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Pontiac GTO 2004-2006 The Modern Goat

Poly trans mount experience

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Old 01-04-2017, 09:45 AM   #1
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Default Poly trans mount experience

im looking for some input from anyone that has installed one of these?

I put the hinson one in right before christmas and test drove it and while it felt more solid it created an odd harmonic in the drivetrain. Feels almost like gear whine but its coming from the front of the car well more middle. I have their engine mounts as well. My factory one wasnt trashed but I could feel a lot of vibration in the shifter down the highway. I got this and a onepiece driveshaft at the same time but didnt install the driveshaft yet, as I noticed the mount was 3/16" taller than the OE mount. I ended up shimming the crossmember, but I didnt account for any compression measurements as Im sure the rubber mount would squish a bit. I still have the same feeling though so is this just NVH from the ploy mount or did it just highlight another issue the rubber mount was absorbing?
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Old 01-04-2017, 07:53 PM   #2
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Most likely highlighted another issue, I'd venture to guess it's the driveshaft. How is the carrier bearing?
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Old 01-04-2017, 08:15 PM   #3
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Looked OK from what I could see of it under the car and the rubber idolaters looked good to. Pulling it out tonight to install the one piece to see if that reduces it. I'll report back how it goes
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Old 01-05-2017, 08:23 AM   #4
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got it out and the carrier bearing did have a tear in it so I was hopeful that the one piece would solve the problems, but after my drive this morning not so much. Somethings were better but others seemed unchanged. 1st and third gear represent a majority of the problem, best I can describe it is feels like the car has an unlbalanced tires all through the rpm band in those gears. 2nd and 4th dont seem to show anything until 3k, the wierdest part is that once it shows up it doesnt progressively get worse its just there. I have a poly kit from energy suspension that I have yet to have time to install, is it possible I have a worn suspension piece in the rear somewhere thats showing up now that the driveline is more solid?
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Old 01-10-2017, 12:27 PM   #5
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kind of surprised more people didnt chime in on this.

Even more surprised/ dissapointed I never got a response from Hinson.
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Old 01-10-2017, 01:01 PM   #6
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Try LS1GTO
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Old 01-10-2017, 02:23 PM   #7
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dont have an account there
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Old 01-14-2017, 05:32 PM   #8
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Yeah the carrier bearing sucks in these especially when you put better mounts in. I've replaced mine it's not to hard but I think next time it's going to get a solid one piece
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Old 01-16-2017, 03:47 PM   #9
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yeah the one piece shaft definitely makes things feel more connected and eliminates what I describe as that rubber band feeling I sometimes feel when engaging the clutch due all the isolaters and carrier bearing of the two piece shaft.

on a side note I did manage to find a thread specifically on the hinson mount going through google. Said allow two weeks for the poly to soften with daily driving and most if not all NVH should go away. That said a majority of mine has and gets better every day with the exception of 40MPH mark. I think this is due how much the rubber mount compressed under the weight of the tranny plus how tall the new mount is and doesnt seem to compress. May have to check my angles and add more shim to the crossmember.

shifts feel so much more solid than with the rubber mount which I like, but If I cant get rid of the rumble strip feeling over 40mph I may go back.
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Old 02-01-2017, 08:31 AM   #10
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So decided to report back on this. after a couple of weeks the 40mph vibration is still present. got under the car to check driveline angle and ive got 4.3 down at the tail and 4.3 up at the pinion.

what are the odds of getting a unbalanced/missbalanced shaft?
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Old 02-03-2017, 12:02 PM   #11
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Rotate the driveshaft 180 degrees. Disconnect it, rotate it 180, reconnect it, report back.
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Old 02-03-2017, 12:30 PM   #12
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I'll give that a shot this weekend
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Old 02-04-2017, 02:47 PM   #13
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Quote:
Originally Posted by blackbyrd View Post
dont have an account there
You don't really want one there, bunch of ******** mostly and green peas without info.

I had done some minor R&D on a poly mount for our car. I had a prototype of one on my car years ago and also a production piece. I never got around to producing a mount as I was buried in other driveline R&D with stubs and diffs. I did give Hinson advice on how to succeed on this project, but I don't know if it was considered or employed.

Static and dynamic height is more important than the durometer of the piece. This needs a close look. 3/16" higher without weight on it, will likely lead to a significantly higher install height. I've found that driveline angles over 3.5 degrees at each end will contribute to vibes and harshness. The oem 2 piece ds calms much of the nvh. The 1 piece will amplify it. 8.8 and 9" kits pose this problem as well, one of the reasons I won't touch one. I was forced to learn how to build a stock configuration diff that could hold high hp cars, partially because of this.

Moral of the story, pay attention to these things for a better chance of not having any of these issues.

Hope this helps someone.
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Old 02-04-2017, 07:33 PM   #14
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To your point tail shaft angle was 1.3 degrees before shimming the crossmember. It got better after the shims but still has 40+mph vibration. Oddly I have not found one bad thing said about either product.

The mention of the break in period was actually on ls1gto. I'll see if indexing the driveshaft has an effect. That said you have quite a bit of experience in the driveline department. Are those angles too harsh on a GTO? First IDS setup I've worked on and I was always taught keep your angles between 3-5 degrees respectively.

edit I re read your last post 2qwik you answered my question.

Last edited by blackbyrd; 02-07-2017 at 03:04 PM.
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Old 02-07-2017, 10:43 AM   #15
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I have the revshift 80A tranny mount, motor mounts and a driveshaft shop carbon shaft and I have some of the same vibration type issues you are describing. I have poly everything and a harrop cover also. I knew this going from a 2 piece to a 1 piece through what I had read and a few other people I know with similar setups. And the aluminum ones do it even worse. I have yet to check my driveline angle though,
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Old 02-07-2017, 10:44 AM   #16
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And yes, 2Qwk is absolutely right about LS1GTO. That site needs to dry up and blow away, either through new people or the tyrants that run it.

Last edited by vx355; 02-07-2017 at 10:46 AM. Reason: spelling
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Old 02-07-2017, 11:28 AM   #17
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It actually seems to get better each time I drive it ( or im just getting used to it) I need to just get it on the high way and see how bad it truely is up to 80MPH. still havnt rotated it though
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Old 02-07-2017, 02:15 PM   #18
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I would try to 180 the drive shaft. I would also look into a shop that can align the front and rear cradle and the trans mission as well they can all be out a lot and if you don't have the alignment tools you wouldn't know. IDK how warm TN is right now but it wouldn't surprise me if the NVH would be a little bit more pronounced in colder temps either.
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Old 02-07-2017, 03:04 PM   #19
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its actually been oddly warm for us this time of year...couple of weeks of 50 and 60's when we are usually low 40's or colder this time of year. I actually have the poly subfame bushings to go in just havent got around to it like most of my car projects these days.
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Old 02-10-2017, 10:05 AM   #20
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Usually, you want the transmission mount to still have some give, which is why I always recommend doing the Revshift insert or filling the gap with Window Weld on a new OEM mount. That way, you retain some of the rubber in the driveline while still firming things up.

Have you tried putting the OE mount back in?


Quote:
Originally Posted by vx355 View Post
And yes, 2Qwk is absolutely right about LS1GTO. That site needs to dry up and blow away, either through new people or the tyrants that run it.
But then where would all of the Facebook groups link to in order to answer all of their questions? Love it or hate it, the site is a treasure trove of information for the car.
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