Forward Bogging Down UpHill, But Reverse Good?

[Dreq]

I have a Simplicity ZT Series 16 HP with a 44" Deck. It is a zero turn mower that is about 12 years old.

This season it started great, but something is different. When I go uphill in reverse, I have plenty of power and I zoom right up the slope. When I try to do that going forward I come to almost a complete stop. If I back off the controls, it feels like it is trying to catch. Then it catches and I can proceed very slowly.

I have topped off the fluid which was a little low, but I have cut three more times and it still doesn't call for more.

Last year my uncle, who is far more mechanically inclined than I, changed the rider drive belt.

What is totally weird to me is that when I go up the hill backwards, it is a smooth work horse. When I go up forward it slows and stops and then gets to a slow walking pace.

My friend suggested changing the transmission filter, but the manual I have doesn't list one on the parts list.

Any ideas? or is it time to replace after 11 seasons?

[Dreq]

http://bsintek.basco.com/BriggsDocum...EWj7mRgtLvBCd6

Manual

[SPYDERLK]

Is it the engine losing power?? ~Water in fuel tank. If it has a manual choke try putting it on momemtarily when it happens.
larry

[Dreq]

The motor has plenty of power and doesn't seem to be losing power.

It appears to be the transmission.

[kiotiken]

That sounds odd. I had a Gravely 3 wheel mower that used to slow down when it started getting hot. It would become slower on flat ground, but struggle to get up any type of incline. It was the pump and wasn't worth the cost to fix.

If yours is working just fine in reverse but not forward, that wouldn't make sense. The pump must be pumping and if it's not trying to turn on you, the motors are both working properly. If it's a even reduction in flow (speed) to each motor, it has to be the pump or a valve.

[kiotiken]

I'd also try posting this in the hydraulics section, those guys know their stuff and this is a hydraulic issue.