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post #1 of 23 (permalink) Old 06-07-2004, 05:55 PM Thread Starter
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Rear differential mount issues

I have a set of the poly front differential mounts and the tranny/crossmember mounts on the way (thanks mn12 performance!!!), and I'm looking at how the metal and rubber have separated on my rear differential mount. I've read the 11 threads a search came up with, and found only a few guys that ran a large (1/2") bolt through the rear mount. Not much in the way of feedback on the durability of this, other than CobraR Thunder's info about driveline vibration lessening.

Anyone else have any results to report?

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post #2 of 23 (permalink) Old 06-07-2004, 06:06 PM
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What do you mean by durability? If you use a heavy duty bolt, you don't really have to worry about it.
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post #3 of 23 (permalink) Old 06-07-2004, 06:16 PM
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Actually...this is what hes talking about.....



And this is what it got me.....



Heres how it happens. The rubber (that deteriorates) absorbs the shock of the drivetrain. Which is less in automatics then in my 5-speed. Well when the rubber goes, the mount flops around in the brace. So thats why i put a bolt in it. BUT.....that left no rom for shock absorption. So something had to give, and it ended up tearing the stamped sheet metal like paper. Try Wynn over ot www.texasthunderbirds.com I just ordered one of his custom made heavy duty mounts.


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post #4 of 23 (permalink) Old 06-07-2004, 06:17 PM
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Honestly I wouldn't trust it just because bolts are not meant to be used in that manner. What I mean is that installing a bolt like that puts shearing forces on it but its intent is to withstand tension forces.

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post #5 of 23 (permalink) Old 06-07-2004, 06:55 PM
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Wow, I've never seen these before!

My factory mount is shot, alot of the rubber is missing, and I'm sure that's contributing to some of my wheel hop. Not to mention clunking. Wonder why Bill E. doesn't carry this piece - I got alot of poly stuff from him recently?

Oh well - I've just emailed my order for a piece - putting a bolt in there doesn't look like a good long term solution to the problem.

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post #6 of 23 (permalink) Old 06-07-2004, 09:02 PM
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Quote:
Originally posted by miller1995
Honestly I wouldn't trust it just because bolts are not meant to be used in that manner. What I mean is that installing a bolt like that puts shearing forces on it but its intent is to withstand tension forces.

-Miller
Thats what I pointed out in my post. It was, at the time, a quick fix to a nasty clunk because the rubber went to Pooo.

I would not recommend this in a high HP application. But if you are just the average bolt on guy, and most of you are running automatics....you should be fine.

I run stickies out back, and power shift all the time. SO, I had it coming. But its only fun when you break stuff. Plus the lady friend doesnt let me put money into the car hardley at all anymore.....so I practically have to break the parts If I want to upgrade

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post #7 of 23 (permalink) Old 06-07-2004, 09:15 PM
 
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My OEM rubber rear diff. mount looked as good as the day Ford installed it. With the OEM rear mount & poly front diff bushings, I still hopped Bad (5-spd car). How many people do you know who hop the 2-3 shift?

Anyway, I installed one of Wynn's (Tbird88) poly rear diff mounts. It helped some, and for the price is a GREAT DEAL!!!!!!!!!

I also now have the mn12performance IRS pinion brace on my car now. It helped the most, but I can still get a fair amount of hop on the street. Haven't taken the car to the track yet to test the anti-hop capacity of the IRS brace.

The poly front diff mounts (by themselves) didn't help much, if any.

With poly front & rear mounts & the IRS pinion brace, I'm confident that the diff. isn't dancin' around back there. Sooooooo, the source of HWH is NOT a changing pinion angle, as it is in solid axle cars.

I still believe that the source of HWH is the large squishy sub-frame bushings. I believe that the whole subframe is hammering back & forth.

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post #8 of 23 (permalink) Old 06-07-2004, 09:30 PM
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I installed the ADDCO 1-3/8" rear bar the other day and was out testing the bar on launches...I think the bar helped out a TON. But, I didnt get to take it to the track and see what it did on the hot rubber, before I knew something was broke back yander.

So, wheel hop was down with the bar...then the mount broke. I also have the IRS bushings, AIR bags, and Knuckle bushings. After I get the mount from wynn...I will test. If that doesnt stop it enough, I am going to try the pinion brace. And I am running sticky tires at the track.

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VORTECH BLOWN w/3.12" Reichard ultra-grip pulley
TEA Stage2 PI Heads, 9.5:1 manley slugs/manley H-beams, cobra crank, VTStage3 blower cams, Trick Flow track heat intake, FMIC TR1245 intercooler, ART Dual 2.5" exhaust/Stainless/no cats, KOOKS coated headers, 4.10 w/ Auburn Pro, aluminum 8.8 housing, Dynotech driveshaft, Koni's, Eibach Springs, Baer 13" big brake kit. cobra rear brake/hub conversion, VMP Slot Blowthru setup, #60 Inj. 75mm TB,
615 rwhp/500 torque 15.5psi best of [email protected] still needs tuning.
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post #9 of 23 (permalink) Old 06-07-2004, 11:07 PM Thread Starter
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I love this place... Exactly the discussion I was hoping for here. Thanks for the info.

As you can see from my sig, I'm not exactly high in the power range, but after seeing the torn up bracket in CobraR's other post, I figured I'd see if anyone else had problems. I understand the bolt (even grade 8) isn't really designed to take shear force, and it's tough to get much clamping force through the rubber. It does seem, at first thought, to be a usable crutch until poly or solid welded mounts are available. In the thread I found where Wynn made his poly-lined mount, he said he wasn't ready to make them for anyone, other than the one that went to Canada.

I love the way the Dennis R tranny shifts, especially with his chip, but I'm concerned about destroying the rest of the driveline. Rich at mn12 performance told me today that he's working on something for the rear mount, but it's not ready yet, and a Ford mechanic in the Memphis SVTOA was telling me that he's seen a few Cobras with broken rear covers, like racecougar's. I have a lot of miles on mine, so I figure it's due anyway, even though the car has never really seen any salt. I want to make sure the suspension is set up right before I get to the next stage, which is some intake work, the Mk 8 converter, and MM driveshaft, since the chip bumped up the shift points to higher than the stock torque converter is rated to. After seeing the shape the rear mount is in and noticing the new, higher shift points, I'm leery about going to the track again until I fix a few things.

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post #10 of 23 (permalink) Old 06-07-2004, 11:19 PM
 
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Quote:
Originally posted by CobraRThunder
I installed the ADDCO 1-3/8" rear bar the other day and was out testing the bar on launches...I think the bar helped out a TON.
Any rear (anti) sway bar will only help HWH if the wheels are hopping vertically, and NOT in sync. with each other. I believe that our HWH is fore/aft, not up/down. Fore/aft hopping would also contribute Greatly to a busted sway bar mount.

I also have the 1 3/8" F&R sway bars. They make my car handle GREAT, but did Nothing to help or cure HWH.

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post #11 of 23 (permalink) Old 06-07-2004, 11:23 PM
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I seriously doubt you will ever break the bolt you put in there. Clamping force is not needed either, just enough to keep the bolt in place. its up and down motion mainly, not side to side. Chris

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615 rwhp/500 torque 15.5psi best of [email protected] still needs tuning.
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post #12 of 23 (permalink) Old 06-07-2004, 11:41 PM
 
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Quote:
Originally posted by CobraRThunder
its up and down motion mainly, not side to side
The diff. motion is vertical (actually rotational). The wheel hop is fore/aft.

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post #13 of 23 (permalink) Old 06-09-2004, 09:26 AM
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I never noticed ANY wheelhop on my 5.0 92 w/4.30's, until I put in a rear SC sway bar, Eibachs, and Koni's on their stiffest setting.

Now I get it all the time! Now the rubber may have just given up with all the additional strengthening the car's got.

Does anybody know if the Texas T-Bird guy still sells the differential brace? Emailed him a few days ago and haven't heard anythin, just sent another. Damn I'm impatient eh ?
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post #14 of 23 (permalink) Old 06-09-2004, 10:47 AM
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he sells the rear differential mount all beefed up. His name is Wynn Carter. Give him a call from the number on the website.

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VORTECH BLOWN w/3.12" Reichard ultra-grip pulley
TEA Stage2 PI Heads, 9.5:1 manley slugs/manley H-beams, cobra crank, VTStage3 blower cams, Trick Flow track heat intake, FMIC TR1245 intercooler, ART Dual 2.5" exhaust/Stainless/no cats, KOOKS coated headers, 4.10 w/ Auburn Pro, aluminum 8.8 housing, Dynotech driveshaft, Koni's, Eibach Springs, Baer 13" big brake kit. cobra rear brake/hub conversion, VMP Slot Blowthru setup, #60 Inj. 75mm TB,
615 rwhp/500 torque 15.5psi best of [email protected] still needs tuning.
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post #15 of 23 (permalink) Old 06-20-2004, 10:37 PM Thread Starter
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Update to my differential mount issues...

Looking under the back of the car, I had my wife take it from Park to Reverse and Drive, and noticed the differential bracket moved up and down almost a 1/2 inch in either direction.

I e-mailed Wynn at Texas Thunderbirds, and he's short on cores to make the poly-filled rear diff mounts, so I decided to bolt mine tight. To eliminate shear force as an issue, I installed (vertically) two 3/8", 1.5 inch long, grade 8 bolts from Lowe's, located fore and aft, and used more grade 8 flat washers as shims between the two metal u-shaped pieces in the rear mount. I also installed the poly front differential mounts from MN12 Performance. So far, no problems, and my seat of the pants meter isn't that well calibrated to say it's an improvement, but the differential doesn't move anymore when going through the gears while stopped. All of the shifts seem a little firmer now, too, not just the 1-2.

I also put in the solid rubber tranny mount, but I couldn't get the tranny crossmember out, due to the exhaust pipes and floorpan, so the poly crossmember bushings will have to wait until I swap torque converters someday.

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post #16 of 23 (permalink) Old 06-30-2004, 12:57 AM
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I sent Wynn an e-mail about 2 weeks ago now asking about his rear diff mounts, and if he needed a core or not. I got a brand spanking new rear Diff mount form Dan, $32.95 THANKS DAN! Now I just need to hear back form him to have him do his magic to it, rather a good one that'll last a while than put another crappy one in and have to replace it sooner.

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post #17 of 23 (permalink) Old 06-30-2004, 02:49 PM
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But there is a difference in the early model rear diff mounts and the late model. The early model units are thucker metal and much better design. The late model ones are a thinner metal and thus the reason my mount tore. But, after Wynn does what he does to it, I doubt you will ever do what i did to mine. Chris

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VORTECH BLOWN w/3.12" Reichard ultra-grip pulley
TEA Stage2 PI Heads, 9.5:1 manley slugs/manley H-beams, cobra crank, VTStage3 blower cams, Trick Flow track heat intake, FMIC TR1245 intercooler, ART Dual 2.5" exhaust/Stainless/no cats, KOOKS coated headers, 4.10 w/ Auburn Pro, aluminum 8.8 housing, Dynotech driveshaft, Koni's, Eibach Springs, Baer 13" big brake kit. cobra rear brake/hub conversion, VMP Slot Blowthru setup, #60 Inj. 75mm TB,
615 rwhp/500 torque 15.5psi best of [email protected] still needs tuning.
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post #18 of 23 (permalink) Old 06-30-2004, 03:05 PM
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This is how mine looks now. (without the bolt through it) Bottom part of rubber missing.
Quote:
Originally posted by CobraRThunder


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post #19 of 23 (permalink) Old 06-30-2004, 04:44 PM
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Quote:
Originally posted by Al_Florida
This is how mine looks now. (without the bolt through it) Bottom part of rubber missing.
That's what my new one from Dan looked like.
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post #20 of 23 (permalink) Old 06-30-2004, 04:45 PM
 
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Couple dumb questions probably, but, are you able to drill the mount for the bolt while its in the car, or does it all have to be taken out? Also, how can you tell by looking if the mount is shot? I have a 95 LX and it seems to clunk back there when downshifting coming up on a stop at times. I was under the car the other day installing a bad MLPS and looked at the mount. The rubber looked all there on one side(rear I believe), but has a big gap like some is missing on the front side down at the bottom. Going to sell the car before long and thought this may be a cheap fix for the occassional clunk. By the way, I noticed the clunk after installing my Transgo shift kit on stage 2 a couple years ago and scratching the tires into second alot . Something has got increasingly looser.... lol Thanks!!!
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post #21 of 23 (permalink) Old 06-30-2004, 11:07 PM
 
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How much vibration does that bracket actually see/absorb? I've been toying with the idea of making a rigid solid mount. I know you wan't some movement in the driveline, up front anyway, or stuff starts to snap. Anyone see any problems with makig a solid read diff mount?
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post #22 of 23 (permalink) Old 07-01-2004, 07:03 AM
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Ah finally got ahold of Wynn, talked to him on the phone this time, Really nice guy too. My new mount is going in to get his magic done this week.
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post #23 of 23 (permalink) Old 07-01-2004, 10:10 AM
 
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Reduces HWH!!!!!!

Quote:
Originally posted by BIG PERV
Ah finally got ahold of Wynn, talked to him on the phone this time, Really nice guy too. My new mount is going in to get his magic done this week.
You won't regret it! I primed & painted mine with rustoleum. I could immediately tell that I had less HWH after installing his poly rear diff mount.

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