Need help with a transmission problem

[Keith]

We have a 1966 50' Yacht Fisherman with 871 naturals and Alison transmissions. I always check the transmission oil level with the engine running after about 15 - 20 minutes of run time. The port side tranny always shows a little low. We have run the boat up from San Francisco and are now in Juneau, Alaska. Over this distance I have added Delo 100 40 weight oil to the tranny whenever it showed low. In Ketchikan I noticed that the transmission started leaking between the transmission and the bell housing. Before this, there was never and apparent leak. I kept running north towards Juneau because I could find no one in Ketchikan would could work on the Alison. By Petersburg the oil was coming out faster. In desperation, I put a bucket under the transmission to catch the drips and just poured the oil back in the transmission. Now in Juneau, I drained the oil from the transmission. There were twelve quarts! Should be six! The dip stick always showed low. I compared dip sticks between engines - the same. I changed the filter and checked the strainer. I refilled the transmission with six quarts of oil. Ran it up to temperature - the dip stick showed low! I let everything cool down. The oil level showed about one inch above the full mark - same as the starboard side. So, the oil is pumped into the system but fails to return to the sump when the transmission is running - I think. The only thing left to check is the oil cooler. What do you guys think? By the way, now with only six quarts of oil, the pressure gauge shows 100 psi at start up and drops to between 50 and 75psi when I put it in either forward or reverse.

 

[REBrueckner]

The leak appears at the forward end of the tranny, right?? Are your transmission oil pressure readings normal at cruise RPM??

Obviously a leak needs to be fixed....I'm addressing the dipstick readings first.

Instructions say to check oil level hot, idle, neutral, right?

If you check oil level when the engine is off, and the dipstick showed full at hot,idle,neutral, I have found the dipstick reads overfull...by maybe 3/4 inch.....

Alternatively, if your dipstick showed full with the engine off, it will likely show low when the engine is running. But I assume from your description that when running there is a difference between the port and starboard dipstick readings whereas the readings are the same when the engines are off???.

Regarding 12 qts vs 6qts, my recollection is that the oil lines and oil cooler on my 8V71TI's held roughly a quart or a bit more of tranny oil...so where another five qts might be going IS a total mystery.

You tyranny oil is the same clear color in both trannys, right??

If the oil leak or tranny oil is a dark color, try this discussion for information, but your symptoms, if I understand them correctly, appear a bit different.:
http://www.samsmarine.com/forums/showthread.php?t=11754&highlight=allison+transmission

 

[Keith]

When the transmission was over-filled, the pressure readings were good! When I put the correct amount of oil in the transmission, the readings were 100 psi at idle in neutral - when I put it in either forward or reverse they drop to between 50 and 75 psi.

Dip stick readings have always been at warm and running. The starboard transmission and port transmission dip sticks are the same length and at cold not running both show about 3/4 to 1" above full (now that the port transmission has the correct amount of oil in it).

First thing I thought was the forward seal but, the oil is as clean as the day I put it in, not a hint of black!

Again, do you think there is some sort of clot in the oil cooler? I even thought of replacing all of the transmission hoses in case there is a restriction in one of them. In fact, I have already replaced the hoses to the high pressure pump at the back of the engine.

This is a perplexing problem!

 

[yachtsmanbill]

Color is the big indicator... trans should look like new. If the oil is dark, its lube oil. The Allisons' run a wet flywheel IN trans oil. Try tighteneing the flywheel housing bolts and dont forget the starter; thats in the same bath and uses a gasket as well.
If the trans oil is dark, and overfull on its own, the rear main seal on the engine is leaking. Its a BIG repair so merely suck extra oil out and save for replacement.
My static stick reading is a good ONE INCH above the full mark and at the line when running. Once started, the pumps' requirements take care of the excess. It takes a minute to fill the system, and maybe a few to drain back. The screen is clean and no leaks right? My pressure was about 130 and then I had the unit rebuilt. The pressure now lags at about 90 when running and the pump needs overhaul. Max pressure at the pump is only 90 via an adjusted regulator. Thats all she gives! Use the book numbers as a guideline but rely on the stick/pressure. Typically, an overfilled gear will foam and run hot. Id recommend a flourescent die check to ID the real oil leak. Thats ok... no one listens to me so who cares... right Reb?? ws

BELL HOUSING GASKET

WET FLYWHEEL INSTALLED

LEAKING REAR MAIN SEAL AND WET BATH STARTER

 

[yachtsmanbill]

You may have a partially collapsed return hose to/from the cooler. Stranger things have happened! ws

This shows a relief valve or internal screen in the filter head...Maybe a malfunction point?? EXSPURTS???

 

[Keith]

All good suggestions. I didn't think about the relief valve but I will check that today. I did think about the hoses and will get them replaced on Monday. I will let you know the out come of this problem.

Keith

 

[saltshaker]

Make sure you are checking the oil level with the gears at operating temp, not just idling at the dock. Willy's post are right on, an overfilled Allison will aerate the oil and whip it into a milky foam in less than a minute. It's been a while since I had Allisons but 6 quarts seems too low. 12 does seem like a lot but it really depends on your set up. I had remote filters that probably held 2 quarts each. I can't remember what the correct pressure was but what your seeing seems way too low. Do the gears take a while to engage after you shift. Is there a difference between forward and reverse?

 

[REBrueckner]

My mechanic set my transmissions at 125 psi and they remained that way for 11 years...so BIll's post of 130 psi is right on. (I never monitored reverse oil pressure.)

"...When the transmission was over-filled, the pressure readings were good! When I put the correct amount of oil in the transmission, the readings were 100 psi at idle in neutral - when I put it in either forward or reverse they drop to between 50 and 75 psi..."

Those are too low!!! When my mechanic did a pre purchase survey, readings like that led him to adjust the pressure UP to 125 psi.

What does the other transmission read???

What has me baffled is the six extra quarts information....a blocked oil cooler or hose can't "hide" that much oil.....and I don't know the feects of such overfilling....

I'm now wondering if all that extra oil bubbled out somewhere and is appearing as a leak, simply running out a low spot. Now that the transmission has the correct amount of oil as evidenced by dipstick at hot, idle, netural, all that MAY be required is a simple pressure adjustment....which takes only five minutes....

We discussed this adjustment once before some years ago, and I know the adjustment is on the top of the transmission, but I do not recall the details....Anybody know??? It's a buffer type "screw" adjustment which changes bypass oil pressure spring tension....should be shown in an Allison diagram.

PS: While I don't think this is the issue, it would be a good idea to monitor tranny oils temps via infrared at operating temperature underway...compare port and stbd...I added oil temp gauges and with 170 thermostats (engine coolant) my transmission lube oil temp was about 185 degrees at 1500 RPM....Maximum spec temp is 200 degrees according to my old Allision book.

 

[Keith]

I'll look in my book and see if I can find the by pass adjustment. Again what's weird is that when the transmission was over-filled, the pressure was right on. Both transmissions would read the same - around 140 psi.

I have ordered oil temperature gauges from the lower 48 and they should be here on Monday. I'll install them first thing and run the transmissions up to temperature again to see what they read.

I agree with you - six quarts is too much to hide so, where is it going? I think I was probably 'hiding' three or four quarts for a long time. Then when I kept adding more to bring it up to the full mark, it started leaking. Also, when the oil was leaking it was very hot and water thin. I don't know the temperature of the oil, that is why I have the temperature gauges coming. I checked in my book and it did say that over filled transmissions heat up.

 

[yachtsmanbill]

The oil coolers are part of the closed cooling loop... see mine in the block, yours may be on the HE itself (8-71s). 180 on the temp will probably keep it around 200-225 F just for semantics.
The pressure regulator is on the Hydreco pump. Its coverd by a 3/4" LONG nut. Remove that (dont lose the gasket) and break the lock nut loose. Tighten the slotted screw in 1/8s, and tighten the lock nut. Two people can adjust and read the gage at the same time. As I noted earlier, mine will only make about 100 psi. The pumps tired.
Due dilligence is the key to maintaining a level. Check it hot or check it cold, just check it the same way every time. I digress about the temps/oil level. The hot oil will expand, maybe 1-2 per cent. The idea is that the pump needs to fill the cooler, the filter, the pressure train, and, last but not least, the flywheel cavity which has a forward and reverse (2) clutch discs, and the the pressure plate. The flywheel part probably holds two quarts in itself.
Where are you gonna mount the temp sender? That needs to be in the oil flow. ws

shitty pic, cap is in extreme upper RH corner

Nut is facing up by tach signal generator

nut has rusty wire wrapped around it

 

[mike]

Keith,

You might want to check the bottom trans cover and make certain it is tightened and not leaking. The bottom cover has two pick-up cavities that are sealed by the cover gasket. One side is for the pump pick-up the other is for the dipstick. If the gasket is leaking or the cover is loose or has a corroded hole to the cavity area, when running it could be a source of air into the pick-up side to the pump sourcing air, and potentially leading to low oil pressure. The rest of the system in the main case that is accessible to the outside world is gravity fed. The front half of the case has a drain-back port as part of the casting that mates to the bell housing on the engine, which is seen in the gasket that Willy posted. If this area is leaking it will not be under much pressure other than gravity and what the spinning flywheel throws off. A failure in this area would not explain the low pressure; but it could be a oil to bilge leak path. Also try tightening the bottom bolts on the tans to bell housing as a potential start. (expect the 3/8” bolts to be rusted and a B…. to get too; had to use a metric size because of the wasting of the bolt) Again, it won’t explain the pressure drop. The bottom cover is constructed of aluminum and can be corroded from high bilge and or raw water pump leaks, (mine had a lot of corrosion holes and had to be repaired and epoxy coated). It’s a B…. to change in the boat, if this is the problem you will need to decouple the shaft and jack up the backend to get enough clearance to remove the bolts and clean the gasket surface on the trans case. Have some pics of the trans case etc if interested. By the way really like following the log of your trip North.
(see pic on this site for oil pickup location mentioned above) (http://www.samsmarine.com/gallery/files/8/0/m20_-_torquing_driven_shaft_inner_nut-med.jpg)

 

[Keith]

Thanks for all of the great suggestions.

Mike - I will check the tightness of the pan bolts. I've tried the very few at the back that I can easily reach and the are very tight, I can't budge them! Glad you enjoy our blog - we are having a great time and have met some wonderful people along the way. Just yesterday evening, we were walking to the top of the ramp in Juneau and a guy stopped us and asked if we were the ones with the transmission problem. I thought to myself, how did he find out but, it is a small town. He told me he has a Hatt and if I'd like, I could borrow his transmission book. I told him that would be great and asked his name. He told me his name was Bert and that he was an Alaskan Senator. I was astounded. Here was a guy, dressed in Levis and a work shirt with greasy hands, a normal guy who happened to be a boater first and by the way - a Senator also...

Yachtsmanbill - I will check that pressure relief valve out. My transmission has a drain plug in the pan. I planned on installing my temperature gauge in that hole. The problem with this transmission has to be simple - I just don't see it yet. But, I'll keep plugging away. We have had our third beautiful sunny day in Juneau, Alaska. Hard to work with my head in the bilge in weather like this!

Keith

 

[REBrueckner]

Keith:

Sorry introduce yet another uncertainty, BUT BEWARE: when I ordered two tranny temperature senders and gauge sets, for port and stbd main engines, both sets read about a hundred degrees off!!!! But the readings were the same ???? An infrared thermometer confirmed the actual tranny cases were at about 185 degrees at cruise.....I think the gauges read about 285!!!! I don't remember the brand name....

So I copied down the sender and gauge numbers stamped on them, figuring they were mismatched, and asked my mechanic to check his source to see which was incorrect...A few days later when I checked his parts guy, they told me the sender and gauges WERE properly matched....??? [of course they likely were NOT] So I had no way to order something that gave the proper temps!!!!

Since I was leaving for the summer I just left them installed and used them for relative readings, all that I really needed.....since if the readings remained consistent, then I knew what the real temp was.....That was maybe eight or ten years ago.....Never did figure out the incorrect readings....they still read steady but way too high...??

Per your post, interesting that an overfilled tranny gets hot.

 

[Boatnut]

Just a FWIW

I don't know a thing about the Allison Units, but on my capitals I had a low pressure problem, at the suggestion of some true experts, I replaced the bushings in the pump, and it solved the pressure problem. I did remove the pump, and took it to a machine shop, and they bored new bosses into the unit, sleeved the bore, and installed the bushings for me. It worked out great.

 

[Keith]

I think I am finally getting to the bottom of this transmission issue. In the beginning of this thread I said that because the dip stick always showed low, I overfilled the port transmission. Yesterday, I decided to change the oil and filter in the starboard transmission. Remember, the book says they hold 6 quarts and should be checked while the transmission is running and up to temperature. My starboard transmission has never leaked a drop nor has it ever showed less than full and the oil pressure has always read around 140 psi. So, I drained the oil from this transmission and filter housing and, what do you know - 9 quarts of oil! How can that be? My only guess is that the book refers to the transmission only and not the filter housing, oil cooler and hoses. I know the filter housing holds about 1 - 2 quarts. I'm guessing the cooler holds about a quart and the hoses - who knows but, let's say a quart. That is roughly 3 quarts of oil plus the six in transmission is 9 quarts.

When I refilled the port transmission, I poured in exactly 6 quarts. The pressure only read 100 psi then dropped when I put it in gear to around 60 psi. The dip stick while running and up to temperature showed below the low mark. I added another quart. The pressure came up to 140 psi but the dip stick still showed a little above the low mark. One mechanic told me, put enough oil in to bring the level up to the full mark while the transmission is running and up to temperature. He said if it takes 8 or 9 quarts - so be it.

Has anyone else experienced anything like this?

Keith

 

[saltshaker]

read post#7