G-Series Front Axle Boot Replacement

IA EURO illustration of a BMW G-series front axle shaft inner joint: the inner boot and both clamps circled in red marker, all the work happens from this end, the shaft runs on to the wheel

On a G-series xDrive BMW, a front axle boot is a bench job: shaft out, both boots done from the inner end, shaft back in. Before you buy a boot kit, one measurement tells you whether BMW allows it on your shaft at all.

Is it the boot, or the whole shaft?

BMW's own inspection rules for its G-series X models are a good test for any of these cars:

A film of grease or dirt on the boot is normal. BMW says don't replace anything for that alone.
Replace it for: a crack or tear, a missing clamp, a clamp that turns or slides easily, or grease slung onto the parts around the joint.
Clean before you judge. A rag and silicone spray. No brake cleaner or solvent: it eats rubber.

Shop rule of thumb, not BMW's: a torn boot on a joint that's quiet and still full of clean grease gets a boot kit. Clicking on tight turns (outer joint), a shudder when you accelerate (inner joint), or grease that feels gritty means the joint is worn. Replace the shaft.

Rear axles: whole shaft only. BMW's repair data has no boot job, and its parts catalog lists no boot kit, for any G-series rear axle we checked. A torn rear boot means a new rear shaft, and on a G20 that job drops the rear differential. This guide is the front axles on xDrive cars.

Measure before you buy

BMW's G20 family shafts come from more than one maker, and BMW doesn't let you re-boot the Neapco ones. The only way BMW gives to tell them apart is one measurement on the inner boot, called dimension A.

106 mm106 mm is a Neapco shaft: BMW says no single boots, inner or outer. Buy the shaft. 126 mm: both boots can be replaced.

Which kit fits

Boot kits by BMW number, from BMW's parts catalog up to 2020. The same car can have either of two front shaft versions, so check yours by VIN before you order. The 4 Series (G22, G23, G26) came after that catalog: BMW's bench steps are the same as the G20, but confirm the kit by VIN.

G20 330i and M340i xDrive, first shaft versionOuter kit 31 60 8 488 705, inner kit 31 60 8 657 288.

330i xDrive, second shaft versionInner kit 31 60 8 680 223. BMW doesn't sell the outer boot on its own for this shaft.

X3 and X4 (G01, G02)Inner kit 31 60 8 680 223. Same bench steps as the G20. No outer kit listed for them up to 2020.

X5, X6, X7 (G05, G06, G07)Inner kit 31 60 8 680 223. BMW's procedure for these covers the inner boot only.

5, 6, 7 and 8 Series xDrive (G30, G32, G11, G12, G14 to G16)Outer kit 31 60 8 657 723, inner kit 31 60 8 657 288. A different shaft: on these, BMW presses the outer joint off to change the outer boot. The bench steps below are for the G20 family.

Also new every time: the hub collar bolt with its spring (31 20 6 866 022 on G20, G30, G32, G11, G12 and G14 to G16), the anti-roll bar link nut, the clamps, the tripod circlip and the circlip on the shaft end. Kits differ in what they include and grease is often sold separately, so check the box against this list.

Grease, by weight

Outer joint90 g

Inner joint, kit 31 60 8 680 223140 g Renolit CX-TP 1

Inner joint, kit 31 60 8 657 288165 g One Lube Improved

BMW sells these greases in 100 g and 110 g bags, so the inner joint takes two bags. Every bit of old grease comes out first.

Torque

Hub collar bolt, M16, new bolt and spring210 Nm + 90°, brake pedal held down

Anti-roll bar link nut, new nut56 Nm

Front diff plug, new plug60 Nm

Wheel bolts140 Nm

IA EURO illustration of a BMW G-series hub collar bolt with its spring: new bolt and spring every time, threads clean and dry with no grease, 210 Nm plus 90 degrees with the brake pedal down — The hub collar bolt and its spring. Both are new every time, and the spring goes back the same way round.

Shaft out

Crack the collar bolt with the car on its wheels and the brake on.
Car up, wheel off. Front underbody panel, stiffening plate and steering cover off. BMW says never drive without the stiffening plate.
Free the wheel speed sensor cable from its holders.
Anti-roll bar link off the strut. Hold the stud with a Torx bit while you undo the nut.
Collar bolt out. Swing the knuckle outward and slide the shaft out of the hub.
Support the shaft. Knock it out of the front diff (left) or the bearing support (right) with an aluminum drift.

Shaft in

New circlip on the shaft end. Check the splines and the seal. BMW replaces the diff seal on this job.
Coat the splines with the front diff oil.
Push it in with a sharp shove until it clicks. You should feel and hear it lock. If it needs brute force, something is damaged.
Into the hub, link back on with a new nut, 56 Nm.
New collar bolt and spring, spring the right way round, bolt and splines clean and dry. Hand tight, check the splines sit tooth in tooth, brake pedal down, 210 Nm then 90°.
Covers and stiffening plate on, wheel to 140 Nm. The stiffening plate torque and screws vary by model: send us your VIN for yours. Check the front diff oil and top it up.

On the bench: both boots, G20 family

Two hard rules from BMW. Everything happens from the inner end: never push off or take apart the outer joint (it's held by a snap ring). And don't bend the shaft more than 18° at the inner joint or 45° at the outer while it's out.

Aluminum jaws in the vice, clamp the shaft. Measure dimension A on the inner boot. 106 mm: stop, it's a Neapco shaft.
Inner clamps off. Cut ear clamps across the ear. Pull the boot off the housing, then pull the housing off. Don't pull or push at the seam between the shaft and the inner joint.
Circlip off the tripod. Thread a bolt into the hole in the shaft end, as BMW does, then pull the tripod off with a puller.
Old inner boot off. Cut the outer boot's clamps, pull it back off the joint and slide it off over the shaft end.
Outer boot: wipe the joint and shaft clean, slide the new boot on, pack the joint with 90 g of grease, seat the boot. Then vent it: slip a smooth blunt tool between boot and shaft for a second to let the trapped air out. New clamps.
Inner boot: new clamps, then the new boot onto the shaft. Tripod back on with its flat side toward the circlip, tapped on with a 24 mm socket until the new circlip fits.
Grease the tripod and housing (140 g or 165 g by kit), housing on, boot on. The boot sits on the taper of the shaft, the clamp's hook centered on the housing. New clamps, tight.

Clamps, done right

Ear clamps: close them with ear clamp pliers until the gap left at the ear is 1 mm or less.
Flat band clamps: they stretch when they come off, so they're never reused. There are two types that each need their own pliers. Squeeze until the hook catches. If it doesn't catch, start over with a new clamp.

IA EURO illustration of an axle boot clamp: the clamp hook sits centered on the joint housing, and the clamp is new every time — The clamp hook sits centered on the housing.

Where people mess it up

Buying a kit for a 106 mm shaft. Measure first.
Hammering the outer joint off a G20 shaft. That's how the G30 and 7 Series do it, not the G20.
Old grease left in the joint, or one bag where the inner joint needs two.
Skipping the vent. Trapped air balloons the new boot.
Reusing clamps, the collar bolt or its spring, or putting the bolt in greasy.

Steps, torque values, grease amounts and part rules come from BMW's repair instructions for the front output shafts (main group 31) and BMW's US bulletin on front axle inspection. Kit numbers come from BMW's parts catalog up to 2020. Check yours by VIN.