What is the deal with solid diff mounts?

[HLS30-08077]

All good questions and I considered that after I hit the "Submit" button. I just like that "Bullet-Proof" idea before the wheels even hit the ground. I won't have that much HP to the wheels but it's always nice to know that it'll never fail under "Dumb ass" conditions.

 

Thanks again Jon,

Dave

 

P.S. That 79' 280ZX at the Arlington Pull-A-Part has a complete rear in it. (Diff, Mustache Bar, extra diff in the hatch area, etc, etc.) Just FYI. It's in Isle I-2 in the middle and the 78' 280Z is in Isle G-1 toward the back fence.

[johnc]

FYI... driving in reverse isn't the highest torque load you can put on the diff mount. A bad downshift that locks the rear wheels puts a pretty good shock load on the mount. I've done that and not had any problems. Even if the mount fails the crossmember is still in place to keep anything bad from happening.

[HLS30-08077]

I know, I just keep thinking of the stock mount and keep forgeting about the interlocking (failsafe) feature of the GM mount.

 

Thanks guys, I can never be too informed. The more answers I get, the more informed I am, the more info I can give when someone asks me. You get the idea.

 

Dave

[HLS30-08077]

So here's my Progress so far. This is all on an early 260Z (2/74) I got the mount and POR15'd it after media blasting it to help the POR stick better. I went to go mount it and found that the 260Z's exhaust hanger is in the way. 4 spot welds, an air hammer and large mallet later, the hanger is gone and I'm ready to slip the RT in place.

 

Of coarse, the fuel lines and the rubber bracket are in the way. So I move the bracket forward and gently push the brake and fuel lines upward to clear the R/T. After that, the instal was smooth. Couple smacks with the plastic mallet to align the bolt holes and we're good to go. Had to lift the diff into place and ballance it on my shoulder while I was bolting it to the Mustache bar, then lifted the front to bolt up the poly to the R/T.

 

In the 4th pic, you can see that I tightened the Poly so much (to make sure it was tight) that the inner plate started to twist. I fixed it shortly after the picture was taken.

 

Here's the pics....

 

Dave.

[bjhines]

I used 2 bolts on top of the poly mount to keep it from twisting. The single hole the "RT mount" was designed with, will allow the pieces to twist when you tighten them.

[HLS30-08077]

I ended up dropping the mount, and welding a dot of steel on the mount so when I tightened up the Poly, the weld caught the hole and kept it from twisting.

[erehemantresni]

Where does one purchase one of these mounts?

[BRAAP]

Where does one purchase one of these mounts?

 

The mount that this discussion evolved into is called the RT mount, named after Ron Tyler, (member RTz).

For more information about it, just search RT mount. To purchase one, go here;

http://forums.hybridz.org/index.php?/topic/85384-rt-mounts-are-ready-for-shipping/

 

Hope that helps,

Paul

[LowCarbZ]

I recently installed an RT mount on my car in tandem with the existing factory lower mount. I had a decent used mount from a parts car so i used it on the lower, to fit the diff in the car with the new Energy Suspension mount and RT setup I simply ground some of the poly material away to help it form to the top of the diff nose. This kept the driveline angles relatively stock and everything bolted right up into the car based on the RT mount plans previously posted in this thread.

[Nigel]

I went to go mount it and found that the 260Z's exhaust hanger is in the way. 4 spot welds, an air hammer and large mallet later, the hanger is gone and I'm ready to slip the RT in place.

 

Too late for you now, but if your 260 is anything like my '73 240, it's actually pretty easy to just hammer the exhaust hanger in a bit, and then it clears the mount just fine.

 

Nigel

'73 240ZT

[Nigel]

I recently installed an RT mount on my car in tandem with the existing factory lower mount. I had a decent used mount from a parts car so i used it on the lower, to fit the diff in the car with the new Energy Suspension mount and RT setup I simply ground some of the poly material away to help it form to the top of the diff nose. This kept the driveline angles relatively stock and everything bolted right up into the car based on the RT mount plans previously posted in this thread.

 

What's the advantage to keeping the lower mount? The poly bushing is more than strong enough, and hardly deflects at all. I was all too happy to ditch the lower mount. Without it, it's so much easier to R&R the driveshaft bolts!

 

Nigel

'73 240ZT

[LowCarbZ]

What's the advantage to keeping the lower mount? The poly bushing is more than strong enough, and hardly deflects at all. I was all too happy to ditch the lower mount. Without it, it's so much easier to R&R the driveshaft bolts!

 

Nigel

'73 240ZT

 

I guess i'm just overkill with things? Hahaha.

 

It crossed my mind to get rid of it and I know that I can. I just honestly wasn't a fan of having a single bolt holding it from above. That, and the lower mount helps protect from debris and the fact that my car is low I suppose.

[Drax240z]

How is the Noise/Vibration/Harshness with the RT mount and stock mount in place? Comparable to stock?

[LowCarbZ]

How is the Noise/Vibration/Harshness with the RT mount and stock mount in place? Comparable to stock?

 

Vibration isn't noticeable to me at all. Again, the car is low and loud so it's a little "bare bones" in the comfort/sound department. However, there is no shuddering through the car or anything like that it's very comfortable IMO.

 

To be honest though, noise/vibration/harshness is entirely subjective. What I consider comfortable you may not be able to stand. My car is stiff and the ride is slightly harsh but tolerable for my tastes.

 

I think it would be important to profile the poly to the nose of the diff when using the RT in combination with the lower mount. When I took the poly material down enough that the two tabs on the GM transmission mount were flush to the bolt holes everything lined up and bolted in basically as if it were stock.

 

I suppose I should've taken some pictures of how I did it. Next time it's on the lift I will do just that.

[crazyoctopus]

Thanks LowCarbZ for mentioning the use of both the solid lower mount (MSA style) in conjunction with an RT mount. Now that I know it is possible i am doin it.

 

The new search is now on solid mustace bar bushings! if anyone has any hints send them this way.

[Nigel]

Thanks LowCarbZ for mentioning the use of both the solid lower mount (MSA style) in conjunction with an RT mount. Now that I know it is possible i am doin it.

 

I'm still not convinced that this accomplishes anything other than making extra work and adding unnecessary weight. I've been running an RT mount for two years now with many runs down the drag strip, and some road course time, and the GM poly mount is more than strong enough by itself. Under acceleration, the stock lower mount (don't forget it too is only held in place with one bolt) was the weak link to begin with, which is the whole reason the RT mount came into being, so the lower mount is not going to help there. The GM poly mount has internal locking tabs to keep it from deflecting under deceleration, so I doubt the softer stock lower mount is going to be of any benefit there either.

 

Nigel

[crazyoctopus]

Thanks for the clarification, I'll take I into consideration when mount gets in. And if it is more hassle to keep it In then I will get rid of it.

[LowCarbZ]

I'm not in disagreement with you at all on the subject Nigel.

 

There's no doubt that the RT setup can handle the duty and stress that the diff puts on it, it has been proven by multiple owners on this very forum. I just chose to retain the lower factory mount as i've seen others on this forum do in the past as well. The nice thing is, if you need the clearance, room for exhaust, or want to shave half a pound then the RT mount is a great design that is more than up to the task.

 

I just like the idea that using the RT mount in combination with the factory lower mount things aren't going to move anywhere period. No deflection and it will likely increase the longievity of the poly GM mount due to no downward stresses to speak of from diff movement.

 

But I do appreciate you sharing your thoughts on it, in the future when I change my suspension around and such I may re-evaluate it. And you're right, eliminating the factory lower mount would make it much easier to remove the driveshaft (however I work on the Z under a lift so it is pretty much a non-issue for me). All good points though.

[kj280z]

Well - I'm having some difficulty with the driveline angles and could use some help.

 

I had the RT Mount installed today. It lowered the nose of the diff so low that the installer had to notch the crossmember so the 2 bolts woudl clear, and I now have a noise on deceleration which I would characterize as interference - it matches RPM and is continuos until I give it gas.

 

Also, I have been frustrated by a vibration in my driveline - (I have an LS1/T56 JCI conversion) - prior to the install of the RT Mount, the vibration started at 80 mph, now it starts at 55 mph.

 

I hope to be able to get it on a lift tomorrow and check out the angles better...

 

Can anyone share any experiences?

 

I have always felt the the JCI 280z Tranny mount (not the 240z mount) causes the rear of the tranny to be about an inch too high... just eyeballing it

[duragg]

Wish I would have read (and followed) the heart of this thread yesterday.

 

With my new R200 I went and saw Dave at Arizona Zcar and bought one of his solid diff mounts.

Sure makes attaching the drive-shaft easier.

 

I got about 75' down the road and decided I'd had enough.

Its coming back out. Noisy. Obnoxious noisy, not cool noisy.