Develon DL250-7: Transmission Slow to Engage Forward
Fault Codes & Symptoms
Transmission slow to engage Forward Related symptoms: - Slightly harsh downshifts into lower forward gears. - A feeling of slipping before engagement. Operator reports that when selecting Forward, the machine takes several seconds to begin moving. Reverse engages normally. The issue is worse when the machine is first started for the day.
Confirmed cause: A torn inner piston seal on the Forward clutch pack. Repair performed: Removed the transmission and disassembled the Forward clutch pack. Found the inner piston seal was torn. Replaced the inner and outer piston seals, reassembled the clutch pack, and reinstalled the transmission. Verification: After repair, started the machine from cold. Shifted into Forward, and the transmission engaged immediately. Pressure at the Forward clutch test port rose to specification instantly. The machine was operated through all gears and directions to confirm normal operation. Technician notes: - The delay was longer when the oil was cold and thicker, which masked the leak slightly. As the oil warmed up and thinned out, the leak became more pronounced initially, but the faster-flowing oil could fill the clutch volume more quickly, reducing the perceived delay. - When swapping solenoids, be sure to label them to avoid confusion. - Pre-filling the new transmission filter with clean oil can help ensure a quick prime on startup.