Allison Gear Box Problem

[Jasper]

Re: Allison Gear Box Bad News

Bad news!

Finally was able to take the boat for a run.
At idle the port gear box has just over 150 psi pressure. When I put it in gear, takes about 5 seconds to engage. BUT:
When I revved the engine up to get going, there is hardly any thrust. Tried a few times. Increased the pressure on the adjustment screw. No change. As soon as I put it in gear the pressure drops to 60 to 75 psi.
I think the gear box is going to need to be worked on. Whether it is the piston or seals I have no idea.
Damn! Besides the money, it is the best time for game fishing.
Damn!!!

 

[bobk]

Re: Allison Gear Box Bad News

Bad news!

Finally was able to take the boat for a run.
At idle the port gear box has just over 150 psi pressure. When I put it in gear, takes about 5 seconds to engage. BUT:
When I revved the engine up to get going, there is hardly any thrust. Tried a few times. Increased the pressure on the adjustment screw. No change. As soon as I put it in gear the pressure drops to 60 to 75 psi.
I think the gear box is going to need to be worked on. Whether it is the piston or seals I have no idea.
Damn! Besides the money, it is the best time for game fishing.
Damn!!!

This sounds exactly like the problem I had a year ago. Find an EXPERIENCED mechanic who has the proper tools to do it in/on the boat and change the rear main seal while you are at it. Also take a careful look at the transmission output shaft. If there is any corrosion put a speedy sleeve on it. They are only about $30 from Acadian.

Bob

Bobk

 

[bigbill]

if i remember right , your gear should have 150 psi at idle in fwd gear. you might need to boost your pressure. sorry if this has been said, i didn't read the whole thread

 

[Jasper]

if i remember right , your gear should have 150 psi at idle in fwd gear. you might need to boost your pressure. sorry if this has been said, i didn't read the whole thread

Thanks for the thought bigbill.
Tried this, with a bad result...the oil pressure jumped to 210+ and before I could get from the pressure guage to the adjustment screw so that I could lessen the pressure, the oil was overflowing the oil filter. So I changed the filter & gasket.
Re-started it with lesser pressure, same overflow problem at the oil filter, replaced the gasket again. So now the adjustment screw is turned right down & giving the pressure of 150psi at idle.
At least I have a good pressure pump now...touch wood.

 

[Jasper]

Re: Allison Gear Box Bad News

This sounds exactly like the problem I had a year ago. Find an EXPERIENCED mechanic who has the proper tools to do it in/on the boat and change the rear main seal while you are at it. Also take a careful look at the transmission output shaft. If there is any corrosion put a speedy sleeve on it. They are only about $30 from Acadian.

Bob

Bobk

Good advice Bobk.
As time goes by I am learning to do more & more myself or with assistance from a mechanic so that I can do things the next time on my own. Unfortunately, in this case, I am in the dark except for your advice & the advice of others on this forum.
Result is that I put an awful lot of faith into the guy I choose to work on my boat.
The mechanic that I spoke with yesterday has been recommended by someone I trust & knows Allisons. His first opinion, which was made on the phone only using my description, is that it is the Forward Piston Clutch seal.
He said parts are "probably" available & not the expensive part. The main cost is labour which he estimates at 20 hours!
I will pass on your advice to him when he checks in with me this week.