53my Allison Transmission Issue

[SereneWarrior]

Got underway yesterday having done all my pre-start up checks (including transmission oil level checks). Engines had been idling for 20-30 minutes prior to casting off. Ten minutes after getting underway I noticed I had no starboard shaft power even though the engine was running and the shifter was forward. A quick check confirmed that the starboard shaft was not turning. I immediately returned up the creek to the slip and berthed using the port engine. A recheck of the starboard transmission revealed the oil level had dropped just below the low mark on the dipstick. Subsequent inspection showed a streak of oil on the transmission case and a quart or two in the bilge. That much had leaked in less than an hour of running.

As a first step, I refilled the transmission to the full mark on the dipstick. Upon restarting the engine, tests of the shifter lever, transmission showed all to be operating normally both ahead and astern. This confirmed that the "transmission problem" was really a low oil/oil leak problem. While the engine was running a steady drip (drop every second or so) fell from the pump mounted aft on the blower shaft. I thought that perhaps something had vibrated loose and attempted to tighten the four pump mounting bolts, but they were already secure. Same story on they hose fittings leading to/from the pump. The leak is definitely coming from the seam between the pump foundation and the pump body. Common sense would indicate that I at least need to disassemble the pump and replace some gaskets. However, I also noticed a metallic knocking/rattling coming from the area of the pump that is not present on the other engine/transmission. Pump pressure remains 100-120 psi, just like the port engine/transmission's pump.

My thoughts now are that my starboard transmission oil pump is in the process of failing and that I should rebuild/replace it. Does that sound about right? Has anyone on the forum done this job and do you know of the parts I'll need? Approximate cost for parts/entire pump? Any good sources for parts? Any special tools required? It looks like a simple enough job, but I'm still somewhat new to this having only owned the boat (my first) for eight months. Thanks in advance for any help/info.

[yachtsmanbill]

I had to pull my HYDRECO pump apart to change a tach drive cable. Very simple, but the clearances as with any oil pump are CRITICAL. Mine had no gaskets, just O rings. While apart, you need to check hoses/fittings for cracks. Oil pressure is a force to be reckoned with! My pump is mounted on the back of 12-71Ns.
A google search will land you at the mfgr.--- general signal. They are very helpful. ws

[yachtsmanbill]

I also noticed a metallic knocking/rattling coming from the area of the pump that is not present on the other engine/transmission.

You should probably inspect the drive coupling off of the blower shaft. There may have been a bushing failure on the pump causing an O ring to burn and also causing a drive mis-alignment.
Call the guys at General Signal. I lost their email address, but it was real easy to find. If you can give them the tag info, the rep will tell you immediately what pump model etc you have.
FWIW--- All hydraulic pump fasteners are grade 8 or better. When I re-assembled mine it had a slight bind that was no good. I had to loosen the frame bolts and ease them tight a few time to make sure it turned perfectly free. After that was all good and installed, I re-tightened all the bolting with a box wrench and a few light raps with a 10 oz. ball pein hammer. Pumps like these have a resonant vibration and the stuff needs to be gutentite! ws

[SereneWarrior]

YactsmanBill, Many thanks! I'll get down to the boat this week and pull the pump, inspect coupling, etc. Will let you know how it goes.

[SereneWarrior]

Found and salvaged a Hydreco pump in perfect condition from a disused 8V71TI engine from a burned 62ft Pace here locally. Installed it on my 8V71N and all is perfect despite having to do some hydrauic hose contortions (will replace the hoses soon anyway). Pump produces great pressure, no leaks and all is happy.... except for one thing. The tachometer drive on my original pump was not the square cross section stub, but rather was a splined stub shaft that fit neatly into the tachometer worm gear. I thought this would be no problem and a simply matter of pulling out the square stub/housing and repacing it with my splined stub/housing in the pump. Unfortunately, no amount of clamping, pulling, Sailor-style cursing, sweat or fortitude will get that square stub out of the pump housing. Until I can do that, I have no tach reading on my starboard engine.
Anybody got any suggestions? I'm currently soaking the offending stub in penetrating oil, but think it will take more that that to break it loose.

Jeff

[yachtsmanbill]

What else is left on the Pace?? Any pics ? How long is your tach cable? I have a brand new one I bought thats too short. Its 107 inches. Ive never seen one with a spline before... Are you sure its not a hex? You may need to change the tach, unless there is a right angle drive you can change. ws

[SereneWarrior]

Unfortunately, the Pace burned over a year ago and all that's left are the engines sitting undr a tarp next to a barn here in MD. The owner (from whom I also bought my boat) has offered to give these engines to me in their entirety. I've also been given permission to salvage what I can from them. They are not mint...far from it. But there are many parts that I'll save (alternators, starters, exhaust headers, hydreco pumps, raw water pumps/brass piping, etc.). Just wish I had a storage area and a way to move them, so that I could really take my time about it...but that's another story.
Interestingly, both of my 8V71Ns have the same splined stub that goes into the tachometer worm gear drive. The splined stub is approx. 1.5" long. The stub's cross section is circular with a ridge spline. The stub fits into a socket-like drive fitting in the pump. That fitting has a squared cross section on its other end (larger than the stub in my salvaged pump) that fits into the pump. That socket-like fitting came out of my original Hydreco pump very easily. It actually almost fell out in my hands. The salvaged pump also has a similar socket fitting, although it is made for the squared stub. It is this fitting that I need to remove, so that I can replace it with my splined fitting. Just not sure how to get that bugger out!

[yachtsmanbill]

Hey SW...
Are you having trouble with the stub shaft or main cable? My stub shaft (3") broke off at the square, on the Hydreco shaft, and I had to drill and tap it and use a slide hammer to pull it out. It was a SOB to remove !! The right angle unit has a keyed drive and the tach has a square. The cable pic with the square drive is new cable with a bigger nut than my tach uses, so I have to cut the end off and braze the old one on. The new cable I bought was 107 inches (8'11") and the correct one I bought is 252 inches or 21 feet long. Its another Anaconda ! You should see the routing. Never a dull moment with a Hatterascal... ws

[SeaEric]

Heh, I think I know that burned up Pacemaker. She had 1100 hours on those 871ti's. I believe this to be the boat in question. Here she is in better days.

[SereneWarrior]

Yes, the problem is with the stub shaft which just will not come out of the Hydreco pump no matter how much I pull on it. The stub shaft is square and the drive gear is keyed shaft. I need to remove the stub shaft and its socket fitting in the pump and replace it with my keyed fitting. Good idea on the slide hammer...and another excuse to buy more tools! I'll look for one this weekend and try to finish the job. Thanks!