jsmacks

I've noticed that under mid-throttle condition, there is a jarring lag when the car shifts from 3rd to 4th gear. Always exactly from 3rd to 4th gear.. no other gears. The car will literally lurch as if the gas is cut momentarily. If the pedal is mashed to the firewall (which.. it frequently is).. then it shifts fine.

What is this? Is this normal?

DougHII

Caused by use of synthetic oil.

Ryanmcd

I think Doug is right, I have 9k and never had this issue.

jsmacks

Doug dug deep for that one. I'm at 7xx miles.

05RollaXRS

Synthetic transmission or engine oil?

I am curious since I am a huge proponent of synthetic oil and will have an RCF in the not so distant future. I drive a car with over 200,000 KM (and an 8400 rpm rev limit) and synthetic oil has kept the engine very smooth.

Fysisist

that plus improper lug nut torque I would speculate.

jsmacks

Nope. Checked along with the muffler bearing.

BOBFSPORT

Doug is obviously busting ***** but funny reading people agreeing with his synthetic oil comment. Engine oil has Zero affect on the transmission.

Every Lexus model forum on clublexus has the one guy who starts numerous posts about "issues" they are having with their car. I'm not claiming the op is this guy but just some food for thought. Auto hypochondriacs ?

jsmacks

lol.. this isn't a transmission or an auto-hypochondriac thing. The engine seriously pauses/cuts out enough to make you violently lurch forward.. and always at the same spot. Always 3rd-4th gear change, always at the same point in the pedal. In the 20+ cars I've owned in my life, I've never experienced it.

*shrug*

Bumper fluid check tomorrow.

JCtx

For some stupid reason, Lexus decided to buy a controlling stake of Aisin, and use those transmissions, rather than the tried and true, plus much more sophisticated ZF units. The best way to diminish such complaints is to use manual mode, which I do all the time. And still get an annoying lurch every time the torque converter locks up from 1st to 2nd gear, around 2,500 rpm. And that can be violent, if you happen to need to accelerate quickly around that point, like changing a lane during traffic, or so. The tranny is the most disappointing aspect of this car, but still prefer it over its competition since I drive it in manual mode, where the drawbacks are a lot less than in auto mode. Oh, and few have complained about the annoying gear whine it makes when accelerating above 2,500 rpm from 2nd and up. Thankfully, it's not that loud, but one more tranny aspect to hate.

jsmacks

Thank you for the explanation! As long as it's a known issue with the car.. and yeah.. there's things to love about this tranny and obviously things left to be desired. Overall, though.. this vehicle is a pure work of art and I fall more in love with her every day. The only thing that could possibly get me off of her is the 2017 RC. Waiting and seeing.

ISF001

The car is designed for higher rpm shifts. I always accelerate with 1/2 to 3/4s throttle (in the least). I do not notice a prominent, jarring lag at any rpm--certainly not one that equates to gas being cut out.

At what rpm do you experience the lag?

RCFun

I have this EXACT problem as well. I have 2,600 miles. It's so bad I'm going to make an appt to have it looked at. And no I'm not an autochondriac, and no its not a shift lag (at least not like I've ever experienced in my life). It's a solid 1.5-2 seconds where the RPMs fall, and there is no gas going to the engine. Like the OP states, always between 3-5 gear and at normal/mild acceleration after a bit of coasting.

Best way I can describe it is you're going 50, red light ahead so you start to coast, brake a little, get to about 35 then go to accelerate again as the light turns and the car just f'in stalls on you. Totally lame.

lorenr

iTrader: (1)

Take it to the dealer. Sounds like the transmission computer. Had a similar problem with my IS F. After several visits and me continuing to tell them that it was the computer they started to believe me.

Normally they won't do anything until it sets a code. Sometimes even then they will not do anything unless the shop manager can see the fault. Something is cutting your fuel and I'm saying the CPU dozen't like the something.

Good luck.
Loren

I finally got lucky. New computer, problem solved.

ISF001

This does not sound familiar to me. I would take the car in to Lexus for some testing, or at least put a call into Lexus engineering.

My 2012 IS F had this issue in the beginning until the ECU trained on my driving style. Do you push the car much or drive it at a leisurely pace? If it is the later, try more spirited driving and see if the ECU trains on the new driving patterns.

One easy option is to have Lexus reset the ECU.