01
Gearbox will not sit flat on the block?
The rear flange face was machined after the bolt pattern, so the two faces are not parallel. The box tips, the input shaft loads the pilot bearing off-center, and the clutch disc wears unevenly.
Truck Drivetrain Components
Manual Gearbox Bell Housing, CNC Machined for Truck Powertrains
We machine the cast aluminum blank, then cut the bores and flange faces that set gearbox alignment. Send a drawing or a worn part and we return a quote plus DFM notes within 12 hours.
Ø400 mm rotary table±0.005 mmADC12 / 6061-T6No minimum orderISO 9001:2015IATF 16949:2016
16Simultaneous 5-axis centers
127High-precision CNC machines
±0.005 mmTolerance on critical faces
12 hQuote and free DFM analysis
Where bell housings fail
Four Alignment Problems We See in Truck Gearbox Housings
Each one traces back to a mating surface that was not cut in one setup.
02
Input shaft bore off center?
A bore that drifts 0.05 mm from the crank centerline shows up as vibration at idle and gear rattle under load. Once the housing is welded or worn, the original centerline is gone and has to be re-established from the block face.
03
Bolt holes do not line up at refit?
Cast housings creep and distort after years of heat cycles. If the mounting holes are drilled from the casting datum instead of the machined block face, the bell housing fights the transmission on the dowels.
04
Cracks at the mounting ears?
Thin as-cast walls at the bolting ears crack under torque. The fix is not more material everywhere. It is local thickness where the load path runs and a fillet radius the casting can actually fill.
How we make it
One Setup Per Critical Axis
Cast blank in, machined housing out, with the block face as the only datum that matters.
Machining Strategy
Cut Both Mating Faces Before Anything Else
A manual gearbox bell housing is a distance piece. Its job is to hold the gearbox input shaft on the same axis as the crankshaft, at a fixed distance, under torque and heat. That only works if the block face, the transmission face, and the input shaft bore are cut from the same datum.
On our 5-axis centers we face the block side first, then bore the input shaft bore and the dowel holes without moving the part. The transmission flange is cut last, referenced back to the block face. On a 4,000 mm machine bed we can hold the whole housing in one fixturing cycle, so there is no second-setup shift between the two faces.
- 1Bore and dowels in one passRemoves the stack-up that causes radial offset at the input shaft.
- 2Flange face parallel to the blockKeeps the gearbox sitting square instead of loading one dowel.
- 3Ø400 mm rotary tableReaches the inner wall and clutch release bore without re-chucking.
Material and Casting
Aluminum Gravity Casting, Then Machined Where It Counts
Truck bell housings are usually aluminum because weight at the rear of the block matters, and because the casting can carry a complex rib pattern that a billet part cannot afford. We work with ADC12 for gravity and die cast housings, and 6061-T6 or 6082 for low-volume parts cut from plate.
Castings get a raw material check, then the first operation establishes the block face. Walls stay as-cast except at the bolting ears and the input shaft boss, where we take light cuts to control thickness. Machined surfaces land at Ra 1.6–3.2 μm as-machined, or Ra 0.8–1.6 μm on gasket faces that need a finer seal.
- 1ADC12 and 6061-T6Cast for ribbed production housings, plate for prototypes and short runs.
- 2Light cuts at load pathsReduces distortion at the ears without thinning the whole wall.
- 3Gasket-face finish controlRa 0.8–1.6 μm where a paper gasket has to seal.
Selection Guide
When a Machined Bell Housing Is the Right Call
Match the process to the volume and the tolerance that actually matters.
| Situation | Recommended route | Why |
|---|---|---|
| One-off repair or prototype | Machined from 6061-T6 plate | No tooling cost, geometry changes are free |
| 20–500 units, ribbed housing | Gravity cast ADC12, then CNC | Ribs come free in the mold, machining sets the bores |
| High-volume OEM program | Die cast, then CNC finish | Lower piece cost once tooling is amortized |
| Bent or welded original | Re-machine from a new blank | A distorted casting cannot be re-datumed reliably |
| Tolerance looser than ±0.2 mm | Casting with spot facing | Full CNC on every face adds cost with no gain |
What we run
Machining and Finishing Under One Roof
Six capabilities that show up on most bell housing jobs.
01
5-Axis CNC Machining
16 simultaneous 5-axis centers cut the input bore, dowel holes, and flange in one fixturing cycle. Contoured inner walls and clutch release bores are reached without re-chucking.
02
4-Axis and 3-Axis Milling
12 four-axis mills and 27 three-axis machines handle face work, bolt patterns, and mounting ears on housings that do not need full simultaneous motion.
03
Mill-Turn
16 mill-turn centers cover turned bosses, bearing seats, and threaded ports in the same program as the milled faces, so concentricity is held between them.
04
Metal Die Casting
Casting and machining sit in the same supply chain. The casting draft, rib layout, and machining allowance are agreed before the tool is cut.
05
Rapid Prototyping
For a fit check before tooling, we machine or print a housing from your model so the gearbox, clutch, and block can be trial-fitted on the bench.
06
Surface Finishing
Anodizing, powder coating, bead blasting, and black oxide. Laser marking for part numbers and traceability codes down to 1.5 mm character height.
Capability Range
Equipment and Scope for Truck Housings
Numbers from our three plants in Dongguan and Singapore.
| Item | Capability |
|---|---|
| Maximum part size | 4,000 mm |
| Large machine travel | 4,000 × 400 × 150 mm |
| Medium machine travel | 750 × 1,150 × 550 mm |
| Compact machine travel | 500 × 500 × 450 mm |
| Rotary table | Ø400 mm |
| Achievable tolerance | ±0.005 mm |
| As-machined finish | Ra 1.6–3.2 μm |
| Fine finish | Ra 0.2–0.8 μm |
| Order quantity | One prototype to 10,000+ parts |
| Production start | Within 24 hours of PO |
Why GreatLight
Six Numbers Behind the Part
No adjectives. These are the figures that decide whether the housing fits.
15Y
15 Years in Precision Machining
Founded in 2011. Three wholly-owned plants and 150 technicians working on drivetrain, aerospace, and industrial parts.
±0.005
Tolerance on Critical Surfaces
Held on bolt holes, shaft bores, and flange faces. That is ±0.0002 in for drawings written in imperial units.
99.99%
Qualification Rate
Raw material check, in-process monitoring, and final inspection on every lot. Inspection reports on request.
12 h
Quote and Free DFM Analysis
Send a drawing, a STEP file, or a worn sample. You get pricing and manufacturability notes within 12 hours.
3–5 d
Parts Ship in 3–5 Days
Production can start within 24 hours of a confirmed order. Historical late-delivery probability is below 2%.
ISO 27001
Confidentiality by System
Uploads are secure. ISO 27001:2022 for information security, plus an NDA on request before we see the drawing.
7,600 m²Manufacturing space
150Technicians on staff
127CNC machines total
<2%Historical late-delivery rate
Industry Requirements
What Truck Programs Ask For, and What We Deliver
Commercial Truck Powertrain
Housings that hold gearbox alignment under sustained torque and heat cycling.
- ±0.005 mm on bores
- ADC12 gravity cast
- IATF 16949:2016
Fleet Rebuild and Repair
Replacement housings for units whose original casting is cracked or out of true.
- 6061-T6 from plate
- No minimum order
- 3–5 day shipment
Prototype Fit Checks
A housing machined or printed before tooling so the block, clutch, and box can be trial-fitted.
- Rapid prototyping
- Free DFM analysis
- Geometry changes free
Industrial and Off-Highway
Bell housings for stationary engines and off-highway gearboxes with non-standard bolt patterns.
- 4,000 mm part size
- Ø400 mm rotary table
- 100% inspection
FAQs
Questions Engineers Ask Before Ordering
Can you machine a housing from a worn sample instead of a drawing?
Yes, but only if the critical surfaces are still intact. We measure the block face, the input bore, and the dowel holes, then rebuild the model around those features.
If the casting is cracked through the bore or the flange is bent, there is no reliable datum left. In that case we need a drawing or a 3D scan of a good unit.
What tolerance can you hold on the input shaft bore?
±0.005 mm on the bore diameter and position relative to the block face. That is the number that keeps the input shaft on the crank centerline.
Holding it depends on the bore being cut in the same setup as the block face. If your design forces a second setup, expect the position tolerance to loosen.
Which aluminum should I specify?
For a ribbed production housing, ADC12 gravity cast then machined. It fills thin sections and takes the rib pattern without tooling cost at low volume.
For prototypes and short runs, 6061-T6 or 6082 cut from plate. Higher strength, no tooling, and geometry changes cost nothing until you commit to a casting.
How do you keep the two mating faces parallel?
Both are cut from the same datum in one fixturing cycle. The block face is established first, then everything else references it.
We do not drill the bolt pattern from the raw casting datum. That is the mistake that makes a housing fight the dowels at refit.
What surface finish do gasket faces need?
Ra 0.8–1.6 μm for a paper gasket that has to seal against oil. Rougher faces rely on the gasket to fill the grooves and can weep over time.
As-machined faces at Ra 1.6–3.2 μm are fine for dry mounting surfaces and bolting ears.
Do you offer an NDA before I send the drawing?
Yes. We can sign your NDA or provide ours. Uploads are handled under ISO 27001:2022 controls.
If you prefer, send a simplified envelope model first and we will quote the machining scope before you release the full drawing.
What is the minimum order quantity?
None. We run from one prototype to 10,000+ part runs.
For a single repair housing, cutting from plate is usually cheaper than opening a casting tool. For 500 units, casting starts to win.
How fast can you quote and ship?
Quotation and DFM analysis within 12 hours. Production can start within 24 hours of a confirmed order, and parts ship in 3–5 days.
Those are standard-run figures. A housing that needs a new casting tool has a longer front end, and we will tell you that in the quote.
Send Your Bell Housing Drawing
Upload a STEP file, a PDF, or a photo of the worn part. You get pricing and manufacturability notes within 12 hours.
12-hour quote100% inspectionNo minimum orderNDA on request
