Dyno #'s & vibration issue

principalpony · 10-30-2009, 10:03 AM

I just got my 07 Gt500 back from Paul's High Performance after a JLT-CAI install and custom tune. Hp=533.47 and Torque=482.15

Just a little history - I bought this car from dgussin1 almost a year ago and have had to deal with the problems from his abuse/torture of this car. So far I've replaced the flywheel, clutch, transmission, driveshaft, and complete differential except the housing (changed to 3.73 gears). If you ever come across dgussing1 for any type of deal/transaction - all I can say is "buyer beware!"

I'm not sure what mods may have been left with/on the engine to help make the #'s we see on dyno, as I don't trust any info given to me by the seller. Paul even had problems with the X-calibrator provided with the car as it locked up both the computer on the car and Paul's computer as well. That's all done now, and I am pleased with the dyno results and how much better the car runs with the new tune.

Now for the vibration issue. Perhaps someone else on this site has experienced this or has some advice. The vibration only occurs at highway speeds 65-80 mph, only under a load (accel or decel), but not coast, and only in 6th gear. Sometimes it doesn't vibrate at all and when it does, I can usually get it to go away by downshifting to 5th for 10 seconds or so, then upshifting back to 6th. The vibration is felt mostly in the seat, but a little can be felt in the steering wheel as well. I did not have the vibration before replacing the differential & driveshaft, and have tried putting the old driveshaft back in it to see if that is the problem - no change at all. we've adjusted/aligned the pinion shaft to the driveshaft and replace the UCA bushing - which cured ~80% of the vibration I was having, but this last 20% has me/us baffled. I don't think it's tire/wheel issue as it's not consistent enough - no vibration under coast or in 5th at same speed.

Your help/suggestions are appreciated

STAMPEDE3 · 10-31-2009, 07:32 AM

Did you index the driveshaft?

principalpony · 10-31-2009, 10:50 AM

Quote:

Originally Posted by STAMPEDE3

Did you index the driveshaft?

In switching from one driveshaft to another, I don't think indexing was an issue or possibility.

MVD · 11-04-2009, 08:53 PM

Quote:

Originally Posted by principalpony

In switching from one driveshaft to another, I don't think indexing was an issue or possibility.

You would be incorrect.

V6&V8SHO · 11-04-2009, 09:34 PM

Quote:

Originally Posted by STAMPEDE3

Did you index the driveshaft?

Did that on my 01 and solved the prob for me.

principalpony · 11-05-2009, 11:19 AM

I just got a call from the shop that's checking it out right now. The tech says he can detect the vibration in 4th, 5th and 6th gears at about 2100 rpms. It's most pronounced in 6th gear because the load is greater. He feels it's an engine harmonic issue at that rpm and has become more noticeable since the gear change due to 2100 rpms in 6th is in my typical cruising speed. The engine modifications & custom tune producing more power & torque has probably made the problem worse.

The tech noticed that the engine has a weight mounted on the side and thinks that's probably Ford's solution to address engine harmonic vibration issues.

That's the info so far. Has anyone else come across this before, and if so, what can be done about it?

Black*Death · 11-05-2009, 02:34 PM

My thought is this. If you feel the vibration in 4- 6th gears then put it into neutral while vibrating and see if it improves. Does the vibration go away or change? if so, I would think likely DS isuue? I would place in neutral rev the engine. if the problem is the engine the vibration would likely occur when engine is reved due to harmonics? Basically test with DS under load and without to see if it changes. if this dude beat on the car could he have tweaked the DS a little?

I am not a tech so anyone correct me if I am way off base here.