i own a 98 gs300 with 110k on there.. everything runs fine its just when i drive around 30mph and above when i let the gas pedal off, and press it again, i get this wierd "thump" coming from the rear end? maybe the rear diff? rear axles? i dont know.. sometimes it doesnt make that nosie, but most of the time when i floor the pedal to merge on the freeway and stuff or just for the hell of it. but you can hear and feel the noise as well.... does anyone know what might be the problem??? please help..
thanx.

 

Check your driveshaft universal joints (u-joints) before suspecting any other major components. Reach under the car, grab the driveshaft (connects the transmission to the differential), and try to rotate it. There shouldn't be any sloppy play. Another sign of u-joint failure is drivetrain vibration at some speeds. If it's not the u-joints, then move further down the drivetrain. Jack up the rear end, release the parking brake, and check for sloppiness at each rear wheel. Good luck, and post back the results of your checks.

 

This is a very common issue with Lexus/Toyota RWD products. Manufacturers claim that it poses no issue and I would have to agree.

Does not mean something is not wrong as I cannot hear your thump vs all of the thumps I have heard.

Check CV shafts/joints where it connects to the wheels and also the rear end for unusual wear/noise/lubrication/lateral movement. U-Joints on the driveshaft. Trans mount located above the trans in the back of the trans connecting it to the body. Rear end mounts are harder to inspect but using a breaker bar you can use it to pry the rear end back and forth to look for unusual movement. Check rear end fluid level. Replace if your not sure when it was last changed.

Lee

 

It's about time someone eles has this problem. I have been waiting for the past 4 years for lexus to figure out what is causing the problem. I have changed drive shafts etc. and nothing has worked so far. I have a RMM LSD i need to have it installed then hope fully that will rectify the situation if not I will never buy a lexus again. BTW I even have a new tranny in the car. Ya lexus is a very reliable car but it suck because when there is a problem they have no clue how to fix it.

 

all the fluid have been changed.. and the funny thing is, right when i go it changed, i drove off and like i gassed it and let go.. gassed it again, and heard the fukn noise... i was like wtf? i thought it would solve the problem, but it only happens sometimes, but when it does, it just makes my car seem like its trash, i mean its a lexus.. why is it doin this?? does anyone else have the same problem?? *thanx for the advice, i check it jacked up the car and look around.. seems like everythings in place and lookin good..

 

Mine does the same thing. It's more noticeable with the aftermarket torque converter. I'm just going to live with it. I think it has to do with the rubber bushings in the diff.

-Jeff

 

Bring a old post back from the dead, any fixes for this problem its driving me insane? Ive had the trans flushed twice, differential fluid changed, checked all sub frame bushings in rear, differential bushings, replaced my rear knuckles because the joints where loose, checked motor mounts and trans mount, and checked the drive shaft joints. clunk still present....

 

Change your motor mounts. Your description sounds like the mounts are done. I had mine changed recently. When inspecting, they look fine, but when you take them out, they fall apart. Plus this seems like your engine is tilting soo hard under throttle, that your exhaust is hitting the subframe. It is really close in a few places in the rear, that is probably why you feel it there. And you will not be able to check this in the air, you need the load from the wheels and car being in drive to tilt the engine hard enough. I am really confident that your mounts are shot.

 

Sounds like the tranny mount issue on the SC's. Before you buy anymore expensive parts, replace the tranny mounts, its been proven to fix this problem on the SC. I will be changing my Tranny mount on the SC4 very soon due to this particular issue.

 

Replace all 3. I am sure that all 3 of them are worn out. Search for my name and engine mounts, a few people had them replaced at different mileages, and all of the mounts were torn, even though on visual inspection they looked fine. Plus if you have vibration when all of your accessories are off, and the car is in drive, then you deffinatelly need the mounts anyway.

 

yes motor mounts are brand new along with transmissions mount, replaced differential bushings all 4. I had the car on the lift and was looking into my problems a little more with some other techs, It appears that the axle hubs that connect to the diff. have some play in the joints so i am going to grab another gs from the lot that does not have the noise and compare axles. Ill describe the problems a little more, after accelerating ill let the car decelerate and verry light throttle you will hear a clunk in the rear like there is to much backlash in the differential but its all every thing is checking out alright. I am down to the point if the axles check out ok with another gs i am going to call one of the Lexus zone rep to help out because I have all the techs at my work clueless. Ill keep every one posted and hopefully this will fix the R to D clunk also.

 

I just had my whole driveshaft with flexable couplings replaced with new and problem is still there. so far i have replaced Tranny, diff, drive shaft. i have had this problem for 8 years. pls keep this thread alive and post all updates.

 

Stayin' alive, Stayin' alive...

Any updates to this issue?

 

have any of you checked your Strut top mounts?

 

Sounds like it has to do with the drive shaft, differential, and the U-Joints which is inside of the differential.