Allison Transmission had low oil, would not engage in forward

[osonegro]

After a 200 mile run from Manzanillo, Mexico to Ixtapa, my port engine would not go into foward when we were leaving the anchorage. I checked the oil in the transmission and it showed to be below the low mark. I put almost 4 qts of fresh 40W oil in and the transmission engaged. Now when I check the oil with the engine running it looks kind of brownish and not the normal oil color. I want to know if I'm in trouble and what to do from here. I am thinking of draining all the oil from the transmission and filling with new fresh oil.

[saltshaker]

After a 200 mile run from Manzanillo, Mexico to Ixtapa, my port engine would not go into foward when we were leaving the anchorage. I checked the oil in the transmission and it showed to be below the low mark. I put almost 4 qts of fresh 40W oil in and the transmission engaged. Now when I check the oil with the engine running it looks kind of brownish and not the normal oil color. I want to know if I'm in trouble and what to do from here. I am thinking of draining all the oil from the transmission and filling with new fresh oil.Any signs of oil leaks? What's the engine oil level look like? Does the oil look dark or milky brown? Does the oil look normal after the engines are shut down and set for an hour or so? If you overfilled them the oil will get aerated and look milky but clear up after it sits. Not a big deal but you do need to get it to the proper level if this is the case. In order to get an accurate reading the oil needs to be checked when the unit is running and preferably up to temp.

[Jasper]

Unfortunately I have had a lot of experience with this problem and Allison Gear Boxes. A quick education I have paid dearly for. I still have a lot to learn before I am at the level of some of the Senior Members here, but maybe I can point out some things to look for. As Saltshaker has asked, is there an oil leak? If not:
What is the oil pressure of the gears in idle?
What is the oil pressure of the gears in Forward?
Is there a "burnt oil" smell?
When you checked the oil level, was the engine running?
Have you checked the screen/filter? You will find this on the hose going into the oil pressure pump.
Is the oil pump a Hydreco?

The fact that the gear now engages with an oil fill up is a good sign that you may have saved the clutch and other parts. It may be a pump problem which is a relatively cheap fix. The lack of oil and oil pressure can burn your clutch away. Find out why before using the boat, it may save you a lot of trouble.

[AL BAUMER]

Try filling with oil, then check filter, right side of gear under 3 bolts. If full of metal, you will have to rebuild gear. If not Hydreco pump may be bad. This is located on ( I think ) left accessory drive rear of engine.

[AL BAUMER]

Strange as it may seem, these gears will engage in reverse with low oil pressure, but not in forward. Had 1973 58YF, 8V71TI with Allison M gears, and 1979 58CY 8V92TI.

[osonegro]

Any signs of oil leaks? What's the engine oil level look like? Does the oil look dark or milky brown? Does the oil look normal after the engines are shut down and set for an hour or so? If you overfilled them the oil will get aerated and look milky but clear up after it sits. Not a big deal but you do need to get it to the proper level if this is the case. In order to get an accurate reading the oil needs to be checked when the unit is running and preferably up to temp.

No sign of oil leaks. Engine oil level is OK. The oil in transmission looks milky light brown. I've not checked what the oil looks like after shut down. Will do that tomorrow. I checked the oil with the engine running and filled until it was at full mark on dip stick. The engine does engage in forward and reverse.

[Tim Powell]

Unfortunately I have had a lot of experience with this problem and Allison Gear Boxes. A quick education I have paid dearly for. I still have a lot to learn before I am at the level of some of the Senior Members here, but maybe I can point out some things to look for. As Saltshaker has asked, is there an oil leak? If not:
What is the oil pressure of the gears in idle?
What is the oil pressure of the gears in Forward?
Is there a "burnt oil" smell?
When you checked the oil level, was the engine running?
Have you checked the screen/filter? You will find this on the hose going into the oil pressure pump.
Is the oil pump a Hydreco?

The fact that the gear now engages with an oil fill up is a good sign that you may have saved the clutch and other parts. It may be a pump problem which is a relatively cheap fix. The lack of oil and oil pressure can burn your clutch away. Find out why before using the boat, it may save you a lot of trouble.
Jasper and Jack
with no sign of oil leak where would a gallon of oil go? I do understand what Jack said about settling down and air being in it but a gallon.

[osonegro]

Unfortunately I have had a lot of experience with this problem and Allison Gear Boxes. A quick education I have paid dearly for. I still have a lot to learn before I am at the level of some of the Senior Members here, but maybe I can point out some things to look for. As Saltshaker has asked, is there an oil leak? If not:
What is the oil pressure of the gears in idle?
What is the oil pressure of the gears in Forward?
Is there a "burnt oil" smell?
When you checked the oil level, was the engine running?
Have you checked the screen/filter? You will find this on the hose going into the oil pressure pump.
Is the oil pump a Hydreco?

The fact that the gear now engages with an oil fill up is a good sign that you may have saved the clutch and other parts. It may be a pump problem which is a relatively cheap fix. The lack of oil and oil pressure can burn your clutch away. Find out why before using the boat, it may save you a lot of trouble.

The oil pressure with the gears in idle and Forward is normal now. I havn't checked for a burned oil smell but will do that tomorrow. The oil level was checked with engine running. Everything is stock on the trans so I don't know if the oil pump is Hrdreco.

[MikeP]

Rebuilding the pump, should that prove to be needed, is quite easy and the parts kit is around 80 bucks. The seals get old/brittle and may not seal well after many years of use. If the tranny pressures are in spec, or can be adjusted to be in spec, then the pump is ok. I seem to recall that the pressure is supposed to be 130PSI at 1800 RPM in forward but don't hold me to that…look it up.

[osonegro]

As I said in the first post, the trans not engaging occurred after a 200 mile run from Manazanillo to Ixtapa, Mexico. On arrival in anchorage the trans engaged fine while setting the anchor then we sat there for 2 days at anchor. The problem did not show itself until we were trying to get underway and that's when I discovered the low oil condition in the port engine transmission. I know to check the oil with the engine running, but the first thing I noticed was a low oil pressure on that transmission. Now the oil pressure is OK and the oil is up to the full mark but the color is cloudy and a light brown.

[saltshaker]

As I said in the first post, the trans not engaging occurred after a 200 mile run from Manazanillo to Ixtapa, Mexico. On arrival in anchorage the trans engaged fine while setting the anchor then we sat there for 2 days at anchor. The problem did not show itself until we were trying to get underway and that's when I discovered the low oil condition in the port engine transmission. I know to check the oil with the engine running, but the first thing I noticed was a low oil pressure on that transmission. Now the oil pressure is OK and the oil is up to the full mark but the color is cloudy and a light brown.
You are overfilled and the oil is being aerated. Very common issue with Allisons. I'm sure you had a low pressure and even a low level issue but now you are overfilled. Pull some oil out and see how she runs and the oil looks. You may have a pump issue and adding oil brought your pressure up enough. When was the last time you checked the oil before this happened and have you had to add oil in the past? Check the filter screen as other have suggested and see if there is metal in there. Not positive but if the gear is loosing oil you either have a leak that will show externally or maybe a bad transcooler. I know the engine oil can leak into the gear but not sure if the gear oil can leak into the engine. Hopefully some of the mechanics here will chime in on this thread.

[Jasper]

Not positive but if the gear is loosing oil you either have a leak that will show externally or maybe a bad transcooler. I know the engine oil can leak into the gear but not sure if the gear oil can leak into the engine. Hopefully some of the mechanics here will chime in on this thread.

If the oil has leaked into the transcooler, then wouldn't it show in the coolant? In other words, the coolant should have some oil?
If the coolant is clean, the question is, where does the oil go?
Either the ER bilge should be showing it or the engine oil level should raise?
This is a question that I am trying to find an answer to myself. The raw water does not reach the oil cooler (according to the manual) so the oil did not going overboard into the ocean.

[saltshaker]

If the oil has leaked into the transcooler, then wouldn't it show in the coolant? In other words, the coolant should have some oil?
If the coolant is clean, the question is, where does the oil go?
Either the ER bilge should be showing it or the engine oil level should raise?
This is a question that I am trying to find an answer to myself. The raw water does not reach the oil cooler (according to the manual) so the oil did not going overboard into the ocean.
I was thinking the trans cooler was raw water cooled. I don't think the oil leaks into the engine rather the engine would leak into the gear but as I said earlier I don't know this for certain.

[Paul Gwiz]

On mine the trans / oil cooler is bolted into the bottom of the Heat Exchanger. IF the oil didn't show up in the bilge, I would assume it went out the exhaust . a gallon of oil went somewhere , that's enough to show up as a sheen on the water or it's in the bilge.....Good luck hunting.......If the oil is milky my guess would be the oil cooler in the Heat Exchanger......

I had good luck with www.dieselpro.com for replacement parts.....

[saltshaker]

On mine the trans / oil cooler is bolted into the bottom of the Heat Exchanger. IF the oil didn't show up in the bilge, I would assume it went out the exhaust . a gallon of oil went somewhere , that's enough to show up as a sheen on the water or it's in the bilge.....Good luck hunting.......If the oil is milky my guess would be the oil cooler in the Heat Exchanger......

I had good luck with www.dieselpro.com for replacement parts.....
If the oil is milky and stays that way then he has a serious problem as water is in the oil/gear. Allisons will whip up and aerate the oil making it look milky but once they are shut down the air separates from the oil and the oil will look normal again. If the trans cooler is raw water cooled then yes the oil may have gone out the exhaust. May not notice an oil sheen on the water if it's only leaking while under weigh.

[rsmith]

If the oil is milky and stays that when then he has a serious problem as water is in the oil/gear. Allisons will whip up and aerate the oil making it look milky but once they are shut down the oil separates from the oil and the oil will look normal again. If the trans cooler is raw water cooled then yes the oil may have gone out the exhaust. May not notice an oil sheen on the water if it's only leaking while under weigh.

Never seen a raw water oil or trans cooler on a Detroit. If it got in the cooling system it would piss out the relief cap overflow. They don't hold a lot of oil to begin with. Every one I've seen leak(including mine) has been out the rear coupling shaft seal. Probably just got pumped overboard on the run.

[mike]

Never seen a raw water oil or trans cooler on a Detroit. If it got in the cooling system it would piss out the relief cap overflow. They don't hold a lot of oil to begin with. Every one I've seen leak(including mine) has been out the rear coupling shaft seal. Probably just got pumped overboard on the run.

If it´s leaking out the rear seal you should see a small oil trail witness mark from the oil slinging out of the seal area at or near the coupler in the bilge and up along the stringers. If it is really bad the oil trail will show up on the inside of the rear engine room door.

[saltshaker]

Never seen a raw water oil or trans cooler on a Detroit. If it got in the cooling system it would piss out the relief cap overflow. They don't hold a lot of oil to begin with. Every one I've seen leak(including mine) has been out the rear coupling shaft seal. Probably just got pumped overboard on the run.Man I guess I was tired when I typed that post! I fixed all the typos.
I wasn't sure about that either which is why I said if. Not familiar enough with all the mechanics of this but my understanding with regard to the Allisons is that if you are loosing oil you should see the oil in the bilge. No where else for it to go. I know the engines can leak oil into the gear but can the gear leak into the engine?

[Genesis]

Never seen a raw water oil or trans cooler on a Detroit..

Series II Hatteras 45cs with 6v92TA engines had raw-water gear coolers on the suction side of the Jabsco, right after the strainer. I called them "auxiliary sea strainers" -- with good cause.

[captainwjm]

If it´s leaking out the rear seal you should see a small oil trail witness mark from the oil slinging out of the seal area at or near the coupler in the bilge and up along the stringers. If it is really bad the oil trail will show up on the inside of the rear engine room door.

Assuming a small oil trail, what is the easiest remedy, or do I leave it alone for now?

[chris45]

On mine the trans / oil cooler is bolted into the bottom of the Heat Exchanger. IF the oil didn't show up in the bilge, I would assume it went out the exhaust . a gallon of oil went somewhere , that's enough to show up as a sheen on the water or it's in the bilge.....Good luck hunting.......If the oil is milky my guess would be the oil cooler in the Heat Exchanger......

I had good luck with www.dieselpro.com for replacement parts.....

If you are referring to an 8v71ti, the oil cooler is bolted under the expansion tank. Internally and just above the oil cooler, is the heat exchanger. Raw water runs through the exchanger cooling the engine coolant which cools the oil cooler. In short, oil cooler is not cooled by sea water, at least not directly.

[Jasper]

The Gearbox is back on the engine!
Tomorrow we test the oil cooler.
It will be interesting.
Here is the gear oil cooler:

[mike]

Assuming a small oil trail, what is the easiest remedy, or do I leave it alone for now?

You have several choices, the first is to leave alone if it is a small leak, but not recommended. The second is to unbolt and back the shaft flange away from the trans flange about 3" to 4” so you can check the torque on the trans flange nut. It should be torqued to about 250 ft/lbs. If it’s not tight you should determine if there is any movement between the splines of the flange and trans output shaft. This should be a hand press fit and not loose. If there is significant movement/play between the splined flanges you have a problem that needs to be fixed. If there is little to no movement/play you can remove the trans flange and replace the seal, not easy but doable in the boat. What trans do you have? Do you have an Alison M20 or MH20 or some other configuration? If you need more info send a pm and I'll try and help you. If interested there are some pics of the problem I posted on this site, or send a PM for more detail.

[osonegro]

As the original poster of this thread I want to let all know what is happening with Oso Negro. What I found after reading the manual and dropping the oil filter canister is that first of all my main problem was low oil level caused by the oil filter canister seal leaking oil into the bilge. Second, according to the manual, once the oil is very low it causes the oil pump to suck air and this causes the oil to look cloudy with small bubbles in it and it can also change the color of the oil. Where did the oil go? Well, prior to arriving at our destination I had run the engines up to full speed to blow out the air box and I ran it like that for about 10 min. I did notice that the bilge pump in the engine room came on at that time but didn't think anything of it. I now think that when I ran the engine up the seal failed on the canister and pumped oil into the bilge and the bilge pump pumped most of that overboard. Once the engine had been off for a day or two, the oil looked clear and pretty much the normal color. So again, I believe that the oil seal failed on the oil filter canister and that was my main problem. I am now waiting here in Ixtapa for new filters to be sent DHL from La Paz, BCS, Mexico. Wish me luck!

[osprey]

Does your transmission have an oil cooler in the expansion tank?

[bobk]

Check the torque specs on the filter canister. For my M15, it is 65 ftlbs. Takes a big wrench. Also be sure you have only the new seal on the canister.

Bobk