lexusdog

iTrader: (1)

I had a loud groaning noise on deceleration in my SC400 when I was on the highway above 50 mph, the noise sounded like a bad bearing noise. After doing a search, it looked like the trans mount could have been the issue. I had an extra transmission mount laying around from my aristo swap on my sc300, this is the same mount that comes on the Supra TT automatic. A few people said this mount would not work, but it worked perfectly fine for me. The mount looked a bit taller then the original sc400 mount, but that could be because the sc400 mount was worn out.

After installing the new mount, I took the car out on the highway and the noise on deceleration was completely gone. I think the culprit was that the worn mount was putting extra stress on the center carrier bearing on the driveshaft making the noise when you would come off of the gas.

For future people searching for this problem I will try to be as specific as possible.

1. Had a loud groaning on deceleration above 50mph, it was even louder above 70mph. Noise only occured when letting off the gas. No noise when accelerating.

2. Thoght it was the carrier bearing on the driveshaft because the noise was centralized over the armrest area.

3. Installed a used a Supra TT/Aristo mount instead of one for a SC400 and it worked perfectly fine. Noise is completly gone.

If you have a noise like this in the future, replace your mount first as it is much easier to do then dropping the driveshaft and having the carrier bearing pressed on and off.

Dougspeed

iTrader: (2)

Same results for me with the past two SC400's I've had. Also, when the mount is worn like that, the top metal bracket sits against the bottom metal portion of the mount transmitting all the vibration from the transmission directly to the frame which also contributes to the noises at hwy speeds.

lexusdog

iTrader: (1)

That makes logical sense. I am just glad that I didn't have to drop the driveshaft and replace carrier bearing. Thanks for your feedback.

Kira X

iTrader: (24)

How hard was it to replace the mount?

Biddles

iTrader: (2)

And what'd it cost?

Rementis

I bought one for under $60, and it's not very hard to replace. Worked awesome, no more noise when slowing down.

lexusdog

iTrader: (1)

It only takes about 30 minutes to replace the mount.

I had a used one laying around with low mileage from a supra TT, you can probably find a used one for $30. I think they only cost about $50-70 new from a recent search that I did.

When installing, make sure to use a 2 x 4 on top of your jack to hold the transmission from dropping when you remove the mount. The 2 x 4 or 2 x 6 is used to distribute the weight on the transmission pan so that you do not dent it.
There are 4 12 mm nuts on the bottom of the mount, remove those first, then remove the 4 14 mm bolts that are attached to the chassis. You can then remove the bottom crossmember from the transmission. Make sure that the transmission is supported prior to removing the crossmember. Then there will be 4 12 mm bolts holding the mount to the transmission, you might need an extension to reach them. Remove the mount, then replace, and torque bolts to factory spec.

Kira X

iTrader: (24)

Thanks for the reply! That doesn't sound too bad. I totally suck at working on cars but maybe I'll give it a shot.

1WILLY1

iTrader: (9)

cool man, ive heard that basically everyone should be replacing the tranny and engine mounts as they are probably worn in one way or another, i want to one day replace all my mounts and bushings, im just worried about the cost

i dont have any noise on deceleration but I have a minor 'clunk' on acceleration and deceleration, its worse in reverse, i think its the tranny mounts or differential bushings.

gtsfire

iTrader: (4)

I've got the same noise on acceleration and deceleration. I've been told my tranny mount looks good. I've also read in other older threads that the mount could still look good but be bad. The noise is also fairly prominent just whille driving down the road. Someone suggested I might have a lot of slack in my output shaft on the tranny. Thoughts?
Oh and it's a 97 SC400 with 106k miles.

SC400slide

iTrader: (11)

It's not too hard at all. I was 15 and barely knew anything about Lexus and I replaced mine. Took me about 45 minutes.

scENFORCER

Whenever these threads pop up I ALWAYS recommend EVERYONE replace their engine and tranny mounts regardless of mileage or how they 'look'. Replacing both the engine and tranny mounts got rid of every last vibration my at had, the car ran smoother and quieter. Felt like a whole new car, even after my mounts 'looked' ok.

gtsfire

iTrader: (4)

One thing I seriously hate is having to spend money on a process of elimination. I wished the problem could be black and white instead being a fuzzy grey. But, I'm just going to accept it's part of owning one of these cars. I'll buy a new tranny mount and start there since they are cheap. It's just a bitter pill to swallow when two Toyota mechanics have told you it's good.