Twins with Twins, Anyone?

C

Cougar281

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kidturbo said:
Far as I know from same batch. Somehow I ended up with all the spares. So it's funny I'm sending replacement pieces to the manufacture.

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What if there was a problem with the batch that caused the gears to be weaker? Hopefully that's not the case...

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kidturbo

kidturbo

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They're all pushing 20yrs old now. I hear that design is used in other racing applications, known to be very rugged. I was hoping maybe a bearing failed and allowed it to run to shallow, however no signs of that.

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clrussell

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kidturbo said:
They're all pushing 20yrs old now. I hear that design is used in other racing applications, known to be very rugged. I was hoping maybe a bearing failed and allowed it to run to shallow, however no signs of that.

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Any chance it was shock load from the props breaking loose and grabbing?
 
MarkBroviak

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clrussell said:
Any chance it was shock load from the props breaking loose and grabbing?
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This would be my guess because that is hell on gears being unloaded and reloaded, like someone who can't/shouldn't be drive a manual trany! Just takes the perfect situation to find the sweet spot and pop goes the weasel so to speak.
 
kidturbo

kidturbo

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The previous owner "turbines" was probably responsible for the most abuse on these units. He ran them on a heavier boat, in offshore conditions, where the boat was constantly flying out of the water. I know he saw bearing failures in the upper gear cases since they decided to upgrade the oiling design from internal to external plumbing..

So envision 100mph, 1700hp, props spinning 5000R, loading and unloading as the props leave the water, and never reducing power. Typically on a piston engine ya pull the power as the boat leaves the water, then apply again when it lands. Some compare the impact force of those blades striking the water as being equal to hitting concrete. Reason cleaver props tend to shed a blade if you get it wrong..

While inspecting the drives before purchase, I saw some video of that 50' turbine boat running. Due to the slow throttle response time on turbines, there is no use pulling the power because by time it responds, it's done traveled another couple hundred yards.. The owner told me that they had previously ran the same Merc #6 drives we took off at start of our project. He says they killed a brand new pair of those in a couple weekends due to the abuse those turbines dished out.

Now there is two possible situations I see that may have played some role in the gear fatigue and failure. First, I have no idea which direction those gears were spinning behind that turbine, or the previous boat's'. Unlike a std transmission, these are dry sumps with an oil pump design that works in either direction. One drive spins clockwise, the other counter clockwise. I have no idea which direction these spent most of their life spinning. Could be they took a beating in one direction for most of their life, and I just reversed em...

Second possibility that comes to mind, in that first video I posted with no sound, the throttle blade slammed shut by accident and stalled the port engine. Betting she backlashed pretty hard when that occurred. As engine stalled, the oil pump in trans would have stopped pumping and released clutches. But that's the same side the gear let go shortly after..
 
kidturbo

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There is a 3rd possible cause I forgot to list.

According to where ya read it, and I plan to verify with Weismann, those units are supposedly rated at 1600lbft, or 1200lbft of torque. When she went BANG, I was half throttle, 20psi boost bouncing, in low range trans gear 1.50:1 ratio, at about 2800R on engines. Do the math on those torque #'s ;)
 
kidturbo

kidturbo

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Weismann is pretty big name when it comes to the sequential gear box world and trophy truck crowd on west coast. By looking at the finish on those gears, they've been treated with something that gives em that light grey look.

I would like him to strip and hard anodize those lower unit cases again like originally shipped. They were scratched up when I got em, so we opted to paint with this special salt water resistant Alwgrip. That I discover a few months later is allergic to most types of oil.....

With current weather in SoCal, I doubt we can find anyone to hard anodize or treat any gear parts this month. So having the designer inspect everything and reassemble with new gears is best we can shoot for in short term strategy.
 
Chevy1925

Chevy1925

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IIRC the light grey is heat treat but the part was put into an air tight tinfoil type bag that keeps the scale off them. or they were just put in a tumbler for clean up.

REM polish is usually what most off road guys do after a good heat treat but thats more for longevity against pitting and wear, not breaking off teeth. Though it does help reduce stress risers.

i dont know if harder is necessarily better for your case. wouldnt hurt to see what rockwell they test out to.

id think it was more of a wear/tear issue from what it had gone through before. if the new set breaks, well that kinda answers that.

do they suggest a "break in" time on the gears to work harden them like gear sets or does that no matter on straight cut gears in your application?
 
WolfLMM

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kidturbo said:
There is a 3rd possible cause I forgot to list.

According to where ya read it, and I plan to verify with Weismann, those units are supposedly rated at 1600lbft, or 1200lbft of torque. When she went BANG, I was half throttle, 20psi boost bouncing, in low range trans gear 1.50:1 ratio, at about 2800R on engines. Do the math on those torque #'s ;)
Click to expand...

Yep, that’ll do it.
 
kidturbo

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Ok finally received a detailed report back on the drives.

Verdict is that a bearing pack failed on one of the upper intermediate shafts. Part of the cage made it's way into the gears, which caused that tooth to break off. All of the other gears and bearing were trashed as a result of ground up debris.

So it was a bearing failure after-all, which puts more faith back in the gears holding our load. But less in the bearings now.. Both drives showed signs of being apart before outside their shop, and it seems a shim was missing in one key area. Unknown hours or service history on both.

At least now after a full inspection and rebuild by the manufacture, we'll learn if they are actually tough as claimed.. Boat is back in Ohio today. And yes the worlds most expensive Duramax project is being towed around behind a FORD !!! :spit:
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kidturbo

kidturbo

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Hehe.. Heck of a lot better ride than the POS 5.9L Dodge I'd been dragging it arond with past 3yrs. Not saying all Dodge are POS, I most of gotten hold of a bad one..

That pic was in NC bottom of Fancy Gap I77. Started up in economy tune 4th gear, switched it to hot and into 5th about half way. Did much better on temps half throttle than pegged out less fuel. No EGT, but I backed her off after rolling some coal past a loaded 6.7 Dodge... lol

I did get to check out some new GM stock of equal or more value while in FL. Head to head a 3500HD is about 8" taller than the SD Ford. And the shop I was sharing had two white ones on hand. They actually towed the boat for me one day and I forgot to get a pictue..

Towing wise, she was probaply about 1000lbs lighter coming home than the trip down hill. I'll be accepting offerers from anyone who wants to drag it around for me with a matching white GMC. And a CDL...



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