I know that you have to take BOTH your 3.7 AND your 3.9 diffs into a shop to convert, or can convert yourself, but what I want to know is if you can't just buy a 3.9 gear set to install in a diff? Does anyone make a gear set like this? That would eliminate the need to find a LSD which are getting rare. Just wondering. Thanks.

 

And feel free to knock me down if this is WAY off!

but what I want to know is if you can't just buy a 3.9 gear set to install in a diff? Does anyone make a gear set like this?

Yeah, subaru does. Do you want just the gear and Pinion? or do you want the LSD, cause i'll let you in on a little secret, if there was an easier way we'd all be taking it.

 

There are plenty of other makes that use the 3.9, plenty of which have lockers and other better traction aids, but unless you want to fab up a new rear diff or whole straight axle in the back, the LSD is the easiest way to go

The other reason for moving the LSD kernel into an open diff is that you won't have to re-shim the ring and pinion gears which is critical to the long life of your new diff.

I know that you have to take BOTH your 3.7 AND your 3.9 diffs into a shop to convert, or can convert yourself, but what I want to know is if you can't just buy a 3.9 gear set to install in a diff? Does anyone make a gear set like this? That would eliminate the need to find a LSD which are getting rare. Just wondering. Thanks.

 

And feel free to knock me down if this is WAY off!

The other reason for moving the LSD kernel into an open diff is that you won't have to re-shim the ring and pinion gears which is critical to the long life of your new diff.

 

actually, the more I thought about this in the past, the more convinced I am that we just get lucky....

 

when I did mine, I moved the side caps/shims from the 3.70 along with the LSD carrier and bearings on it, so that the bearings were matched up with the shims... (actually, it was because I had already mixed up the 3.90 side caps, but keeping the 3.70 stuff with it sounded better to me )

 

just thoughts....

actually, the more I thought about this in the past, the more convinced I am that we just get lucky...

 

Maybe part luck, maybe part good engineering and quality control.

 

I haven't heard of an engine out of Nippon that required selective bearing sizing because of production variances, unlike my 'merican V8. (Hard to buy a set of "some this size, other this size, and one a little bit bigger".)

 

...just a thought...

Maybe part luck, maybe part good engineering and quality control.

 

I haven't heard of an engine out of Nippon that required selective bearing sizing because of production variances, unlike my 'merican V8. (Hard to buy a set of "some this size, other this size, and one a little bit bigger".)

 

...just a thought...

This has nothing to do with bearing size. He got lucky on the gear spacing. If a Nippon rearend was built to a far greater quality than a AMERICAN piece, than it wouldn't need shims to mesh the gears properly. But both use shims to get the gears aligned right.