Allison Gear Box Problem

[Jasper]

Hi All,
Some advice please.
When I was returning from a long fishing trip, I noticed that the port engine revs kept dropping. Checked the port engine throttle/gear control & it had come right out of its bracket. The bracket was badly made and weak. Also now the port engine would not go into forward gear unless I revved up a lot & the transmission oil alarm came on. Checked oil in transmission & it was full, plus new, I had changed oil (40W) recently.
Got home slow & careful. Had new cable & bracket installed.Then at first the port engine would go into fwd after a 4 sec delay. Checked the oil pressure to GB, it was 100 psi.
Checked the screen & found some clutch material, less than a teaspoon.
Cleaned it, new gasket etc.
Now there is NO transmission pressure. Port will not engage ANY gear.
I have a mechanic who is going to help me re-build the oil pump.
It's a HYDRECO Constant flow oil pump. I bought a new seal kit.
IF the re-built pump still does not give transmission pressure, what else could it be & what should I do?

 

[Nonchalant1]

Seems like it has to be the pump if there is no oil pressure. The pump is totally separate from the gear and the pressure is measured at the pump. The pumps are simple to repair, since they separate into two halves and you just put the 2 big O rings into the grooves and bolt them back together. One ring groove is round and the other is a 4 lobed star, but the ring starts out round. Good luck on fixing it. Hopefully the clutch stuff in the strainer doesn't mean going into the gear itself.

 

[Jasper]

Many thanks Nonchalant,
I hope like heck you are right, I don't want the cost of removing a gearbox!
I have removed the pump in the meantime and it turns with a lot of resistance, does this tell anything?
Regards.
Jasper

 

[Genevatexan]

I would check the reassemby and make sure you got all the lines correctly sealed. I have seen on this site before recommendations to make extra sure that your filter side and the seal to the transmission case down at the bottom were correctly sealed on reassembly. I also run 130 lbs of pressure on both M20s, which seems to be the common recommendation. That pressure is adjustable at the top of the pump with the tall hex nut with a keeper nut at its base.

The Allisons are very durable and rarely break. I was advised that reverse takes much less fluid, so you will generally lose foreward first. Finally, there is an expert company down in southern Louisiana that rebuilds these pumps for Hydreco themselves, and will do yours for under $200, if I remember correctly. If you need help, I can search this site, where I found them originally.

 

[Jasper]

I would check the reassemby and make sure you got all the lines correctly sealed. I have seen on this site before recommendations to make extra sure that your filter side and the seal to the transmission case down at the bottom were correctly sealed on reassembly. I also run 130 lbs of pressure on both M20s, which seems to be the common recommendation. That pressure is adjustable at the top of the pump with the tall hex nut with a keeper nut at its base.

The Allisons are very durable and rarely break. I was advised that reverse takes much less fluid, so you will generally lose foreward first. Finally, there is an expert company down in southern Louisiana that rebuilds these pumps for Hydreco themselves, and will do yours for under $200, if I remember correctly. If you need help, I can search this site, where I found them originally.

Thanks Genevatexan,
If we can't get oil pressure and gear engagement by installing the new kit this week, then I will try to find a re-built pump. As I am in Australia, it would be easier to buy a Hydreco that has been re-built by the company you mentioned rather than send mine over to them and then back. I would appreciate it if you could let me know the name of the company that re-builds the Hydreco pumps. As for losing the fwd gear first, this makes sense: the fwd and reverse are both not engaging but before the pressure failed, it was the fwd that had a 4 sec delay while the reverse engaged immediately.
Many thanks for your help.
George

 

[GJH]

The name of the company is Acadian Marine Transmission

http://acadianmarinetransmission.com/site.php

The have manuals and some pump information available for download on their site.

The rebuild is much more than two gaskets. I had one of mine done by my local and it was about 15 gaskets and seals and other parts. MikeP posted pictures of his, you could probably do a search and find the thread where he posted them. Allisons exist all over the world, so I'd think you could source whatever you need there; sounds like your mechanic has the kit.

Edit: here is blow up of a Hydreco from the Acadian FAQ section. Note all the seals and springs involved.

http://acadianmarinetransmission.com/uploads/hydrecopumpbreakdown.jpg

 

[rsmith]

The Hydrecos do wear out. the rebuild kit is just to reseal the pump. If you can, swap the pumps to see if thats a problem. I carry a spare pump with me. The Hydreco pumps have a hi failure rate, at least on SF I dont hear the Motor Yachet peeps complaining about it but they dont use the boats like we do. I've "loaned " my pump several times to other boats offshore. If you ever have to transfer a part at sea put it in an igloo cooler and duct tape the lid tight. Float it over rather than trying to get close and hand it to them.

 

[Jasper]

Many thanks to you all!
the next few days I will be taking the pump apart and with the advice and help of a mechanic who I have known a long time, we will re-build it to the best we can and install the new kit.
I will keep you all posted.
Thanks,
George

 

[GJH]

The Hydrecos do wear out. the rebuild kit is just to reseal the pump. If you can, swap the pumps to see if thats a problem. I carry a spare pump with me. The Hydreco pumps have a hi failure rate, at least on SF I dont hear the Motor Yachet peeps complaining about it but they dont use the boats like we do. I've "loaned " my pump several times to other boats offshore. If you ever have to transfer a part at sea put it in an igloo cooler and duct tape the lid tight. Float it over rather than trying to get close and hand it to them.

Fishing certainly puts more work on the transmissions, but I don't understand how it would affect the Hydreco pump any more.

 

[Nonchalant1]

The name of the company is Acadian Marine Transmission

http://acadianmarinetransmission.com/site.php

The have manuals and some pump information available for download on their site.

The rebuild is much more than two gaskets. I had one of mine done by my local and it was about 15 gaskets and seals and other parts. MikeP posted pictures of his, you could probably do a search and find the thread where he posted them. Allisons exist all over the world, so I'd think you could source whatever you need there; sounds like your mechanic has the kit.

Edit: here is blow up of a Hydreco from the Acadian FAQ section. Note all the seals and springs involved.

http://acadianmarinetransmission.com/uploads/hydrecopumpbreakdown.jpg

Hi George,

Maybe my pumps weren't Hydreco? I thought they were. They were original equipment on a 1978 53MY with 8V71TIs and Allison M20 gears. There are a lot of little gaskets, etc. on the fittings, but only the two big O rings in the actual pump body. Replacing those two fixed it completely.

Regards,

Doug

 

[rsmith]

I think it was the late 70's allison swiched from a cast iron pump to the aluminum body hydreco's. Many people swiched back to the ci pumps after multiple hydreco failures. Dont know what causes them to fail but they do.They were concidered "nonrebuildable" at the time.

 

[gbittner]

Can anyone tell me if this pump is the only place that engine oil can enter the transmission. After my last trip my trnasmission oil went to way over full and was dirty looking like engine oil. The oil was clean the day before.

 

[Jasper]

I think it was the late 70's allison swiched from a cast iron pump to the aluminum body hydreco's. Many people swiched back to the ci pumps after multiple hydreco failures. Dont know what causes them to fail but they do.They were concidered "nonrebuildable" at the time.

Hi rsmith,
the body of my pump is aluminium. Tomorrow we re-install........I will be hoping this is/was the problem. I hear the Allisons GB's are tough and mine were recently (-300hrs) rebuilt. So we will see.
Damn you learn a LOT when you are in the ER with spanners and faith!

 

[Jasper]

Can anyone tell me if this pump is the only place that engine oil can enter the transmission. After my last trip my trnasmission oil went to way over full and was dirty looking like engine oil. The oil was clean the day before.

Before I comment, let me say : I am a rookie to the engine room, learning because I:
a) cannot waste money on people that just tell me what they think is wrong and take a few thousand of mine to find out and b) I am enjoying the work (not so much the stress that I may be causing more crap than was there prior!)
So, here it is: I believe there is a gasket that prevents the engine oil from entering the gear box oil. if this hardens/weakens etc, then you will find the gearbox oil will be blackened by the engine oil to some degree, even after the gearbox oil is changed. It is a gasket the size of a dime, but thicker.
Saw it today as we were rebuilding the Hydreco.
More later.
Regards,
George

 

[captddis]

Can anyone tell me if this pump is the only place that engine oil can enter the transmission. After my last trip my trnasmission oil went to way over full and was dirty looking like engine oil. The oil was clean the day before.

Rear seal on the engine is letting engine oil into the gear.

 

[Boatsb]

Rear seal on the engine is letting engine oil into the gear.

X2. The oil has to get out somewhere.

 

[rsmith]

Mine have been doing it for a long time. But Ive never seen the oil level in the gearbox increase. Just a discoloration of the oil after about 20 hours.

 

[Walter P]

My port engine/trans has the same affliction for a long time also. Level never changes so I don't worry about it much. I do however change the transmission oil and filter every time I change the engine oil. It may be overkill but I visualize tiny carbon particles wearing away at the moving parts of my transmission and reason that oil and filters are cheaper than rebuilding.

Walt

 

[bobk]

This is not an uncommon problem at least with 6V92's. And it seems to be most common on the port engine. I saw it on a couple of boats I looked at before buying mine. My transmission level does increase with time and I need to remove a couple of quarts between oil changes. It's just a PITA. I'll replace the rear oil seal if I ever need to work on the transmission.

Bobk

 

[Jasper]

Okay, the latest:
Had the new kit put into the oil pump (Hydreco) and it was rebuilt using some of the parts from the spare I boought.
Installed it.
the oil pressure gauge showed NO pressure..... so we turned the adjustment nut clockwise. Suddenly oil comes out the oil filter......there is TOO MUCH pressure and my gauge is not working.
The guy I am working with has a gauge so we check the pressure. It is 130psi.
Try to put in FWD gear and it takes 5 secs..
REVERSE is immediate response.
The more we put the GB into gear & out the quicker the response. In other words she is improving?
Left it for the day.

Today I removed the gearbox oil. Replaced with NEW oil. Changed the oil filter. Made sure everything was tight etc.
Started up. My gearbox oil pressure gauge works....shows 150psi.
try going into FWD= 5 sec delay.
So now I have decided to give it a good run. I cannot take her out today because we have floods here in S.E Queensland with lots of crap in the water.
Maybe she will be okay. I can live with a 5 sec delay into gear rather than a gearbox off the engine & new clutch & seals etc.
What are your thoughts?