I truly think that's on the short side of how much it'll cost even buying a used trans and doing the work yourself.

 

I think 3k is probably a good estimate to do what I said, assuming you can fabricate. You're into almost 2 grand between a used tranny and the bell housing. If you follow gutted's list you'd be looking at more like 4-6k and you would be able to keep the PPF.

 

Well to put it into prospective I've figured $10k for a new setup with top shifting and I'm not far off with the est from Taylor Eng. Think the alum trans, top shifter, tilton twin, misc parts, bellhousing are just about $9k +or- and still need drive shaft/crossmember/mount/etc.

 

How fast do you want to go? It's a number that starts with a dollar sign.

 

At least my plan doesn't include duct tape. Oh wait, you said clamp not duct tape. I'm pretty sure with 12" slicks on all four corners my end result would be the same either way. Broken.

 

I just put one and one together. I had a spare gear box with me at Nationals. I wish I had known you all broke. We could have swapped the gearbox out in a couple hours on the Wooten's lift.

 

Thanks! However, it broke on my first run on day two so swapping it out wasn't an option.

 

Not sure how. The clamp would actually end up spreading the load on more area than making a bracket that bolted to the tranny mountin holes on the tranny would. Of course with delrin diff mounts and AWR or delrin engine mount there's really not going to be an serious forces on the PPF anyways.

And I would use safety wire and zip ties, duct tape is for barbarians.

 

 

Subscribed. This subject should not require reinvention of the wheel, there's GOT to be NA/NB Miata's w/Jerico Dog boxes out there.

 

I'm sure they exist in prod racing.

 

So what would guys do with the PPF brace? Just weld up a bracket and bolt it together? Totally remove it and weld up a diff mount/support and tranny mnt? Any ideas out there?

 

With my T5 swap, I bolted the PPF to the new transmission cross member. I assume something simple like that would work with a Jerico.

This is an old picture but you get the idea. Now I have the mount on the back side of the crossmember which gives me more room to adjust pinion angle, and there's some urethane foam spacers (hacked up NB front spring stopper) between the PFF & crossmember instead of being rigidly mounted.


You will need an accurately balanced driveshaft...the PPF does buzzzzzzzzzz like a giant tuning fork.

 

Thx for the pics and that's basically what I imagined. Does that give the PPF enough strength mounted that way?

 

I would hope so, when its mounted like that basically all its doing is holding the nose of the diff up, especially if you have stiffer diff mounts.

 

Yeah I just don't know how much twist 350hp would put on the diff and carrier with 275/15 slicks on the car?

 

Do the math. Figure out how much max wheel torque you put down in first gear. (miata 5 speed is 3.163 first) Assume that PPF is 4 feet long or so.

Summin' like 1000lbs.

 

But you dont know how much of the rotating force the diff mounts are taking, probably almost all of it. Which is why the diff arm with the notch cracks on cars making a lot of torque. The tranny mount and not connecting the PPF to the tranny mount rather than the subframe basically turns the ppf into an overly heavy diff mount. So you'd save some weight nixing it completely and just putting a mount near the nose of the diff.

 

The way I see it, and I could be wrong, is that the miata diff housing sees 2 loads.

1. The twist from the driveshaft trying to rotate the diff housing along the direction of driveshaft rotation. That's taken up mostly by the ears. This should be the driveshaft torque divided by the distance to the ear (divided by two, cause there's two ears).

2. The pinion gear trying to climb the ring gear. that load taken up by the PPF.

I'm not confident on how to calculate #2 but both ways I can imagine it bring me around 1000lbs at the end of a 4 foot PPF pole, using 300ftlbs engine, miata first gear, and ~4:1 diff.

 

Right, there is #2, but if you are already mounting the tranny and not using the PPF to mount the tranny, why does it need to go so far forward.