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Old 10-26-2012, 02:06 AM   #1 (permalink)
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Two Piece Drive Shaft

I have a Mazda B2200 truck with a two piece drive shaft would there be an efficiency gain if I went from a two piece to a one piece?

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Old 10-26-2012, 02:31 AM   #2 (permalink)
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If it were lighter, perhaps. But I can't imagine it would be more than 0.5% overall improvement, so unless you're getting the one-piece shaft cheap enough that you can swap it just to check (with A-B-A testing and number crunching), I'd say it's not worth it.

Maybe look into finding a Ford Ranger rear end with gearing appropriate to your commute? I don't think a rear end swap would be substantially more cost than a driveshaft, but the efficiency improvement would be.
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Old 10-26-2012, 01:30 PM   #3 (permalink)
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You would save the friction of the center support bearing. Almost zero overall benefit.

A one piece drive shaft needs to be designed to have the critical speed well above the fastest RPM it will ever see. The diameter gets large enough that the two piece is a better design overall.

You DO NOT want to find the critical speed of a drive shaft while driving.
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Old 10-26-2012, 02:36 PM   #4 (permalink)
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For that short of a vehicle it shouldn't be too hard to find one. You would reduce the friction of the carier bearing, and 1 u-joint. I really doubt it would be worth it though.
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Old 10-26-2012, 05:31 PM   #5 (permalink)
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I converted a Chevy pickup from 2pc (original equipment) to 1pc (also OEM from another pickup) driveshaft. The 2pc on it was problematic- had some vibes, needed a new carrier bearing, etc. Why, when the exact same chassis/engine/trans/axle combo was available with a 1pc, did they ever dick around with a 2pc??? That was a VERY worthwhile mod from the vibration/service requirements/cost of joints and bearings standpoint. In theory it should help fe too but in such a small amount you will never be able to detect it.
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Old 10-27-2012, 01:59 PM   #6 (permalink)
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I agree that the gain would be nill. If everything's working as it should, leave it alone. If your carrier bearing or u-joints are shot then yes, switch over to a 1 piece. Fe aside, IMO it would be worth it just for simplicity. Also, what rear end gears do you have? My ranger (same as b-series) has 3.45's and was getting almost 30mpg when it was running right.
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Old 10-27-2012, 08:12 PM   #7 (permalink)
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The switch to a GIANT diameter one-piece driveshaft is fairly popular among the DODGE diesel crowd. The two-piece has been replaced in regular production by an OEM one-piece on the latest models. The problems for most had to do with the angle (should be plural) of the DS under different loads.

It's an expensive change. I've seen reports of slightly better performance, but it's a change I would make coincide with R&R of carrier bearing & DS. The one-piece aluminum shaft is lighter in this case over the steel two piece so an FE change is likely . . based on a heckuva lot of miles. Ironically it also may not last as long as the OEM piece (in our case the main DS is over 60").

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