December 11, 2018, 04:08:08 PM

Author Topic: FC Explorer 8.8 Diff Kit  (Read 131921 times)

Offline Tomo

Re: FC Explorer 8.8 Diff Kit
« Reply #855 on: February 06, 2018, 04:11:14 PM »
It sounds like bad  DS Flange angles to me.

Likely the problem picking up a used kit, unless they had the same front mounts, or everything positioned quite the same way you do, the way it was all welded together is going to be suited for a different driveline angle.

Sounds like its largely to your benefit that you can get the angles to be matching by removing the rubber washers and cranking down on the front mount, but it does sound like clearance to your subframe is the cost. As i see it, you've got 2 options. Grind at the subframe until it clears, or use inserts above the subframe mounts to shim it down. 

The second may not work still given the front mount situation, but it could mean that you can put a rubber washer back in there. you'd keep the same angle but lift the nose off the sub frame.
1990 RX-7 FC LS1 Swap
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Offline DrKarrot

Re: FC Explorer 8.8 Diff Kit
« Reply #856 on: February 07, 2018, 09:29:58 AM »
Thanks so much for the advice! Spacing the subframe down seems like the easiest longer term solution if I want to avoid re-welding the mount, it wouldn't need much spacing to add some nose-down at the pinion.

Last night I flipped the crown washers and cranked the diff up so that it is firmly against the body, and kept the front mount washer. I've got maybe 1/8th of a inch of clearance to the subframe, but its still a degree or two nose up, and I couldn't get any contact even with a couple hard launches and immediate release of power. The serious vibrations seem to have gone away, but I also changed out the u-joints, all of which felt fine, but one had some "burnt" grease inside of it.

I have to drop the subframe to weld up the beginning of some fatigue cracking on the front mount and the passenger side diff arm, I might chop off the front mount and reweld it more appropriately to my car then if I'm feeling up to it.

Offline Drsnoopy

Re: FC Explorer 8.8 Diff Kit
« Reply #857 on: March 04, 2018, 05:30:18 PM »
so today i got around to mocking everything up and despite a ton of reading and looking at pictures it didnt work out as planned. so heres how it went: currently have mazda comp differntial bushings and derlin subframe bushing. i mounted the differntial by the two posts. i then lifted the subframe into place (with the hubs/control arms still attachted). i tightened down the subframe. i now positioned the weld on mount and slid the bolt through. i tightened down on the bolt, when i did this it brought the nose of the pinion down to meet the subframe. when it did this it put the weld on mount on a angle away from the subframe making it misaligned. what am i getting wrong? i was under the impression i was going to have to point the pinion upwards to meet with the subframe. as it sits now it seems the differential sits higher than the subframe. im stumped right now and help is appreciated!

the below pictures show the weld on mount aligned with the subframe and the bolt passing through. as you can see the differential is not leaning against the 3 rubber washers and is infact higher than the mount.
« Last Edit: March 04, 2018, 05:36:18 PM by Drsnoopy »

Offline frijolee

Re: FC Explorer 8.8 Diff Kit
« Reply #858 on: March 08, 2018, 03:55:31 PM »
Hey Dr. Snoopy,

Not sure how long ago you ordered this but we've gone away from the rubber washers and now use the factory Ford isolator.   Since that isolator often doesn't come with your donor diff they're included in all kits sold.  It's Ford XW4Z-4B424-BA if you want to track one down.  (We're not very efficient as a middle man so you probably don't want to order from us).    I think we responded to an email inquiry from you as well, but since it might help other folks I'll add that info here.

=============

Focus on the pinion angle and let the mounts float a bit more if needed.  You might try it with the front mount bolted only finger tight.  Part of the reason we prefer compliant bushings is so they can take up a few degrees of misalignment if needed.  It's also acceptable to shim down the rear mounts or shim up the nose further if you find that helps.

If you have non-stock pieces in your subframe mounting vertical link or bushings that's often suspect as well.  For instance, PBM subframe bushing are thin and raise the subframe.  That's no good with our geometry.

So long as the trans output and pinion axis are nearly parallel (equal and opposite angles), that's what matters.

============

Hope that helps!
-Joel
LS2 stroker FC, Mandeville big brakes, widebody, etc
Build thread:  http://www.norotors.com/index.php?topic=1274.0
www.roninspeedworks.com

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Offline FC355

Re: FC Explorer 8.8 Diff Kit
« Reply #859 on: April 15, 2018, 04:47:15 PM »
Hey guys, Iím test fitting the 8.8 in my FC right now and have a few questions, sounds like Iím about where Drsnoopy left off.  Sorry for the length but want to make sure I get the big picture here.  Appreciate if you all can check me, thanks!
 Components:
Iíve got mazda comps on the diff and level zero delrins on the subframe, stock sublink, small pinion flange.  All other rear suspension parts are off right now, but they include spherical bearing, Ronin camber links, new poly bushings. 

Background: 
Iím hoping to do get this kit done first, which would currently go to the 200-4R automatic transmission right now, which is going to a small block chevy.  Then drive it to my mentorís place to swap the engine to a small block we built, then worry about getting the T56 in there, followed by getting a new driveshaft, resetting the pinion angle, and getting someone to weld it.  It sounds like it is feasible to get it driving without doing the welding first?  Or is it a lot safer to install the T56 before driving the car to swap the engine?

Driveshaft question/suspension:
My current DS is way too short, so do I need to put the rest of the suspension components (camber link, toe control hub, axles, etc.) back on to put the car on the ground to measure for a driveshaft?  Or while the car is on 4 jackstands, just measure the diff to the output shaft?  I was thinking buy the driveshaft after I figure the pinion angle and put everything back on.

 Fitment:
1-   Differential.  So here Iím just using washers to find the right pinion angle to pair with the output shaft of the transmission?  In my pics I snugged it down as a starting point, I'm assuming this is problem #1.
 
2-   Subframe. 
-I snugged it down as well and in the current state, it hits the front mount isolator and will not rise high enough to line up with the stock sublink. 
-The small pinion flange fits however (If I were to clearance the isolator however, the flange would hit the subframe). 
-The front support hole is not lining up with the subframe hole.  I assume I need to get the rest figured out first, then this should fit better anyway/require a little trimming maybe?

Offline Supe

Re: FC Explorer 8.8 Diff Kit
« Reply #860 on: July 03, 2018, 10:24:22 AM »
Anyone have issues with the outer CV's slinging grease badly?  I ordered a replacement boot and clamp kit from Ronin, but I'm worried that the mild pitting/corrosion on the outer CV will not let them seal properly.  The inside of my wheels and my hubs were absolutely caked in grease after the last race.

Offline largeorangefont

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Re: FC Explorer 8.8 Diff Kit
« Reply #861 on: July 04, 2018, 01:44:31 PM »
Yea, I had that problem. I think it was from brake heat.

I vented the small side with a small piece of WD40 red straw. I used some black RTV to fill the gaps. I cleaned and re strapped the large side of the outer. It has been good ever since.
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Offline Supe

Re: FC Explorer 8.8 Diff Kit
« Reply #862 on: July 04, 2018, 10:52:30 PM »
Yea, I had that problem. I think it was from brake heat.

I vented the small side with a small piece of WD40 red straw. I used some black RTV to fill the gaps. I cleaned and re strapped the large side of the outer. It has been good ever since.

I had a huge rear brake bias issue, so that may be the case.  Will try the RTV first and vent the small end if need be, thanks.

Offline onefastrx7turbo

Re: FC Explorer 8.8 Diff Kit
« Reply #863 on: November 10, 2018, 10:57:33 PM »
Just a sanity check. I did my driveshaft measurements and here is what I came up with:

From the transmission face to the 8.8 differential flange, I got 38 1/2 inches with the shaft sticking out 5/8s inch. Does this sound right?
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