How to properly mount your 2g Rear Diff

[dsm-onster]

But he has no "BS" in mechanical engineering

BTW, fatigue occurs over time. That time interval is determined by the magnitude of the forces applied and the frequency. Who has calculated the shear force even to announce so dogmatically the tab would fail in the lifetime of the car? After that, you then can form your opinion on how frequently the piece will see the various loads at magnitude. And then, you still have calculated a big fat guess. . .

Thankfully, Tim will bypass all that waste.

 

[bostonhatcher]

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'll just let Tim's car do the talking.

 

[twicks69]

Great....I get brought into the "fight" now.... rofl

I will get the car up and running here soon; I am waiting on my fuel cell and tubular control arms to get it back running.

 

[Boosted98gsx]

But he has no "BS" in mechanical engineering

BTW, fatigue occurs over time. That time interval is determined by the magnitude of the forces applied and the frequency. Who has calculated the shear force even to announce so dogmatically the tab would fail in the lifetime of the car? After that, you then can form your opinion on how frequently the piece will see the various loads at magnitude. And then, you still have calculated a big fat guess. . .

Thankfully, Tim will bypass all that waste.

Oh right, my bad. I must have forgot there is a whole industry based on keeping you safe from forces you would otherwise neglect.

My bad. I guess all these classes I am taking are a total waste since all I can do is calculate big fat guesses.

 

[elementalwindx]

My bad. I guess all these classes I am taking are a total waste since all I can do is calculate big fat guesses.

I dont think there has been a single week for the past entire year where I have not heard you say something like this. ..

 

[bostonhatcher]

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.

BTW my mounting plate is provided.

 

[debbie]

BTW my mounting plate is provided.

Ah sorry did not realize that
But you get what i mean, if people want to beef up the mounting plate how hard could it be?

 

[bostonhatcher]

Ah sorry did not realize that
But you get what i mean, if people want to beef up the mounting plate how hard could it be?

There's no need to. You'd shear the mounting bolt in half before the plate sheared. Not to mention there's no way your ring and pinion would live through this kind of scenario.

 

[Boosted98gsx]

I dont think there has been a single week for the past entire year where I have not heard you say something like this. ..

Well it's true. If someone is going to doubt engineering as some kind of voodoo witch craft that serves no purpose, why is engineering the top paid field for BS's right out of college?

Again, I wouldn't recommend this for a street car, but for a dragster that's going to see very little load time in comparison, sure, it has a purpose. So don't get me wrong.

I would add a damped insert to the brackets for those people wanting these parts for regular street warrior driving.

There's no need to. You'd shear the mounting bolt in half before the plate sheared. Not to mention there's no way your ring and pinion would live through this kind of scenario.

And it's not the plate that's going to shear, it's the weld that's going to fatigue and break off, as IT WILL BE the weakest part in the suspension of the rear differential, without subsequent damping being utilized.

 

[bostonhatcher]

And it's not the plate that's going to shear, it's the weld that's going to fatigue and break off, as IT WILL BE the weakest part in the suspension of the rear differential, without subsequent damping being utilized.

It depends on the weld. It's up to the user to make sure it gets a good weld. It could potentially be the weakest point of this kit but with enough heat and using the proper gas and wire it shouldn't ever be a problem. Your car is full of welds that see vibration but it holds together because it's a quality weld. I could have used a 1/4" mounting plate and still had a huge factor of safety given the forces exerted but the only reason I went to 1/2" is for more surface area for the weld and also to be able to use much more heat on the weld.

 

[SlowSpyder]

The weak part wouldnt necessarily be the weld, most likely its going to be the portion you weld the steel bracket to. You can put as much weld on to the bracket what looks like at most 2 inches wide, its probably going to rip that section out. The section that that piece is welded to is thin metal. The only thing I would suggest (hopefully no one attacks me) is to redesign where that 1/2" metal bracket welds to. Just my opinion

 

[debbie]

There's no need to. You'd shear the mounting bolt in half before the plate sheared. Not to mention there's no way your ring and pinion would live through this kind of scenario.

What I'm Driving at is, if you bought this kit you are going to have to have some welding work done on to the carrier any way right, Well if you are concerned about its strength or any other capabilities you could just as easy have some thing else added to satisfy your needs. In short and what I a trying to say is why complain about something that could so easily be changed. Weather it needs changing or not is up to who ever buys this.

 

[Boosted98gsx]

I should have stated it's going to be the heat affected zone of the weld (ie the material the weld adheres to) that's going to fatigue and break, not the weld itself.

 

[bostonhatcher]

I should have stated it's going to be the heat affected zone of the weld (ie the material the weld adheres to) that's going to fatigue and break, not the weld itself.

Call up Magnus and complain about their welded tubular subframe they've made and raced that houses their rear diff. I'm tired of hearing it.

 

[Boosted98gsx]

Call up Magnus and complain about their welded tubular subframe they've made and raced that houses their rear diff. I'm tired of hearing it.

Once again, you are ignoring the fact that I am simply arguing against using this for a car that will see the increased harmonic loads from street driving. For a race car, by all means run this.


Also tubular subframe, having more mass and a longer body to extend forces to, is going to be much more adept at dispersing harmonic and fatigue forces than a single solid machined part will.

 

[jjrock5]

All I'm reading is big words that people are trying to forcefully shove in others' faces in order to prove their point and attempt to sound smart.

I have a B.S. in Mechanical Engineering and currently working on my Master's in the same field. Does this mean I have to f up this guy's thread? No. The quality control seems to be there, now let the testing do the rest, just like in any high profile manufacturing facility (which I work in btw).

In other words, stop bs talkin', and keep this thread quiet until somebody ACTUALLY puts some stresses/forces on them. Just sayin'

Addition to a member's post that was deleted:

C'mon, Tim already said himself he's going to run them. And by watching his vids, he has come as close to "killing himself" by blowing up his diff, as possible. The brackets will NOT makie it any worse. They may fail according to some ppl's theories but will not do worse damage.

 

[twicks69]

Once again, you are ignoring the fact that I am simply arguing against using this for a car that will see the increased harmonic loads from street driving. For a race car, by all means run this.


Also tubular subframe, having more mass and a longer body to extend forces to, is going to be much more adept at dispersing harmonic and fatigue forces than a single solid machined part will.

Andrew, you are simply arguing for the sake of arguing. Thats it. Yes, the Magnus piece is nice, it is also $2500.00 vs. a $300.00 fix. You want pretty tubular control arms? Go make them, they aren't that difficult. If you think that we should be using a tubular cross-member on our cars instead of a 4-mount setup that utilizes the stock cross-member, fine. That is your choice.

This is not as big of a deal as you are making it. If you are looking at this mod, your car is more than likely not a street car, and at power levels substantially higher than the average DSM'er that is causing rear diff breakage under launching conditions with a GOOD suspension in place. If you already have solid rear diff and subframe bushings in place with just the three mounting points and you are driving the car, you already are going to be dealing with a helluvalot of vibration that a person with stock rear diff bushings would never see.

If you are really concerned about all this increased vibration that will affect fatigue forces leading to breakage, you should look at running a less aggressive bushing in the subframe (stock rubber/polyurethane/aluminum w/ poly insert), and make a tubular torque arm from the subframe back to the chassis with solid rear diff bushings.

The weak-ass stock 2G driveshaft is likely going to break first in real-world testing. A 1315 stock U-joint and the bearing cap for the rear diff end of the rear driveshaft will break way before the weld on the 1/2"-thick tab (If you know what you are doing and have a professional-level welder doing the work and get good penetration without excessively thermally fatiguing the subframe).

In my scenario, the stock driveshaft is a temporary piece to get the car back up and running. The entire unit, transfer case, and rear end connecting flange will be replaced with substantially stronger parts, hence why I am replacing the rear diff mounts and rear diff cover, as these would be the first things to break if they were left stock and the driveshaft and transfer case were upgraded only. The energy has to transfer somewhere. Let it transfer to the tires, the way that it was meant to be.

 

[efrainz28]

I purchased a set and I want to run it on my DD. Is this a bad mod for a DD? I’m building a 2.3l and an awd swap.

 

[bostonhatcher]

I purchased a set and I want to run it on my DD. Is this a bad mod for a DD? I’m building a 2.3l and an awd swap.

If you still have full interior and sound deadening you can barely hear it with the radio all the way down and a stock exhaust.

 

[twicks69]

Here's pics of the bushings/mounts installed on the diff and subframe. The fitment was excellent, and I jus had to do a bit of clearancing to the subframe mount tab due to variations in the mount location.

Excellent fitment!

 

[greengoblin]

Looks good. Very clean weld. I was looking into doing exactly this on my car and will more than likely go this route too. I'd really like to add another cross brace on the side with the new mount like the factory one. Great work!

Kevin

 

[twicks69]

While an additional gusset isn't a bad idea, it is crucial that you weld the seams of the two 16-gauge sheet steel pressed pieces of the subframe together so that it doesn't tear away the spotwelds that hold it together.

I would prefer to still have a non-binding slip-tube torque arm going from the rear subframe towards the center of the car's chassis to help with preventing shock-loading. I would utilize Chromoly 4130 tubing with Chromo rod ends for this for weight and flexability.

 

[1995gsx20g]

Twicks- I couldn't help but notice that you have two bolts instead of two studs making your diff cover girdled. Was this because the load required less clamping force and more of a lateral load than lets say a headstud with loads fighting to lift the head? Or was it a cleaner and easier fit that had nothing to do with strength?

 

[greengoblin]

I venture to guess he did want to have to cut windows in his cross member to clear the load bolts that came with the girdled cover.

 

[twicks69]

I wanted it fully installed first, then I will cut the holes required in the frame to clear the load bolts. It is mainly for installation ease currently.