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2015 GX460 Luxury - Harsh Rear Ride Over Speed Bumps (New KYB Shocks & AVS/Air)
I’m seeking some diagnostic help for a specific ride quality issue on my 2015 GX460 Luxury (78k miles).
The Symptoms
Low Speed: At crawl speeds, the suspension feels great—smooth and plush in both front and rear.
Moderate Speed: As soon as I take a speed bump at a "normal" or slightly faster pace, the front stays soft, but the rear feels incredibly hard/stiff, almost like it’s bottoming out or has no travel.
High Setting: When I manually lift the rear suspension to "High," the ride becomes extremely bumpy/jumpy over the same bumps.
Visuals: The truck looks perfectly level and sits at a normal height.
What I’ve Done/Changed So Far:
Shocks: Replaced stock rear shocks with KYB Excel-G (The issue existed before the swap and remains unchanged).
Hardware: Replaced shock absorber cushions (No. 1 and No. 2).
Tires: Brand new tires installed (issue persisted across previous and current sets).
Tools Available: I have Techstream and am ready to pull data.
My Theory/Questions:
Leveling Sensors: Could the rear height sensors be adjusted too high? Even though it looks level, if the bags are over-inflated, there might not be enough "down-travel" or "rebound" room, causing that harsh kick.
AVS Logic: Does the AVS system struggle to match the rear damping to the front when speed increases?
Calibration: Since I have Techstream, what are the specific Height Offset values or sensor voltages I should be looking for to confirm the rear isn't "tricking" itself into an over-inflated state?
Has anyone encountered this specific "speed-dependent" rear harshness? Any advice on what to check in Techstream would be greatly appreciated!
My bags seems healthy, there is no hissing noise and no leaks as i tested it with soap spray, and I live in a place where there is no snow, salt or any corrosion that could affect under, what but now that you mention I haven't tested going over a bump with the lowest setting of the bags, i guess i will try that
Last edited by guzzy92fs; Jan 5, 2026 at 07:23 AM.
these are symptoms of air bag pressure.
try this when first starting the car. set height to H. once it gets to high set it to N.
if you do this each time and the ride goes back to how it was then there can be a small leak.
this leak can come at the compressor pump/valve joint on the compressor side.
If i get you right, you are telling me the air bags might be over-pressurized to compensate for a problem. I will try to check the values for the height sensor voltage in techstream and check if there is some odd values
Guys, I believe I found the issue for the harsh rear ride quality on my GX. After testing, it turns out it wasn't the air bags or the shocks it was mechanical stiction in the height sensor linkages.
I hooked up Techstream and monitored the live data for the Rear Height Sensors. I noticed that when I cycled the truck from Normal (N) to High (H), the values didn't seem to move fluidly. I crawled under the truck to inspect the sensors and found the linkages (the rods with the two small ball joints) were covered in grime and were almost completely seized. They were very hard to move by hand.
I thoroughly sprayed the upper and lower ball joints of the sensor linkages with WD-40 to break down the old, dried-up grease and dirt, manually moved the linkages side to side until they were completely loose and moved with zero resistance then clleaned everything off, I applied white lithium grease to the joints to ensure long-term lubrication and protection against humidity.
I started the truck, cycled it to High, then back to Normal.
Back in Techstream, the values now change significantly and instantly when the height is adjusted, much more range than before. My theory is that the sensor was "stuck" at a higher value than the actual physical height. When hitting a bump, the computer saw a conflict between the sensor data and the actual movement, defaulting the suspension to a "Full Stiff".
The truck rides completely differently now. It’s back to that legendary plush feel. I can take speed bumps at normal speeds and the rear stays just as soft as the front.
For those wondering about leaks, while down there, I did a soapy water test on the bags and lines, no bubbles, no cracks. The truck is rust-free and has spent most of its life in the tropics, I also remember that the pervious owned told me that the truck sat for a long period recently. It seems that "sitting" is what caused the grime to turn into glue on those sensors.
I’ll monitor this for a week and report back.
Btw, I noticed an option in techstream to calibrate the hight sensor, it's at Chassis / AHC / Utility / Height offset.
I might do that when I find a perfectly leveled ground to do so and be 100% sure the system is calibrated.
Last edited by guzzy92fs; Jan 5, 2026 at 03:51 PM.
If i get you right, you are telling me the air bags might be over-pressurized to compensate for a problem. I will try to check the values for the height sensor voltage in techstream and check if there is some odd values
over or under pressured, thus the H then N check. both over and under can have the same result but different causes
Guys, I believe I found the issue for the harsh rear ride quality on my GX. After testing, it turns out it wasn't the air bags or the shocks it was mechanical stiction in the height sensor linkages.
I hooked up Techstream and monitored the live data for the Rear Height Sensors. I noticed that when I cycled the truck from Normal (N) to High (H), the values didn't seem to move fluidly. I crawled under the truck to inspect the sensors and found the linkages (the rods with the two small ball joints) were covered in grime and were almost completely seized. They were very hard to move by hand.
I thoroughly sprayed the upper and lower ball joints of the sensor linkages with WD-40 to break down the old, dried-up grease and dirt, manually moved the linkages side to side until they were completely loose and moved with zero resistance then clleaned everything off, I applied white lithium grease to the joints to ensure long-term lubrication and protection against humidity.
I started the truck, cycled it to High, then back to Normal.
Back in Techstream, the values now change significantly and instantly when the height is adjusted, much more range than before. My theory is that the sensor was "stuck" at a higher value than the actual physical height. When hitting a bump, the computer saw a conflict between the sensor data and the actual movement, defaulting the suspension to a "Full Stiff".
The truck rides completely differently now. It’s back to that legendary plush feel. I can take speed bumps at normal speeds and the rear stays just as soft as the front.
For those wondering about leaks, while down there, I did a soapy water test on the bags and lines, no bubbles, no cracks. The truck is rust-free and has spent most of its life in the tropics, I also remember that the pervious owned told me that the truck sat for a long period recently. It seems that "sitting" is what caused the grime to turn into glue on those sensors.
I’ll monitor this for a week and report back.
Btw, I noticed an option in techstream to calibrate the hight sensor, it's at Chassis / AHC / Utility / Height offset.
I might do that when I find a perfectly leveled ground to do so and be 100% sure the system is calibrated.
good to hear you got it working and what the issue was
Guys, I believe I found the issue for the harsh rear ride quality on my GX. After testing, it turns out it wasn't the air bags or the shocks it was mechanical stiction in the height sensor linkages.
I hooked up Techstream and monitored the live data for the Rear Height Sensors. I noticed that when I cycled the truck from Normal (N) to High (H), the values didn't seem to move fluidly. I crawled under the truck to inspect the sensors and found the linkages (the rods with the two small ball joints) were covered in grime and were almost completely seized. They were very hard to move by hand.
I thoroughly sprayed the upper and lower ball joints of the sensor linkages with WD-40 to break down the old, dried-up grease and dirt, manually moved the linkages side to side until they were completely loose and moved with zero resistance then clleaned everything off, I applied white lithium grease to the joints to ensure long-term lubrication and protection against humidity.
I started the truck, cycled it to High, then back to Normal.
Back in Techstream, the values now change significantly and instantly when the height is adjusted, much more range than before. My theory is that the sensor was "stuck" at a higher value than the actual physical height. When hitting a bump, the computer saw a conflict between the sensor data and the actual movement, defaulting the suspension to a "Full Stiff".
The truck rides completely differently now. It’s back to that legendary plush feel. I can take speed bumps at normal speeds and the rear stays just as soft as the front.
For those wondering about leaks, while down there, I did a soapy water test on the bags and lines, no bubbles, no cracks. The truck is rust-free and has spent most of its life in the tropics, I also remember that the pervious owned told me that the truck sat for a long period recently. It seems that "sitting" is what caused the grime to turn into glue on those sensors.
I’ll monitor this for a week and report back.
Btw, I noticed an option in techstream to calibrate the hight sensor, it's at Chassis / AHC / Utility / Height offset.
I might do that when I find a perfectly leveled ground to do so and be 100% sure the system is calibrated.
Wow, this is great. Do you have any photos of the linkages you cleaned? I also have a 2015 GX460 luxury with a similar 'rough' ride and stiffness from the rear over potholes, speed bumps, etc. Would love to fix mine - I took a look at the airbags, didn't see any linakges to clean..
As a follow-up to this fix, I want to clarify that there are two sensors at the rear (RH and LH). Initially, I only cleaned and lubed the passenger side (RH), but I eventually located the one on the driver’s side (LH) tucked behind the gas tank.
After plugging in techstream, I noticed a significant discrepancy between the two sides. This height difference is what makes the rear suspension feel so harsh; the ECU tries to compensate for the "lean" by over-inflating one of the airbags, leaving it with close to zero travel.
Initial Sensor Values:
Rear RH Sensor: 0.1 inches
Rear LH Sensor: -0.7 inches
Total Variance: 0.8 inches (This caused the "stiff" feeling over bumps)
I performed a manual adjustment. I loosened the 10mm nut on the LH sensor bracket and moved it while monitoring the live data until I got both sides as close to zero as possible.
Final Values:
Rear RH: 0.0 inches
Rear LH: -0.1 inches
I took the GX for a test drive over several speed bumps and the rear feels much plusher and the harsh "thud" is gone. If your GX feels like a tank in the back, check your sensor balance
I couldnt take a photo of techstream with final values but here is a pic of how it was moving while adjusting:
Last edited by guzzy92fs; Feb 20, 2026 at 01:30 PM.
Thanks. I’m going to try this adjustment this weekend. I’ve had all 4 corners of shocks and struts changed (18 months ago) and it has started to ride so rough. The thud is similar- over any bump it feels like it hits the bump stops.
I did check my ride sensors and cleaned them, but they were not dirty at all. I’m going to check the movement and values thru tech stream and see how it goes.
thanks for keeping up on this threat, very helpful and I can’t seem to find any other information about this issue. Most comments refer to tires and shocks- both of which I’ve had changed recently. Thanks again!
Just took a look at my sensor values. I am in a similar boat:
Initial Sensor Values (Normal):
Rear RH Sensor: -0.6"
Rear LH Sensor: 0.8"
Total Variance: 1.4"
Normal Height
HI Height Initial Sensor Values (HI):
Rear RH Sensor: 0.5"
Rear LH Sensor: 1.9"
Total Variance: 1.4"
LO Height Initial Sensor Values (LO):
Rear RH Sensor: -1.4"
Rear LH Sensor: 0.0"
Total Variance: 1.4"
Normal height (graph)
I've ordered 2 x ride height sensors and will have them installed within the next week or so and will report back. Hopefully my shop can install and calibrate them to dial them in to 0.00 for both. I think/hope that this is part of my rough ride problem that I've been having for a couple years - even after new shocks/struts and Michelin tires.. fingers crossed, thanks for your help!
2015 GX460 Luxury - Harsh Rear Ride Over Speed Bumps (New KYB Shocks & AVS/Air)
