I've searched through hundreds of other videos and pictures and I've been unable to find anyone with a mount that's this loose. The following are the best pictures I can find of other LS400 mounts and how much of a gap there is on them. I've been unable to find a 98-00 twin-ear mount, such as my car has. I've only been able to find the earlier single-ear examples.





9:30 in this video:


And now I present pictures and videos of my differential mounts. Both of them are like this, nothing changes if the car is in the air or on the ground. The rubber bush is sliding inside of the metal ear, and is not being "pressed up" into it by the bottom plate. This tolerance slip is allowing the entire differential to rotate and move nearly an inch when it's put under load of the driveshaft. It's quite a lot of movement.


This is the quarter inch gap between the rubber of the mount and the bottom plate



When the car is on the ground and in the air, I cannot move the driveshaft by hand. It feels rigidly mounted. I can get 1\16th or 1\8th of deflection if I stick a screwdriver into the mount and lightly flex on it with maybe 5\10lb of pressure.

Is this amount of deflection normal? I've been complaining for years that the rear of my car feels like it has an unusual amount of "Secondary vibration". If the front of the differential mount is this loose and is bouncing up and down while i'm driving, to me, that certainly can produce the secondary vibrations I'm feeling. Not to mention the "CLUNK" you can hear in the video of the differential slamming into metal when I put the car into gear and load up the driveline.

Here's another video that gives a good look at the upper mounts. I have since replaced all 3 control arms in the rear since this video was filmed.


It almost feels like the differential mount is missing the "mount upper stopper" as seen in the service diagram

 

how many miles are on your car?
seems the rubber has deteriorated and needs replacement. the deflection is excessive in my eyes! that top mount is likely overly compressed over years of use, making it look like it's missing.

remember you also have two rear mounts that contribute to the overall bracing of the diff.

 

165k. The two rear mounts are doing okay. I've seen way, way, WAY worse deflection in my research. I would say they are only minimally worse than what it should be and are still healthy. I can't do much about them anyway, the rear mounts are much more difficult to replace because you have to drop the diff to get them out. And I will not open that can of worms unless the axles fail.

I ordered new upper mounts, plus a insert kit I'm going to give a whirl. The two rear mounts I am leaving alone, the other two mounts have an upper and a lower half. The lower mount is pressed into the metal, the upper half is a loose bushing that's held in place by the bolt. The lower mount is what it is, and shouldn't be causing my problems as it doesn't control much of the vertical height (mostly lateral side-to-side). In theory you can press it out with the diff still on the car but that's beyond scope for now. I'll see what the condition of it is when I install these. The upper mount and whatever space on the bottom between that and the bottom plate are where the issue is. There is nothing holding the front of the diff up other than the driveshaft.


Honestly it feels like with how much gap there is, either someone removed the upper mounts, the bolts aren't fully tightened because a mechanic ****ed with the car years ago, or the upper mounts are so collapsed that they aren't even there anymore somehow. The latter would be strange because the rest of the car is in great shape, there's no reason that specifically would be so ****ed. Now that I've learned how this all works, I'm curious what I'll find when I dig in there.

 

Man, I wish I knew about that kit sooner. I'm working on the CBS Racing LSD swap, and one of the things I wanted to do before I put this spare diff in was to take care of those bushings. I opted to go the Strongflex soft polyurethane route, and it has been more trouble than I thought it could be. That kit would have saved me a ton of time.
The part that sucks is, I don't think those front differential bushings are serviceable; the repair manual doesn't outline any steps for replacing those, and I don't see them outlined in the parts diagram. If you're careful with an airhammer, you can get them out in one piece, but I don't think there are any official replacements, aftermarket or otherwise. I think the only options are to either torch the rubber to leave the sleeves inside the diff for inserts (like I'm doing), or that spacer kit.

EDIT: My issue with the Strongflex bushings was mostly my fault, but partially on them for not including instructions. However, after I reached out to them and I sent them some measurements, they sent me another set of bushings that fit perfectly for my specific situation. Huge props

 

Amayama has replacements for those lower mounts.

https://www.amayama.com/en/part/toyota/4165440010

In the original post, the video I linked at 9:30, they take out these pressed in bushes without removing the diff from the car. Though yes it is an absolute pain in the *** either way.

P.S these collapsed diff bushings would explain so many symptoms my car has. The clunk I get going into gear. General vibrational unease of the car. Feeling of "slack" in the driveline when I step on the gas, almost like there is a tiny delay like you get from collapsed trans mounts. The package arrived today but it's cold as hell outside, the weather won't be nice until Sunday. I want to get these things installed though lol. As I've been doing my research, I'm worried about having done damage to the driveshaft joints and diff\trans gears from being this out of whack when it comes to the angle. The u-joints, the center support bearing, pinion flange, etc. The Toyota manual has instructions to adjust this using 1mm mounting shims to accurately dial the angle of the driveshaft, yet I have half an inch of play in mine. Not good.

 

Interesting, hopefully the kit doesn't transmit any additional NVH. Let us know how it goes.

 

what the ****

I didn't install the poly bushings.

The ****ing bolt was loose. Backed them out, re-torqued it down to 70lb\ft and my world has changed.

• no longer makes that rusty door hinge sound when going between drive and reverse
• no longer has that huge driveline shock when shifting between drive and reverse
• no longer hear the driveline thud from inside the car
• no longer get a jolt in the 2-1 downshift when braking to a stop, making a smooth deceleration very difficult as the clunk would upset the balance of the car slightly
• gear changes while driving enormously smoother, bigger change than any transmission mount or transmission fluid change I've ever done. By a lot. 2-3 used to lurch your head back under partial throttle, 3000-4000rpm. Full throttle way okay.
• secondary vibrations in the rear completely gone, no longer feels like someone is hitting the rear axle with a rubber mallet on certain road surfaces
• "rocket start" 1st gear engine surging problems completely gone, car can California roll stop signs and parking lots without needing to be ultra gentle on the throttle
• creeping on the highway used to be a serious problem and sometimes the driveline would "clunk", very loudly, at 2-4mph when shifting 1-2 at ultra low throttle
• no longer a delay, when hitting the throttle, from hearing the engine surge and power actually transmitting to the wheels. The dif was moving and "absorbing" that, causing the delay
• ride quality is enormously improved due to lack of secondary vibrations. Bumps don't cause "judder" in the rear of the car, similar in amplitude to wheel balance being 1-2oz out at 80mph.

The above video is what the vibrations were like on the wrong otherwise perfectly smooth road surface with no bumps or grooves. This is what I've been chasing for 5 ****ing years. Half a dozen threads I've made here.

I.

****ing.

KNEW something wasn't right.

And I figured it out. Nobody else caught it. Nobody here, not the dealership, not the pro mechanic near me who worked on these cars from new and I've mentioned my concerns to. Not my neighbor mechanic who I recorded the video with in the original post and we saw the whole rear diff moving. Everyone missed it. And it wasn't even a broken part. The bolts holding the ****ing diff were not fully torqued down. Why? I have no idea. Maybe someone 5 years ago was ****ing with me. Maybe a repair had to have them removed and the person fastened them down, but didn't torque them fully the final couple of rotations.

Happy days folks, happy days.

 

Crazy stuff. I have attached a page from the repair manual and it turns out the torque spec for those 2 bolts is 108ft-lbs. If I were you I would go ahead and re-torque the bolts for the rear bushings as well.

 

108! I'll be honest I was looking at that earlier in my manual, completely forgot, and went off of what the bushing kit said. Since I was planning on installing said bushing kit up until I took the bolt out. Good spot, thanks.

 

wow at that torque how can it come loose?! someone must have been there before and missed it. glad it's all sorted! amazing what this loose bolt can do negatively.

 

So I actually installed the lower diff mount poly insert, as after the car sat overnight the stock configuration deteriorated and developed some of the slop back. I was unable to install the upper insert as I couldn't get the old upper mount out. There just wasn't enough clearance, even cranking on the diff with a 2 foot bar.

I am probably ever so slightly out of alignment on the driveshaft, but it's probably WAY less worse than it was before with how loosey goosey it was. IT is tight as **** now, even with most of my bodyweight hanging off of one of the ears.

No perceptible negatives to NVH from the poly insert, only positives.

 

glad there are are no negative NVHs to report and glad it's rock solid.

any direct links to the poly insert you used, for future member's benefit?

 

It's in the video description, but here's the source.

https://whitelineperformance.com/pro...-mount-bushing

 

I’m so happy for you! Stuff like that makes it feel like the weight of the world is off your shoulders.
I will be checking that part out next time I bring my car to a rent a bay.

Just last week I felt this same way because I had my issue fixed after chasing it for almost a year now. I’m making a thread about it check it🙂
I bet you are smiling like joker as you’ve fixed it.

cheers man!