Need help with high rpm viberation

WHITESTRIPES

Member
Established Member
Joined
Oct 23, 2012
Messages
375
Location
Colorado
I've searched and oddly enough came up empty. Usually I can just search and someone has already made a thread and answered my question. And I posted it here because I'm not sure if it's an engine or drivrtrain vibration. So with that out of the way....

Last winter I installed a cobra engineering M122 swap on my 03 cobra amongst other things such as a steeda tri ax shifter and aem wide band.
I had a poor email tune update so I stayed out of the throttle.
High rpm (4k +) I get a bad vibration and I can feel it most in the shifter. It rattled like crazy until I shifted.
I believe it does it in neutral when revving also. It doesn't get worse with wheel speed, only with engine speed.

The things I've tried already:
Replaced clutch and flywheel (twice)
New frpp tob/fork/pilot bearing/pivot ball
Topped diff off and torqued pinion nut
U joints are tight.
Fresh synchromesh fluid
Checked that balancer and crank pulley are running straight, all pulleys turn nice and straight.
Idles normal and no CEL
I replaced the tri ax with a mgw
Do short throws really vibrate that much?
I'm at a loss here, the trans and motor mounts look good. I should note the car drives perfect at low rpm. I've put almost 700 miles on the new spec 3+ clutch. You can feel the vibration the most in the shifter handle but also in the pedals/floor boards.
I'm going to have 04 sleeper tune it, but I need this issue fixed first. Any insight or things to look for would be awesome.
 

WHITESTRIPES

Member
Established Member
Joined
Oct 23, 2012
Messages
375
Location
Colorado
The mods that would matter are:
Ported M122
2.93 upper
Metco 4lb lower
Spec 3+ clutch (light pedal option)
Rebuilt flywheel
 

408Stang

New Member
Established Member
Joined
Feb 8, 2015
Messages
24
Location
Denver, CO
Have you checked the harmonic balancer? Seems like you have an out of balance issue in the rotating assembly if it does it while not in gear or moving.

Sent from my A0001 using Tapatalk
 

roy_1031

roy1031
Established Member
Joined
Apr 20, 2011
Messages
4,796
Location
Rancho Cucamonga, CA
When did it start vibrating? Immediately after the blower install? Does it vibrate sitting at zero mph just sitting there and revving it, or only when rolling?
Is it a 10 spline or 26 spline clutch? Was the input shaft shimmed properly if it has been upgraded?

Did you mark the drive shaft and re-install it the way it came out? Maybe it's out of phase?

Just throwing ideas out there.

Be sure to update the thread once you figure it out. Good luck with it.


Sent from my iPhone using Tapatalk
 

WHITESTRIPES

Member
Established Member
Joined
Oct 23, 2012
Messages
375
Location
Colorado
That's why it's so hard to pin point what it could be, last winter i did the blower swap and shifter. I hardly drove it due to a bad tune. I did notice the vibration around that time so I parked it and replaced pretty much everything in the drive train. I did replace the tob retainer sleeve also. The input shaft is stock, didn't seem to have play and spun smoothly.
I need to verify if it does it or not in neutral, it if does it's nowhere near as bad in gear in the higher rpm.
The vibration was bad enough I couldn't read the numbers on the shift knob.
As far as the drive shaft, I marked it and put in back in it's spot. I even took it back out yesterday to retorque it..


Sent from my SM-G930V using the svtperformance.com mobile app
 

2Rare

Against All Odds
Established Member
Joined
Oct 31, 2013
Messages
606
Location
OC, MN
Does the vibration occur only under load? What about during normal driving? I would check to see if your short throw is adjusted properly. Some short shifters can be loud and bad trans mount will likely lead to a vibration. In reality it, could be on of my things. Hope you get it figured out.
 

WHITESTRIPES

Member
Established Member
Joined
Oct 23, 2012
Messages
375
Location
Colorado
No during normal driving it drives fine. I can't really feel a vibration. I only notice it 4500rpm and above. I originally thought it wss the steeda shifter so I replaced it with an mgw. The problem carried over. I didn't install the set screws because I read not to use them with the t56. I looked at the trans mount and it looked fine, but I may pull all the mounts and really check them out.
Has anyone had a bad motor mount or trans mount on a 03-04 cobra? I searched and can't find any symptoms to compare mine too.
Thanks for the replies
 

Stage 4.6

Well-Known Member
Established Member
Joined
Dec 31, 2010
Messages
2,074
Location
Colorado
I had a very similar issue, just like you i replaced about everything you mentioned. Hardly drove the car due to going out of town and stored over the winter, then the issues arose.
Had a local friend pull the tranny cause a lot of my issues came after RXT, input shaft, axles, etc... Ironically he found a bent input shaft and shimming issues. I purchased everything new from Lethal but since everything was over a year old i end up buying it all new again. But my slight vibration problem is solved.
 

WHITESTRIPES

Member
Established Member
Joined
Oct 23, 2012
Messages
375
Location
Colorado
That's funny you mention the input shaft being bent, that's what my neighbor thought it was right away. I've had the input shaft out not long ago, it looked great, bearings too. How did you check to see if it was bent?
I put the stock one back in when i replaced the sleeve and checked for play, I thought I could feel a SLIGHT bit of end play but I thought I was going crazy.
Can the stock shims flatten and give excessive end play?
Any way to check that it's the input shaft before I pull the tranny?
Thanks for the reply man. I know what I'm doing this weekend...
 

Stage 4.6

Well-Known Member
Established Member
Joined
Dec 31, 2010
Messages
2,074
Location
Colorado
Its frustrating as HELL, especially when you buy new parts and rely on reputable shops to do this expensive work. Anyway my mechanic that did it the 2nd time was very thorough and dissembled my tranny to the shell.

He placed the input shaft on a dial indicator and discovered that it was .070" bent at low RPM you couldn't feel it, but like you under hard acceleration it felt bit weird under hard deceleration like in 3rd gear it was pretty bad! My TOB was also pretty worn, The shimming from what i understand is critical, i was told to ensure to get the TREMEC shims.

All this happened within 4000 miles car was put away for almost a year. That's why it took so long to repair plus the shop I always had my car worked on is in Denver so i hated the drive!

Hope this helps bud!
 
Last edited:

CobraBob

Authorized Vendor
Established Member
Premium Member
Single Barrel Sirs
Joined
Nov 17, 2002
Messages
105,349
Location
Cheshire, CT
Sounds like you should definitely check the input shaft. That seems the most logical source of the vibration at this point. Keep us posted. Like Stage 4.6 said, a slightly bent shaft won't likely be noticed at lower RPMs. But as the RPMs increase, the disturbed equilibrium of the rotating shaft will increase.
 

WHITESTRIPES

Member
Established Member
Joined
Oct 23, 2012
Messages
375
Location
Colorado
I think I forgot to mention I had a tob explode and destroy a sleeve, maybe it put too much stress on the input shaft and bent it or at least put it out of tolerance.
Thanks for you input stage 4.6.
What shop in Denver did your work? I lived in Colorado Springs for years, just moved to the Seattle area last year.
 

Stage 4.6

Well-Known Member
Established Member
Joined
Dec 31, 2010
Messages
2,074
Location
Colorado
I think I forgot to mention I had a tob explode and destroy a sleeve, maybe it put too much stress on the input shaft and bent it or at least put it out of tolerance.
Thanks for you input stage 4.6.
What shop in Denver did your work? I lived in Colorado Springs for years, just moved to the Seattle area last year.

How ironic! I am from the Springs don't see many Terminators in the Springs, what color is yours? Most of my buds drive old school Fox bodies or the new Coyotes, also I moved from Seattle to here.

Most of the work done on my car was done at RWR.

My TOB was in bad shape as well, I haven't had much luck ever since i installed this RXT twin disc, but like you I did a lot of the mods all at once so it was hard to pin point the problem. Now that i think about it my tranny has been dropped 3x in the last 2 years, the first time was due to the TOB getting chewed up at about 1000 miles I could never get it to adjust properly.

Good luck keep us posted!
 

WHITESTRIPES

Member
Established Member
Joined
Oct 23, 2012
Messages
375
Location
Colorado
Oh wow, that's awesome. Mine is black. What color is Yours? I may have see it around. I might be moving back there, the rain is killing me here.
Robs a good tuner, he did my first pulley swap/dyno tune.
I also have a white built fox body.
I thought the 3rd time taking the transmission out would be the charm for me too, but i guess 4 times it is! And it's still a pain in the ass to drop.
 

Stage 4.6

Well-Known Member
Established Member
Joined
Dec 31, 2010
Messages
2,074
Location
Colorado
Yeah I like Seattle but the rainy weather can make you depress lol. I love black Cobras they look so mean, and you have a Fox too. I have a GT i am considering doing a coyote swap, My Cobra is mystichrome.
 

WHITESTRIPES

Member
Established Member
Joined
Oct 23, 2012
Messages
375
Location
Colorado
Today I took the car off the jack stands for a little drive before I started pulling it apart.
I confirmed that the vibration is present in neutral and that it's coming from the transmission.
I took the shift boot and all the sound deadening I put in out. I can feel the trans vibrate when I rev it. (Reaching through the shifter hole with everything removed)
I'm going to pull the trans tomorrow so I'll keep the thread updated.
Hopefully it just needs the input shaft shimmed.
 

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,125
Location
Cali
I remember a guy having some weird issues with his car. It had some weird vibrations and made some funky noises. He pulled the trans to find whoever swapped the clutch forgot to put the new pilot bearing in.
 

Users who are viewing this thread



Top