FC Explorer 8.8 Diff Kit

[ebdyguy]

The pmb pieces are interesting - but the way I read their info is that you  "must" use their solid diff mounts if you use the spherical ball subframe mounts.  It sounds like it is ok to use only their solid diff mount alone which indicates that the geometry is not changed though.

Good luck with the spherical mount - let us know how they work out.

[frijolee]

Jeff,

Glad you're getting this squared away.  I'll update the install instructions with some stronger language regarding what needs to happen with solid mounts.  They're unforgiving in terms of letting you rotate the diff up to land where it needs to.  Since the rear mounts are from above, rocking the diff up also pushes the front mount on the housing forward.

-Joel

[eage8]

Appreciate the responses, I went ahead and ordered the diff mounts, and the pbm sub frame mounts.

You're right, $200 for 2 sub-frame mounts is silly.

Hoping this will remedy my issue.

I'll update in the next week or so when they arrive and I get a chance to test it.

The PBM subframe bushings raise the subframe a bit to attempt to correct geometry (that probably doesn't need correcting imho).  Their subframe bushings don't have a top to even this out.  you might run into additional issues running mazda diff bushings with PBM subframe bushings.

Bowtie7 on this forum sells a spacer for the PBM subframe bushings to make them stock thickness again.

[RX7V8Builder]

I have the Mazdatrix Pro Differential bushings and PBM spherical bushings in my setup now.  I am also using the spacers made by Bowtie7 on top of the PBM sphericals to make them the same height of the original subframe mounts. I also run the PBM camber arm to aid in camber adjustment


I used to have solid subframe mounts with the Mazda Pro differential bushings and the stock subframe camber arm when I first installed my 8.8.
Everything lined up perfect during the original install and continued to be the same after the installation of the MAX spherical subframe mounts and adjustable camber arm.


A 5/16" misalignment seems a bit too much, specially when nobody else has run into this issue before.  Is there a possibility your subframe could be bent?

[Heffe]

I have the Mazdatrix Pro Differential bushings and PBM spherical bushings in my setup now.  I am also using the spacers made by Bowtie7 on top of the PBM sphericals to make them the same height of the original subframe mounts. I also run the PBM camber arm to aid in camber adjustment


I used to have solid subframe mounts with the Mazda Pro differential bushings and the stock subframe camber arm when I first installed my 8.8.
Everything lined up perfect during the original install and continued to be the same after the installation of the MAX spherical subframe mounts and adjustable camber arm.


A 5/16" misalignment seems a bit too much, specially when nobody else has run into this issue before.  Is there a possibility your subframe could be bent?

No, I don't think my sub-frame is bent.

Your setup is was a bit different from mine, I have solid sub-frame, and diff mounts.

I do have the pbm camber arm as well.

Once the comp diff mounts, and pbm sub-frame mounts get here I will test fit again. Also should probably get the spacers you are talking about.

[largeorangefont]

Just to reiterate..

If you ordered PBM subframe mounts you need to PM Bowtie7 and get his spacers for the PBM subframe bushings. The PBM subframe bushings raise the subframe in the chassis, and will cause extra problems with the pinion angle for you unless you space them down to a stock height.

[Heffe]

Yeah, apparently my bad luck continues, PM'd him last night, he has none left.

Anyone have a picture of these things so I can possibly make my own?

I'm about over rx-7's haha, such a colossal pain in the ass to get anything done.

[largeorangefont]

They are very simple Delrin or UHMW spacers.

Contact these guys Via Ebay. They have or did have subframe mounts. Their diff and subframe mounts may be interchangeable, I do not remember for sure.

http://www.ebay.com/itm/Rx7-Rx-7-FC-Rear-Solid-Differential-Mounts-Turbo-FC3S-/110906828507?pt=Motors_Car_Truck_Parts_Accessories&hash=item19d28fe6db&vxp=mtr

[Bowtie7]

They are very simple Delrin or UHMW spacers.

Contact these guys Via Ebay. They have or did have subframe mounts. Their diff and subframe mounts may be interchangeable, I do not remember for sure.

http://www.ebay.com/itm/Rx7-Rx-7-FC-Rear-Solid-Differential-Mounts-Turbo-FC3S-/110906828507?pt=Motors_Car_Truck_Parts_Accessories&hash=item19d28fe6db&vxp=mtr

Ash, those are the standard Delrin subframe bushings. The pieces we had done drop in to the upper portion of the PBM 2 piece bushings to make them stock thickness. PBM bushings were made to raise the subframe up for the slammed drift cars effectively changing roll center but not really in a good way for us especially when running bigger tires. I think I had some pics of bushings on here somewhere.

[ebdyguy]

Just posting a couple pics of my clearanced subframe only because I stiffened it a little different than most have done.

Since the subframe flexes pretty easily before all the material is removed I deffinitely think that something does need to be added to stiffen it back up after clearancing it for the 1350  u-joint.  I chose to add the stiffeners on the front and back vertical surfaces using 3/16 thick material.  They are a minimum of .75" tall which basically is 2.5x stiffer than a 4 inch wide x 1/4" thick plate that most people have used.

The parts were a bit of a pain to make though because of the curvature but I think they came out OK.

[largeorangefont]

They are very simple Delrin or UHMW spacers.

Contact these guys Via Ebay. They have or did have subframe mounts. Their diff and subframe mounts may be interchangeable, I do not remember for sure.

http://www.ebay.com/itm/Rx7-Rx-7-FC-Rear-Solid-Differential-Mounts-Turbo-FC3S-/110906828507?pt=Motors_Car_Truck_Parts_Accessories&hash=item19d28fe6db&vxp=mtr

Ash, those are the standard Delrin subframe bushings. The pieces we had done drop in to the upper portion of the PBM 2 piece bushings to make them stock thickness. PBM bushings were made to raise the subframe up for the slammed drift cars effectively changing roll center but not really in a good way for us especially when running bigger tires. I think I had some pics of bushings on here somewhere.

Agreed Charlie. I was just offering the guy other possible avenues to get this fixed, as using the PBM subframe  bushings on their own, without your spacers will cause more problem than it solves.

[bikedad]

Another happy Ronin Speedworks customer. 

http://youtu.be/J_tZq8kzQ4E

[Heffe]

I'm insanely jealous.

Grats on getting yours working!

[largeorangefont]

You'll be selling another one of these soon Joel. Robert blew up his Turbo diff today at Willow Springs.

[eage8]

My kit is finally done an installed!

a few notes of things I found.

- How to make a driveshaft (fairly rotary specific, but my still be useful to some)
http://www.rx7club.com/2nd-generation-specific-1986-1992-17/how-make-your-own-aluminum-carbon-driveshaft-1081644/

- when setting the pinion angle, it's a pain in the butt to actually measure the pinion angle, and measured the angle of the ronin mounting ears and it worked great.  Your results may vary...

- Motive Performance 5.14s are loud as crap

- grease your u-joints before you install the driveshaft...


autocross this weekend to test it out!