(Hopefully not dumb) question on transmission behavior in new S40s...mine is a 2009 T5 AWD with over 9K miles.

When accelerating at/near highway speeds, after pressing on the gas, the RPMs go up with the downshift and then reduce a bit (few hundred) soon after. There's no clunking or abrupt shifts. The car accelerates fine and I don't notice the RPM shift when when giving it close to full throttle. I also don't notice it when manually shifting (although I put the transmission in that mode too often).

Is this expected/OK transmission behavior? I was thinking that the lockup torque converter is at work here but I don't know if that would worn in all gears or just in 5th.

I've become accustomed to the behavior but if it's a sign of some early failure then off to the dealer I go...

 

I might be way off, but it sounds like the trans might be slipping.

 

Tried a bit of a road test this morning...I definitely see the behavior under light throttle downshifts at highway speed. RPMs go up and then down by a few hundred within a second or two...almost as if the car is "easing into" the new gear.

When I gave it heavy throttle on a downshift I did not see it happen.

Edit: I see the behavior in 4th gear but not in 3rd...that would explain why I only see under lighter throttle downshifts. I can also make the RPM fluctuate when downshifting from 5th to 4th using the paddle shifter and applying some gas.

 

I've noticed the same issue with my 2010 XC70. Right after a shift, the tach goes up by a couple hundred RPM and then back down again (within a second or so). This occurs only under lighter acceleration (when RPM are about 2,000). Under harder acceleration this does not occur at all. Not sure if the transmission in the 2009 S40 is the same as the 2010 XC70 though.

 

I recently asked a friend about it, and he said that the transmissions are designed to lock in 3rd and 4th gears, depending on how hard you are accelerating. When it locks, your RPM's will drop. So possibly, it could be that your transmissions are just locking earlier then you are used to.

 

Might very well be the case, but I have an appointment with the dealer next Thursday just to make sure. Can't hurt...car's under warranty so it won't cost me anything but a little bit of my time (and possibly a small cost for a loaner) for some peace of mind.

 

Took it for a test drive at the dealer...shop foreman said that he didn't see anything indicating a problem. Told me at the transmission does have a lockup in 3rd through 5th gears and that is what I'm most likely noticing. He offered to have the car hooked up to the diagnostic computer but I didn't want to tie up the car in the shop for a day...I'll just wait on that until the 15K service unless anything else comes up.

 

Does it act the same way after driving awhile vs cold start (first few miles in the morning)?

 

As far as I can tell, the shifting behavior is the same. I don't see any delayed shifting like I do on my other car, a Toyota Highlander.