LLADNAR

Well i just put 3.73s in my car and ditched the 2.73s,,, i am a Ford tech that specialises in rear diff and manual trans but this one has got me for some reason and of course its my car.

the setup went well thats pretty much all i can say .0010" backlash good gear pattern but when you get up to about 75 you can hear and feel a vibration from the rear.

i was thinking at first that it was u joints, i mean the d-shaft is making 1 more full turn than it used to so i replaced them,,and it moved the viration about 5 mph up,,,from 70 to now 75.

my main question is has anyone else had these problems before.


the only thing i can think now is maybe i have a warped pinion or ring gear.

mdvaldosta

Replace your driveshaft with an aluminum Ford Motorsport unit. They cost about $150.00 and it will make your shaking woes disappear. Drivetrain vibration is a fairly common thing when changing gear ratios - the driveshaft is balanced, or as Ford calls it "tuned", to the gear ratio in the car. The vibration you feel was always there, it was just "tuned out" and was at a higher speed (27% higher due to the ratio change, so from 70 mph it was at about 90mph before). They always design driveshafts to put the vibration out of the normal driving speeds, but its always there.

VertStangGT86

Yea, quite a few people have said the aluminum driveshaft helped with vibrations from gears.

BlueStang225

yeah but there is still a problem. Might help but does not eliminate. I have just did the same thing with my 373's. My brother is more of a rear end guy then me. He told me it was a clip that popped out causing it to do that. So you might want to take cover off and look and see if tthe clip is in or look in the gear oil lol. But that was my prob, and now it is gone. but yeah the aluminum drive shaft will help get rid of vibration.

VertStangGT86

Well what mdv was saying is that the drive shaft may be the problem in itself. If it was balanced to the old gears it may not run well with the new ones. That's why an aluminum one would help, not cause it would soak up vibrations from something else.

gmkilla

any of this stuff apply to me...I have a vibration at high speeds, but only when i let off the throttle, gets worse if i push in the clutch, and it is a rebuilt 2.73 rear...thanks

VertStangGT86

Possibly. I'd look for other problems first though since you have a stock setup.

89muscle

I HOPE YOUR BACKLASH WASNT .001 IT SHOULD BE BETWEEN .08 AND .15. OTHERWISE I WOULD CHECK TO SEE IF YOU PUT THE DRIVESHAFT ON THE EXACT SAME WAY IT CAME OFF.

LLADNAR

actually .010" is what i meant

roundman

take your driveshaft to a shaft shop and have them double check the balance on it and see if this doesn't make the vibration go away. like you said, it is now turning faster than it was before and the balance tolerance from the factory might not be close enough now with the lower gears. I'm assuming you changed the bearings in the differential when you replaced the gears!