carderoni

Interesting, I don't recall being able to feel it nearly as much in the AWD. Maybe I just got used to it and need to get used to it all over again.

Aeromotive

Thanks for starting this thread. I was looking forward to this comparison! I'm currently deciding between AWD and RWD because I would love the 8-speed transmission.However in my area we get a lot of snow. Do post general driving and performance impressions when you get the chance! Is the 8-speed worth sacrificing AWD?

carderoni

The first week is in the books and that has given me enough time to gather some early, real world impressions of the differences in driving characteristics of these two cars, specifically regarding the transmission and ride quality.

I'm still within Lexus's recommended break-in period - and my own - so I have not been driving the car particularly hard or over long stretches of highway yet. I'll update this thread with some relative "at the limit" driving impressions once I'm past 1,000 miles or so. I'm currently at 526.

Transmission Performance and Behavior in Routine Driving Conditions
In full automatic mode both transmissions exhibit supremely smooth shifts - hardly noticeable, really, with the downshifts slightly more so. There really is very little difference between them in routine driving. Both are geared and programmed to keep the engine speed between 1,500-2,000RPM when puttering along at city speeds (25-50MPH), and both keep the engine spinning at or just above 2,000RPM on the highway. Any advantage the RWD model has in gas mileage is probably due to extra drivetrain loss in the AWD model than anything. This transmission was clearly designed for keeping you in the engine's sweet spot at higher RPM's with improvements in gas mileage an afterthought, if that.

Once you put the transmissions into manual mode, however, the differences become more apparent.

Engine breaking is one such area. In the middle gears (3, 4, 5) the effect feels more pronounced with the 6 speed. Down shifting into 3rd at 35MPH with the 8 speed is relatively uneventful, but results in pretty significant engine breaking with the 6 speed. I don't pretend to know enough about the inner workings of these things, but it may have to do with the closer gear spacing of the 8. Engine breaking in first and second gears feels slightly more pronounced with the 8 speed; it is significant with both transmissions.

Shift response is certainly a bit quicker with the 8 speed. By this I'm referring to the transmission's reaction time, not the actual shift time - the time from when you first pull the paddle to when the transmission initiates the shift. The 6 speed is no slouch - it reacts more quickly than most electronic automatic transmissions and puts the 5 speed auto in my Subaru Legacy GT 2.5 to shame - but there is a brief pause between the pull and the actual shift. It is near instantaneous with the 8 speed. Comparing the actual shift times will have to wait until I can get into more spirited driving with the new car.

Shift points are naturally going to be different between the two. Based on my scientific approach of eyeballing it, below are the lowest speeds the transmissions will shift/allow you to shift into each gear. Which brings me to another thing the two share - the nannying that nearly all electronic automatic transmissions engage in. Both transmissions will downshift into lower gears if you stray too far from the comfort zone of whatever gear you were cruising along in. And both will limit how far ahead you can get (IE, you cannot shift into 4th gear at 10MPH).

8 Speed

• 2 - 8MPH
• 3 - 14 MPH
• 4 - 18MPH
• 5 - 24MPH
• 6 - 29MPH
• 7 - 35MPH
• 8 - 50MPH

6 Speed

• 2 - 10MPH
• 3 - 15MPH
• 4 - 20MPH
• 5 - 25MPH
• 6 - 35MPH

My memory could be a little off about the 6 speed's shift points - please correct me if I'm wrong and I'll update the post.

carderoni

Following up on my initial impressions/comparisons of the transmissions, I thought I'd touch on ride quality and NVH.

Ride Quality and NVH in Routine Driving Conditions
The entire time I owned my AWD 350 I was floored by the suspension. How could this car maintain such sublime ride quality without sacrificing handling? How could this car stay so straight through the turns, with so little body roll, yet soak up bumps and road imperfections like cotton candy?

I'm pleased to say that, for the most part, this is the case with the RWD model as well. The suspension feels deceptively softly sprung is on the straights. You feel - you know - you are planted through the turns, the car feeding your confidence each time.

With identical suspensions and ride heights, the minute differences I've noticed can be firmly pinned on the tires. There is a bit more noise at highway speeds. Not noticeable at lower speeds, the tires - while not exactly howling - are grumbling a bit when you leave the confines of suburban speed limits. The ride quality also drops a tick, with minor flaws in the road making their way into the cabin and steering column. Perhaps this is due to stiffer side walls on the summer tires or simply differences in material? It's still a plusher ride than one would expect from a car in its class, but its personality isn't quite as split as the AWD model's. And because of that a tiny bit of the magic is lost.

onepointon

Sorry about your luck, but looks like its worked out. I took home a 2WD 350 F-sport before I bought mine. I felt that the 2WD car was "peppier" that my AWD. I wanted the 2WD car bad, but I do a lot of snowboarding. AWD was a must for me to get around in the snow. I've had mine since November and I have been thankful quite a few times I had the AWD.

Also, for Lexus of Richmond. How was your experience there?

Slust

+1 for the snowboarder above! :P


So have you driven the RWD in the snow yet? What are your thoughts on the two in that category? I don't know how its been in VA but its been MILD here.

How different is the turning radius between the RWD and AWD?

The suspension felt different to me (maybe a bit firmer) in the IS250 loaner they gave me while waiting for mine to come in. I was curious if this difference would apply to all the 6-speed transmission variants but sounds like no.


When you went witth Silver did you choose that because you knew you wanted a change or because you got tired of white and the silver looked so good? I ask because when I had my accident I felt like I didn't want that vibe again. I thought Nebula/Rioja would be my color combo of choice... but when I had the chance to get one I just couldn't do it. I can't explain it and I have no real reason to say why, but just kind of curious if you felt the same way when you went back to get another 3IS.

AndyL

Thanks for your great findings. Your write up definitely helps many to understand the difference between RWD and AWD IS350.


I wonder do you find the AWD IS350 nose heavier when compared to its RWD version?

Aeromotive

Thanks again for your informative posts. Allow me to comment and ask a few questions as I'm in the market for a 350RWD and I'm wondering if the 8-speed transmission is worth sacrificing AWD in Quebec.

So you're saying that for the same speed, say 60mph/100kmh, both transmissions will run the engine at the same RPM? That's a bummer . I wanted the 8-speed tranny because I do a lot of highway driving and a low-RPM cruise is important for me...
By the way I've read that the automatic transmission won't go into 8th gear at highway speeds and you have to switch to manual to do so. If this is true, where does it stay for highway driving? 6th? 7th?

You mean engine braking?

Please do so when you can. I'm looking forward to this.

Care to elaborate on this please? I'm not sure I understand what you mean?

05RollaXRS

I believe from seeing both AWD and RWD at the dealership, the AWD has a very noticeably larger front wheel-to-fender gap compared to RWD.

The RWD seems to have a much smaller fender gap.

AndyL

From what I observed last time in the dealership, both AWD and RWD seem to have the same wheel-to-fender gap for this generation.

JGard18

If you look at the ratios I do believe 6th and 8th in the respective transmission is very close to the same, which means the revs will be the same. The difference is only in between gears.

Also, the 8 speed loves going into 8th gear. It'll do it at like 30mph most of the time. The only time it won't is when you're in S or S+ mode, that's when you have to use manual shifting to get it there

carderoni

This is correct - the wheel gap/ride height is identical on both models, unlike say the BMW 335i and 335Xi.

carderoni

Yes, the 8 speed will go into 8th gear in both Normal or ECO mode, automatic or manual. The engine is spinning right at 2,000RPM at about 69MPH, which is very, very close to the 6 speed.

I was personally expecting something closer to an "idling down the freeway" experience, but let's remember that this transmission was originally created for the IS-F. I doubt many IS-F owners would sacrifice more aggressive gearing for highway mileage.

JDR76

Just wanted to say thanks, carderoni, for creating this thread. I'm enjoying your posts.

carderoni

Yes, engine braking - must've typed this up before my morning caffeine binge

As for the ride quality, what I was trying to describe was how well the suspension absorbs small bumps and cracks in the road - you don't feel the car jolt or jiggle as much as you would in, say, an E90 or E46 BMW, the poster children of cars in this class.

The ride isn't silky, but is much smoother than I'd expected considering how well the car composes itself around the bends. We've been raised to expect one or the other - ride on a cloud and tip like a boat, or stand straight as a pillar and feel every pebble on the road. Lexus did a fantastic job balancing both of aspects with the 3IS F-Sport suspension.