Gear ratio swap in LSD?

[DirtE Thirty]

I have a '89 325i I am prepping to run Chump Car. It came with an 3.73 open diff. I picked up a complete rear subframe for cheap with driveshafts for spares. It came with a LSD with a 2.93 ratio.

Can I switch out the gears in the 3.73 open diff into the 2.93 LSD?

[!kid]

I am not 100% sure because I've never had an open and LSD diff in front of me to compare. Most of the time you can just swap the ring gear. Only down side is unless you know how and have the tools to set the back lash. Your kinda dead in the water. The pinion gear may need to be swaped out too. For the price of tools and parts you may end up spending the same amount to just find an LSD diff with the ratio you want.

[Wanganstyle]

nope. geometric offset of the 2.65-3.07 gears is different than 3.15-4.88 gears.

you need a LSD center capsule from 3.15 or higher number to plug into your 3.73 gearset.

for chump car just weld the open 3.73 and drift more!!!

[rcarradine]

nope. geometric offset of the 2.65-3.07 gears is different than 3.15-4.88 gears.

you need a LSD center capsule from 3.15 or higher number to plug into your 3.73 gearset.

for chump car just weld the open 3.73 and drift more!!!

Will the 3.15 components from a Z3 3.15 open diff fit into my E30 3.73 LSD giving me the 3.15 ratio but LSD capability?

[TobyB]

Yes, IF both are the same size (188 or 168)

t

[Wanganstyle]

Will the 3.15 components from a Z3 3.15 open diff fit into my E30 3.73 LSD giving me the 3.15 ratio but LSD capability?

Why not just bolt in the entire 3.15 torsen z3 diff? It bolts in.

[rcarradine]

Why not just bolt in the entire 3.15 torsen z3 diff? It bolts in.

The 3.15 diff I found at the yard wasn't a torsen/LS differential. It appeared to be an open 3.15 (which I didn't know existed). It got me thinking. "Could I take the ring gear and put it in my diff making it a 3.15 LSD?"

[TobyB]

The Torsen may act like an open if both wheels have absolutely no resistance.
One of the reasons (I've heard- I weld mine) it's not all that popular in racing.

t
spreading internet myth

[Wanganstyle]

Gear ratio swap in LSD?

The 3.15 diff I found at the yard wasn't a torsen/LS differential. It appeared to be an open 3.15 (which I didn't know existed). It got me thinking. "Could I take the ring gear and put it in my diff making it a 3.15 LSD?"

If it was a 3.15 and from a z3 (only car in USA with e30 housing that had a 3.15 in 188 size

Then it was either a Torsen or a clutch type.

Any gearings in 3.15-4.45 in 188mm will interchange