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

 

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?

 

I have an 07 GT500 with full bolt on's...pushing 511 rwhp 505 rwtq....and I have to say that I have not had any issues.......... My car drives really smooth even at high speeds! (i plea the 5th on that one...lol).

I was going to say the problem might be with the harmonic balancer but you mentioned that it only does it in 6th gear

If that was the problem then I would think it would do it in every gear......



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Did you change the rear gearset? <---edit--->NM, just read the second post, I had a similar problem years ago when I swapped the 2.73s to 3.73's in my old Fox-body, IIRC at the time I rotated the driveshaft 180 degrees and that reduced the problem.

IMO, it doesn't seem like an engine related problem unless something is off due to the tune casuing some funky harmonics in the engine (or perhasps the balancer itself has taken a crap) and then I'm thinking the harmonic balancer and S/C drive upfront and trans out back would eat alot of that.

In any event keep us posted, I'd like to see what the ultimate problem is and hopefully at little or no detriment and cost to you.

 

Now that I know what to look/feel for, I have noticed the vibration in 4th and 5th as well as 6th. 6th is when it is the most noticeable as it has the most load on the engine and it's right in my cruising speed. I can still get it to vibrate less, or even go away by downshifting to 5th, then easing it back in to 6th with very light or coasting application.

I did change the 3.31 (which were noisy due to a poor install job) to 3.73.

I'm leaning towards the harmonic balancer as the possible cure. It was recommended to go to the '08 balancer which would indicate that Ford changed it in some way. If anyone can enlighten me that, I would appreciate it.

Thanks for you help on this.

 

I did some checking on the Harmonic Balancer and the 08+ is different from the 07. I can get a new one with a new bolt for $260.00. Has anyone else changed/upgraded theirs? Is this a good price?

I have some time to think this over as we've just had our first snow fall here in Michigan and I won't be on the road with this pony anytime soon.

Thanks

 

Did that fix the issue.

 

Keep us posted...