Quicktime_GT

So I had FRPP 4.10 gears put in last fall by a very respectable garage, Hang em High Motorsports. Their car actually won the wildstreet class at beech bend NMRA finals.

Since I've had the gears, i've had a slight vibration come on right at 85-90 mph, It was not there before. I know there is no reason to being driving continuously at 90 mph but when I want to I dont want to feel this slight vibration. I thought it may be coming from the driveshaft, or that maybe it is suppose to only go back in one way (according to 5.0 magazine ) so I took out the 4 bolts on the yoke and turned the driveshaft at different spots test driving it inbetween every place, each still has a vibration.

What could this be? Just my junky factory driveshaft out of balance? something in the rear end?
Anyone else ever notice this?


EDIT: Also .. my car has no weight under the rear diferential, could this actually make a difference?

Quicktime_GT

anyone?

ericdiver

well this is why i did my gears myself and i have no whine or vibrations, you want something done right learn it and do it yourself, not thatthat helps, but simply put... go back to the shop and complain and tell them to setup the gearsright, thats why you paid them???

Dan04COBRA

Wheel weights all set? I'd figure the vibration would occur all the time if it were your gears?

Quicktime_GT

Exactly, there is no whine or anything from the rear, I'd almost bet money its my driveshaft but i'm not sure what to do

2 kwik

I hope you installed an aluminum driveshaft to help damp'in the vibration...and car has no dogbone on rear?

SINISTER

Go check the balance of the wheels. If that isn't the problem, go to a shop and have them check to make sure the driveshaft is balanced. Then after you have ruled out the simple things, worry about what could be next.

tomsa55

The vibrations are more than likely drive shaft. The two piece drive shaft is not balanced dynamicaly and any changes to the drive train, ie gears, control arms, ect will create a situation where you might experience driveshaft vibration. Take your car to a truck drive line shop, these places are very experinced with the two piece driveshafts and understand about balancing them. I took my 2006 mustang to Midwest Tire and Wheel here in Kansas City, they under stood what was happening and knew how to fix it. Dyno balancing a two-piece drive shaft was no problem, and they informed me that this was a very normal occurance with that design. Ford was going to replace the drive shaft, but the driveline shop told me that I might go thru 2 or 3 different dirveshafts before finding one that was balanced. I have had no vibration problems since, and was money well spent, about $110.

Changing the gears did and did not cause this vibration. The gears could be installed correctly and you would still have a vibration. This is due to the driveshaft is now rotating at a higher rpm than oem set up. The driveline/suspension was designed as a package, you change the rpm's of the drive shaft due to gear ratio change and you change the dynamic balance of the whole system.

Good luck and drive safe.

bransdaman78

wheels or tires.. not the gear

Quicktime_GT

Thanks for everyones reply. I still have the factory driveshaft, and the previous owner removed the "dog bone" i suppose, or the differential weight..