Removing heavy iron bar between gearbox and diff
 

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Hi guys in my hunt for weight loss I'm thinking about making traditional diff and transmission mounts instead of the big heavy iron. Bar. I think it's only there to provide rigidity and my car has a 10 point rollcage so I don't really worry about that.
Has anyone done it ore am I crasy?

It's called the powerplant frame (PPF) and deleting it is common in LS swaps. I don't think anybody bothers to remove it unless they are swapping to something other than a 13b because the weight loss is offset by the fact that the driveline is no longer rigidly locked together into a single unit.

i see that reason its there. however with my rollcage i hopings its pretty rigid.
However i am very heavy compared to my competion. Could it be solution goint woth solid engine and diff mounts. that way it dosnt move all over the place

You'd have to install a mount at the tail of the transmission to keep it from moving up and down. You can probably tie into the existing mounting point on the transmission and fabricate a bracket and reinforce a spot on the unibody to connect it to.

Without the PPF, the front of the diff will rotate down so you'll have to fabricate a bracket and figure out how to tie it into the body or the rear subframe.

It doesn't weigh that much, don't bother.

"Bridgeporting a Renesis is the same as taking a $6000 cash loan, digging a hole in the ground, putting the cash in the hole, pouring gasoline over the cash, and lighting it on fire. - -TeamRX8"

Just wanna remin you what your avatar says about 30-50 hp at 6000 dollars at 40 hp thats 150 dollars pr HP . If i spend 2500 dollars removing ppf, safety tank. light seat brackets, and so on i might loose 200 pounds thats 7 % of the weight 7% off 231 hp is 16,7 hp thats 149,7 dollars pr HP.

DO you still think im crasy haha.

However if it will cause alot of issues ot wont be worth it. ive just done 5 rallies in 4 weeks without any mazda related problems. every problem has been with aftermarket stuff, so i really dont want to cause problems.

You are crazy, the picture in the first post is evidence ;)

Read carefully what was said: if you remove the PPF you're going to need some other way to make sure the driveshaft isn't bearing the forces the PPF is meant to take, like the diff rotating down and the engine twisting all over the place. Solid mounts would be a must, followed by additional mounting points for the diff and trans AND some way to align the whole thing (the PPF has alignment slots to get things just right).

If you really want to lose weight, perhaps you could recreate the PPF out of tubular steel or drill lightening holes in it.

TL;DR


This.

Sorry i dint know that TL;DR means haah however im gonna pull it in a few weeks and do som measurement, the car is tarmac rally only and it only does arround 1500 miles a year and is a full on racecar. ive searched the ls conversions and i see that they dont use it and on other vehicle they dosnt need it. My car is arround 200 pounds heavier than my competion i need to get that down to at least 100 since on the small tracks they out manuvre me alot on bracking and entering coners. and the PPF will give me at least 40 pounds

40 lbs is not going to happen

The PPF only weighs 31 lbs and you have to add sufficient structure back to support the transmission and differential for rallying purposes. Which means it needs to be even more heavy duty to take abuse a road/track car will never see if making the same modification.

Hmm im gonna have to pull it of i have it writen down to weigh 50 pounds an i figured i need 10 pounds og support. I guess i have to take it down and wieigh again. Thanks for all the replies when the season is over in a month ill get it off and come back to you. perhaps theres a difference in USA and Europe models in the structure of the car. that could be why i see people with cages saying they are down to 22-2400 pounds when mine is still stuck at 2550.

There is a metal plate bolted to it that 'may' be removable. I assumed it was there for NHV reasons.

It is removable, but it won’t buy you much. Might even be a step backwards if it fills up with mud, rocks, etc.

Dont remove the PPF.

As someone who has a good bit of experience trying to keep an RX8 differential in place without one, your opening up a can of worms trying to mount the differential differently, and will never save enough to justify the headache.

The 4.44:1 Differential ratio leads to it applying an incredible amount of force on its mounting as you brake/accelerate. The aluminum dog bone mount is not strong enough to be utilized without a PPF setup. Your looking at heavy steel mounting to keep the differential in place and a marginal reduction in weight.

Ive broken 2 aluminum upper mount bars, and the last experience it tore a 1/4" plate off its front mount, sheared a M12 bolt on the other side and the diff literately fell down from its mounting, slamming the CV's into the subframe brace and pushing the diff to the side which had one CV tear apart and spread parts all over the road. Result was a ruined differential, ruined CV's, ruined driveshaft and I am lucky as the diff nose pushed up it didnt shove the rear U joint through the tank as it heavily damaged the head shield, along with twisting the subframe as it all landed onto the lower support bars.

I wish I could use a PPF with my V6 Setup! Leave it!

That is exactly the kind of answer I was looking for. Also I pulled the thing of and weighed it my self and as stated by teamrx8. The thing only weighs about 35 puound and that’s is almost half off what I had it written down to weigh. So the PPF stays where it is and thank you everyone for your replies.
Dont know how I got the 50-60 pounds weight but it might have been my mate who weighed it when we dismantled it 2 years ago