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How to properly mount your 2g Rear Diff

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bostonhatcher

15+ Year Contributor
148
21
Sep 28, 2006
Kansas City, Missouri
I've been working on a good, lightweight solution to mounting the 2g rear differential into the 3-mount subframe for the past few months. What I've noticed, is that the differential likes to rotate around the passenger side bolt that's on the front mount. The driveshaft gives the differential a torsional force like a helicopter, resulting in breaking the far left diff cover bolt (force x radius). Of course some are even breaking both diff cover bolts, because once the left lets go the right side bolt has twice as much load to hold onto. Well now the days are over where you take the entire rear end of your car and you can have 4 solid mounts just like the 1g's and evo's.

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The mounts are 6061 billet aluminum and weigh 1.2 lbs a piece (stock weighs 2.4 lbs). The third piece is 1/2" thick, water jet cut steel. I had to drop the subframe to weld it on because it's too close to the gas tank. I was able to lift the entire subframe with all the suspension parts on it by just the mounting plate.
 
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Look's good. I've seen a few different variation's of ways to mount rear diff's . Has this been tested and if so how much power is the car that tested it making ?

My car is not currently running right now but I have no doubts whatsoever. :thumb:
 
I like the idea but it looks like you need to do some more reinforcing of that tab. Looks like it will break off after a while.

I like the mounts did you have those made or are they a prefab?
 
I like the idea but it looks like you need to do some more reinforcing of that tab. Looks like it will break off after a while.

I like the mounts did you have those made or are they a prefab?

The tab is 1/2" thick steel. Like I stated in the first post, I was able to lift the entire subframe with all the suspension parts attached by just the mounting tab. I hit it with a hammer, stood on it, etc. trying to break it off. When you launch the car, there is no horizontal force on the tab, only vertical compression and tension. The weakest point of this entire setup is going to be the weld on the tab to the subframe, so the customer will have to make sure to get a nice solid weld on it.

The mounts were made on my cad software, and are cut by a 4-axis cnc machine to ensure consistency on every part.
 
i know you said you did quite a bit of testing on that tab to make sure it was welded on strong enough, but. if it needs to be more secure you could notch the sub frame where you have the tab welded now and make the tab about 2 inches longer. that way it can extend up the flat face of the sub frame and you could weld the tab on either side. only thing you would need extra would be a spacer for the mount because the tab might be a little further back than it is now.
 
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i know you said you did quite a bit of testing on that tab to make sure it was welded on strong enough, but. if it needs to be more secure you could notch the sub frame where you have the tab welded now and make the tab about 2 inches longer. that way it can extend up the flat face of the sub frame and you could weld the tab on either side. only thing you would need extra would be a spacer for the mount because the tab might be a little further back than it is now.

You'd be really surprised if you got a set and welded the tab on. The pics make it look like a toothpick LOL but it is much stronger than it looks. If I would have added any more material to the tab it would have been dead material which would just weigh the car down and serve no beneficial function.
 
I lost most of my CAD files but if anyone needs any help I have 2010, and 3ds max :p. I cant wait to see what happens with this.
 
Hence why I purchased them!

I was going to fab up my own, but it is nice to have someone do it before me and use their design. This design will definitely help the rear diff survive with the plate-steel rear diff cover I am running.
 
That tab you welded to your rear subframe is going to need additional support, as the diff is not going to apply pure tension / compression to it. There will be a shear involved, and your weld will fatigue.

Try grinding down the back weld, and adding a rib or two (still maintaining clearance for the axle of course). This should provide adequate support to help prevent fatigue failure.
 
That tab you welded to your rear subframe is going to need additional support, as the diff is not going to apply pure tension / compression to it. There will be a shear involved, and your weld will fatigue.

Try grinding down the back weld, and adding a rib or two (still maintaining clearance for the axle of course). This should provide adequate support to help prevent fatigue failure.


False. Shear force would only occur if the diff was sliding front to back or side to side.

If that tab gets a good weld it's not breaking. I stood on mine and jumped up and down on it and I weigh 175 lbs. It turns out my math was correct. :thumb:

These mounts are seriously over-engineered.
 
False. Shear force would only occur if the diff was sliding front to back or side to side.

If that tab gets a good weld it's not breaking. I stood on mine and jumped up and down on it and I weigh 175 lbs. It turns out my math was correct. :thumb:

These mounts are seriously over-engineered.

Yes, they are!

Beefy is an understatement!

The weld-tab is 1/2" thick. If you know how to weld a good bead and do a few passes on each side with a TIG or a good MIG and get good penetration, you will not have any problems whatoever with the weld tab. It is beefier than anything else on the rear subframe for the 2G AWD.

As for the bracketry, they are very nice pieces as I have a set in front of me right now for installation into my car. High quality, very thick, well machined, and very nice fit.

I'll post up some pictures when I get around to installing them.
 
Noone is trying to ruin your unofficial sales here by pointing out concerns (although, you might want to consider becoming a supporting freelancer before you run afoul of the rules too badly), so try to take it in the spirit it's being given: constructive criticism.

North/south drivetrain movement happens, and the subframe flexes like a limp noodle to absorb it. You can make that tab as thick as you want, but it's only as strong as the garbage it's attached to, and there's an enormous amount of leverage being applied to the outboard end of that tab at launch (on a car that would need this setup, anyway).

Will it work in the real world? Probably, but that's for Tim to figure out. ;) Folks are simply making suggestions for improvement.

(The whole subframe is such an incredibly poor design. Marco really did have the right idea here.)
 
False. Shear force would only occur if the diff was sliding front to back or side to side.

If that tab gets a good weld it's not breaking. I stood on mine and jumped up and down on it and I weigh 175 lbs. It turns out my math was correct. :thumb:

These mounts are seriously over-engineered.

I assume then that you have a degree in mechanical engineering and know about fatigue load then? Because I could have sworn that I have already taken a class in (and made an A) in machine design, which deals with loads, and stress analysis.

You're going to tell me there's not going to be any vibrational loading in that tab at all (especially w/o the use of a damper to stifle it)? There's not going to be ANY fore/aft accelerations, and thereby subsequent loads, placed on that tab? If you do tell me that, I can straight faced call you a liar.

Please don't tell me I am wrong, my education has been quite expensive.
 
I don't know what the argument is about.
The guy isn't providing the metal tab that's welded to the diff carrier, He is supplying the brackets.
If people want a thicker mounting bracket, or a one with a bush, then have it made that way. :confused:
 
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I think it's beautiful. And frankly if twick69 gives it his seal of approval I'm sold. I don't think anyone has destroyed more drivetrain components that twick69(tim zmer, owner of tmz performance). I'm pretty sure tim is also still reigning champion of the highest hp 7 bolt 2G awd Dsm in the world. If he's happy with design so am I.
 
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