94tbird

im having a weird problem with my car. my mods are in the sig.

When the problem started:
we had just installed the Spec Stage 3+ Clutch, Spec Aluminum Flywheel, and the Powerhouse Aluminum Driveshaft. This did not cause my current noise, but it did result in the driveshaft scraping the tunnel. The fix for this was to install an adjustable control arm. This would allow us to reset the pinion angle. the desired angle is negative 3 degrees for drag racingas im told.

We ordered the CHE Double Adjustable Upper Control arm and the CHE Anti Squat Brackets (Equivilent to the BMR LCA Relocation Brackets). We installed these items and using the adjustable UCA, we set the pinion angle to negative 3 degrees in relation to the driveshaft. The driveshaft measured at 3 degrees and the pinion at 0 degrees. This is the correct setting for drag racing as i was told by CHE and many members on TMS and Mod Fords. Here is where my current problem starts:

The noise is best described as a whirring or a wobbly noise when accelerating. it is most noticable at speeds of 60-70mph but does happen around 40mph as well. seems to get louder with speed. There seems to be no power loss or loss of acceleration power. ive had the car up to aprox 150mph and there is no vibration in the driveshaft at all.

some things i tested were:

Car out of gear:
Revving the engine can not reproduce the sound

Car in gear:
Accel: the car will make this noise on slight accel but will eventually get drowned out by the exhaust until higher speeds are reached. even on the slightest accel the noise will appear. as soon as i release the throttle, it dissapeares completely.

I set cruise control to 70mph on the highway. when the road is completely flat, and the computer is maintaining the speed, it makes this noise that is def coming from the rear of the car. with the cruise set and gonig slightly downhill, the noise goes away completely. if going slightly uphil the exhaust will almost drown it out but it can still sort of be heard. definately more noticable with the windows up than down. even on the slightest accel the noise will appear. as soon as i release the throttle, it dissapeares completely.

Decel:
There is no noise on Decel.

Today i had the car on the lift. There are no rubbing marks or anything on the driveshaft. We accelerated the car while on the lift suspended in the air and it did not make any noise. We used a stethascope on the rear end and my buddy tells me it is quiet with no noise whatsoever coming from it. we then lowered the car and using a floor jack, raised only the rear end in the air to keep the rear suspension loaded. once again this did not reproduce the noise. we did note wit hthe car in the air the driveshaft is spinning with no vibration and is spinning perfectly smooth.

I called JDM and spoke to Jim Jr and he said they have done 5 or 6 high powered cars thus far with aluminum driveshafts and they all have had noise, including their own car.

I spoke with someone at Powerhouse and he said that 4.10 gears will inevitable have noise to them. its jsut the factory bushings on the LCA's and UCA are rubber so they deflect and deaden the noise. the bushing on the new LCA's and UCA are poly urethane and are much stiffer and will transfer the noise through the drivetrain. The aluminum driveshaft sort of acts liek a tuning fork, further transfering the noise. This seems liek the most likely cause to me but why wont it reproduce the noise when the wheels arent touching the ground?

Does anyone have any idea or insight into this matter? It is rather annoying!

Treadhead

I have no idea but, the title of this thread cracked me up!

manystangs

Maybe just NVH from the adjustable control arms? The rod end ones transmit more noise.

94tbird

i have poly, not rod ends. yea this is getting sick if u take it that way haha rear ends and rods lol

manystangs

I have the Poly end ones as well, and I noticed more noise, more of a whirring sound coming from the "cars rearend". It is more prevelant at around 35 to 40 MPH.