5S1/41802SD Vermeer SC30TX Main Hydraulic Pump - 17cc 11 tooth Spline Gear Pump - Rear Thru-Drive Flange - Replaces 163618001

5S1/41802SD Main Hydraulic Pump for Vermeer SC30TX Stump Grinder

Your Vermeer SC30TX main pump has failed — the cutter wheel has lost power, you're hearing a whine from the pump, the hydraulic oil is full of metal, or the pump has seized completely. The Vermeer dealer wants $575–$750 for a replacement and the lead time can stretch to weeks. Your stump grinder is parked on a job site, and every day it sits is lost revenue.

We sell the direct replacement main hydraulic pump for $549 — saving you up to $200 vs the dealer. This is the same specification 17cc Group 2 gear pump with the critical rear through-drive flange that makes the SC30TX pump unique. It bolts directly into the pump mount and mates with the tandem hydrostatic drive pumps on the rear. Replaces Vermeer part numbers 5S1/41802SD and 163618001.

Why This Pump Is Hard to Find

The Vermeer SC30TX uses a "piggyback" hydraulic system. The main gear pump doesn't just drive the cutter wheel — it also provides the through-drive for the two piston pumps that power the left and right tracks. That means the pump has a rear Z-flange with a through-shaft that spins the tandem hydrostatic pumps behind it, all driven off the Kohler engine.

This is why a standard 17cc gear pump from a hydraulic supply house won't work. A standard pump has a sealed rear cover — it doesn't have the rear through-drive flange and spline output. This pump does. It is built specifically for piggyback tandem pump applications like the SC30TX.

⚠️ Critical: Inspect the Internal Spline Coupler Before Installing

When a pump fails on the SC30TX, it often shears or damages the internal spline coupler that connects the pump shaft to the engine or the rear hydrostatic pumps. Before you install the new pump:

1. Inspect the female spline coupler on the engine side. Look for worn, rounded, or "shark-toothed" spline teeth. If the teeth are visibly worn or have a pointed, triangular profile instead of square, the coupler is bad.
2. A worn coupler will strip your new pump shaft in 50 hours. The coupler hammers on the new splines under load, chewing through the hardened steel in weeks.
3. If the coupler is damaged, you'll need to replace it. The pump mount kit or specific coupler is typically available through the Vermeer dealer — it is custom machined for the Kohler engine bell housing interface.

This is not optional. Installing a $549 pump with a bad coupler is throwing money away. Inspect the coupler. If there is any doubt, replace it.

Specifications

• Vermeer OEM Part Numbers: 5S1/41802SD, 163618001
• Type: Group 2 Gear Pump (Fixed Displacement)
• Displacement: 17cc (1.04 cu in/rev)
• Rotation: Clockwise (Right Hand, viewing shaft end)
• Front Flange: SAE A, 2-Bolt Mounting
• Rear Flange: Through-Drive (Z-Flange) — drives tandem hydrostatic pumps
• Shaft: 11-Tooth Spline (Standard SAE A)
• Application: Main Hydraulic Pump — Cutter Wheel + Track Drive Through-Drive
• Condition: Brand New

Compatible Equipment

The 5S1/41802SD main hydraulic pump fits the following Vermeer models:

• Vermeer SC30TX (Track-Driven Stump Grinder)

⚠️ Verify your Vermeer part number (5S1/41802SD or 163618001) in your parts manual or on the data plate of the existing pump before ordering. The SC30TX has gone through production revisions — confirm this is the correct pump for your serial number range. Contact us with your machine serial number if you're unsure.

How the SC30TX Piggyback System Works

Understanding out how the pump interfaces with the rest of the hydraulic system helps with diagnosis and installation:

1. The Kohler engine drives the pump shaft via a spline coupler through the engine bell housing
2. The main gear pump (this part) takes that engine rotation and does two things:
   • Produces hydraulic flow to power the cutter wheel motor and auxiliary functions
   • Passes the engine rotation straight through the rear through-drive flange to the tandem hydrostatic piston pumps
3. The two hydrostatic piston pumps (mounted on the rear of the gear pump) each drive one track motor — left track and right track independently

This means if the main gear pump fails, you lose everything — cutter wheel, tracks, and auxiliary functions. The entire machine is dead.

Installation Notes

• Drain the hydraulic system and relieve all pressure before starting
• Disconnect the hydraulic lines from the pump body — label each line and port location
• Support the tandem hydrostatic pumps before unbolting — they will be hanging off the rear of the gear pump
• Remove the two front flange bolts (SAE A mount) and slide the pump assembly forward off the engine bell housing
• Inspect the internal spline coupler on the engine side — check for wear, rounding, or shark-toothing
• Slide the new pump into position — align the 11-tooth spline shaft with the engine coupler
• Bolt up the SAE A front flange
• Reconnect the tandem hydrostatic pumps to the rear through-drive flange
• Reconnect all hydraulic lines to the correct ports
• Refill the hydraulic system with the correct oil (check your operator's manual for spec and capacity)
• Bleed air from the system — cycle all functions slowly several times with no load
• Check for leaks at every connection
• Test: cutter wheel rotation, left track forward/reverse, right track forward/reverse
• Run the machine under load and monitor pump temperature — a properly installed pump should not run excessively hot

Symptoms of a Failing Main Pump

• Complete loss of all hydraulic functions — cutter wheel and tracks both dead
• Cutter wheel loses power or slows down under load
• Tracks are sluggish, weak, or won't move the machine up grades
• Loud whining or grinding noise from the pump area
• Hydraulic oil is black, burnt, or contains visible metal particles
• Pump is leaking oil from the shaft seal or body
• System pressure is low (check at the test port — should be at rated spec under load)
• Pump housing is extremely hot to the touch
• Machine operates fine cold but loses power as it warms up (internal bypass from worn gears)

Frequently Asked Questions

Why can't I just use a standard 17cc gear pump?
A standard 17cc gear pump has a sealed rear cover. The SC30TX requires a pump with a rear through-drive flange (Z-flange) that passes engine rotation through the pump body to the tandem hydrostatic track drive pumps mounted on the back. Without the through-drive, the tracks won't work — the piston pumps have no input shaft to spin.

What is the "Z-Flange" or "through-drive"?
It's a rear mounting face on the pump that has a splined output shaft protruding from the back. This shaft is driven by the same engine input that drives the pump gears. It provides mechanical power to the tandem piston pumps bolted to the rear of the gear pump, creating the "piggyback" pump stack. The Z-flange designation refers to the specific bolt pattern and pilot diameter on the rear face.

My old pump sheared the coupler — do I need to replace that too?
Yes, almost certainly. If the pump seized or failed catastrophically, the internal spline coupler likely took damage. Inspect it carefully — if the spline teeth are rounded, pointed (shark-toothed), or have visible wear marks, replace the coupler before installing the new pump. A worn coupler will destroy the new pump's spline shaft in weeks. The coupler is typically available through your Vermeer dealer — it is custom machined for the Kohler engine bell housing.

Can a mechanic install this?
Yes, but this is a more involved job than a simple bolt-on swap. The tandem hydrostatic pumps need to be supported during removal, the hydraulic lines need to be labeled and reconnected correctly, and the system needs to be bled of air after installation. A qualified hydraulic technician or Vermeer-trained mechanic is recommended. Expect 2–4 hours for the complete pump swap.

Does this come with the tandem hydrostatic pumps?
No. This is the main gear pump only. The two hydrostatic piston pumps (Hydro-Gear) that drive the tracks are separate components that bolt onto the rear through-drive flange of this pump. If your hydrostatic pumps are also failed, contact us for pricing on a complete pump stack.