REAR SUSPENSION BUSHINGS AND MOUNTS

[Jeff G 78]

I have a 1/8" air gap in mine and while it's a race car with lots of noises, gear whine isn't one of them.

[grannyknot]

4 hours ago, heyitsrama said:

@JTO i think you are on the money about creating a little bit of space between the diff and the snubber. I noticed less noise in the cabin. Details are in this thread.

 

 

3 hours ago, Jeff G 78 said:

I have a 1/8" air gap in mine and while it's a race car with lots of noises, gear whine isn't one of them.

My diff is squished between the mount and the upper snubber so I think I will give this gap a try and see if that improves the amount of noise.

Thanks

[Jeff G 78]

5 minutes ago, grannyknot said:

 

My diff is squished between the mount and the upper snubber so I think I will give this gap a try and see if that improves the amount of noise.

Thanks

Here is a picture of mine. The gap is smaller than it looks. The mount has about 20 race hours on it. 

[jonathanrussell]

On 3/6/2021 at 3:04 PM, JTO said:

To all that responded, thanks for the info. Much appreciated.

On another matter, I had noted in a previous post above that I had purchased the PU bushing kit for the transmission cross member mount from Performance Suspension but the bushing kit they sent doesn't fit. The bushings and sleeves are too long and the bushing diameter is too big. I have attached a photo of my cross member. The distance between the brackets that carry the bar is 2.135". If anyone happens to have a spare cross member sitting around or a cross member out of their car, could you take a measurement between the two brackets and let me know if you get the same or different measurement. I know my cross member is OE but for some reason may be different than most.

Thanks...Tim

 

It has been a couple of years so make sure what I remember looks reasonable. I installed the energy PU bushings in the same transmission mount you show here. You are right...they are too long. I removed any sleeves from the rubber bushing and my recollection is that they slide right into the mustache bar hole. I solved the "too long" problem by using a belt sander to remove material on the bushing. I am pretty sure I removed material from the outside portion of the bushing. It was tedious because I wanted them to fit snug and didn't want to remove too much material. So, I worked a little at a time until I had removed the same amount of material on all 4 sides and the fit was snug. Hope this helps. Sorry I don't recall 100%.

[JTO]

Jonathan...Thanks for your comments. I ended up doing exactly as you described - sanding down the PU bushings (slowly) with a belt sander and bench grinder/sander. The sleeves provided with the PU bushings were the same diameter but longer so I ground those down to the required length as well. The existing sleeves seemed in good condition so I ended up using a new ground down sleeve on one side and a cleaned up existing sleeve on the other side. Apparently, this type of transmission mount cross member was installed on 240Z's manufactured up until July of 1972, then the newer type cross member was used (my 1972 240Z was manufactured in November of 1971). Energy Suspension (and others) only provide a PU bushing kit for the newer type cross member. I also procured a new transmission mount but it was for the newer type cross member as well. I could not find a new transmission mount that fits the older style cross member so I Installed the new mount on my cross member and it seems to work fine.

[inline6]

I happened to see this thread and thought I would mention an alternative solution I used.  I don't recall if I saw someone else do this, or I came up with the idea, but it consists of using a simple bracket in the shape of a U like this:  |______|  

I bent a piece of 1/8" (.125) or similar thickness plate which I installed underneath the front diff mount/crossmember, so that the motion is stopped by the bracket coming in contact with the bottom of the front diff mount/crossmember instead of the stock design or the RT design that stops movement up above the diff. 

With this solution, the front diff insulator fits in between the walls of the U and the floor of the U passes under the front diff mount/crossmember.  A tight fit to the stock insulator is not needed, but just close fitment.  I removed the front diff mount/crossmember and front diff insulator from the car.  I bolted the insulator to the crossmember.  Then I placed spacers between the floor of the bracket and the bottom of the crossmember so there was a 1/4" between the two parts.  I clamped it into place, so that I could drill two holes through the front and rear walls of the plate and into the metal of the front and rear of the diff mount.  I then removed the clamps, set the U bracket aside, and tapped the newly made holes in the front and back of the diff mount for metric bolts (6M X 1.0 pitch).  Final touches were to glue 1/8" thick rubber mat material (I used a reinforced rubber from Tractor Supply) to the inside floor of the U bracket, and paint it black.  At that point, simply re-install the diff mount and insulator as stock, and slide the U bracket in place from the bottom of the car.  Two bolts with lock washers on the front, and two on the back, and the bracket is installed.  There should be a 1/8" air gap between the rubber glued to the floor of the U of the bracket and the bottom of the front diff mount/crossmember after installation.  

Cheap - light - easy to remove and install.  I don't happen to have pictures because I did this a long time ago, but can add some if needed by anyone who is intrigued by this solution and wants more info.  

Edited October 30, 2021 by inline6

[Namerow]

20 hours ago, inline6 said:

I happened to see this thread and thought I would mention an alternative solution I used.  I don't recall if I saw someone else do this, or I came up with the idea, but it consists of using a simple bracket in the shape of a U like this:  |______|  

I bent a piece of 1/8" (.125) or similar thickness plate which I installed underneath the front diff mount/crossmember, so that the motion is stopped by the bracket coming in contact with the bottom of the front diff mount/crossmember instead of the stock design or the RT design that stops movement up above the diff. 

With this solution, the front diff insulator fits in between the walls of the U and the floor of the U passes under the front diff mount/crossmember.  A tight fit to the stock insulator is not needed, but just close fitment.  I removed the front diff mount/crossmember and front diff insulator from the car.  I bolted the insulator to the crossmember.  Then I placed spacers between the floor of the bracket and the bottom of the crossmember so there was a 1/4" between the two parts.  I clamped it into place, so that I could drill two holes through the front and rear walls of the plate and into the metal of the front and rear of the diff mount.  I then removed the clamps, set the U bracket aside, and tapped the newly made holes in the front and back of the diff mount for metric bolts (6M X 1.0 pitch).  Final touches were to glue 1/8" thick rubber mat material (I used a reinforced rubber from Tractor Supply) to the inside floor of the U bracket, and paint it black.  At that point, simply re-install the diff mount and insulator as stock, and slide the U bracket in place from the bottom of the car.  Two bolts with lock washers on the front, and two on the back, and the bracket is installed.  There should be a 1/8" air gap between the rubber glued to the floor of the U of the bracket and the bottom of the front diff mount/crossmember after installation.  

Cheap - light - easy to remove and install.  I don't happen to have pictures because I did this a long time ago, but can add some if needed by anyone who is intrigued by this solution and wants more info.  

Intriguing idea.  Not so much 'outside the box' thinking, but more like, 'What if we turn the box upside down?'  Some pix would be nice.

[Zed Head]

It is essentially an upside down strap, like the factory one over the nose of the diff, but oriented longitudinally under the crossmember and made of metal. 

Does it really effect the movement much, compared to the rubber strap over the top?  Not seeing large benefits.  It does look like a simple strap replacement though, if you have the tools.

 

p.s. if the large chunk of vibration damping metal is there on the crossmember it can't be used.  Most of us remove that anyway, just saying.

[inline6]

I found a few relevant pics of the bracket from when I was fabricating a 3" exhaust.  Here they are:

Looks like my air gap is more like 1/4".  In the first pic, you can see the rubber padding glued to the floor of the U bracket:

    

Here is a close up of the bracket going under the crossmember.  I used yellow contact cement to glue the reinforced rubber belt material to the floor of the "U".  You can see the air gap nicely here (top left of the photo):

 

Edited November 8, 2021 by inline6