Transmission down shift clunk, FIXED

FJMainiac

Member
Oct 3, 2024
32
12
PA
In a previous post, I described a harsh downshift clunk when slowly coming to a stop. Most noticeable in stop and go traffic. Sometimes felt like two bumps, one around 3-5 mph, and the second just when I come to a full stop. I was not sure if this normal for that type of transmission or if something else was wrong.

I was at the dealership for 10k service, and went for test drive with tech to demonstrate the issue. The tech said no mechanical issue, no problem codes, and no software update (yet) but cleared the transmission memory.

Now the shifting is absolutely smooth, no harsh downshift at all.

While I was there I also had the break squeal repair (known issue).
 
In a previous post, I described a harsh downshift clunk when slowly coming to a stop. Most noticeable in stop and go traffic. Sometimes felt like two bumps, one around 3-5 mph, and the second just when I come to a full stop. I was not sure if this normal for that type of transmission or if something else was wrong.

I was at the dealership for 10k service, and went for test drive with tech to demonstrate the issue. The tech said no mechanical issue, no problem codes, and no software update (yet) but cleared the transmission memory.

Now the shifting is absolutely smooth, no harsh downshift at all.

While I was there I also had the break squeal repair (known issue).
So what was done to stop the harsh trans shifts, as mine does this as well, and dealership acknowledged it when they fixed my brake squeal?
 
The description on the paperwork states "Technician verified harsh downshift into first gear when coming to a slow stop. Technician cleared transmission memory."
 
Correct, the tech mentioned something about the software learning driving habits and reset apparently "unlearned" whatever was causing the hard downshift to 1st.
 
I drove my 1998 Porsche with 175,900 miles on the odometer yesterday. If there's a clunky downshift, it's completely my fault. It's such a simple joy to drive. The radio has been broken since November of 2017 when my then-2.5-year-old stuffed the CD player full of coins from the ashtray and I haven't bothered to fix it.
 
Cars are just too damn complicated these days. It freaks me out that computers control critical things like this.
I had to remind someone that things are just different, in all regards. Complex, yes, but with that complexity we get a lot of improvements.

I reminded him that my 1991 Mustang, with the 5.0 V8, that we all remember... sounds so good. Muscle car. 225 HP. Rated higher back then than it would be now.

So the tech can bring some unfortunate downsides... but you can get 225 HP out of a 1.2L now a days. So technology has also brought us amazing things in cars.

Just something to keep in mind :)
 
Cars are just too damn complicated these days. It freaks me out that computers control critical things like this.
It's a gradual, but logical, progression when when you consider that cars with ECM's have 'learned' things about the drivetrain for a long time.

As an example, as carbon builds up in the throttle body, the throttle body position sensor adjusts to compensate. It's not entirely evident that this 'memory' is happening, until it is erased (by, for example, a dead battery) This can cause drivability issues - stalling and low rpm stumbling- which will remain until the throttle body is cleaned.

I'm grateful for all that computers have brought to the table, especially for things like adaptive cruise control, lane assist, and all that stuff that optimizes engine power and torque.

Says the guy who enjoys driving and setting the timing on his 1970 GTO.
 
I just picked up my GX from its 10,000 mile service. Only 9,100 miles on it but I'll be driving a couple thousand miles over the next month with very little time to get it in for service. I took one of the techs on a short drive and it only really clunk-shifted once. But it definitely been doing it more often lately. They reset the transmission memory so we'll see if it makes any difference. They want me to report back because they've had lots of similar complaints but this is the first they heard of resetting the transmission's memory.

They also ordered new brakes to cure the squeal, should take a few weeks to a month to get the parts in.
 
I just picked up my GX from its 10,000 mile service. Only 9,100 miles on it but I'll be driving a couple thousand miles over the next month with very little time to get it in for service. I took one of the techs on a short drive and it only really clunk-shifted once. But it definitely been doing it more often lately. They reset the transmission memory so we'll see if it makes any difference. They want me to report back because they've had lots of similar complaints but this is the first they heard of resetting the transmission's memory.

They also ordered new brakes to cure the squeal, should take a few weeks to a month to get the parts in.
Hi Bill, did your brakes squeal from the start, or begin later? I have about 650 miles on mine so far, no squeal (but I'm still treating them with a light touch during break-in).
Thanks
Mark
 
I picked up my GX on June 7th and my brake squeal didn't start until we took a family trip to San Diego in late July. My theory is that the higher humidity on the coast caused the squeal (but they only squealed in reverse). They started squealing here in Arizona when we started getting a bit of rain in August. Now they squeal all the time in slow reverse (like backing out of the garage and down the driveway every day). They also squeal in slow forward sometimes. While I was in the Lexus cubicle offices adjacent to the service drive explaining the squeal to the service rep, someone moved my GX and the squeal practically shattered the windows. The rep said no need to explain anything further and he proceeded to order the brake parts.
 
I had to remind someone that things are just different, in all regards. Complex, yes, but with that complexity we get a lot of improvements.

I reminded him that my 1991 Mustang, with the 5.0 V8, that we all remember... sounds so good. Muscle car. 225 HP. Rated higher back then than it would be now.

So the tech can bring some unfortunate downsides... but you can get 225 HP out of a 1.2L now a days. So technology has also brought us amazing things in cars.

Just something to keep in mind :)

Not to derail this thread too far…

I loved my 89 5.0! Nothing quite so fun & sounded great! But, yes, it produces what we’d consider economy car levels of power nowadays since only the very cheapest cars on the market would have less. Granted, the fox body was pretty light then, but we also expect cars nowadays to have a little more structural integrity than a used beer can to have a hope of surviving a crash.

One might argue cars have also never been more expensive, perhaps largely due to the amazing tech in cars nowadays. That may be true, after all new cars back in the day were pretty cheap even adjusting for inflation, especially relative to average incomes. But. In 1990 a 15yo used car was a 1975. You could find an American hoopty then, or a Japanese nothing as they’d all rusted away. Today you could go buy a 2010 Corolla & expect some reasonable service out of it if it’s been taken care of.
 
I picked up my GX550 on April 11th, I’m almost at 20k miles and it’s on the 3rd transmission. It started with the harsh down shifting again recently but Lexus agreed to buy the vehicle back so won’t be taking it back in for a repair. It’s a shame, really like it but too many issues and only 8 months in. I also had the brake noise issue but they replaced everything and it’s been fine since.
 
Wow, 3rd transmission. Just curious what the symptoms were prior to failure, and if the dealership provided any postmortem explanation of what broke/failed. Glad you were able to work a deal for Lexus to buy it back, but I'm sure it was a very frustrating and inconvenient experience.
 
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