DK Audio

I just got a 1998 LS400 with 125,000 miles on it. The car has been maintained well and rides nice. However, there is a slight vibration in a few areas between 2K and 3K RPM. Everything else is very smooth. Since higher speeds result in the engine running at a little over 2K RPM's, I feel the vibration when on the freeway.

Any ideas? I tried Seafoam already...

Thanks

LiCelsior

iTrader: (32)

where is the vibration coming from?? steering wheel? if so then u need to rebalance your wheels.

DK Audio

No, it is the engine. I put the car in neutral and reved to verify.

LiCelsior

iTrader: (32)

motor mounts maybe?

Thermactor

iTrader: (1)

Have the same exact issue with the Atari Ferrari. I think it's mounts but I don't have $250 for new ones. Do MkIV Supra Turbo mounts fit our cars? They're $60 instead of $125!

PureDrifter

iTrader: (10)

no, they dont. i'd replace the trans mount (~$40) before doing the motor mounts.

DK Audio

Is this something major and needs to be done or is it just a comfort thing? The reason I'm asking is because it is the middle of winter and I need to save money since I just bought this thing.

Thanks

curiosul

The only serious consequence I can think of is that if your exhaust is ALMOST gone (meaning weakened by rust), it will brake a lot easier due to engine vibrations, other than that, it's just comfort, but there might be something else I can't think of.
What's for sure is that it's only going to get worse.

P.S. a "quick" fix is trying to fill them with polyurethane ... maybe you can find more info somewhere else

PureDrifter

iTrader: (10)

the trans mount is a 20minute job if you have a jack and a pair of jackstands...

Thermactor

iTrader: (1)

Our mounts aren't the doughnut type that you can find in a Honda. They're... like a rubber ice cream cone with studs pointing out of both ends. No place to put the urethane that I know of. They usually fail by shearing in half, perpendicular to the stud orientation.

DK Audio

I will start with the trans mount. I read the tutorial sticky but do I need to jack/support the engine at all if I just do the trans?

JimsGX

No, There's no impact on the engine at all. You can even use a block or two of wood to hold up the drive shaft up near the tranny to hold the back of the tranny up when you take the cross bracket off. From my experience, there isn't a whole lot of weight being supported when you remove the cross member and mount. Maybe about fourty pounds or so of resistance.

PureDrifter

iTrader: (10)

you'll need a jack and a scrap of wood to jack up the back end of the trans ~2 inches as most of the time the mount is completely collapsed.

DK Audio

Ok, I replaced my tranny mount and these are the results...

If I rev it in neutral or park I get no vibration now, it's perfectly smooth!

However, when driving there is still a little vibration at higher speeds (not a huge deal). What bugs me is at a stop while in gear the car vibrates more now. It is not major or anything but I know the engine is supposed to be perfectly smooth.

I think I reduced the problem to lower RPMs while at a stop and in gear. As you know while in neutral or park there is no load on the engine and the RPMs increase slightly.

Any ideas?

amcdonal86

Is this vibration at higher speeds occurring with the car in neutral as well?