allison gears loss of pressure

[omecojh]

When I pulled out of my slip on July 4th, I soon realized I had no pressure on the starboard clutch.

After getting back in the slip, I shut down the engine, checked oil (ok) and restarted engine. Pressure was up and I ran out for a couple of hours with no problem.

Someone told me it was an airlock but I find that hard to believe. Less than 200 hours since the clutch was rebuilt.

Any thoughts.

 

[Nonchalant1]

Sometimes there can be an air LEAK in the intake line from the gear to the pump, like if the elbow at the engine mounted pump has moved and loosened the threads, which I had once, or the seal at the 3 bolt flange is bad or clamp loose. This causes air to get into the pump with the resulting pressure loss.

 

[tw_collins]

I've had this happen from time-to-time. Think of it as a loss of prime. Slightly reving the engine restores the prime.

 

[chris piazza]

Allison's trans have to be checked with the engines running near operating temps, just a FYI

Chris
Superior Nights 53C

 

[Pascal]

Typical of low oil level in the gear... You will not have forward or experience a couple second delay in forward but reverse will work. If level is just a little low, you may be able to get some pressure by bumping rpm a bit

As Chris mentioned, you need to check the level engine running at idle although usually you can mark the dipstick to check it off. On mine it s about 1.5" above idling mark

 

[Tim Powell]

Allison's trans have to be checked with the engines running near operating temps, just a FYI

Chris
Superior Nights 53C

You are correct so i put a mark on the dip stick with a drenal tool at cold level works for me !
!!

 

[omecojh]

Thanks, I'll double check the oil level although I'm sure it is sufficient.

 

[manderley]

I had the exact same problem when I first got my boat after I had the filters, screens and oil changed from 30 to 40 weight. To trouble shoot and eliminate possible problems, we ended up switching or replacing hoses, moving parts from port to starboard and even replaced the pump with a new one.

The problem became unpredictable; it would work perfectly most of the time and suddenly I would have no pressure. It came to a head when I lost pressure underway when we went over a large wave and gulped some air causing a sudden turn from asymetrical thrust. This was the final hint and we figured out with the Allison factory guys that the full line on the dipstick had not been adjusted for the angle of the transmission. We used an inclinometer and came up with a correction. I cannot remember the exact direction from Allison but it may have been 1/8" for every degree. We added some oil and the problem was solved and has never reappeared. I also changed back to 30 weight.

This may not be your problem but it's worth a consideration.