Opinions needed on my rear end

[marcar1993]

The vibe is speed related, but it does not pass through. Starting down around 60 you can faintly feel it then it just gets worse well up past 110-120 or so. That makes me think it could be a bearing?

And yes it is a ford 8.8 rear out of a mustang with all the stock mounts and trick chassis upper arms/instant center correction buckets.

 

[lilbowtie]

Does it change (go away) letting of the gas @ that speed?

 

[DRIVEN]

I'd probably go 9" but I bet you can do it for less than $2500.

 

[olds307 and 403]

Your car will be putting out serious torque, probably 500+ ft/lbs. It depending what the buying cost of the 8.5" is then add $1000 to finish it the right way. Too bad Olds went away from the bolt in axles from the factory. Your car has the power to justify a 9" rear.

 

[marcar1993]

No throttle input doesn't change the vibe.
What do you suggest for a 9" cheaper than $2500? I was thinking buying a complete means that at least if it has a problem I have someone to hold accountable.
And thanks! Yeah it makes some torque and it isn't light, and it has a stick, so that combo will be tough on components.

 

[pontiacgp]

I've always wondered about testing for rear vibration - would the axle, being supported by axle stands, not show any vibration well due to being solidly supported? On the other hand, letting the springs/shocks hold it, would alter the driveline angles causing vibration?/

I would put it the axle on the stand so the rear suspension is at normal ride height. If you don't find the vibration then I would place the stands under the frame. If the vibration is coming from the differential pinion gear then you'll see it and there should be some leakage of fluid from the pinion seal.

 

[pontiacgp]

No throttle input doesn't change the vibe.

if you lightly apply the brakes does that change the vibration?

 

[motorheadmike]

https://www.strangeengineering.net/...ac-lock-35-s-t-axles-coil-spring-mounts.html/ $2300 complete.

Might even be able to find a sale on Black Friday...

 

[olds307 and 403]

https://www.strangeengineering.net/...ac-lock-35-s-t-axles-coil-spring-mounts.html/ $2300 complete.

Might even be able to find a sale on Black Friday...

That is basically an aftermarket Dana 60, correct? That should be plenty strong and not a bad price.

 

[64nailhead]

We have well under $2k in our 8.5 converted to 8.6 with 31 spline Mosers from Quick's. And we make 500ft/lbs at the wheels before 4K rpms. I just can't bring myself to put a 9" in a G-body lol.

Regarding the vibration - put it on a dyno and see if it's still there. If engine load has no bearing on the vibration, then I'll bet you're looking at the wrong end of the car. How's the alignment look including toe and camber on the rear axle? And yes, I just asked for the toe and camber readings on the rear axle.