MustangSal

I agree, if it's significant enough that you believe it's not normal, take a tech out on a test drive.

Gs21

I should have mentioned in my post. I had a lexus specialist look at my car for rough shifting into reverse.

he put the car in drive and then shifted it into reverse while the car was moving forward and the car jerked hard and then while reverse he put it back in drive while the car was moving backward. He did this 4 times, I was shocked that he did that, do you think this caused damage to the transmission?

bclexus

No, no harm. The technician was testing the transmission to see if reverse and 1st gear engaged smoothly with proper clutch and band engagement. The transmission's internal clutches and bands are designed to slide a little when engaging, which provides smooth shifting (the lack of which is the issue you are complaining about). Thus the test!

When an automatic transmission locks into gears it is done by these clutches and bands (which is much like brake shoes with a frictional facing), and is activated by hydraulics of the AT fluid pressured through tiny orifices and ports within the transmission's internals. The transmission is not damaged when shifting into drive while the car is still slowly moving backwards (or when shifting into reverse while the car is still slowly moving forward) because there is no hard mechanical links (e.g. engaged gear teeth) between anything in the automatic transmission. The relatively slow engagement of the clutches and the cushioned effect of the torque converter absorb any low speed differentials and allow you to do this without any harm to the transmission whatsoever.

Automatic transmissions need a method to be in gear and be able to have the car stopped without stalling the engine. This is achieved by using a torque converter, which connects the engine to the transmission through a fluid coupling. The torque converter works like a KitchenAid stand mixer - mixing a thick batter or pudding in a bowl; if you beat the pudding without holding onto the bowl, the bowl will spin. But, if you hold onto the bowl (like applying the brakes in your car) the mixer's beater will continue to turn the pudding, but the bowl (your transmission/drive shaft/differential/wheels) will be stopped. Like the transmission's clutches and bands, the torque converter's operation can also be a source or clue to problems as well. Needless to say, nothing happens without automatic transmission fluid. It is critically important to always use the proper ATF (preferably the exact OE fluid) and maintain the proper fill.

So, I see that you've already had Lexus look at it! I guess you weren't planning on telling us... Care to share with us what the technician told you?

MustangSal

You're not seriously asking that question....

Gs21

I'm seriously asking it because I'm not an expert on automatic transmissions, plus I'm shocked that a lexus specialist would do this to my car but yes I'm seriously asking it

Gs21

First, thanks for the explanation I appreciate it. I did take the car to get checked out but that was for a different issue which was my car was difficult to shift into reverse out of park, with that issue naturally they told me its "normal".

I haven't taken the car yet to get checked out for the jerk when coming to a stop that I explained in this post.

I don't know much about auto transmission but just to be clear, when he put the car in reverse while driving forward, the car did shake pretty hard and you could hear a clunk sound and he did this 4 times. He also put it in drive while the car was reversing as well.

You know a lot more than I do but I can't see how doing that would not cause damage to the transmission. In the manual it states not to put the car in gear while the vehicle is in motion. It has me worried and if I tell the dealer it will be the Lexus specialist's who did that to car vs my word, not sure what to do

bclexus

As I explained in my reply - the technician did no harm. It was a way for him to see how your transmission reacted to shifting and engaging. Remember the KitchenAid mixer bowl example I gave you in my previous post? The shake or shudder you detected was the torque converter reacting - same as the mixer's beater turning the pudding in the mixer bowl without holding the bowl - the bowl will turn and wobble...just as the torque converter shook and shuddered. No harm was done...

Your car should not be difficult to shift into reverse from park - that is not normal... And neither is a jerk or clunk when coming to a stop. I'm assuming this jerk happens in Normal drive mode with the transmission in full automatic in lieu of manual. I would take the car back to your Lexus dealership and ask the service advisor (to look up your last visit and) to make sure your car is looked at by a different technician than looked at it when you brought it in last time to report difficultly shifting into reverse from park...because you are still having difficultly shifting into reverse from park, and you are 'also' experiencing a jerk and clunk at times when coming to a stop. You want these two transmission problems checked out and fixed. Say no more - let them report back to you their findings. Be sure you get a loaner...because you may have it for a few days while they fix your car...

MustangSal

The moment a Lexus "person" started putting your car into gear while it's moving the opposite direct should have been the moment you unloaded on them. I am pretty sure you're not supposed to do that with any vehicle...and surprised the Lexus will actually let you to be honest.

You're actually on here asking if it's ok and if you should be concerned?!?!

Yeah you should be concerned.

Gs21

I thought since the torque converter had to deal with the extra stress that was put on it, maybe some damage was done to the torque converter itself. I'll take it in and see what they say, should I tell them about what the lexus specialist did?

bclexus

The torque converter is basically a spinning drum of transmission fluid, and it connects the engine to the transmission through this fluid coupling. (If you had a KitchenAid stand mixer with the mixing bowl partially filled with pudding - and you started the mixer stirring or beating the pudding, the mixing bowl would spin around and around if the bowl wasn't secured in the stand. But, either way (bowl secured, or free to spin around) neither the mixer nor the bowl would be damaged as they are not directly connected...because the two (mixer & bowl) only connects [couples] the mixer to the bowl of pudding through a fluid coupling (the pudding being the equivalent of fluid), which is exactly what a torque converter does in an automatic transmission by connecting [coupling] the engine to the transmission through a coupling of fluid in the torque converter. Again, the technician did no harm because doing what he did could not cause any harm.

You can certainly express your 'surprise' at what the last technician did to give it a quick test, but I can assure you it did no harm...and any technician checking it would likely do the same. You're worrying over something that is equivalent to damaging the paint by tapping your knuckles on the hood.

bclexus

Below is a nice video that explains how torque converters work. Beginning at 5:00 is a good example using two fans, which explains how the two sections of the torque converter (engine section & transmission section) of the torque converter are interfaced/coupled only by means of fluid...and do not have a direct mechanical connection. (Thus, the torque converter cannot be damaged by engaging a gear while the car is traveling in the opposite direction as executed by the technician.)

Gs21

Thanks for all the help I appreciate it , I'll take the car in and see what they say

CharleeRX

Did you ever figure out what the problem was? My RX does the same thing. They have replaced the whole transmission 😱 and after a month or so, it started doing it again. Everyone is baffled by it, but to be honest, I've noticed the same slight jerk in at least two loaner RXs too. So weird. I wonder if it could be the ABS, brakes, or something like that?

jgscott

iTrader: (1)

Seen this problem before on Lexus in the past. Need to do a good check on all the Motor mounts and transmission mounts. They can shift and lift and cause that exact condition. Sometimes they look good but they can be bad cracked gone soft and more.

CharleeRX

Thanks for this! I reached out to my dealership and they will check my mounts. I really hope they can find and fix the problem. It has really baffled them so far.