Bryan wrote:


 The pictures of the 4 planet that failed look a lot
like the 6 planet gear sets that keep coming out of
my pickup truck (E4OD).  The transmission guys
keep telling me that I am not to haul 27,000 lbs with my
poor little pickup over the mountains.  Too much power
 with too much load gives a failure that looks just like
your pictures.  Moving up to the 6 planet set should
sure help handle the power a turbo 3 rotor turns out. For
my work we found extending the life of the gear set was
directly related to how cool we keep the transmission oil.
Bigger coolers (NOTICE  PLURAL)  have extended the
gear set life out to almost reasonable.  Just my 1 1/2
cents worth.  Bryan Princeton B.C.

Yes you are right Bryan. That is exactly where the gear set came front.
I am disappointed that they will only handle 27,000 pounds up
and over the mountain. If you tell me how fast the truck moves
and the grade of the hill I can calculate how much HP the gears
are handling.

Example:
If the truck is going 50 MPH on a 5% grade that is 2.5 MPH
straight up. 2.5 X 5280 feet is 13,200 feet per hour straight
up. Dividing by 60 is 220 feet per minute straight up.
One HP is 33,000 pounds moving straight up at one foot per minute.

27,000 pounds times 220 feet per minute is 5,940,000 pound foot
per minute.

Dividing by 33,000 is 180 HP not counting tire rolling
resistance or truck aerodynamic drag.

If the truck is 8 feet
high and 8 feet wide the frontal area will be 64 square
feet. The aerodynamic drag factor will be around .35.
The dynamic pressure at 50 MPH is about 5 pound per square
foot at sea level. Lets say it is 4 pounds per square foot
at the altitude you are traveling in. The drag will
there fore be 320 pounds times .35 or 112 pounds.

At 34 fps the drag HP is 34 X 112 or 3,100 foot per second
or 7 HP due to aerodynamic drag. Lets say another 7 HP
for tire rolling but probably five times that as that
would be for a 4000 pound typical car. Lets say 35 HP
for tire rolling drag We are now up to 180 + 35 + 7 or
a total HP of 220.

Very interesting and in the same ball park we are asking
from these gears on a continuous basis.

Paul Lamar

Bryan wrote:

   The truck most days will  hold 50 miles per hour on a 5% grade
  The last big failure was on a 8 to 9 % grade at about  35 miles
per hour.  Now with that said we are overlooking ( IMHO ) 2 important points

1.  The diesel engine in front of the gear set has a very nasty
torque pulse and it gets worse under load. Picture someone
with a 5 lb hammer beating on your gear set all day.

2.  The failures usually occurr at gear change- the shock load
finishes the job the load and the hammer started.

I do not know how to account for those factors in your calculations.
But my gut feeling is that you should be fairly safe with the 6
planet set up as you are under constant (compared with a truck) 
load and a steady torque load with the prop.  The only shock loading
would be in the event of some other mishap like a prop strike. You
might ask the transmission guys if the gear set in the latest Ford
products behind the 7.3  power stroke are the same as the
E4OD.  The newer transmissions are very bullet proof at
much higher horse power than the E4OD ever thought of being.
   Hope this contributes something.  Bryan in Princeton B.C.

It sure does Bryan and thanks for the hard data.

Paul Lamar
 
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