I had a 2004 T2499 and there was just standard gas cylinder/springs on it. I'm assuming you are pushing down semi equal and not all on one side? If not try that pushing equal in the middle.
If it "stuck" when fully extended (up) maybe try pushing the gas cylinder side inward slightly where the extension rod come out of the end. It may be bound up being fully extended.
Mine have always gone down, but sometime I have to push harder until it starts retracting. My 2004 T310SR has the same gas cylinders/springs as the T2499, same bed setup and same year, odds are high the same brand spring even.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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