sc400ny2va

O.K. the problem is my 95 sc400 has developed a new problem . It seems i feel a shake(vibration) when im gently on the accelerator between 40-45 mph between 1500-2000 rpm's.. Once i either get above 45 it goes away ,or if I press on the accelerator hard at these speeds it goes right away. It's hard to explain where its coming from,it seems throughout the car. It never does this at any other speeds ,or at any other time when im between 1500-2000 rpms its fine. The car drives perfect besides this. It has been sitting for about 8 months i just tuned it up. I know it needs a tranny fluid change but i dont see this as being the problem.Anyone experience this before i might know what the problem can be. It is very annoying.. I appreciate any help before i bring it to a shop and dump more $$$ into it.. thanks alot for your help

np20412

How heavy is this shake? Sometimes if the car is in 4th gear at low RPM and you gently push the pedal, it won't downshift out of 4th and will try to pick up speed in 4th. If that makes any sense to you, it basically means the car is accelerating using a gear that is not best fit for it. If you've ever driven a stick, you know when the gear you are in is too high for the speed you are at because when you hit the gas it will vibrate a lot. I know this happens to some cars with an automatic transmission. The reason it goes away when you step on it is because the car downshifts into 3rd or 2nd gear where it is more fit to accelerate from. Where in NY are you located?

sc400ny2va

im located in yonkers,ny ... It is pretty heavy, once i step on the gas it goes right away and then it gets aboved 2krpms and it 's fine.. and its funny it only does it between 40-45 mph.. so if basically im cruising with my foot on the pedal lightly at about 40-45 its's shaking(heavy enough) i step more on the pedal it goes right away. No foot on the pedal at these speeds and it doesnt happen.. I understand what your saying about it down shifting but it never did this before.

Spitfire86

have you replaced your motor mounts and transmission mounts? these could be the culprit, means that the engine is right against the frame w/o a rubber bushing to absorb vibrations.

I had this problem on my sc4, loud vibrations could be heard when I was decelerating! Replaced these and it was silent like a lexus should be !

sc400ny2va

You know this is what i thought it might be, either that or a bushing. i had this problem on a 300zx i used to have. How much did it cost to change them on your lexus?

Psionic

Isnt that the torque converter? I thought that was the speed that it locked up and started vibrating...

I'm still trying to find a solution for a 12-15mph vibration under hard acceleration (transmission mount replaced already)

SupraCoup3

been more threads about this then I can shake a stick at.... heck back in 2001 I had this problem and posted a thread about it!

It's most likely your ATF. Toyota specs call for a tranny flush every 15k... SC4s typically don't get that.

Replacing 4 quarts will help, but a dealership powerflush will do the trick. What's really important is using T-IV toyota tranny fluid. The SC4 AT really behaves poorly with dextron and other non-OEM ATFs.

-John

sc400ny2va

im going to try the atf tomorrow or thursday ill let you know how i make out

am8soccer

Sorry to threadjack but im having a similar problem.
My car vibrates and makes an annoying vibration noise (dull, low pitched noise) whenever i am at ~1800 rpms. It only does it at this rpm and if i go any higher or lower the noise goes away. However this happens in any gear unlike the original poster. It is definitely most noticeable when i am going 45-50 though because the rpms stay more steady. Should i try the transmission flush or is my problem different?

sc400ny2va

hey man if you do the atf flush and it works let me know.. My mechanic advised me against since i hadnt changed mine in so long. He seemed to think its the catalytic converter starting to go bad. Let me know how you make out if you flush.
thanks

rublex

Hey guys I am starting to have the same problem in my car. Mine is a 97 5-speed. Seems to happen just like the other posters stated. It starts of with a dull metallic grind noise high pitched. Then if you press the accelerator slightly more the car starts to vibrate there is a sweet spot where the car vibrates the most and the noise is the loudest. Then if you give it more gas the vibration goes away, but the noise stays sometimes.

Here is some other things I have noticed.

First I just did a transmission flush so could be the problem with that (no problem before that).

Second when I filled the gas tank the problem went away, so I though maybe it was just a bad tank of gas (I always use premium). But now I am down to about 3/4 tank and the noise is coming back again.

Third when you put it in neutral then everything is fine.

Any ideas?

mkorsu

I would advise you leave your mechanic!!!!!

Any mechanic that told me NOT to flush the fluid because "hasn't been changed in so long" would scare the poop right out of me.

Run fast!

jibbby

Check tranny and motor mounts for failure...Driveshaft could be out of balance but not likely....Just a few suggestions to consider..

Lexmex

Bingo, absolutely correct.

About the only time I needed a flush is when there was the fluid had a silvery/pinkish look to it (full of particles) and a flush cleaned that out.

A drain and fill (about 3 over 3 weeks) should get things looking good again for
our friend in NY.