Forums/Z31P/z31-performance-upgrade-forums driveline-aa/Broken Poly diff mount
Imported from Z31Performance.com Forums{{#if:Shady195| — original post by Shady195}}{{#if:2009-08-14 22:35:04|, posted 2009-08-14 22:35:04}}{{#if:29| · 29 post{{#ifeq:29|1||s}}}}{{#if:/Z31performance_archive/forum/z31-performance-upgrade-forums/driveline-aa/8153-broken-poly-diff-mount.html|
Local archive: view archived thread on dev.z31library.com}}
Shady195: (2009-08-14 22:35:04)
I e-mailed jason about it and have heard about ti happening to a couple other members.
Went to the track for the 3rd time ever today with this mount on. Did a quick spin at 5 grand nice and smooth put the clutch in and coasted to the staging lights. To my suprise the track official was telling me to stop and cut my engine. I get out look behind and see gear oil everywhere along with my drain plug. See my diff hanging down and pushed the car back to the pits..
My subframe looks twisted and the wheels are sitting inwerds, i dont know if my axles are trashed yet and the diff casing is completely cracked.
anyways i dont blame jason but either way it sucks as I probably cant afford to fix it ATM..
sprtcrazy17: (2009-08-14 23:25:25)
This is what sucks about aftermarket parts.
ZFast88Z: (2009-08-15 03:11:51)
Poly crossmember bushings? Poly control arm bushings?
Racinjitter: (2009-08-15 03:36:00)
Did you notice any wheel hop while doing the burnout? I know quite a bit about this issue… But it never happened to me.
Shady195: (2009-08-15 03:59:54)
Right as it was winding down it hopped a few times.. I belive this was due to the diff mount breaking
I have new OEM bushings.. when the rear end went on the car when my dad owned it the replaced them.. they are completely torn as of now from the subframe dipping down.. IIRC Keven had poly mounts in his and it snapped in the exact same fashion as mind did, even jason stated its a possible issue as its the weak point of the mount.
When i bought the mount last year jason recommended using his IRS bushings with it when i emailed him.. now i see he lists "must be used with them" as this was one of my concerns when purchasing it… Unfortunatly i cant find the email but he said it should be just fine.. my rear end was making a horrible clunk with my old mount and the new one solved this issue.. Also I belive jason pulled the poly diff stock due to this issue and trying to prevent further issues with customers.
The drain plug came out because when the diff mount broke and hit the ground it cracked the rear diff cover and diff casing causing the plug to just fall out .. Unlike kevin i did not have an exhaust to help keep it up
While I do believe poly bushings would have prolonged the use of the rear diff mount i think its inevitable that it would have happend without a completely solid drivetrain setup
Either way im out some coin for this which i dont know if i will be able to get the car back on the road this year…
Itd be nice if Jason could send me a new mount,due to this being now a known issue and him himself knowing its a little weak in that spot id imagine hed replace it for me.. if not oh well i dont have poly IRS bushings so its completely up to him.. either way i was under the impression id be fine without them from a convo i had with jason when i purchased it
I still think its a great product as it seems to be working for many people.. just a few of us go very unlucky
Untill jason comes out with a new revised mount I will probably go back to a stock one for now
ZFast88Z: (2009-08-15 16:35:07)
The use of OE rubber bushings (even new) is never recommended when using poly mounts. Poly engines should always be paired with poly transmission. Poly Diff always paired with poly crossmember and rear suspension bushings.
Im 99% certain that you didnt wheel hop because the diff mount broke, but broke the diff mount because you wheel hopped. More then likely the diff mount was stressed/fatigued and wheel hop is what finished it off.
NissanEgg: (2009-08-15 16:51:29)
Instead of the making the angle "L" portion of the mount in aluminum, swith the "L" to a 1/4" or even 5/16" thick steel.
Not hard to make, just need the length of each leg of the "L", and overall length, then decide on which thickness you want and drill holes as necessary and notch and contour as needed. Should hold up to torque alot better than aluminum.
Crazy: (2009-08-15 19:07:30)
[quote]ZFast88Z wrote:
While I do believe poly bushings would have prolonged the use of the rear diff mount i think its inevitable that it would have happend without a completely solid drivetrain setup
Itd be nice if Jason could send me a new mount,due to this being now a known issue and him himself knowing its a little weak in that spot id imagine hed replace it for me.. if not oh well i dont have poly IRS bushings so its completely up to him.. either way i was under the impression id be fine without them from a convo i had with jason when i purchased it
The use of OE rubber bushings (even new) is never recommended when using poly mounts. Poly engines should always be paired with poly transmission. Poly Diff always paired with poly cross member and rear suspension bushings.
Im 99% certain that you didnt wheel hop because the diff mount broke, but broke the diff mount because you wheel hopped. More then likely the diff mount was stressed/fatigued and wheel hop is what finished it off.
I agree,wheel hop destroys everything. I used my stock mount. I pressed it together in a vise and welded it solid. It works great.
Shady195: (2009-08-15 19:37:26)
Like I stated before, When i talked to jason about my rear end issue when he directed me to the poly diff mount he said hed recommend using his IRS bushings with it but it should be fine without it… I belive this was before anyone had an issue with the bracket snapping at the "L"
However I do belive this would have happen regardless of weather or not I had poly bushings or not as Kevins snapped in the exact same fashion as mine did earlier this yea with his poly bushings. It would have just taken a little bit more of abuse before snapping.
.... Now at least I have a good reason to get underneath and change everything out and even possibly move to solid rear IRS mounts if I can find some. In the long run I'd like to have every mount in the car converted over to solid.
Like I said I don't blame Jason at all it happens especialy with products such as his which are not mass prodeuced and tried and tested liek some parts for bigger platforms are.
Whitesmoke: (2009-08-15 21:12:31)
I always recommend to everyone, solid crossmember, solid differential mount.
Virtually eliminates wheelhop, car feels MUCH more agile.
SATAN: (2009-08-22 15:46:18)
This is what I did out of 3/8" steel L angle. 3/8" is WAY over kill, but it is what I had laying around. But again, as has been stated many times now, all of your mounting points should match in what they are mounted with.
On a side note though. If you are using 3/8" aluminum L angle, it would be plenty strong as well, as the cover on the LSD is only made out of aluminum and not steel.
Jason84NA2T: (2009-08-22 22:08:26)
Yup, live and learn… there have been 3 reported failures out of the 100+ sold. While the stress should have been low enough and the AL thick/strong enough to not flex (and hence not fail) in normal conditions, the additional stress from stock crossmember bushings is a factor, as is wheel hop, driveline shock loads, or any other conditions. No excuses: the longer-term testing proved that the design needed revision. The new version of the diff mount is all steel, no aluminum and is a captured mount so it cannot fall free. We are offering a NO CHARGE replacement of the angle bracket for anyone who purchased one of the older mounts as well as a discount on upgrading to the new mount design. Have yet to send out e-mails to customers and put a notice on the website about it…
New version:
[archived image: diffmount20.jpg]
Old version:
[archived image: Z31Partsdiffmount.JPG]
Matt89: (2009-08-23 23:09:31)
Overkill is good.
Rick88ss: (2009-10-21 07:37:21)
If I'm using solid rear crossmember mounts should I use a poly diff mount or a solid diff mount?
Will either be OK?
Matt89: (2009-10-21 13:51:36)
You need to use a solid diff mount.
matico40: (2009-10-21 16:44:26)
I saw it too over at TRs house…OMG!!! it's heavy as hell too [archived image: smile.png]
Jason84NA2T: (2009-12-12 21:53:13)
Z31Parts is now offering an upgrade for all V1 mount owners to fix the potential angle failure issue. You can select from the simple upgrade angle for durability, or the Version 2 Upgrade Kit which converts your V1 mount to V2 spec. Please see the V2 Poly DIff Mount description here for more information:
http://www.z31parts.com/polyparts.html
Turbo86: (2010-04-10 18:56:30)
OH WOW! That is SCARY :shock:
I have been running Jason's poly engine, transmission, diff, and rear crossmember bushings as well as the Z31R type 2 springs and poly spring seats in my '86 Z since early 2008. I am very glad that I came across this post by chance otherwise I never would have known about the possible catastrophic damage that the mount can allow to happen, although I do have poly throughout so chances should me much less for my application based on what I have read. I've never been to the track in my Z or any car for that matter, but I have done a burnout or two but nothing major. I have been more than satisfied with all of the parts I purchased from him and I am very glad that he is willing to provide the upgraded mount for free. I am actually considering "upgrading" to the newer design as well. My stock diff is about to give out, so this new discovery definitely increases the priority of replacing that at the same time…if only I could find an LSD at a decent price.
DudeZX: (2010-04-18 06:32:26)
Broken diff mount crew. Where's my membership badge?
[archived image: 004.jpg]
[archived image: 005.jpg]
Looks like the mount and the axle boot were the only casualties. Was able to limp it home.
My Z does have all poly bushings, including the rear crossmember.
DeleriousZ: (2010-04-18 07:23:05)
dang is that 1/4" aluminum?
DudeZX: (2010-04-18 07:38:18)
Mine was the original version, without the upgraded L bracket.
I'd like to get the V2 conversion asap, guess I'll have to shoot Jason an e-mail and hope he gets back to me.
Racinjitter: (2010-04-18 16:20:19)
Yea, either 1/4" or 3/8" aluminum angle stock.
DudeZX: (2010-04-22 03:01:07)
During my initial inspection I did not find everything that was actually damaged…
Ends up, the axle boot was actually split all the way around, not just dislodged. It attaches on the inside of the housing somehow, I'll have to take a closer look at it. Also, the housing is scraped up from riding on the exhaust. The metal inner structure of the poly isolator has separated from the poly itself. I was able to loosen one bolt, but when trying to loosen the other, the metal just spun around inside the isolator. Does anyone know if I can just run down to the local parts store and swap it out for the ones they keep on the shelves, or will I have to contact Energy Suspension directly? Also, the rear section of my cat-back exhaust is bent and has a large dent in it. At first I thought it had just shifted, but it is actually damaged. No easy or cheap fix there, I will have to have the rear portion made up again at the exhaust shop or just run it how it is, dented and hanging lower than usual.
More pics, excuse the bug, they are everywhere now that it has gotten warmer:
[archived image: 001.jpg]
[archived image: 003.jpg]
[archived image: broke.jpg]
[archived image: broke2.jpg]
[archived image: broke3.jpg]
[archived image: 009.jpg]
- -?
Dave@SBC: (2010-04-25 03:01:07)
extra weight? Kinda like a drive shaft loop, you complain about it until it saves your a** one day. lol Looks like a nice product Jason.
Careless: (2010-04-25 06:32:37)
Energy Suspension 3.1108G
Transmission Mount
[archived image: energy_suspension_3.1108G.jpg]
862sik: (2010-04-25 10:05:50)
I got one from another member on this site that he made which is the same construction as the ones that jason carried. You guys are making me nervouos about running it now. It has been good so far.
Jason84NA2T: (2010-04-25 19:25:10)
All I can say is this sort of thing happens, and we are sorry. Russ designed and manufactured the mounts from aluminum because it was deemed strong enough at the time. The only thing in questionwas fatigue resistance. Despite LOTS of durability testing on both our parts before selling them, we have had 5 failures that I know about out of well over 100 sold. This is a low but unacceptable failure rate, and we stopped selling them very shortly after the first faliure was reported. Obviously it's not something Russ or I are happy about, but we are being proactive and replacing the angle part for free and offering an upgrade at cost. The new design is far better, so there should be no failures in the future. I would be cautious of anyone continuing to make or sell them similar to the old design. I'll have to find out who that is… Ignorance of a design flaw can be a partial excuse in this case, but continuing to sell a known flawed design is another issue altogether.
862sik: (2010-04-25 21:47:29)
what you think of that one? its the one I got.
BLOZ UP: (2010-04-25 22:18:38)
What a stand up guy.