IDAK125

I'm currently driving what's listed in the title. Here's what I noticed... the IS AWD is a 6 speed auto with manual mode. While driving in auto mode I notice 6 distinct gears as expected. However, while in manual mode I notice what appears to be "mysterious" gear changes (where I notice a distinct 500-750 rpm drop as if shifting gears) within gears 4 and 5. For example, I get the expected rpm drops going to 2nd, 3rd and 4th, another unexpected drop within 4th (I'll label it 4.5 for simplicity sake), the expected 5th then another unexpected in 5th (5.5), then the final at 6th. This only occurs in manual mode as these "mysterious shifts" aren't noticed in auto. Also these extra two shifts occur automatically.

So here's my theory... and I'm looking for some opinion on this crazy idea....

The 350 AWD is a 6 speed while the RWD is an 8 speed. Is it possible that lexus did not create two different trannies for the IS and in fact only used one where the on board controller for the AWD is simply programmed to appear as a 6 speed when in fact it is really an 8 speed. If true, then it would explain these extra two rpm drops.

Thoughts?

otakusan

It is a 6 Spd.. if you're curious on what gear you're actually in, use your steering wheel controls and switch your dash display to show gears. I do notice that this 6 spd has a very "lazy" torque converter and does make it feel like it's in between 2 gears and trying to decide to shift up or down than eventually shifts down.. but it was actually still in the same gear all along.

IDAK125

The steering control is the first place I checked. What's weird is that it doesn't seem like a lazy shift but more like an additional shift in 4th and 5th. When I'm accelerating in manual mode I'll shift it to 4th and get the rpm drop but then at around 2500 rpm it'll drop again to 2000 on its own. It'll do it again while in 5th.

otakusan

ya that's what i meant... the IS doesn't have the most responsive transmission unfortunately. actually, it's so sluggish that sometimes I feel like I have a CVT haha

IDAK125

ugh. I got rid of my 14 Maxima and moved the IS to get away from the CVT feel. It does seem a bit slow on the shifts. Maybe I'll record the acceleration and post it to get a better idea of what's happening... still better than a CVT though.

otakusan

But to be fair, all in all, the IS holds a good balance between comfort/style/reliability/performance.. It was never meant to be super zippy weekend track saloon.

compared to a great deal of cars I've test driven before I got the IS (Audi S4, Merc C450, CLA 45 AMG, GLA 45 AMG, Infiniti Q50S, BMW 335) The IS is BY FAR the least fun and performance orientated, but it does win with reliability(as stats can proof), while comfort is very comparable if not a slight edge, and style is a personal taste thing.

Sasnuke

I believe what you are noticing here is the torque converter locking up...which is normal as it attempts to improve fuel economy.
Back in the day, automatic transmissions would only go into lockup after the transmission shifted into the highest gear...once the vehicle was at operating temperature.
In modern vehicles, the transmissions are programmed to go into lockup in several of the high gears in order to improve fuel economy...most noticeable in manual mode.
In Auto mode the transmission simply upshifts rather than go into lockup until it reaches the highest gear...then it goes into lockup.
When you notice it happening in manual mode, if you simply press the accelerator just a hair, you will see that the RPM will increase by the same amount it just dropped without the vehicle actually accelerating...which it is just simply it coming out of lockup.

Fsport4sho

My is300 noticeably does the same thing in 4th gear. Once it reaches 4-4.5k rpm it steps down about 1,000 rpm and goes up again. you can feel the torque difference when it does it as well. I kind of like it ; its like a boost if your low in 4th. At first i thought it was my tranny misbehaving like it was missing a tooth or two on the gear. The only time it doesn't do it is when your at WOT. My guess is because the converter is already locked up.

cbus

Torque converter lockup. Reaching a point of zero slip (full engagement) between the trans and engine.