What Are 68155868AB Splines? Wheel Hub Spline Count Guide
The splines on a 68155868AB front wheel hub assembly are the internal teeth machined into the centre bore of the hub flange; they mate with the external teeth on the constant-velocity (CV) joint stub axle and carry drive torque to the wheel. If the tooth count, tooth form or bore size is wrong, the hub will not seat correctly, the axle nut will not hold its clamp load, and the joint will wear early. Catalogue listings under one OE-style reference can differ, so spline data for 68155868ab must be confirmed against the manufacturer’s drawing and a physical sample, as HJDP of jnhjdp.com does for every hub unit order.
What Are 68155868AB Splines on a Front Wheel Hub Assembly?
A spline is a set of teeth cut around a shaft or inside a bore so that two parts can transmit torque while still sliding axially. On a front hub unit sold under an OE-style reference such as 68155868AB, the splines are normally the internal teeth in the centre bore of the wheel flange. The stub axle of the outer CV joint passes through that bore, the two sets of teeth lock the wheel to the driveline, and the retaining nut clamps the joint to the hub.
Because those teeth carry the whole drive torque at the front wheel, they are a fit-critical feature rather than a detail. A hub with the wrong tooth count, the wrong tooth form or the wrong bore size either will not slide onto the stub axle at all or will fit loosely and fret, which later shows up as a clunk, a worn bore and a joint that has to be replaced together with the hub.
Why the Reference Number Alone Does Not Define the Spline
An OE-style number identifies a part family and an application; it does not publish a spline count, a tooth form or a spline length. Aftermarket listings under one number are often built from more than one drawing, so bore detail, encoder type and thread can differ between suppliers. In many OE numbering systems the trailing letters (AA, AB, AC) mark engineering revisions, and a later revision is usually intended to supersede the earlier one while remaining interchangeable, but that convention is not a specification. For that reason the spline data that matters is the data on the manufacturer’s drawing and the data verified on a sample, which is the rule HJDP applies to the 68155868AB front wheel hub assembly it lists.
Splines, Tone Rings and Axle Threads Are Three Separate Specifications
Three independent features decide whether a hub unit is correct: the spline, the ABS encoder or tone ring, and the axle-nut thread. The spline decides whether the hub drives; the encoder decides whether the ABS system reads wheel speed; the thread and clamp load decide whether the joint stays tight. A hub can match the spline count and still be wrong on encoder type or thread pitch. Record all three separately on the enquiry and, where the volume justifies it, verify all three on the sample.
How Do You Confirm the Spline Count on a 68155868AB Hub?
Confirm the spline count by counting the teeth on the mating shaft and in the hub bore twice, recording the tooth form and the key diameters, and checking that data against the supplier’s drawing before a sample is approved. Counting teeth from a screen image is not confirmation, and a catalogue photograph rarely shows the bore clearly. The sequence below is the one to follow when a hub or a complete vehicle is on the bench.
- Start from the reference and its revision chain. Write the number down exactly as it appears on the old part, including the trailing letters, and ask the supplier which drawing revision applies. Do not assume that a later letter leaves the bore detail unchanged.
- Clean the splines first. Grease, rust and burrs hide tooth flanks. Brush the shaft, wipe the bore and let both dry; a rust ridge counted as a tooth is the most common single source of a wrong count.
- Count the shaft first, then the bore. Mark the first tooth with a paint pen, work around the circumference back to the mark, then repeat in the opposite direction. Photograph the shaft square-on so a colleague can count independently from the image.
- Copy the profile onto paper for fine teeth. Press a strip of thin card or paper against the shaft so the teeth leave an impression, then count the impressions on the bench under strong light. This works well on dirty or slightly worn splines where visual counting is unreliable.
- Measure the diameters and the engagement length. Record major (outside) diameter, minor (root) diameter, spline length, lead-in chamfer and the retaining-nut thread. Two hubs with identical tooth counts can differ in every one of these.
- Compare with the drawing, then confirm a sample. Send the recorded data and photographs to the supplier, ask for the drawing of the offered hub unit, and request a sample. HJDP confirms spline data against drawing and sample before production, and only then releases the agreed custom packaging and brand marking.
A complete confirmation sheet fits on one page: reference number, tooth count, tooth form, major and minor diameter, spline length, encoder type, nut thread and a photograph of the shaft. With that sheet an importer can compare two quotations that look identical on price but are not identical on fit.
Which Spline Type Is Used on Wheel Hub Assemblies?
Automotive hub units use either straight-sided (parallel) splines or involute splines, and the two are identified and measured differently. Both are well established in general engineering practice, as described in the spline (mechanical) reference; at the parts counter the practical question is which one is in your hand.
| Spline type | Tooth profile | How it centres and drives | What the buyer must record |
|---|---|---|---|
| Straight (parallel) spline | Flat-sided teeth with roughly parallel flanks | Torque taken on the flanks; centring depends on the shaft-to-bore fit | Tooth count, major and minor diameter, tooth width |
| Involute spline | Curved flanks similar to a gear tooth | Self-centring on the flanks, with more even load sharing | Tooth count, module or pitch, pressure angle, major and minor diameter |
| Serrated or interference-fit drive | Fine radial ridges pressed into a bore | Torque carried by friction and form after pressing | Ridge count, interference, press-fit data |
Straight (Parallel) Splines
Straight splines have roughly parallel, flat-sided teeth and are cheaper to cut, so they appear on many simpler and older front-drive connections. They are identified by tooth count, tooth width, outside diameter and bore size, all of which can be taken with a caliper and a bore gauge. Because the flanks are not self-centring, the quality of the fit depends heavily on shaft-to-bore clearance, and a slightly loose straight spline will fret long before it fails structurally.
Involute Splines
Involute splines use curved flanks similar to a gear tooth, spread load over a larger contact area and centre themselves on the flanks. They are described by tooth count, module or pitch and pressure angle, none of which can be read from a photograph. A straight spline and an involute spline with the same tooth count will not interchange: the flanks meet on a line instead of a surface, which concentrates stress and produces noise and rapid wear.
What About Hubs With No Splined Bore?
Some hub assemblies have a plain bore because the drive is taken elsewhere. On non-driven axles there is nothing to connect, and on some driven designs the outer constant-velocity joint bolts to the flange face so torque is carried by friction at the flange rather than by teeth. Confirm the presence or absence of a splined bore from the drawing, not from a low-resolution catalogue thumbnail, because externally splined stub axles and internally splined hub bores are regularly confused in aftermarket listings.
Which Spline Dimensions Should Be Recorded Before You Order?
Record tooth count, tooth form, major diameter, minor diameter, spline length, lead-in chamfer, retaining-nut thread and encoder type; a photograph supports that data but does not replace it. These fields describe the fit precisely enough for a supplier to compare an offered part with the original without seeing the vehicle.
| Data field | What it describes | How to capture it | Why it decides the fit |
|---|---|---|---|
| Tooth count | Number of teeth around the circumference | Count twice around with a mark on the first tooth | Primary identity of the spline; a mismatch means the part will not fit |
| Tooth form | Straight or involute profile | Visual check plus profile gauge or paper impression | Straight and involute teeth do not interchange even at the same count |
| Major diameter | Outside diameter across the spline teeth | Caliper or micrometer across the tooth tips at two points 90 degrees apart | An oversize shaft or undersize bore blocks assembly |
| Minor diameter | Diameter at the tooth roots | Pin gauges or an internal micrometer in the bore | Controls engagement and tooth strength |
| Spline length | Length of the toothed section | Rule or caliper along the axis | Short engagement reduces torque capacity; excessive length can foul a shoulder |
| Lead-in chamfer | Chamfer at the mouth of the bore | Visual check and gauge | Guides the shaft square and prevents damage during assembly |
| Retaining-nut thread | Thread size and pitch on the stub axle | Thread gauge on the shaft | Separate from the spline, and often why a hub that fits will not tighten |
| ABS encoder or tone ring | Encoder type and pole count | Visual check against the supplier drawing | Independent of the spline; a hub can match on splines and still be wrong for the ABS system |
How to Measure Spline Outside Diameter and Bore
The major diameter is measured across the tips of the teeth at the widest point, not across a single tooth. Take two readings roughly 90 degrees apart, on a clean and burr-free surface, and use an internal micrometer or a telescopic gauge for the bore. If the shaft and the old hub are both available, measure both and compare the difference: the running clearance tells you how much the original fit has opened up. The HJDP wheel hub bearing and hub unit range is specified on drawing data of this kind rather than on catalogue photographs.
Where Spline Measurement Errors Come From
Most wrong spline counts come from the part, not from the tools: rust ridges, chamfers, damaged teeth and grease are counted as teeth. Other frequent errors are measuring across a single damaged tooth instead of across the tips, using an inside caliper on a curved involute flank, working from a superseded catalogue entry, and assuming that a later revision letter guarantees the same bore. Repeat every count in both directions and have a second person confirm it from a photograph.
Which Hub Bearing Generation Are You Replacing?
Generation 1, generation 2 and generation 3 hub bearing units mount differently, and that changes where the splines sit on the assembly. Establish the generation before comparing prices, because two suppliers can quote the same reference for parts that are not the same assembly at all. Most manufacturers, including the hub units and running-gear assemblies supplied under the HJDP brand, quote on the assembly, not on the reference alone.
| Generation | Construction | How it mounts | Spline relevance |
|---|---|---|---|
| Generation 1 | Double-row angular contact bearing with no flange on either ring | Pressed into the steering knuckle and onto the hub or spindle | Bearing is usually plain-bored; the drive splines sit in the separate hub flange or on the stub axle |
| Generation 2 | Bearing with a flange on the outer ring; a separate hub flange carries the wheel | Flange bolts to the suspension; hub flange is fitted to the bearing | Splined bore is in the hub flange that carries the wheel |
| Generation 3 | Flanges on both rings, forming a complete bolt-on unit | Bolts directly to the suspension; wheel and disc mount to the unit | Splined bore in the wheel flange on driven axles, commonly with an integrated ABS encoder |
How to Identify the Generation Quickly
Look at the flanges and at how the bearing is retained. A plain cylindrical bearing pressed into the knuckle with a separate hub flange is generation 1. A bearing with one flange and a separate wheel-carrying hub flange is generation 2. A unit with two flanges, where the wheel flange is part of the bearing and the mounting face is bolted, is generation 3. A retaining nut on the stub axle, a snap ring or a bolted flange each point to a different assembly method, and each places the splines in a different component.
Why the Generation Changes the Spline Conversation
On generation 1 units the bearing is usually plain-bored and the drive splines belong to the separate hub flange or stub axle; on generation 2 and generation 3 units the splined bore is in the hub flange that carries the wheel. That matters when a workshop replaces a bearing rather than a complete unit: a correct generation 3 hub with the correct splines cannot be substituted for a generation 2 bearing and flange, and a supplier quoting only a bearing number may be answering a different question from the one being asked.
How Do Splines Wear Out, and What Are the Failure Signs?
Spline wear is usually a fit or clamp-load problem rather than a load problem, and the symptoms appear as noise and movement before the wheel bearing itself fails. Splines are designed to transmit torque, not to absorb relative movement; once the fit allows movement, the teeth begin working against each other.
| Symptom | Usual cause | What to check |
|---|---|---|
| Clunk when drive is taken up or reversed | Movement between shaft and hub bore | Spline wear, bore clearance and retaining-nut clamp load |
| Red-brown powder around the splines | Fretting from micromovement | Fit clearance and spline engagement length |
| Grease weeping at the joint | Seal damage caused by axial movement | Spline play and joint axial end-float |
| Vibration at road speed | Runout or uneven wear | Spline runout and flange-face runout |
| Hub will not slide onto the shaft | Wrong count, burr or damaged lead-in | Re-count the teeth and inspect the chamfer |
Where Spline Wear Actually Comes From
The main cause is insufficient clamp load or excessive clearance between the shaft and the bore. When the retaining nut is not tightened to specification, or when the bore has already opened up, the shaft moves slightly under every torque reversal. That micromovement rubs the flanks, produces the characteristic red-brown fretting powder and progressively removes material until the fit is visibly loose. Corrosion accelerates the process on vehicles used in humid or coastal conditions.
What a Workshop Should Check Before Replacing a Hub
Check the spline fit, the nut thread and the encoder before ordering a replacement hub. Slide the new hub onto the shaft dry and feel for play; a hub that rocks on the shaft will not be saved by tightening the nut. Inspect the nut and the stub-axle thread for damage, confirm the encoder type against the old unit, and clean the splines so the joint is assembled free of grit. If the bore of the old hub is visibly worn, the mating stub axle should be inspected as well, because a worn shaft will damage a new hub in the same way.
How Should an Importer Write an RFQ for a Splined Hub Unit?
An enquiry that carries drawing-level spline data, quantity structure and packaging requirements gets a usable answer; an enquiry that carries only a part number gets a guess. The list below is the minimum that lets a bearing manufacturer compare an offered hub with the original part without a vehicle in front of them.
What to Put in the First Message
- The reference number as marked on the original part, including revision letters, plus any superseded numbers you already know.
- Tooth count and tooth form, together with the method you used to count them.
- Major and minor diameter, spline engagement length, chamfer detail and retaining-nut thread.
- Encoder or tone-ring type, and whether the axle concerned runs ABS.
- Assembly type: complete hub unit, bearing only, or hub flange only.
- Photographs of the old part square-on, showing the splined bore and the flange face.
- Purchasing pattern: annual volume band, order frequency, packing type, and whether you need custom packaging or your own brand marking.
What to Ask the Supplier to Send Back
Ask for a drawing that shows the spline data, a sample of the offered part, and the marking and packaging plan, in that order. A drawing lets your technical contact check the bore before you spend money on freight. A sample lets your own workshop test the fit on a real shaft. The marking and packaging plan confirms that the goods can be sold without a rework step at the warehouse.
Why Sample Confirmation Protects Both Sides
A sample approved against measured spline data locks the specification and turns any later change into a clearly identifiable new revision. That is the practical purpose of drawing and sample confirmation: it removes the argument about what was ordered. HJDP applies this process to the front wheel hub assembly listed for reference 68155868AB, alongside custom packaging and own-brand marking for importers, wholesalers and workshop channels.
Frequently Asked Questions About 68155868AB Splines
What is the spline count on a 68155868AB front wheel hub?
There is no single spline count that applies to every part sold under that reference. Different manufacturers build to different drawing revisions, and aftermarket listings sometimes use a number loosely. The reliable figure is the one shown on the supplier’s drawing and checked on a sample. Count the teeth on your own stub axle, then ask the supplier to confirm that the offered hub matches that count, tooth form and bore size.
Can I use a hub with the same tooth count but a different tooth form?
No. A straight spline and an involute spline with the same number of teeth do not interchange. The flanks meet on different surfaces, so a mismatched pair sits loosely, transmits torque over a fraction of the intended area and wears quickly. Tooth count is only one of several fields; always confirm the form, the major and minor diameter and the engagement length together.
Does the ABS tone-ring count have to match the spline count?
No, they are independent specifications. The spline carries drive torque, while the encoder ring tells the ABS controller how fast the wheel is turning. A hub can have the right spline count and the wrong encoder type or pole count, which may trigger an ABS warning even though the hub fits and drives correctly. Record both on the enquiry and check both against the original part.
How do I order an HJDP hub unit if I only have a sample and no part number?
Send the sample or accurate measurements taken from it. Photograph the splined bore square-on, record tooth count, spline form, major and minor diameter, spline length, encoder type and nut thread, and state the vehicle and axle position. HJDP confirms the specification against drawing and sample before production, and can supply custom packaging and own-brand marking for importers and distributors.
