{"id":407,"date":"2026-03-17T02:06:30","date_gmt":"2026-03-17T02:06:30","guid":{"rendered":"https:\/\/metalite.net\/?post_type=product&p=407"},"modified":"2026-03-17T05:33:08","modified_gmt":"2026-03-17T05:33:08","slug":"rotary-mower-gearbox-for-comer-t-305j","status":"publish","type":"product","link":"https:\/\/metalite.net\/ja\/product\/rotary-mower-gearbox-for-comer-t-305j\/","title":{"rendered":"Rotary Mower Gearbox for Comer T-305J Replacement 83.8kW"},"content":{"rendered":"
\n

<\/p>\n

HZPT Rotary Mower Gearbox \u2013 Direct Replacement for Comer T-305J, 183.8 kW<\/h2>\n

Model: T-305J \u00a0|\u00a0 Input: 540 \/ 1000 RPM \u00a0|\u00a0 Output Torque: up to 2,335 Nm \u00a0|\u00a0 Ratio: 1.20 \u2013 1.35<\/p>\n

<\/p>\n

\u2714 Drop-In Comer T-305J Fit<\/span>
\n\u2714 Max Torque 2,335 Nm<\/span>
\n\u2714 540 \/ 1000 RPM Input<\/span>
\n\u2714 1\u00be” Z20 Spline Shaft<\/span><\/div>\n

<\/p>\n

Rotary Mower Gearbox Product Overview<\/h2>\n

The HZPT T-305J rotary mower gearbox is an industrial-grade power transmission unit engineered as a bolt-on replacement for the original Comer T-305J gearbox. Built from high-alloy cast iron housing and precision-hardened steel gears, this rotary mower gearbox handles continuous input power of 183.8 kW while delivering peak blade shaft torques of 2,335 Nm<\/strong>\u2014numbers that match or exceed the OEM specification without the OEM price tag.<\/p>\n

Designed primarily for tractor-mounted rotary cutters and flail mowers, the gearbox accepts PTO input via a 1\u00be” 20-spline shaft (Z20) and steps up speed through fixed gear ratios of 1.20 : 1<\/strong> or 1.35 : 1<\/strong>, depending on the configuration selected. The planetary-influenced gear arrangement keeps noise below 78 dB(A) under rated load and significantly reduces vibration transmitted back to the tractor drivetrain. An integrated oil-splash lubrication circuit, SAE 80W-90 GL-4 compatible, maintains consistent film thickness across all operating temperatures from \u221210 \u00b0C to 80 \u00b0C.<\/p>\n

Each unit ships with pre-filled gear oil, a slip-clutch-compatible input interface, and all mounting hardware required for a direct swap on Comer T-305J-equipped machines. No machining. No adapters. No guesswork.<\/p>\n

\"Rotary

Rotary Mower Gearbox for Comer T-305J Replacement<\/p><\/div>\n

<\/p>\n

Rotary Mower Gearbox Technical Specifications<\/h2>\n

All values at rated continuous duty. Shaft dimensions follow ISO 5211.<\/p>\n

\"Rotary<\/p>\n

<\/p>\n

\n\n\n\n\n\n\n\n
Ratio (i)<\/th>\nInput Speed N\u2081 [RPM]<\/th>\nInput Power P\u2081 [kW]<\/th>\nOutput Torque M\u2082 [Nm]<\/th>\nShaft Type X<\/th>\nShaft Type Y<\/th>\nShaft Type Z<\/th>\nInput Side<\/th>\n<\/tr>\n<\/thead>\n
1.35<\/td>\n540<\/td>\n183.8<\/td>\n2,335<\/td>\n1\u00be” Z20<\/td>\n1\u00be” Z20<\/td>\n1\u00be” Z20<\/td>\nX<\/td>\n<\/tr>\n
1.20<\/td>\n1000<\/td>\n183.8<\/td>\n2,043<\/td>\n1\u00be” Z20<\/td>\n1\u00be” Z20<\/td>\n1\u00be” Z20<\/td>\nX<\/td>\n<\/tr>\n
1.35<\/td>\n1000<\/td>\n183.8<\/td>\n2,298<\/td>\n1\u00be” Z20<\/td>\n1\u00be” Z20<\/td>\n1\u00be” Z20<\/td>\nX<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

* Shaft Type X = Standard output. Alternate shaft options Y and Z available on request. Oil type: SAE 80W-90 GL-4.<\/p>\n

<\/p>\n

What Is a Rotary Mower Gearbox \u2014 and Why Does Yours Need to Handle 2,335 Nm?<\/h2>\n

A rotary mower gearbox is the mechanical brain sitting between your tractor’s PTO shaft and the cutting deck. Its job is deceptively simple: take the rotational input from the PTO (540 or 1000 RPM), multiply torque to the level the blade spindle demands, and keep the engine shielded from the shock loads generated every time a blade hits a rock, root, or thick brush stem.<\/p>\n

The T-305J rotary mower gearbox sits in the high-demand tier of this category. At a 1.35 ratio and 540 RPM input, it puts out 2,335 Nm of torque<\/strong>\u2014enough to drive large-diameter blade assemblies on 2.5\u20133.5 m cutting-width machines without thermal runaway or fatigue cracking at the gear flanks. The planetary-style bevel gear set inside distributes tooth load across multiple contact points simultaneously, which is why this unit runs cooler and quieter than conventional single-pair bevel boxes at the same power level.<\/p>\n

In short: if your Comer T-305J has failed, is showing housing cracks, or simply has too many hours on it, the HZPT replacement rotary mower gearbox gives you the same mounting footprint, same shaft dimensions, and same rated power\u2014at a fraction of the cost of an OEM unit.<\/p>\n

<\/p>\n

Where This Rotary Mower Gearbox Gets the Job Done<\/h2>\n
\n
\n

\ud83c\udf3e Agricultural Field Mowing<\/p>\n

Roadside verge maintenance, hay field trimming, and cover-crop termination on fields where blade speed consistency directly affects cut quality. The 183.8 kW rating handles 100+ hp tractors at full PTO engagement.<\/p>\n<\/div>\n

\n

\ud83c\udf3f Pasture & Rangeland Management<\/p>\n

Thick brush, saplings up to 25 mm diameter, and uneven terrain put extreme intermittent shock into the gearbox. The integrated torque buffer and hardened spiral bevel gears absorb those spikes without stripping teeth.<\/p>\n<\/div>\n

\n

\ud83c\udfd7\ufe0f Municipal & Infrastructure Maintenance<\/p>\n

Highway shoulders, drainage canal banks, and airport perimeter vegetation control. Continuous-duty cycles demand a gearbox lubrication system that stays effective across temperature swings\u2014this unit’s oil-splash circuit manages it without external cooling.<\/p>\n<\/div>\n

\n

\ud83d\udd27 OEM Retrofitting & Fleet Repair<\/p>\n

Equipment dealers and agricultural machinery repair shops sourcing a cost-effective, spec-matched replacement for Comer T-305J units across customer fleets. Bulk pricing available for B2B orders of 10+ units.<\/p>\n<\/div>\n<\/div>\n

<\/p>\n

Installation Guide \u2013 Replacing a Comer T-305J Rotary Mower Gearbox<\/h2>\n

Estimated time: 45\u201390 minutes with standard hand tools. Always disconnect PTO and engage parking brake before starting.<\/p>\n

    \n
  1. Disconnect the PTO shaft<\/strong> \u2014 Slide the PTO yoke off the tractor’s output shaft. Secure the free end so it cannot drop onto the gearbox housing.<\/li>\n
  2. Drain old gear oil<\/strong> \u2014 Remove the drain plug on the existing T-305J gearbox. Allow full drainage (approx. 0.8\u20131.0 L). Dispose of used oil per local regulations.<\/li>\n
  3. Remove the blade assembly<\/strong> \u2014 Lower the cutter deck to the ground. Remove the blade bolt(s) and slide the blade(s) off the output spindle. This relieves spring tension on the output shaft seal.<\/li>\n
  4. Unbolt the old gearbox<\/strong> \u2014 Four M14 flange bolts secure the T-305J housing to the cutter deck frame. Mark the orientation before removal to match during reinstallation.<\/li>\n
  5. Inspect the mounting face<\/strong> \u2014 Clean the deck mounting surface. Check for cracks or warping exceeding 0.5 mm. A warped face can misalign the new gearbox and cause premature bearing failure.<\/li>\n
  6. Mount the HZPT replacement<\/strong> \u2014 Align the new rotary mower gearbox to the marked orientation. Torque M14 bolts to 95\u2013110 Nm in a cross pattern using a calibrated torque wrench.<\/li>\n
  7. Reinstall the blade assembly<\/strong> \u2014 Thread blade bolt(s) finger-tight first, then torque to manufacturer spec (typically 180\u2013220 Nm for single-blade spindles).<\/li>\n
  8. Fill with gear oil<\/strong> \u2014 Add SAE 80W-90 GL-4 oil through the fill port until oil reaches the level plug. Capacity: approximately 0.9 L. Re-install both plugs.<\/li>\n
  9. Reconnect the PTO shaft<\/strong> \u2014 Slide the yoke fully onto the input shaft until the locking pin engages. Confirm free movement through full articulation range.<\/li>\n
  10. Run-in check<\/strong> \u2014 Engage PTO at low idle (600 RPM) for 3 minutes. Listen for abnormal noise. Increase to working RPM and verify smooth operation. Recheck all bolt torques after the first 8 operating hours.<\/li>\n<\/ol>\n

    <\/p>\n

    Frequently Ordered Together<\/h2>\n

    These three components are commonly paired with the T-305J rotary mower gearbox for a complete drivetrain service or upgrade:<\/p>\n

    \n
    \n

    \u2699<\/p>\n

    PTO Drive Shaft with Overrunning Clutch<\/p>\n

    1\u00be” Z20 spline, 1000 mm collapsed length. The overrunning clutch prevents blade inertia from back-driving the tractor PTO when you disengage\u2014a key cause of T-305J gear failure when not fitted. CE-certified to Category 6.<\/p>\n

    Recommended pairing<\/span><\/p>\n<\/div>\n

    \n

    \ud83d\udd29<\/p>\n

    Gearbox Input Shaft Seal Kit<\/p>\n

    Full set of NBR and FKM lip seals, O-rings, and gaskets sized for the T-305J housing bore. Replacing seals during gearbox installation costs 12 minutes; replacing a leaking seal on a mounted gearbox costs 90 minutes. Do the math once.<\/p>\n

    Recommended pairing<\/span><\/a><\/p>\n<\/div>\n

    \n

    \ud83d\udee1<\/p>\n

    Hardened Rotary Cutter Blade Set<\/p>\n

    Brinell 400 HB chrome-molybdenum steel blades, balanced to \u00b13 g. Worn or unbalanced blades create vibration loads that can reduce rotary mower gearbox bearing life by 30\u201340%. Always replace blades when replacing the gearbox.<\/p>\n

    Recommended pairing<\/span><\/p>\n<\/div>\n<\/div>\n

    <\/p>\n

    Frequently Asked Questions<\/h2>\n

    <\/p>\n

    \n
    \n

    Q1: Is this rotary mower gearbox a true direct replacement for the Comer T-305J, or will I need adapters?<\/p>\n<\/div>\n

    \n

    It is a true bolt-on replacement. The mounting bolt pattern, housing dimensions, and 1\u00be” Z20 input spline are dimensionally identical to the Comer T-305J. No adapters, no machining, no custom hardware. The only tool you need that you might not already own is a torque wrench.<\/p>\n<\/div>\n<\/div>\n

    <\/p>\n

    \n
    \n

    Q2: What gear oil should I use, and how often does it need to be changed?<\/p>\n<\/div>\n

    \n

    Use SAE 80W-90 GL-4 gear oil. The initial factory fill should be drained and replaced after the first 50 operating hours to flush break-in particles. After that, change the oil every 200 hours or once per season, whichever comes first. Capacity is approximately 0.9 L. Do not use GL-5 oil\u2014its additive package can degrade the yellow-metal bushing materials used in some internal components.<\/p>\n<\/div>\n<\/div>\n

    <\/p>\n

    \n
    \n

    Q3: My original Comer T-305J ran at 540 RPM. Can this HZPT gearbox also operate at 1000 RPM PTO?<\/p>\n<\/div>\n

    \n

    Yes. The HZPT T-305J replacement is available in both 540 RPM and 1000 RPM input configurations, and both deliver the same rated power of 183.8 kW. The 1000 RPM variant is available in ratio 1.20 (output torque 2,043 Nm) or 1.35 (output torque 2,298 Nm). Select the configuration that matches your tractor’s PTO speed and your existing PTO shaft coupling.<\/p>\n<\/div>\n<\/div>\n

    <\/p>\n

    \n
    \n

    Q4: What causes a rotary mower gearbox to fail, and how can I extend the life of this replacement unit?<\/p>\n<\/div>\n

    \n

    The three most common failure modes are: (1) oil starvation from running low or using the wrong viscosity, (2) shock-load damage caused by operating without a PTO overrunning clutch, and (3) vibration fatigue from unbalanced or worn blades. To maximize service life: check oil level before every use, always fit an overrunning clutch to your PTO shaft, and replace blades at the first sign of imbalance or edge chipping. Following these three practices typically extends gearbox service intervals from 400 hours to 700+ hours.<\/p>\n<\/div>\n<\/div>\n

    <\/p>\n

    \n
    \n

    Q5: Do you offer bulk or B2B pricing for agricultural dealers and OEM manufacturers?<\/p>\n<\/div>\n

    \n

    Yes. HZPT works directly with agricultural machinery dealers, fleet maintenance programs, and OEM manufacturers. Orders of 10 or more rotary mower gearbox units qualify for tiered volume pricing. Lead times for stocked configurations are 3\u20137 business days. For custom ratio, shaft, or housing specifications, our engineering team can quote a modified unit within 72 hours. Contact us via the B2B inquiry form for a formal quote.<\/p>\n<\/div>\n<\/div>\n

    <\/p>\n

    What Customers Are Saying<\/h2>\n
    \n

    <\/p>\n

    \n

    \u2605\u2605\u2605\u2605\u2605<\/p>\n

    “We run a fleet of 14 Kuhn FC rotary mowers for municipal roadside contracts. Three Comer T-305J units cracked housings in the same season\u2014classic fatigue from improperly sized blades by the previous contractor. We replaced all three with HZPT units. Eight months later, 400+ hours on each, zero issues. The bolt-on fit was exact; our mechanic completed each swap in under an hour. The 2,335 Nm torque rating gives us headroom we didn’t have with the originals.”<\/p>\n

    \u2014 James R., Fleet Maintenance Manager, Midwest Municipal Services<\/p>\n<\/div>\n

    <\/p>\n

    \n

    \u2605\u2605\u2605\u2605\u2605<\/p>\n

    “My old Comer gearbox finally retired itself\u2014loudly, dramatically, in the middle of a 40-acre field, two days before hay season. My therapist calls it ‘catastrophic failure.’ I call it $800 of unscheduled vacation planning. Found the HZPT T-305J replacement, ordered it Thursday, installed it Saturday morning before my second coffee. Bolted right on like it was born there. Finished the field the same afternoon. My tractor hasn’t been this happy since the Obama administration. Five stars. Would trauma-bond again.”<\/p>\n

    \u2014 Dale T., Row Crop & Hay Producer, central Kansas<\/p>\n<\/div>\n<\/div>\n

    <\/p>\n

    \n

    Stop Losing Field Time to a Failed Gearbox<\/h2>\n

    The HZPT T-305J rotary mower gearbox ships ready to install, pre-filled, and built to the same power rating as the Comer original \u2014 at a price that makes stocking a spare unit sensible, not extravagant.<\/p>\n


    \nOrder Now \u2013 Get a Quote
    \n<\/a>
    \n
    \nContact B2B Sales
    \n<\/a><\/div>\n

    Fast shipping \u00b7 B2B volume pricing available \u00b7 12-month warranty \u00b7 Engineering support included<\/p>\n<\/div>\n


    \n<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

    The HZPT rotary mower gearbox is a heavy-duty replacement for Comer T-305J, designed for PTO-driven agricultural mowers. Built with hardened spiral bevel gears, it delivers up to 2,335 Nm torque and supports 540 \/ 1000 RPM input, ensuring stable power transmission for rotary cutters, pasture mowing, and roadside vegetation maintenance.<\/p>","protected":false},"featured_media":409,"template":"","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":""},"product_brand":[],"product_cat":[18,25,19,27],"product_tag":[],"class_list":{"0":"post-407","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_cat-products","7":"product_cat-agricultural-gearbox","8":"product_cat-reducer","9":"product_cat-rotary-mower-gearbox","11":"first","12":"instock","13":"shipping-taxable","14":"product-type-simple"},"_links":{"self":[{"href":"https:\/\/metalite.net\/ja\/wp-json\/wp\/v2\/product\/407","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/metalite.net\/ja\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/metalite.net\/ja\/wp-json\/wp\/v2\/types\/product"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/metalite.net\/ja\/wp-json\/wp\/v2\/media\/409"}],"wp:attachment":[{"href":"https:\/\/metalite.net\/ja\/wp-json\/wp\/v2\/media?parent=407"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/metalite.net\/ja\/wp-json\/wp\/v2\/product_brand?post=407"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/metalite.net\/ja\/wp-json\/wp\/v2\/product_cat?post=407"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/metalite.net\/ja\/wp-json\/wp\/v2\/product_tag?post=407"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}