I am glad I read this post, I crawled under my car and mine are in the wrong mounting holes.....I am glad I am curious LOL. Time to break out the grinder LOL.


David

 

That's one of the downsides of the 9-inch.... the pinion is offset to one side, and dropped 0.75" lower than the 12-bolt.

 

but is the offset actually hurting anything or slowing the car down?
from the d/s point of view, going down a couple degrees to meet the rear is the same as going over a few - I think if it were extreme enough to cause u-joint issues it would be a problem. I paniced at first - but after BMR said "don't buy our arm just to use those hols - it's ok" - and looking at it - I've seen trucks with far more degrees of offset driving around. And driving the car felt smoother than my old 10 bolt for various reasons.

It COULD be cured with more offset axles - but the large hump of the housing would be under the driver side rear seat. I bet cars aren't designed for that

Now, I do not like the raised in the air look deal...have to research the proper way to restore ride height now

 

Can you take pics of yours like my pics - before and after you move the arm?
If you simply move the arm over to be parallel with the offset angle of the d/s because otherwise you'd be pulling your housing to the driver side just to get the d/s straight - BMR said as long as the HOUSING ENDS ARE CENTERED IN THE WHEEL WELLS the car will be set up ok. The offset d/s is ok. I'm not so sure i'd want my tq arm at an angle - as Injuneer said - that could cause failures.
Let us know how your angles change.

 

The pinion offset is what makes the rear so strong, the teeth have more contact area. Because of this there is more friction and drivetrain power loss.

Remove the rear spring rubbers, will drop the car down.

I will do the mod with the trans and driveshaft out of the car(it already is) SO I will have no compare pics. The arm will move over roughly 3/4 of an inch in the rear at the mounting holes.

David

 

I knew the 9" was a power robber and heavy - didn't know that was why.
Still - I wonder if your arm change will make it straight in the tunnel, or make it slightly angled like the d/s.
What would a suspension expert say about the arm pivoting and it's direction...? I'm sure they started putting the holes closer to the pinion for 9" housings for a reason - I wish I asked BMR more about it.

 

Yes, offsetting the pinion lower is one of the reasons the 9-inch has higher mechanical power losses. Consider the Dana, with the pinion higher than the 12-bolt, probably stonger than the 12-bolt, and mechanically more efficient than the 12-bolt or the 9-inch.

Then there's the issue of the additional wear on the u-joints and additional power loss because the angle is steeper.