Alpha Drive Banging

[team shadow]

My 2001 Alpha Drive started banging while underway when trimming down. It doesn't do it at idle or at a slow speed. There was some oil sheen in the water last week but tank wasn't low. Sucked what oil I could out of tank and added hydraulic jack fluid. I have ran the drive up and down several times to bleed through the vented cap.I haven't seen the sheen since except for when I first put drive up it looks like residue on the shaft. I'm going to suck out the fluid once more and add the 10-30 oil and try bleeding again but it's not jerky in either direction at dock from what I can feel. I'm thinking may be trim cylinder but may be valve in pump.
Anyone have this issue before?

 

[wahlejim]

Trying to figure out what is going on here.

What banging are you hearing? I would check out your u-joints as their angle is changing as you are adjusting the trim. I haven't heard of banging coming from a trim cylinder, but if there is residue on them, you may have an internal seal leak that needs to be addressed.

What fluid are you draining and topping off? Trim or lower unit gear lube?

We definitely need more info. I think you may be just spinning tires here. I haven't heard of any banging issues getting resolved from changing out trim fluid.

 

[Starcraft5834]

also have never heard of banging due to trim ram issues.... more likely U-joint.. or upper or lower gears in drive.... drive oil milky?

 

[harleyman1975]

is engine running or not when the noise is happening?

 

[team shadow]

It's in the trim. I would say it's a bouncing problem only when trimming down and underway. Not a ujoint type noise

 

[wellcraft-classic210]

So-- Are you saying their is no noise made if your driving with the trim all the way down // But its repeatable if you lower the to the down position trim under a load


--// Is that Correct ? If so I would suspect air in the lines or a trim pump valve body issue but I have not seen that personally.

Was any servicing done recently to the trim system ? If so you might want to try bleeding the system to ensure its not caused by trapped air.

 

[team shadow]

Sorry if I wasn't clear on issue.
While under way and drive trimmed up for proper planing position, only when I would start bringing drive down there was bouncing from the outdrive.
You could feel it throughout the back of the boat.
Didn't do it at dock or in a slow speed no wake zone.

I drained trim tank and removed and cleaned all the residue out.
Then added 30 wt non detergent and trimmed it up and down a few times.
Then removed the 30 wt and added the 10-30 and ran it up and down like 20 times.
OK now. Hope that does it.