PTO Shaft Sizes and Spline Counts – Quick Reference
Before you measure or cut anything, check that the shaft you have actually matches the splines on both your tractor's PTO stub and your implement's input shaft. Almost all modern tractor PTOs use one of three standard sizes:
| Type | Shaft diameter | Splines | Speed | Usually found on |
|---|---|---|---|---|
| Type 1 | 1-3/8" (35mm) | 6 spline | 540 rpm | The great majority of compact and utility tractors |
| Type 2 | 1-3/8" (35mm) | 21 spline | 1000 rpm | Higher-HP tractors driving 1000 rpm implements |
| Type 3 | 1-3/4" (44mm) | 20 spline | 1000 rpm | Large tractors, generally 100HP and above |
The mistake that catches people out
Type 1 and Type 2 are the same diameter. A 21 spline shaft will not slide onto a 6 spline stub even though both measure 1-3/8". Always count the splines rather than just measuring across the shaft – a tape measure alone will tell you the wrong thing.
Speed matters as much as fitment
Implements are built for a rated input speed. Driving a 540 rpm implement at 1000 rpm runs it close to double its design speed, which is hard on gearboxes, bearings and blades, and can be genuinely dangerous. Many tractors have a selectable 540/1000 PTO, and some have a 540E economy setting as well – check what your tractor is set to before you engage the PTO, and check the plate or manual on the implement for its rated speed.
If you are unsure what your tractor has, the operator manual is the authority. Spline counts and speeds do vary on older, imported and specialist machines, so treat the table above as the standard case rather than a guarantee.
Once you have confirmed the spline count and speed match, the next job is getting the shaft length right – which is where most damage actually happens.
How to measure and fit a PTO shaft to match an implement on a tractor step-by-step guide:
It’s important to have the PTO shaft the right length for the tractor and implement being used, the end thrust from over length shafts (or seized telescopic tubes) can damage your tractor PTO drive system or implement gearbox . A common mistake made by novice users as the PTO shaft may connect fine when the implements on the ground but it may bottom out of travel when the implement is lifted causing damage.
How to measure and cut a PTO shaft:
To start with fit the implement to the tractor’s 3 point linkage , with the park brake engaged, you can raise the implement until the input shaft on the attachment is level with the output shaft on the tractor.
1) Measure the groove to groove distance from implement input shaft to
tractor output shaft with implement in shortest position.(when the input and output shafts are level with each other .The distance will change when the attachment is raised or lowered. )
2) Remove the safety guard from the PTO shaft and measure the length between lock buttons or clamp bolts on the yokes with shaft in closed position.
If shaft is shorter than this, ensure that 50% of telescopic tubes overlap.
4) The amount to cut off shaft:
Length of the shaft (step 2) Less groove to groove measurement (step 1) plus 75mm (3”).
Cut this amount off both inner and outer drive tubes and the safety cover using a hacksaw or cut off wheel in a grinder . Remove burrs with a file and make sure there is not debris inside the tubes and then grease tubes before re assembly.
Example of measurements
PTO drive shaft measurement 1000mm
Less groove to groove measurement of 700mm
Plus clearance 75mm
Amount to cut off (1000mm - 700mm = 300mm +75mm )= 375mm
This is example only
Insert your own measurements.
Next Steps
Grease Fittings: If the yoke has grease fittings, Apply grease to the fittings to keep the shaft operating smoothly.
Fitting : Connect the cut PTO shaft to the tractor's PTO output shaft and the implement's input shaft.
Secure Shaft: Use the locking mechanism ( quick-release locking pin or collar) to secure the PTO shaft in place. Verify everything is securely fastened before operation. Connect the safety chains for the safety cover to a suitable location to stop the cover from spinning.
Test : Start the tractor and slowly lift the implement up and down keeping a close eye on the telescoping tubes clearance . Once this is checked it’s safe to engage the PTO to ensure proper functionality. Check for any unusual noises or vibrations, indicating a problem with the installation.
Adjustments: Make any necessary adjustments to the length or alignment of the PTO shaft for optimal performance and safety. Remember keep clear of the shaft when spinning do not go near it with the tractor running or PTO engaged.
Maintenance: Regularly inspect the PTO shaft and cover for wear or damage, and lubricate as needed to ensure safe operation.
Always refer to the manufacturer's instructions and guidelines specific to your equipment for accurate procedures and safety precautions. If unsure, consult a professional mechanic or technician for assistance.
Related guides
Fitting the implement itself? See our guide to 3 point linkage categories and pin sizes for the Cat 0 to Cat 3 dimensions and the parts to match them.