% sure if it's slipping or just breaking traction when I go WOT. Each time I did it went to "LOW TRAC" on the dash when I was trying it from 30-45mph.

 

Switch off your traction control and try again then. Having that kick in will throw off what you think you're feeling.

 

I'll test it on the way home. I also read that a misfire will cause the torque convert to lock and unlock so I will also hook up my laptop and check for that.

 

...also, I read that the 4L60E still uses vacuum modulation. I may have a leak where it mounts to the rear of the manifold from when I pulled my harness for the camshaft sensor fix. I may have disconnected it but I'm not sure and will check when I get home.

Do you think that could cause it?

 

I doubt that could be the cause since the 4L60E doesn't have a vacuum modulator, it's (E)lectric/computer controlled. That's in stock form, unless your trans has been converted using a TransGo vacuum modulator kit.

 

Well, I do know that there is a vacuum line coming off the back of the trans. I know it's electronic but I read something earlier today about a vacuum modulation system on them. Trust me, I thought it was weird too.

I'll check out the manual when I get home to see if I can find a vacuum diagram for it.

 

Did you get this trans "built"? That's what I'm saying, maybe it was modified. And are you sure you're not looking at a vent hose?

 

I'm about 99% sure I'm not looking at a vent hose. There's two lines that come off of the trans and I know one of those is a vent hose. Looks like a 5/16th's rubber hose that's fairly long. The other is a tiny hose just like the vacuum line that runs towards the passenger side of the car. It also has a t fitting on it that once hooked up to the AIR setup's hoses IIRC.

I know that the trans was rebuilt before I got the car but I do not know what is done to it to be honest. I'm pretty sure that the vacuum line coming off of it is factory since it looks exactly like the hose coming off the rear of the intake and running to the passenger side.