Tranny/diff brace
 

My PPF is cracked. I was wondering if I put tranny/diff brace if I could eliminate the PPF, or if I put jut the tranny brace and keep the PPF. I don't really care about vrabration because I can put a sheet of polyurathane to absorb the vibration the same way I did with the poly engine mounts and i got not vibration.

dooood, you cant just get rid of the PPF, it is like the spine of the car.

That's what I though, I just get a tranny brace or get the PPF welded. Hey thanx for the how-to make my engine mounts. I got lucky and had the same one ones you got so it was easy.

um... why not take it off (the ppf), take it to someone which can tig weld and get it welded up with some additional braces welded to reinforce the crack? it boggles my mind on why people automatically assume you must throw stuff away becuase of a simple crack. i cracked my UIM and some people would have though, go and save up money and buy a new one when all i needed to do was to ask my friend which can tig very well to weld up that hairline crack. took him about 30 secs and it was all done and it works very well.

in anycase, it should take you much longer to actually take out that ppf then it will do have someone weld it up correctly and it should have cost a hell of a lot more to have bought those tranny/diff braces rather then to have someone weld it up nicely. (should cost about 20-30 bucks for someone to lay down a nice weld)

BTW: The difference between a welded up ppf and a new one (stocker) is that the old one will look kinda ugly if miged or have a roll of quarters (looking) weld on it where the crack was but you know what, the ppf is under your car and you'll and nobody else will see it after you reinstall it! well that and you save however much a ppf cost :) just remember to paint it with something so that it does not rust and your golden!

wow, very good analogy :)

Yeah, actually you can. :)

I'm with damian and skunks. I think the PPF do more than just hold the tranny and diff. I think got something to do with the ridgity (spelling?)of the body also. I was noticing the tranny still hit the tunnel. I went to intall my strut tower bar and couldn't put it in because I notice that the motor is a bit higher than normal so it might just be that. I think I have to wait till the mounts sit in properly and see. But I still want the tranny brace because I don't want a torque brace. Time will tell.

In stock form, the drivetrain is suspended by four liquid-filled rubber bushings. Exactly how much rigidity could it possibly add to the body?

I agree with jim lab, I think you can remove the ppf. All the ppf does is prevent the tranny and diff. from twisting. The tranny brace is the best idea for making the tranny from turning. It's so solid the tranny prolly won't even move at all. With just the ppf the tranny is no where near as solid. I think if you take out the ppf, put the tranny and diff. brace. Your saving yourself weight, and making the drivtrain alot more stiff.

This is getting my thinking of new ideas for the underbody braces.

If you really think about it. What is doing to make the drivetrain stiffer? Long braces or shorter ones? Which do you think would flex more? It's common sense. I think ppf is just a quick way out of making couple braces. Just my .02

cool, yeah new motor mounts will help tighten it up a lot.

>>I think ppf is just a quick way out of making couple braces. Just my .02

hmmm, this does not make sence to me, look at how much material the ppf uses, a couple of braces would have been cheaper to make so i think if it were that simple they would have done that to save manufacturing costs....

Yes, maybe manufacturing costs, but what about engineering costs;)

true, but one is not much technical over the other?

I already did them the same way you did yours. The only thing that is different is that I'm not experiencing any vibration at all with the poly specer under the mounts.

When I was talking about rigity I wa talking about as colishion wise. I'm not sure if it does but is the only thing I can actually think off why Mazda put a long bar instead of something more simple like a tranny/diff brace.

From Jack Yamaguchi's book The Mazda RX-7: Mazda's Legendary Sports Car...

I believe that over the years people have mistakenly come to believe that the PPF improved body rigidity by reading the sentence "Not only does the PPF contribute to the RX-7's overall structural rigidity". However, no mention whatsoever is made to its contributing to body rigidity, and all of the surrounding text describes the PPF's function in contributing to drivetrain rigidity. Two totally different things.

Again, how can a structure isolated from the body by three (my mistake) liquid-filled rubber bushings and one compression rubber bushing possibly contribute to body rigidity?

"Not only does the PPF contribute to the RX-7's overall structural rigidity, but also it adds a controlled crush zone that prevents the differential housing from coming into contact with the fuel tank in the event of a collision."

This is what I was talking about. The ppf is more than just a brace for the tranny and diff.

Did you not read my post?

I believe that over the years people have mistakenly come to believe that the PPF improved body rigidity by reading the sentence "Not only does the PPF contribute to the RX-7's overall structural rigidity". However, no mention whatsoever is made to its contributing to BODY rigidity, and all of the surrounding text describes the PPF's function in contributing to DRIVETRAIN rigidity. Two totally different things.

Again, how can a structure isolated from the body by three (my mistake) liquid-filled rubber bushings and one compression rubber bushing possibly contribute to body rigidity?

Sound familiar?

Crush Zone IS THE KEY WORD HERE. That's what I wanted to reffere to. not body rigidility actually. I understand that part.

Maybe you should be more specific next time. :)

BTW, the only reason the PPF has to crush in an accident is because it does rigidly tie the engine and transmission to the differential. A frontal impact would drive the differential back into the gas tank if it didn't, a problem that an isolated differential does not share.

Sorry for the miss understanding I wasn't sure how to explain it but you found what I was getting to. Thanx

has anyone tried running without one? Any long term data?

IMHO if you want to solidify the drivetrain with the PPF removed, all you would need are 3 things:

1. The stiffer Mazdaspeed engine mounts.

2. Any tranny brace w/rubber bushings to help control the vibrations.

3. Jimlab diff bushings.

With these 3 things I would think that the drivetrain would hardly have any movment plus you would save alot of weight.

Hell the Jimlab bushings themselves have elliminated alot of my wheel hop all by themselves.