I have been searching the forums and am not really finding an answer. My 05 RL seems to get to 5th gear when driving about 40-45mph, and I notice that the RPM's bounce up and down about 200rpms. It fluctuates just a little. Why? If I switch it to manual and shift to 4th gear, it goes away. It seems like it wants to shift down to 4th but doesn't. Other than this issue, the transmission shifts fine. Seems more like a programming issue or something. Ideas?

 

How many times/for how long does it bounce?

When the car is at the lower end of each gear's RPM range and encountering negative acceleration, it will reach a low and bounce up once before descending again and down shifting. If this sounds familiar, it is normal. If however your RPMs are continuously bouncing, that seems wrong. How many miles on the car? When was the last transmission fluid change?

 

 

torque converter locking/unlocking?

 

I have the exact same thing in my car - except mine is accompanied by a grinding/fluttering/rattling noise. It absolutely seems like it is on the verge of wanting to shift up, which would be fine if it weren't for the noises! I have had it looked at and although the dealer acknowledges the sounds, can't pinpoint the source and reading between the lines, seems to be saying to wait until something fails and then use my extended warranty......

It can be faithfully replicated in 5th gear at approx 1,400 rpm and under any type of load, like a very slight incline - it'll bounce around in rpm's for as long as I let it. Giving a firm press on the accelerator pedal has it kick down into 4th.

 

This describes my situation to a T except I don't have the noises. I can replicate it in 5th going up a slight incline with very little throttle input. It's annoying, but not alarming at least not for me.

 

I'm with getakey. Sounds like the Torque Converter (TC) locking and unlocking. When you first get to fifth, your rpms will be a little higher because the torque converter hasn't locked yet. If you are steady on the gas and there is not a heavy load for a few seconds, the TC will lock and then your RPM will drop about by about 200rpm. It almost acts like a 6th gear, even thought it's not.

Once locked, if you gas it a little or happen to drive up a slight incline (in either case giving your engine and tranny more load), the TC will unlock and cause your RPMs to go up a bit even while you are still in 5th.

It's normal behavior if it's locking and unlocking upon slight load changes. I can replicate this at will by feathering the gas in 5th. If your are not changing load, then it's not normal. Also, noises are definitely not normal.

Hope this helps...

 

I had to take my car in to get the master cylinder recall done (I have been putting it off way too long), and I figured while it was in at the dealer, I would have them replace the transmission fluid. I follow the mid, but I don't think it has asked for this to be done yet. Anyway, I have not noticed the fluctuation / bounce since. I have tried to get it to do it again but have been unsuccessful thus far. Hopefully that was it!

I think I know what you mean about the torque converter locking and unlocking, and I do not think that is it. When that happens, the RPM change is greater that the slight fluctuations I am talking about.

I am glad to see I am not the only one with this issue. I thought I was, since I could not find any other posts about it. (not that I wish any misfortune on anyone else)

 

Multiple threads on this topic over the years. It is common and easily reproducible. I'll try to find some threads when I get a chance today.

 

I've had the same problem you described. I went and done a 3x3 transmission fluid flush, and it solved the problem. I'd recommend you to do the same.