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All About Casting Numbers

Decoding The Numbers on Your Parts

This Section Will Cover Casting and Molding Numbers Found Directly on Your Parts and How they are Not Only Helpful,
but Sometimes Required when Searching for
Tractor and Heavy Equipment Parts.

Table of Contents

What is a Casting Number Exactly?

Many tractor and heavy machinery parts are cast; meaning material such as plastic, steel, iron, or aluminum is poured into a mold before it hardens. Every part made with the same mold comes out identical to the one before and after it. Thankfully, manufacturers used numbers and letters in their molds so each one bears the same “code.” These are most commonly found on axle, transmission, or rear end housings, lift top covers, engine blocks, fuel tanks, and other non-moving parts.

Why are Casting Numbers so Important?

In almost all cases, when we are trying to verify that the part we offer will fit your machine the number on the part itself will tell us if we have a match. That is not the case 100% of the time, and we have found most of the exceptions the hard way. 


Most cast parts are heavy and have multiple dimensions to match: bolt spacing, diameter, length, thickness, height, etc… I have literally set two water pumps side-by-side and turned them every possible way I could for hours, and still couldn’t detect the difference between the two with my eyes, measuring tape, or micrometer. If only there had been a casting number on the housing, I could have avoided a frustrating learning experience, and I’m trying to help you avoid it, too.

Where Should I Look for the Casting Number?

The short answer is “directly on the part.” That is always true, but it’s not always jumping off the machine at you. Here are some common parts with casting numbers, and where to look for them:


Axle Housings: For most wheeled machines you will find the numbers from the rear of the part. Some casting numbers are on the underside of the axle.


Engine Block: Most commonly on the right-hand side of the engine. (If you would like a quick refresher, see “My Right or Your Left? How to Properly Orient Your Machine”). Make sure you are looking at the block directly because many engine components have their own numbers.


Cylinder Head: This depends on the manufacturer. Some can be found on the side of the head. Some are found on top of the head, underneath the valve cover.


Front Axle Support (Bolster): Almost always on the underside of the bolster. You either have to scoot yourself, your camera, or someone else under the machine to see it. It will also be covered in grease and grime.


Now that you know where to find some common casting numbers, I’ll tell you WHAT numbers to look for


Casting Number Format by Manufacturer:

Ford/New Holland: 

Uses numbers and letters. Ex: D4NN7006AB

Old Ford tractors (Pre 1950) Use Shorter Codes or Numbers. Ex. EAE8006B or 310665

New Holland Uses Mainly Numbers. Ex. 80067568

All Have a Similar Format, but Rarely Matches the Part Number.



Mostly Numbers With One Letter. Ex: 81107C91, or A184267

Matches Part Numbers Less than Half the Time



Almost all Start With a Letter Followed by Six Numbers. Ex: T151503

Matches the Part Number Almost all of the Time.



Mostly Numbers Divided by Two Dashes. Ex: 20Y-30-66250

Matches Part Numbers Less than Half the Time



Seven Numbers Separated by a Dash. Ex: 117-2305, or Five Numbers with a Letter in the Second Position. Ex: 6E2426

Matches the Part Number Most of the Time.


Massey Ferguson:

Usually 8-9 Numbers Only. Ex: 37111500


Matches Part Number About Half the Time


Notable Exceptions:

There are some important things to note. Just because a casting number on a part housing matches your casting number, it does not guarantee that the entire assembly will fit. Transmissions are a good example. The casting number tells us that the housing or casing will bolt up to your machine, but the internal gears and shafts may not be compatible with yours. If the input shaft diameter, length, and/or spline count do not match, the transmission will not work.


Another notable exception is a Ford 3-cylinder tractor hydraulic pump used on thousands of 3000, 2000, and 4000 series tractors, and 172ci engines. EVERY pump assembly has the same front housing with the same casting number: C5NN905,  but there is a fitting on the rear of the pump that comes in two different styles and diameters. In this case, the casting number is not the only piece of the puzzle we need. Only the style and diameter of the rear fitting can tell us if the pump is a match.