Look inside of a diff that had the M Clunk

[bigjae46]

The play on the passenger axle stub? is/was causing most of my issues/noises.

It’s a possibility. Need to diagnose the issue which isn’t always easy. Not outside the realm of possibility that it is something else (driveshaft, axles, rear suspension) and/or multiple causes of a clunk.

I didn’t take a video before dismantling the diff but there was a lot of lash in the spider gears inside the diff case so it is a likely this was a source of clunks.

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[bigjae46]

The 4 spiders (small ones) and the 2 side gears (large ones) don't rotate on a straight road, so they are harmless. They rotate only during a turn. I wouldn't replace these gears for no reason.

Just shim up the side gears for less plays between side gears and spiders.

How is that? The axles are splined to the large spider gears. If you look into the output flanges, the splines that the axle stub inserts into is large spider gear. The left side on the V1 actually goes through a gear which is splined with the clutch plates and the large spider gear.

The spider gears rotate at the same speed. When you turn, the large spider gears will rotate at different speeds since the wheels are rotating at different speeds. When there is slippage, the diff case/steel plates are spinning at a different speed than the spider gears/clutch plates. The slippage engages the GKN unit to apply force to press the steel/clutch stack together which locks the diff case/steel to the spider gears and transfers torque to the slipping wheel.

Gears have a backlash or free-play spec. I don't know what that is for the spider gears or if there is a spec in existence.

[TheElite///M3]

RacingDiffs just has a small discount on the rebuild kits plus washer for slack. I may have to tackle this project diy, source a press from HF, and then learn about setting lash. Glad to see more folks are diy vs waiting for a pumpkin that runs $5-7k…

[sapote]

How is that? The axles are splined to the large spider gears. If you look into the output flanges, the splines that the axle stub inserts into is large spider gear. The left side on the V1 actually goes through a gear which is splined with the clutch plates and the large spider gear.

The spider gears rotate at the same speed. When you turn, the large spider gears will rotate at different speeds since the wheels are rotating at different speeds. When there is slippage, the diff case/steel plates are spinning at a different speed than the spider gears/clutch plates. The slippage engages the GKN unit to apply force to press the steel/clutch stack together which locks the diff case/steel to the spider gears and transfers torque to the slipping wheel.

Gears have a backlash or free-play spec. I don't know what that is for the spider gears or if there is a spec in existence.

Your question is about why worn down clutch stack has no effect on the spiders/side gears plays, or about I suggested not to replace these gears (that seem to be worn)?

The clutch stack do not exert a thrust force on the side-gears and so it has no effect on the spiders/side-gears mesh or plays.

"If you look into the output flanges, the splines that the axle stub inserts into is large spider gear." The axle stub is also called the output flange.
"The left side on the V1 actually goes through a gear which is splined with the clutch plates and the large spider gear." That gear and the large spider gear (it's called side-gear, as the spiders are the ones attached to the carrier via a rod) actually is a one piece, the left side-gear. For the Opened Diff, the side-gear has no extended section that splined to the clutch stack, and only the LSD has one of the side-gear with the extended section splined to the clutch.

"Gears have a backlash or free-play spec. I don't know what that is for the spider gears or if there is a spec in existence" I think the backlash or plays is specific to application and not the gears themselves. It seems most differentials have a lot of backlash for the spiders/side-gears and I don't know the reason.