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PostPosted: Fri Sep 01, 2006 10:14 am 
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Location: Orlando, FL
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I d like to get an idea of the consequences of a particular parts failure. I am not concerned with being left on the side of the road as long as being left there doesn't include a spinning out of control hault that could kill me. The reason I am concerned with this is that I hope to not up grade everything all to once and would like to get an idea of the risk facters involved with each failure.
I am planning on installing a high torque/HP engine soon and leaving the 904 with small input shaft and 7 1/4 rear. My sig. shows tire and ratio sizes.
If the input shaft fails - what happens? Can this do likely damage to the new engine. Keep in mind that I do have a rev limiter set to 5000 rpms.
If the rear fails what happens? Does the driveshaft fly off or the rear freeze up sending me spinning out of control? Lossing the rear - does the trans shift up so fast as to damage it?
Do I have to worry about trans scatter coming in and ripping off my legs?

I know anything can happen under the right curcumstances. What I am looking for is what usually happens.

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PostPosted: Fri Sep 01, 2006 10:28 am 
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Location: Portland-ish
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It's highly unlikely you'll break the trans input shaft. You're most likely to break a spider gear in the differential. Another possibility that I've experienced is pounding out the cross pin hole in the diff case then breaking a spider gear and the cross pin, but that was with a 4 speed. Automatics don't shock load the drivetrain as much. Neither diff failure will kill you, but if you loose a spider gear under hard acceleration you can cause transmission damage. Search recent messages for overrunning clutch for details.

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PostPosted: Fri Sep 01, 2006 10:32 am 
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Quote:
I am planning on installing a high torque/HP engine soon and leaving the 904 with small input shaft
There is no reason to think the early trans is weaker because it has a "small" input shaft.
Quote:
and 7 1/4 rear
Could be a weak point, how "high" of a high torque/HP engine are you looking at?
Quote:
If the input shaft fails - what happens?
The car will no longer move under its own power. You coast off to the side of the road and call for a tow. Depending on the extent and nature of the failure, there may be collateral transmission damage.
Quote:
Can this do likely damage to the new engine
No.
Quote:
If the rear fails what happens?
In the worst-case scenario, one or more spider gears exits the diff housing at great velocity, makes a noise like a rifle shot and scares the piss out of you. You coast to the side of the road and call for a tow.
Quote:
Does the driveshaft fly off or the rear freeze up sending me spinning out of control?
Life is not like a Hollywood movie, so...no.
Quote:
Do I have to worry about trans scatter coming in and ripping off my legs?
Geeze, dude, how do you sleep at night, thinking up all these awful things? :lol: Relax, you drive a Mopar, not a Chevrolet. There won't be any trans scatter coming in and ripping off your legs.

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PostPosted: Fri Sep 01, 2006 10:44 am 
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Joined: Fri Nov 08, 2002 4:48 pm
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Location: Burton BC canada
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So....buy a trans blanket and install a driveshaft loop. Cheap insurance you will need if you want to race the thing.

I have dropped the driveshaft out of my Valaint on a 1-2 shift(5 speed) without a driveshaft loop. It cost me a driveshaft and a pair of pants.

You can add U-joint failure to your list.

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PostPosted: Fri Sep 01, 2006 11:06 am 
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Location: Park Forest, Illinoisy
Car Model: 68 Valiant
If you're that worried about parts failure, how come you're using all the weakest drivetrain parts you can? :shock:

You'd be better off to build up the drivetrain first and a motor later. 8)

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PostPosted: Fri Sep 01, 2006 12:37 pm 
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Location: Orlando, FL
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I am using the parts I all ready have. Its not like I shopping and buying these weaker parts. Building the engine shows results now and maybe provides good stories for the freind when things do break.
I do have a 8 1/4 lined up to be bought soon. (just got to get it picked up) The 7 1/4 will likely stay until it whats to come out. (which I think with time I'll convince it to) :o

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PostPosted: Fri Sep 01, 2006 1:39 pm 
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Its way easier to add a built motor to a proven drivetrain than it is to try and sort out a built motor as things grenade around you.

Its way easier to sort out a new drivetrain with a proven motor(stock) than it is to be fixing broken parts as you dial in a new motor.

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PostPosted: Fri Sep 01, 2006 7:43 pm 
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I can think of only one scenario that might have results that you describe. Breaking the front u-joint, without a driveshaft loop, and having the front of the drive shaft drop into a pothole as you go over it. This would give you a bit of a "pole-vault" effect. Depending on how fast your moving at that moment, the worst case would be a rear end that gets driven out from under the car. The odds of all those conditions coming together at once are really steep, though.
If you have to build your car in the order you describe, exercise some self-control, and baby it until you can build up the rest of the drive train.

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PostPosted: Fri Sep 01, 2006 7:53 pm 
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The car won't pole vault when it breaks a driveshaft. Most of the time the driveshaft drops down, gets caught, breaks the rar u-joint, and gets driven through the trunk floor.

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PostPosted: Fri Sep 01, 2006 8:08 pm 
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Location: Portland-ish
Car Model: Fiat 500e
Quote:
The car won't pole vault when it breaks a driveshaft. Most of the time the driveshaft drops down, gets caught, breaks the rar u-joint, and gets driven through the trunk floor.
That's really not very good either. Most all of our cars have a gas tank under the front of the trunk floor.

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PostPosted: Fri Sep 01, 2006 8:09 pm 
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So as long as I am not driving from the trunk, it should be hard to hurt my self from breakage.
:D 8)

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PostPosted: Fri Sep 01, 2006 8:12 pm 
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Gas tank-Humm- good point. :shock:

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