March 17, 2025, 07:08:42 PM

Author Topic: Strange crack on FC diff front mount  (Read 2613 times)

Offline FC3S Murray

Strange crack on FC diff front mount
« on: December 29, 2012, 02:38:23 PM »
Was leaving work last friday and did a nice 2nd gear pull and started to get a little wheel hop. Right when I let off the gas i heard a noticeable bang...wasn't to loud but enough to get my attention.  Right away I was like, "well there goes the diff mount finally lol".

I kept driving and had no clunking when shifting and even did some more WOT pulls in 1st-2nd-3rd dropping the clutch hard each time just to see if I did break the bastard.  To my surprise no clunk or bang. Thought I may have lucked out.  :gruffy:

So yesterday I had to change the oil and perform some routine maintenance. I put it up on jack stands in all four corners. I decided to take a look at the diff mount since the car was in the air.

I counldn't get a good picture due to the angle and my exhaust being in the way but I found these pics on the other forum and drew a red line to show you where the crack is:



...Looks like the bottom half liberated itself BUT to my understanding and my inspection the actual diff mount is still intact and doing its job correct

Look at this new mount:


It looks like it cracked where those 2 pieces mate together on the bottom of the mount.


I wonder if I cracked this OR if this original 24 year old mount just rotted away and seperated over time?  Most broken mounts from our "8 rotors" either break off the tab mount on the subframe or rip the rubber from the vertical diff mout bracket off.

What you all think?




13 years of abuse and still running STRONG!

SRM Performance Tuning LLC
https://www.instagram.com/fc3s_murray/?hl=en

Offline largeorangefont

Re: Strange crack on FC diff front mount
« Reply #1 on: December 30, 2012, 11:46:04 AM »
I would go with the 24 year old mount finally let go due to the added power. That is an odd failure of the diff mount though.

If you grab the front of the diff does it move up and down?
Quote from: cool
Sell it to spacevomit.  He'll finish it.

Offline FC3S Murray

Re: Strange crack on FC diff front mount
« Reply #2 on: December 30, 2012, 12:07:06 PM »
no movement at all. That is why I think it may be dry rotted.



13 years of abuse and still running STRONG!

SRM Performance Tuning LLC
https://www.instagram.com/fc3s_murray/?hl=en

Offline largeorangefont

Re: Strange crack on FC diff front mount
« Reply #3 on: December 30, 2012, 12:47:59 PM »
I would replace it proactively. Driving around with it broken will be hard on the U joints of your driveshaft.
Quote from: cool
Sell it to spacevomit.  He'll finish it.

Offline Bowtie7

Re: Strange crack on FC diff front mount
« Reply #4 on: December 30, 2012, 02:00:24 PM »
I dont think that it is broken due to what you are showing. The rubber block is what normally breaks in shear. If it is original you def cant hurt anything by replacing. Go with the higher durometer part from Mazdaspeed.
I do love what I do!

Offline FC3S Murray

Re: Strange crack on FC diff front mount
« Reply #5 on: December 30, 2012, 06:25:51 PM »
I dont think that it is broken due to what you are showing. The rubber block is what normally breaks in shear. If it is original you def cant hurt anything by replacing. Go with the higher durometer part from Mazdaspeed.

Thanks for the tip guys, ALWAYS appreciated. I was actually just looking at that Mazdaspeed mount...you use it? They say it is 40% stiffer and I wonder if anyone here as ripped that one.  $104.00 is not too bad I suppose.



13 years of abuse and still running STRONG!

SRM Performance Tuning LLC
https://www.instagram.com/fc3s_murray/?hl=en

Offline largeorangefont

Re: Strange crack on FC diff front mount
« Reply #6 on: December 30, 2012, 10:12:01 PM »
The OEM mount is more than the Mazdacomp mount.
Quote from: cool
Sell it to spacevomit.  He'll finish it.

Offline ncaudio

Re: Strange crack on FC diff front mount
« Reply #7 on: February 04, 2013, 05:45:14 PM »
the mount on my '88 FC L33 CAI T56 T2 rear end sheared a while ago. I read Bikedad's thread on dropping the rear subframe and welding up 2 bars to reinforce it, but still leave a little movement capability, but it looked like a lot of work, so here is my solution>

First off I have to preface this by saying if I read someone did this I'd probably think they were crazy and "it's not the right way to do it" but it works really well and costs very little.

There is not a lot of room between the top of the diff nose and the bottom of the chassis, not sure if the coupes are different than the verts, but anyway, the rubber mount on the side was clearly sheared, when readjsuted and retightened the mount bolts weren't holding and the diff was flopping up and down and hitting the underside rubber snubber which is about 1/2" above the diff nose.

I had a big hunk of truck tire scavenged off the side of the highway saved for just this application. I cut a big chunk of it out, (maybe about 3X6) cut and ground a low spot to fit around the chassis pinion snubber and under the cross brace on the underside of the chassis, used a bar to push the diff nose down a little, fitted it into place and secured it with a big hose clamp.
 
No more problems and I didn't notice any extra chassis noise, launches are a lot smoother with no wheels hop, Yeah

I'll probably get a lot of crap about it on the forum and if someone looked at the big hose clamp around the diff nose, they'd probably think WTF, but it works great, I could have screwed the pad to the underside of the chassis, but the hose clamp was a lot faster, saved $100 and it will never shear   ;)
'88 FC LS T56, 94 FD LS T56, '93 FD was LS turbo T56 Ford 8.8 IRS Ablake's old car (project)

Offline FC3S Murray

Re: Strange crack on FC diff front mount
« Reply #8 on: February 07, 2013, 10:14:19 PM »
I just replaced my OEM front diff mount with a mazdacomp unit last week......that was fun .

Anyway, my oem mount was not broken. That pictured area I previously posted was just slightly dry rotted. Damn thing actually looked to be in great shape given its age.......I needed to get familiar with dropping my rear subframe anyway lol.

I did however transfer my oem front rubber block from my old mount to the empty mazdacomp bracket. Figured it was needed for harmonics.



13 years of abuse and still running STRONG!

SRM Performance Tuning LLC
https://www.instagram.com/fc3s_murray/?hl=en