Prothane trans mount
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Joined: Jun 2010
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From: Corpus Christi, Texas
Prothane trans mount I just recently replaced my broken stock trans mount with a prothane motion control mount from summit and i noticed driving home a slight vibration shrugged it off being a harder material than standard rubber but the next morning going to work going down the freeway from 60 on it has a really noticiable vibration/thumping sound that you can feel in the seat and center console area big time. More of a thumping because you can feel the thump in the shifter. Anyone ever heard of any kinda issues similar before??? Motor mounts are still factory also. Thank you
do a search man...there are literally hundreds of threads on this topic. The condensed version is if you use a prothane trans mount you need to do prothane engine mounts or solid mounts. Regardless though you will have more vibration with prothane. Most people use it for a while...get tired of it....and put on a stock rubber mount.
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From: Augusta Ks.
Did you install it with the spacer?I did and noticed good amount if vibration then took out spacer and it smoothed out.It throws the drive shaft angle off and the U-joints are not correct angle to the rear end.
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From: Corpus Christi, Texas
No i did not use a spacer but stupid me found that i left off a washer, that was the only thing i could see that wasnt right when i put it in the air saturday after work, took crossmember down and double checked everything put it back on and the vibration practically went away, now can barely feel anything till about 70 then its a slight vibration, i'll give it some time to see if it breaks in any and go from there. Thanx guys.
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Thread Starter
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Joined: Jun 2010
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From: Corpus Christi, Texas
It seems like its already going away been a week already. I just need to get everything i need to install my headers and while i tackle that im gonna get poly motor mounts. Hopefully the stock ones will be alright till then.
I have used just poly trans mounts in multiple cars without ever using poly motor mounts. Granted, I would rather have the poly motor mounts too. But I've never ever had a problem with tailshafts breaking. Thats 3 Firebirds, one 82 SE, one 85 T/A, and one 91 Formula. Formy was a manual. All others were auto. But I've also used them in Mustangs without problems. I don't get where ya'll are getting this from. Have you actually broken a tailshaft doing this before? I dare not say I'm an expert but I would say I've done it enough to know it is safe. To hell with the stock rubber mounts breaking. I'm not replacing those things every other week. I replaced 3 in the Formy in 2 weeks. NO NO NO. Not me. Ya'll do what you want. Just my opinion. I'm not pissed in any way. Please don't try to flame me.
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From: Corpus Christi, Texas
I have used just poly trans mounts in multiple cars without ever using poly motor mounts. Granted, I would rather have the poly motor mounts too. But I've never ever had a problem with tailshafts breaking. Thats 3 Firebirds, one 82 SE, one 85 T/A, and one 91 Formula. Formy was a manual. All others were auto. But I've also used them in Mustangs without problems. I don't get where ya'll are getting this from. Have you actually broken a tailshaft doing this before? I dare not say I'm an expert but I would say I've done it enough to know it is safe. To hell with the stock rubber mounts breaking. I'm not replacing those things every other week. I replaced 3 in the Formy in 2 weeks. NO NO NO. Not me. Ya'll do what you want. Just my opinion. I'm not pissed in any way. Please don't try to flame me.
I did Poly Trans mount last year, Ended year with lots of vib's. Early this year i Did Poly Motor Mounts this spring, Calmed it down, a lot! Defiantly Match the mounts: Poly to Poly or Rubber to Rubber.
I personally had no more vibration with the poly mount than with the rubber mount. I'll put it this way. I was a hell of a lot less with the poly than it was with the broken rubber mount!!
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From: Corpus Christi, Texas
I had the same problem with my poly tranny mount. I returned it and put a stock rubber one in (bought a lifetime warranty one) and that took care of the problem like these others have said. I believe im on my 2nd or 3rd free lifetime warranty tranny mount 
