I'm tracking down drivline vibes in the driveshaft area but I also have a vibration in park as I raise the rpm's it gets worse at certain rpm's and seems worse when slightly letting back off the throttle.

Feels like the flexplate convertor area so I shot a digi cam vid of my flexplate/convertor with the engine running and in park and there's deffinently some wobble but idk it this is normal...

Flexplate is a heugh's (spelling?) SFI plate and is only about a year old but I have ZERO confidence in my local trans shop anymore and dont know if they could have somehow bent it when bolting the convertor up to it... Also the plate seems to have some shitty welds around the ring gear dont know much about the brand or their quality... Convertor Is a yank PT3800 .... Also I have no way to measure how much exactly it wobbles hence the vid.

 

hey welcome to my world, i have the same damn issues that you do and has been an on-going thing with me. I have upgraded the flexplate,installed a different converter and still have vibration issues. I can tell you that when the converter was swaped with a different one alot of the vibration went away at certain rpms. Tell me something about your vibrations, ist it pretty bad around 2k-2,200 rpm (my car shakes a bit at the rpm).. How is it on the highway when you let off the gas, do you get some vibration. Mine vibrates in park, cant really feal it too much when driving unless im on the highway and let off the gas then i can feal it.. My problem was that my trans took a dump so i upgraded to a new trans and a new converter. Installer did a botch job on the trans swap(took it to a what i thought was a decent place,someone i knew even worked there and did the inital install but left bolts out as i was told) and when i got it back i got some bad vibrations in alot of different rpms. Talked to a bunch of people that figured it was either the converter or the flexplate that was possiably bent on the install(kinda sounds like you hu) so i bitched about the converter and got a new one sent out and i also had a new tci flexplate installed. Alot of the vibrations went away but its definately still there and im thinking its the converter as i dont have the best of brands but you on the other hand have a yank so i dont know what to tell you. All i can say is if you figure it out you better tell me what you did lol...

 

Yea In park its deffinently vibrating above 2k.. As far as on the freeway I'm not sure how much of my vibrations are coming from the flexplate Since I've had a terrible drivline vibration for almost a year now ever since I blew my rear end which twisted my driveshaft...

New 3.73 ring and pinion, new driveshaft(balanced/stock piece) And still a terrible vibration! I dont even drive on the freeway if at all possible cuz I cant go over 65-70 and even at those speeds its dam annoying and can barely see out of my mirrors sometimes...
Then sometimes its a little better but still there and sometimes its really bad at even 50-60... I do know its 10 times smoother when I drop it in neutral though.

I know my u-joints on the new shaft were good when i put it in and the vibes were there. I did swap the yank in while i had the vibration and it got no better or worse. Tomorrow car is going in to change out the tailshaft bushing and see what that does...
If that doesnt do it I might go back to the rear end shop that did my gears and see if there is a problem with the pinion bearing or how the gears were set up allthough I have no gear whine or anything a buddy of mine got bad vibrations after his gear install beause they f'd up the pinion bearing and that was the only thing he changed or did to it so thats something to look at...

I've tried about every goddam other thing! shimming the crossmember down/ shimming the trans mount up/ balance tires ect. But because mine started vibing when I broke the rear I'm looking to the rear next although I know that could have shocked about everything in the driveline so idk wtf to look at really! I just want my smooth ride back so I can start racing again

 

yep sounds just like me but i blew the trans and not the rear. Got to love jerking around with this crap trying to figure out whats wrong. On your issue, do you have an adj torque arm, what about your trans mount did you chang it to a poly mount by any chance?

 

Stock torque arm So the only means to f-with pinion angle is shimming the crossmember but pinion angle shouldnt have changed when the rear went I dont think???
And I have the prothane motor and trans mount combo not energy suspension so no load plate or anything with the prothane And had I it on before the rear went and the vibration was only slightly more noticable, mostly in 3rd gear under accel...

But that was nothing compare to now!!! Seriously @ 100mph feels like its going to fly the **** appart! Its rediculous! Idk much about rear ends, or if setting one up wrong could cause this much vibration even?? idk maybe I tweaked an axle shaft I'm thinking might be a possible cause too, but where do you start! lol And how much is it going to cost this time!

 

this is my exact problem and with the way things are going with jobs money is a bit tight at this point.
As with the stock torque arm, the only way the angle would change would be if you installed lowering springs or put a big speaker box/extra weight in the trunk. Other than that, do you think that maybe you have a bent rim/wheel, that could cause a nice vibration too, oh the list never ends on what could be the issue, again welcome to my world

 

bent wheel could yes, but the rear end going isn't going to bend a wheel by itsself and thats all i did that is causing me this hell...
Plus I ran er up to about 40-50 with jackstands under the rear end and while the car was vibrating the rims looked to be spinning true... tried to get a look undeneath while doing this buuuut Its a little nerve wracking crawling under a shaking car thats doing 40mph on jackstands lol. Go ahead try it! haha

 

Most all aftermarket flexplates are not balanced as supplied
they expect you to do the balance job during the engine build.
I would look there and get rid of the Poly transmission mount

 

how do you like the pt 3800? do you have any track time on it yet?

 

Unfortunatly no I dont have any times with it yet, Mainly due to this vibration I've had since before I installed it!
Times in sig were with some off brand 2800 stall... I can tell you though that its a bad *** convertor! Hits alot harder than the old stall, Flashes straight to about 4500rpm's from a roll, and the shift extension keeps rpms above 5k at WOT! I might need more suspension mods, have LCA's and a PHB But this convertor lights up street tires in 2nd gear at 40-50 mph when it hits!!! The old convertor never did that!

Was told its perfect for a mild cam setup and you can spray this convertor without blowing through it, but still has the bad *** top end I hear PT series convertors are known for... Maybe yank can chime in and tell ya more if he checks back in my thread...

 

on another note picked up the car from the shop yesterday new tailshaft bushing and the cars still vibing just as bad!
On the test drive the shop owner was revving it in park and neutral commenting on the vibration and agrees that vibing in park has to be the flexplate/convertor area. and its a brand new yank convertor that hasn't been beaten on yet sooo i'm thinking the wobble in the plate is my problem.

He got the plate from bell and gaines and is going to try to have them send a new one and i told him to go with a different brand sfi piece but I was looking online and am not sure which one to go with also some are ZERO BALANCED and some say EXTERNALLY BALANCED Whats the difference and with type should i get? I'm guessing zero balanced for a stock internal motor/stock dampener car correct?

 

i wish i could help but i don't know. i think i would get a gm unit if you didn't want an sfi rated flexplate. i ended up getting a meziere flexplate, which are a solid $400. i don't know if it was worth it or not but it appeared they were of higher quality. they are one solid piece, nothing welded, etc. i have no idea if i have that vibration or not because i haven't driven it more than up and down my driveway.

 

Same issue dead stock.

Happened after I broke the tranny mount and went poly..

so yeah there is my .02 cents

 

if i had to guess id say you have a stock steel drive shaft and when you put the poly mount on it killed your ride... i had this issue tried tracking everything down even got my stell ds balanced it works fine on a stock mount but the poly needs an aluminum one

 

01 trans am... I do have aluminum ds... I have two actually now haha! anyone need one?

 

I had the prothane mounts and developed vibration from the driveline angle change, they are taller. Spent the big money on the factory mounts and vibration was gone, or the feeling was gone. If your problem developed after the R&P change, check and see if whom ever did the job had a hard time removing the yoke. I've seen guys beat it off and bend it just enough to cause a vibration. Also check and see if the new joints have the right snap rings in them and fit tight to the yoke. Make sure the yoke does not have wear marks where the snap ring go, which keep the joints true in the yoke. Finally make sure the joints themselves are not defective. We did a Mazda and the customer brought his own joints. One was offset just enough to cause a vibration. SPICER!! I feel your pain.

 

Thanks for the replies 328ss I'm gonna start with the trans mount by replacing it with oem rubber. If that does not work next the flexplate will be replaced as mine deffinently has some run out And idk how that couldnt cause vibes with a 30-40 pound convertor bolted to it. And if its still not right I'll check the differential yoke for any run out... Thanks again guys This **** is sooo frustrating! Dont know what i'd do without the ls1tech community!

 

F**K prothane tranny mounts!!!

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Like the title says WOW they really REALLY suck! (cant stress that enough!)

For the last year now I've been trying to trace vibrations/ changing pinion angles/ having my driveshaft balanced, even bought a second driveshaft! / replaced U-joint's/ replaced convertor (well that one just wanted to go bigger) but it didnt help with the vibes! And have been to the transmission shop numerous times trying to get them to figure it out. Not to mention the hours I've spent under the car myself ... and finally FINALLY! thanks to advice off LS1Tech just switched back to a stock rubber mount I picked up at napa for $21 ******* dollars and that just fixed 95% of my vibrations!

Holly **** are you kidding me!? I'm so happy right now I can drive on the freeway again, and at the same time SOOO pissed at prothane and the jackass who designed their poly trans mount I wish I could kick him square in the nuts so ******* hard for all the money and headach that mount has caused me!
Anyone with an automatic who is thinking of using prothane or any poly trans mount for that matter DONT DO IT! Its not worth it I'd much rather have to replace a torn rubber mount occasionally than ever go back to poly!

And btw the napa mount i got is only listed for 94-97 firebirds but it works great on LS1's trust me! End Rant! I think I'm going to go for a drive and actually enjoy it for the first time in forever... THANK YOU LS1tech!!!

 

I might have something to do tomorrow...

 

thats great you got it! i had the same problem with my 2000 SS 6speed
camaro LOL.