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Whole car vibration @ 135+mph HELP!

247
380
Exp. Type
HPDE
Exp. Level
3-5 Years
Wisconsin
Let me give you a bit of back story. Really looking for some help on what do here. Long post warning!

Bought this car a year ago now. Did over 1300 miles with her on track this year and could not be more happy with the cars performance. You can read the mods I have in my build thread but quick summery she is fully built. Car runs near perfectly however I am running into and issues and I am not sure where to go with it. Not like I can go test a solution as the car only does this at 135ish mph +. I think the trans has a new clutch, new flywheel and a MGW race spec shifter. Motor is super built and almost 80% all new. Ok here is what I have going on.

Road America is very fast.. thanks for clearly that up Andy. :) So going down the front straight.... In 5th gear... the car will start a very noticeable FULL car vibration. Not in the wheel, not in dash or a panel. The WHOLE car. I can feel it in my ass. Now I have not tried to push through this as well if something goes.. I am doing near 140 mph. What I have done is shift into 6th gear to try and see if that would do it and the car goes into limp mode. Yep motor goes down to 2k rpm and I need to come off track. Turn the car off and then turn it back on and everything is great. Keep that in mind it also has that going on.

Hear are my thoughts and let me know what you think.

Possibly a transmission issue or driveline issue?
Aero issue? Air getting trapped in the car?
Something else rotating? Brakes are all brand new. Wheels are balanced and have been rebalanced.

I have a friend with a GT350 race car that was also experiencing this same thing. He had the stones to keep pushing the car to 150+ and the vibration went away. In his case was it a aero issue?
With my 6th gear issue I am not really able to push as I am getting close to maxing out 5th gear at around 140+

Please give me any and all input you guys have. Road America is my favorite place to be in the world and this is really hurting me. Got some goals I am trying to get and they are not possible with this issue.

Andy
 
Andy, I'm no expert by ANY means, But I believe your problem is drive train related and more narrowed down to the tranny.....whatever is causing that vibration is related to the RPM's...Flywheel comes to mind...........Who Knows?????..........Good luck finding the truth..................
 
159
134
CA
Also also, I fought vibration issues for years, I could get a set of tires balanced and then after one event....Vibrations.

It ended up being wheel weight glue melting, weights fall off....tires are no longer balanced.

I tape the wheel weights now.

But I agree with others, this sounds driveline related.
 

Mad Hatter

Gotta go Faster
4,805
3,623
Santiago, Chile
Which clutch do you have?? Do you get any codes?? The engine could be thinking its getting knock/detonation from the vibration.
 

Mad Hatter

Gotta go Faster
4,805
3,623
Santiago, Chile
take a look at...
 
247
380
Exp. Type
HPDE
Exp. Level
3-5 Years
Wisconsin
Andy, I'm no expert by ANY means, But I believe your problem is drive train related and more narrowed down to the tranny.....whatever is causing that vibration is related to the RPM's...Flywheel comes to mind...........Who Knows?????..........Good luck finding the truth..................

Thinking the same thing too.

What would you do? Go Calmers?
 

Bill Pemberton

0ld Ford Automotive Racing Terror
7,000
6,142
Exp. Type
Time Attack
Exp. Level
20+ Years
Blair, Nebraska
SMGDHG and I had the same issue, glued wheel weight came off on one wheel, got a nasty vibration at higher speeds and took it right into the local Ford Dealer in Topeka. They found the wheel was way out of balance and rebalancing it and things were fine. Had a similar issue happen years back where a hub was going bad and it only showed up at around 130, replacement and bingo, things were fine. So, with all the suggestions here , you have quite a few things to check and it is often a myriad of items causing these problems, so take all the suggestions listed as good areas to view.
 

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