Hi everyone,

I’m having some transmission issues with my 2005 Lexus LS430 around 149,000 miles, and I’m hoping for some advice or insights.

Symptoms:

• The car jerks roughly when I put it into Drive.
• 1st through 4th gears seem to work fine, with no slipping or jerking.
• When I shift into 5th gear, it drives normally, but when I downshift from 5th, the car jerks.
• There’s no slipping, and overall the car drives fine, but the roughness during these specific shifts is concerning.

Important Detail:

• These issues started shortly before I had the radiator replaced, so I don’t think the radiator replacement is directly related to the transmission problem.

Possible Causes I’m Considering:

1. Transmission Fluid: I haven’t checked the levels yet, but I’m wondering if low or old fluid might be contributing to these jerky shifts.
2. ECU or TCM: I’ve seen mentions of ECU or TCM issues causing rough shifting, but I’m not sure if that applies here since I don’t have a Check Engine Light.
3. Mechanical Issue: Could this be a sign of a mechanical issue with the transmission, like worn parts in the 5th gear or something related to the shift solenoids?

Has anyone experienced anything similar? I’m trying to figure out if this could be a simple fix like fluid or sensor replacement, or if it’s something more serious. Any thoughts or suggestions would be appreciated!

Thanks in advance for your help!

 

if nothing has ever been done to the transmission fluid it is 20 years old
the recall on transmissions ran up to 2005 made in July and August of 2004 (I had one made in August but it was fine)
I would do a drain and fill replacing about 4 quarts of the 11.5 quarts in the transmission and torque converter
this refreshes the addatives that are worn out
finding somebody to do a proper drain and fill is hard, most want to replace all the fluid for more $$$

 

If it happens on the downshifts and not upshifts, it's the ECU. About 75% of the ECU circuitry is devoted to the tranny. I had a similar problem on my 2005 LS430...rough shifting on downshifts into 3rd, 2nd, 1st gear, plus a jolt when shifting into D at a stop. I sent mine to a shop in Texas. Since the repair, I've driven about 3K miles with no issues. Check the threads on this.

 

I had a similar problem. A drain and fill decreased the severity of the rough downshift issue by about 30 to 40%. Then, I sent out the ECU for repair. This was the real fix. After, shifts were silky smooth and the car felt more "lively". My suggestion is to do both. My Toyota dealer did a drain and fill with WS for about $160. The ECU repair runs from about $150 to $250 and it is well worth it.