We have a 1994 Winebago motor home.  The chevy 454 engine was
completely overhauled in May, 2002 because of a broken piston. In July
with 3,130 miles on the overhauled engine we were driveing on flatland
and the transmission quit pulling in overdrive, we shifted down to
drive and drove 10-15 miles further at 55-60 MPH.  The motor came
apart with a rod coming out of the crankcase.  We had a new chev
454=V-8 Vortec motor and a new 4 L 80-E transmission put in at the
Cheverolet dealer in Mitchell, S.D.  The mechanic said the old motor
and transmission had not been overwrapped or overheated or he could
have smelled it.  The transmission fluid was clear.     WHAT COULD
HAVE HAPPENED?

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Request for Question Clarification by alienintelligence-ga on 29 Sep 2002 18:01 PDT

Hi oldjan,

Unfortunately a number of things could have
caused this situation. What RPMs did the engine
have to spin at in Drive to make it go 60mph?

I don't want to point any fingers at someone
but at 3200mi after a rebuild... either the 
mechanic or the motor home operator would look
likely at fault. The mechanic for forgetting
something that was important, or the driver for
overrevving. You guys didn't go past 5000-5500?

Was the rod broken or bent when it came through 
the block? Bending, breaking or becoming disconnected
from the crank or piston would point to different 
things occurring. 

Rods typically need a good reason to break,
overstressing or poor installation.

Any chance the motor home was overloaded? That
would have done it in for the transmission and
then possibly the engine.

What's your rear gear ratio? 4.10, 3.73?

Do you have any pictures... you know they are
worth a 1000 words =)

This engine site claims a broken rod is not 
covered under their warranty. I personally would
not accept an engine from someone that makes
this type of blanket statement.
[ http://www.enginesonly.com/warranty2.html ]

But they did present an interesting question.
Any chance the head gasket blew? If you suck
liquid into the cylinder, on the next compression
stroke, liquid not being compressible... it will 
cause ALOT of damage.

This site summarizes rod failures with this:
[ http://www.rehermorrison.com/techTalk/05.htm ]
"I estimate that nine out of ten connecting rod 
failures are not the fault of the connecting rod.  
Almost invariably, a broken rod is the result of 
a spun bearing -and the bearing failure is usually 
the result of an oil system problem.  If an autopsy 
of a blown engine reveals even the hint of a blackened 
crankshaft rod journal, that's strong evidence that 
a spun bearing was responsible, not the connecting rod."

I take it the oil level was proper? Oiling problems
could be caused by a poor rebuild.

Here is an example of rod/engine damage from an
engine builder.
[ http://sandt38.tripod.com/sandt38snat/id2.html ]
"When I bought the car it was a total loss. The engine was
overreved and it let go at the weakest link. An
inexperienced engine builder put heavy slugs in it and the
weight of the piston created a balance problem. The #3 rod
snapped, hammering the piston into the cylinder head,
bending the valves and cracking the head. The crank
continued it's high RPM rotation and pounded the broken
rod into the cylinder walls, through the pan, into the
camshaft, shattering the cam and ejecting it out the back
of the block. The rod continued it's travel into the
lifter valley, cracking the bottom of the intake. The
camshaft ejected out through the back of the block and
caught the flex plate, shattering it, punching a hole into
the torque converter, and cracking the transmission
bellhousing."


I had to include this page, cause... WOW
[ http://www.teamjdm.com/id159.htm ]


And for your main question, no... Drive will not
make an engine that is in good working condition
come apart. I have a bad habit of aggressively 
shifting my auto trans and then leaving it in drive.
Several miles later I look down wondering why my
revs are so high at cruise =)

 -AI

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Clarification of Question by oldjan-ga on 30 Sep 2002 09:08 PDT

More information:   The driver drove standard shift dump trucks for 38
years and every shift was made useing a tachometer.  He says the RPM
were from 2800 to 3000 at 60 MPH when the engine went out.  He was
concerned about the heat as it was a hot day and was watching the
temperature guage closely.  It was a 3.73 rear axle ratio.  We were on
a short trip and we were not even carrying canned goods in the RV.  We
were not overloaded.
 I have photos of the old engine after it was removed from the
vehicle.  They show bent rods and the huge hole in the engine pan. 
The engine was not torn down and has been disposed of.  The photos are
digital and my son can send them to you with the computer.  Where
should he send them?

---

Clarification of Question by oldjan-ga on 04 Oct 2002 14:28 PDT

Pictures of the damaged engine can be found at
http://home.kc.rr.com/darinjones/index.html

Thank You!

oldjan...

Overdrive is just that, and is not meant to be a required
gear for the engine to run well. It is more for the purpose
of fuel economy at higher cruising speeds. Driving in Drive
gear should in no way tax a healthy engine, as the mechanic
verified.

It's anybody's guess what DID happen, but I can tell you that
I also blew a rod after an engine overhaul, and it was reported
that this was due to the timing being 10 degrees advanced from
optimal, causing the it to overheat and weaken the metal.

For what it's worth...
sublime1-ga

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