Orange part numbers and product names are Amazon affiliate links (we may earn a commission at no cost to you). The problem patterns below are owner-reported and not Kubota-published; the specs, intervals and part numbers are sourced from Kubota’s manual and parts catalogs.

Our source is the B2710/B2910/B7800 Operator’s Manual, code 6C170-6311-3, reprinted March 2003. It names UDT and Super UDT, not Super UDT2. Kubota USA describes Super UDT2 as “fully interchangeable with standard UDT and Super UDT fluids.” Earlier versions of this page listed a D1703 engine, 30.5 HP, 2.6 qt of engine oil and a 4.4 L coolant capacity. These do not match Kubota’s figures. We found no gear-drive B7800 in the sources we checked, and we found no DPF or DEF statement in the manual, so we have not made one.

• Fuel or temperature gauge stops working
• Intermittent no-start, with power present but no crank
• Battery runs down overnight
• The fault comes and goes, a typical pattern for a chafed wire or a bad connection

• Battery terminals and ground straps: clean and tighten. A multimeter should read about 12.6 V at rest and higher with the engine running (general guidance, not a Kubota figure)
• Harness routing: trace the harness along the chassis for chafed insulation touching metal
• Gauge and connector corrosion: unplug, inspect and clean with contact cleaner
• Lamp sockets: look for cracked or burnt sockets

Work from the battery and grounds outward. See our ground strap guide and alternator guide. Earlier versions included owner quotes and cost ranges, which we could not verify and removed.

• Slipping under load
• Weak drive, or no movement in either direction
• Whine or grinding from the transmission area

The transmission and hydraulic system share one fluid: 14.5 L (3.83 US gal) of Kubota UDT or Super UDT, changed every 300 hours (printed pp. 46 and 60). Earlier versions said 400 hours. The 300-hour service also covers the front axle (4.5 L). Check the level and condition of the fluid first, and replace the filters. Dark or burnt-smelling fluid points to neglect. If drive is still weak after fresh fluid and filters, have the HST checked by a dealer.

See our HST transmission problems guide. Earlier versions quoted a $4,000–$6,000 rebuild cost that we could not source.

• Hydraulics run hot after long continuous use
• Slow or weak response
• Wet fittings or pump mounting area
• Fluid level dropping

• Fluid level and colour
• The hydraulic suction filter (HH6C0-37710 per the catalog)
• Hose fittings, quick couplers and the pump mounting area for seepage

If the coolant temperature gauge reaches the red zone, the manual says the coolant is overheated. Its “Precaution at Overheating” (printed p. 58) is to stop work safely, keep the engine idling unloaded, stop it after about five minutes, stay clear while steam dissipates, and find the cause before restarting. We found no statement that the tractor reduces power automatically. See our hydraulic flush guide and fluid change guide.

• Cranks but will not fire
• Solenoid clicks and nothing turns
• Starts on some attempts and not others

• Parking brake set, speed-control pedal in neutral, range lever in neutral, and the hydraulic-control lever in neutral
• Rear-PTO and (if fitted) mid-PTO levers off
• “The engine will not start unless the clutch pedal is fully depressed, and the speed control pedal and the Rear-PTO gear shift lever and Mid-PTO gear shift lever are in the ‘NEUTRAL’ position.”

The manual also describes a B7800-only operator-seat safety test (printed p. 52): with the engine running, the clutch depressed and the rear PTO engaged, standing up should stop the engine after about one second. If it will not start, also check the fuel filter element (6A320-59930 per the catalog), battery and connectors. If your engine has an electric stop solenoid, check its connector for corrosion before replacing it. See our fuel shutoff solenoid guide and won’t start guide.

Check pad thickness, look for uneven braking side to side, and bleed or adjust per your operator’s manual if the pedal is soft. Replace worn parts before using the tractor on a slope or with a loaded loader. We did not verify pad specifications, so use your manual.

• Slow or weak lift
• Bucket drifts down with the controls centred

• Hydraulic fluid level and condition (shared with the transmission)
• The suction filter and other hydraulic filters
• Pump output pressure, if lift is still weak with clean fluid and filters
• Cylinder seals, if the bucket drifts

See our loader won’t lift guide and loader drift guide.

• Loose or wandering steering
• Clunking from the front end on rough ground
• A wheel pointing the wrong way after hitting debris

Grab each front wheel and check the tie rod ends for play. Replace worn ends, and replace a bent or broken tie rod before using the tractor, because a broken tie rod means loss of steering. We do not recommend welding steering parts. Grease the linkage at the intervals in your manual.

The manual has more items in each section, plus the first-50-hour jobs. The symbols that assign jobs to the first 50 hours could not be read, and Messick’s dealer chart marks both the engine oil and filter at 50 hours. Messick’s also lists the filter at 100 hours, while the manual says 200, so we follow the manual. Break-in section (printed p. 22): change the oil earlier than usual and avoid full-speed operation for the first 50 hours.

Earlier versions of this page listed K4562-33700 and HH150-32430 for the oil filter, HH164-09030 for the hydraulic filter, and 12547-14350 for the fuel filter. We could not match them to the B7800. We found no complete serial split for these parts, so confirm by serial at Kubota’s parts lookup or on our parts diagrams page.

• A gear-drive B7800, and any DPF or DEF statement in the manual (we made none).
• The first-50-hour job assignment, and the inner air element part number.
• Intervals for the transmission, suction and HST filters, and serial splits for all filter rows.
• Any automatic power reduction when overheating. The manual only describes the operator’s overheating steps.
• Owner-reported problem patterns, cost ranges and part numbers from earlier versions, which we removed.