Weak Left Side

[hlw49]

Hydraulic Oil Booster & Stop Leak - Lucas Oil Might give this a try. Have you adjusted the tracking. Air the tires up to proper level. Front tires to 15 psi and rear to 10 psi. Find a flat level place push both control arms all the way forward and hold in this position and see how it tracks. If it goes tracks to the left slow down the right side and if it goes to the right low down the left side. There are adjusting bolts on the control arms at the pivot points under the seat. Try that first.​

 

[birdman53]

If you have a rolling strain gauge and measure the belt tension between each section of the belt run with the engine running and both hydros under load you would see it is highest between the engine & the right , then a bit lower between the the right & left then a lot lower between the left & the engine.
This is why the fan belt on your car will occasionally squeal when you start the engine and the alternator is applying a heavy load to the belt .

I have a 07 silver eagle and the same weak left side. It make a cavitation noise when climbing a grade but the left pump/motor/ belt? is a lot slower on level grade. Has gotten worse even with a new belt change???

 

[bertsmobile1]

I have a 07 silver eagle and the same weak left side. It make a cavitation noise when climbing a grade but the left pump/motor/ belt? is a lot slower on level grade. Has gotten worse even with a new belt change???

If it is making the hydro growl then it is deceased.
A couple of options
1) buy and fit a new unit
2) buy and fit the drop in rebuild kit
3) drain & refill with heavier oil to get you through this season then pick between 1 & 2 above .