90LS400Lexus Posted October 27, 2008 Share Posted October 27, 2008 As I am sure everyone here knows the motor mounts in (what was my Lexus - now my moms) are shot to heck! I am awaiting for the mechanic to get with a Lexus tech friend of his to verify that this is the problem. He test drove the car last week (he thinks the vibration problem is motor mounts as well) and I pointed out the what feels like slack when the car is on overdrive and you let off of the accelerator and press it back quickly. I told him I thought that had something also to do with the bad mounts, but he said it could be the torque-converter. He said he was not sure and even if it was, it was not bad, but I am thinking- WOW, this is great- whats next with this car? It only has 215K, which seems to be low for Lexus cars. I would never dream this car would have a transmission problem. The transmission shifts smoothly and perfectly through all gears and even into overdrive/lockup smoothly. It does not slip, shifts are crisp, no leaks, etc. I am hoping he is wrong about the torque converter causing this problem and its the motor mounts causing the "slack/lunge" feeling I occasionally get at 40-55 mph speeds if I have to let off and press the gas a little faster than normal. I guess one way to know for sure is to get the mounts replaced ASAP and see if this eliminated this feeling. If not and it is the torque converter- whats the cure? Transmission removal/repair, or? If thats the case, we will junk the car. Quote Link to comment Share on other sites More sharing options...
jcrome04 Posted October 27, 2008 Share Posted October 27, 2008 I have a strange problem too. When I'm at about 40-55mph and take my foot 100% off the gas, the RPMs suck down maybe 100rpm like an engine brake has been applied, and you can feel the negative G's. When I get down to 40mph and 1000RPM it pops back up to the proper RPM... 1200 i think?? Any ideas on this? I am hoping it's not my torque converter either :( Quote Link to comment Share on other sites More sharing options...
TA in KC Posted October 28, 2008 Share Posted October 28, 2008 As I am sure everyone here knows the motor mounts in (what was my Lexus - now my moms) are shot to heck! I am awaiting for the mechanic to get with a Lexus tech friend of his to verify that this is the problem. He test drove the car last week (he thinks the vibration problem is motor mounts as well) and I pointed out the what feels like slack when the car is on overdrive and you let off of the accelerator and press it back quickly. I told him I thought that had something also to do with the bad mounts, but he said it could be the torque-converter. He said he was not sure and even if it was, it was not bad, but I am thinking- WOW, this is great- whats next with this car? It only has 215K, which seems to be low for Lexus cars. I would never dream this car would have a transmission problem. The transmission shifts smoothly and perfectly through all gears and even into overdrive/lockup smoothly. It does not slip, shifts are crisp, no leaks, etc. I am hoping he is wrong about the torque converter causing this problem and its the motor mounts causing the "slack/lunge" feeling I occasionally get at 40-55 mph speeds if I have to let off and press the gas a little faster than normal. I guess one way to know for sure is to get the mounts replaced ASAP and see if this eliminated this feeling. If not and it is the torque converter- whats the cure? Transmission removal/repair, or? If thats the case, we will junk the car. Tony, It sounds like the motor and transmission mounts are the problem to me. After they are replaced the problem you are describing will likely go away. Transmission failures in LS400s are rare. The only failure I have ever heard of was a transmission with over 600,000 miles! For that reason, used LS transmissions are very inexpensive. There is one on my local Craig's List for $100! I don't think you will have to worry about that though. I have a strange problem too.When I'm at about 40-55mph and take my foot 100% off the gas, the RPMs suck down maybe 100rpm like an engine brake has been applied, and you can feel the negative G's. When I get down to 40mph and 1000RPM it pops back up to the proper RPM... 1200 i think?? Any ideas on this? I am hoping it's not my torque converter either :( Wasn't there a defect with the ECUs on 2nd-generation LS400s that caused a problem like this? I have seen it discussed on this forum before. Try searching for "ECU" and maybe you will come across the same thread I have seen. Quote Link to comment Share on other sites More sharing options...
JeffreyV Posted March 6, 2009 Share Posted March 6, 2009 As I am sure everyone here knows the motor mounts in (what was my Lexus - now my moms) are shot to heck! I am awaiting for the mechanic to get with a Lexus tech friend of his to verify that this is the problem. He test drove the car last week (he thinks the vibration problem is motor mounts as well) and I pointed out the what feels like slack when the car is on overdrive and you let off of the accelerator and press it back quickly. I told him I thought that had something also to do with the bad mounts, but he said it could be the torque-converter. He said he was not sure and even if it was, it was not bad, but I am thinking- WOW, this is great- whats next with this car? It only has 215K, which seems to be low for Lexus cars. I would never dream this car would have a transmission problem. The transmission shifts smoothly and perfectly through all gears and even into overdrive/lockup smoothly. It does not slip, shifts are crisp, no leaks, etc. I am hoping he is wrong about the torque converter causing this problem and its the motor mounts causing the "slack/lunge" feeling I occasionally get at 40-55 mph speeds if I have to let off and press the gas a little faster than normal. I guess one way to know for sure is to get the mounts replaced ASAP and see if this eliminated this feeling. If not and it is the torque converter- whats the cure? Transmission removal/repair, or? If thats the case, we will junk the car. Tony, It sounds like the motor and transmission mounts are the problem to me. After they are replaced the problem you are describing will likely go away. Transmission failures in LS400s are rare. The only failure I have ever heard of was a transmission with over 600,000 miles! For that reason, used LS transmissions are very inexpensive. There is one on my local Craig's List for $100! I don't think you will have to worry about that though. I have a strange problem too.When I'm at about 40-55mph and take my foot 100% off the gas, the RPMs suck down maybe 100rpm like an engine brake has been applied, and you can feel the negative G's. When I get down to 40mph and 1000RPM it pops back up to the proper RPM... 1200 i think?? Any ideas on this? I am hoping it's not my torque converter either :( Wasn't there a defect with the ECUs on 2nd-generation LS400s that caused a problem like this? I have seen it discussed on this forum before. Try searching for "ECU" and maybe you will come across the same thread I have seen. ________________________________________________________________________________ ___________ I found this explanation on the internet.... 1991 Lexus LS400 review from North America "The essence of quality" What things have gone wrong with the car? At 485,000 miles this Lexus has been tested. Problems over the 11 years of ownership: 1. Power steering pump leaking badly at 95,000 miles. 2. A 'faint' engine 'miss' between 40 to 45 mph at time of purchase. The torque converter was replaced years later and the problem disappeared. Endless tune up parts were replaced to remedy this problem earlier, but nothing helped until the torque converter was replaced. ................................................................................ ............................................................. Quote Link to comment Share on other sites More sharing options...
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