Cascade Crew

Red Bird · Posted: Thu Mar 22, 2007 9:06 pm Post subject: Strong vibration above 65mph

I just replaced my T5 transmission in my 91 lo3 firebird. The new transmission shifts awesome thru all the gears. On the freeway today, i took her up to 65 for the first time and there was a strong vibration that is comin from either the middle(driveline) or the rear not sure, when i would drop down to 60 vibration dissapeared. I tried it in both 4th and 5th gear, with the same result no vibration at 60 and once at 65 it would start. I am guessin The u-joint, anyone else run into this kind of problem? Before the swap the car had no vibration when cruisin the same speeds and much higher.

aaron_sK · Posted: Thu Mar 22, 2007 9:18 pm Post subject:

Do you think you might have knocked the driveshaft when you pulled it?

Red Bird · Posted: Thu Mar 22, 2007 9:36 pm Post subject:

No,i pulled it out and set it aside with no issues, had a buddy help put it back in so i would not wind up bumpin it on anything.

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Might be worth unbolting the driveline and turning it 180*.

Personally I don't think it should matter, but I have heard of people that have fixxed vibration problems that way, and it is free.

Worth a try.

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

if you have the wrong trans mount, your driveline angle could be wrong.

Dewey316 · Posted: Fri Mar 23, 2007 7:58 am Post subject:

other than then tranny itself, did you replace anything else while you were working in there?

Twilightoptics · Posted: Fri Mar 23, 2007 3:54 pm Post subject:

Sounds like improper driveline angle or u-joints or as rod said flip the driveline around.

305 302eater · Posted: Fri Mar 23, 2007 8:01 pm Post subject:

Red Bird · Posted: Fri Mar 23, 2007 8:10 pm Post subject:

We changed the clutch and throwoutbearing, while the transmission was out. I'll try flippin the driveline around, i should have scribed a line when i took it off, i spaced on that. ill let you guys know if that works. Thanks for the replies, i did not even think about doing that.

Twilightoptics · Posted: Fri Mar 23, 2007 8:19 pm Post subject:

Unlikely... but if you didn't have the pressure plate balanced with the flywheel it may cause a similar condition. It would be more RPM related though.

Is the vibration the same in 4th and 5th at the same speed?

Red Bird · Posted: Fri Mar 23, 2007 8:31 pm Post subject:

Yes it is, i noticed it while it was in 5th. i then down shifted to 4th gear and at 60 she ran fine no vibration took it to 65 vibration kicked in. i up shifted to fith with the same result again. 60 was smooth at 65 the vibration started.

blue89 · Posted: Fri Mar 23, 2007 8:58 pm Post subject:

If it only happens at speed, you may want to check your tires to make sure they're balanced. Always check the simple stuff right?

Red Bird · Posted: Fri Mar 23, 2007 9:13 pm Post subject:

if the drivline flip doesnt cure it ill try that before i take apart the u joint. And by the way both of ur rides are badass!

izcain · Posted: Fri Mar 23, 2007 11:38 pm Post subject:

I know this is a bit off since you only took the driveline right out and then put it right back in but there was several TSB's for many years in the 80's on thru about them having driveline vibration. Most poeple cure this by going to the local salvage yard or aftermarket and find an aluminum 4th gen one or use the inland empire one. Just some ideas........ If the driveline flip doesn't work I would look at having yours rebalanced to see if it is out of wack.

83Z28BlackBetty · Posted: Sat Mar 24, 2007 1:21 am Post subject:

i'd check to make sure your tires are on correctly, I had some guys at les schwab put em on crooked and they would vibrate at speed. Its an easy thing to check and a total shame to spend lots of money when it could be something simple.

~JAKE

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

check to see if you might have knocked a weight off the driveline when you flip it.

I've never encountered having a driveshaft balanced to a diff. gear set before (or heard of it before)... I bet what actually happens is the u-joints arent centered in at the flange when bolted in just slightly, or there's crud on it from removal that gets stuck in there to cause the vibration, when flipped the crud gets flung out, or joint gets properly secured...

Vibration spots to check for a vehicle speed related concern is driveline angle, driveline phasing, u-joints, ring and pinion set out of balance, differential bent, axle bent, tires have flat spot or out of balance.

blue89 · Posted: Mon Mar 26, 2007 8:29 am Post subject:

Any progress? I just had my tires balanced again on Friday. I had a real bad vibration at 70 with my LT1 with the 18's. The Schwabs guy said that all the tires were out of balance. I hadn't changed anything since I bought them 2 years ago, but he told me that tires will become out of balance by themselves as they age.

Red Bird, got any pics or a cardomain?

Red Bird · Posted: Tue Mar 27, 2007 9:17 pm Post subject:

Flipped the Driveline, and checked the u joint tonight. u joint seems fine, no play at all. hit the free way, vibration still there. Im gonna get the tires balanced tommorow, i'll let ya know how that goes, im crossin my fingers. I dont have any pics or a cardomain, my cars pretty much bone stock, and fairly slow for a TBI, the best i could get out of it at the strip here in yakima was a 16.2 but while i was under the rear today i saw that my muffler is a flowmaster that was a pleasant suprise.

blue89 · Posted: Mon Apr 02, 2007 11:47 am Post subject:

and den?

Red Bird · Posted: Tue Apr 03, 2007 6:52 pm Post subject:

Got the rear tires balanced yesterday, Still vibrates. Im gonna pull the drivline take it to a shop and make sure its still balanced. Kind of frustrating, at the moment my toyota corolla has a higher top end then the bird lol