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Frans
Date registered: Dec 1899
Location:
Vehicle(s):
| Propeller Shaft Dia
Can any of you clever guys tell me why the rear propeller shaft has a larger diameter than the front shaft? Doesn't both develop the same torque when going AWD. Or is it due to space constraints to the front?
PS. My front grease nipple is gone and I can't find the part nr on the EPC. Can anyone help?
Edited by Frans 5/15/2007 2:06 AM
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Boy G
Expert
Date registered: Feb 2007
Location: Bushveld, South Africa
Vehicle(s): Diesel G's: 617A and 602
Posts: 1683
| Re: Propeller Shaft Dia
Frans,
I am now frightened to throw in my two cents worth as I am one of the stupid ones who learns everything the hard way....
Jack up the body of your G on the side of the front shaft until the wheel leaves the ground and look at the minimal clearance between the shaft and the gearbox cross member. Ive seen fat aftermarket shafts smack that thing (and tear the transfer case mountings?). Then you have vibrations!
Incidentally we all spend a lot of time balancing and timing propshafts (which is good) but most old G's I have had have some suspect transfer case mounts and replacing them helps for vibration damping.
Rgds |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: Propeller Shaft Dia
Francois,
if you take the diffs apart you'll also encounter that the front R&P are slightly smaller than the rear.
So, why would the rear components be a tad stronger? (good observation, by the way!)
A semi educated guesss on my side is that the engineers took the stress of hill clims into account.
On steeper climbs the center of gravity changes and the rear axle carries more weight - that
in turn exposes the rear to more torque (remember that torque can only be created when there is
enough counter force [traction] - more traction, more torque). Since the front is "unloaded" it is not
exposed to the same (high) amount of torque.
I noticed many years back that vehicle during hill climbs have bulging rear tires (soft, good footprint,
good traction) and front tires that look like they have 60 psi (even though they are deflated to the
same rate as the rear). That made me aware of the weight shift (center of gravity). Ever since I
deflate my tires (35x12.50R15) for steep climbs 12 rear and 6 psi front. Not only can I now climb
where others fail - the torque load on front and rear is about equal. Ever wonder why Jeep owners
usually break their rear axle and rear drive shaft? Its always the rear that goes first.
Another good point why the G is better than most. |
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Frans
Date registered: Dec 1899
Location:
Vehicle(s):
| RE: Propeller Shaft Dia
I must say Harald, never thought of it that way. This might influence the way I approach hill climbs in the future, not that I do that many though. 
Makes me wonder if there isn't someone out there with a copy of the designers notes as these vehicle where born in the '79's and how much it actually changed from the 460's to the 461's. |
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Inkblotz
Expert
Date registered: Apr 2006
Location: Georgia
Vehicle(s): 90 300GD "Thundering Turtle II", w/ 603A turbo
Posts: 3186
| RE: Propeller Shaft Dia
RE your grease nipple. Is yours an innie or an outie (Needle or a ball type). I would think that any metric nipple of similar thread diameter would work for you. Just take out the remaining threaded piece and match it up with one from an auto parts store.
Mark |
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hipine
Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
| RE: Propeller Shaft Dia
Consider also that on the 460 G at least, the majority of the time, and the times when the greatest traction is available (clear hard tarmac) the rear drive line is taking all of the torque to propel the vehicle. It's being driven with force both accelerating and decelerating all the time the vehicle is moving. Lots of the time the front components are only along for the ride, not transmitting any real driving force until 4wd is engaged. So the rear driveline components have a many times harder and longer life, as far as hours of transmitting driving torque, and cyclic loading (towards fatigue failure) than do the fronts. -Dave G. |
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Warren T
Extreme Veteran
Date registered: May 2006
Location: Montreal
Vehicle(s): 230GE,300GD,300D
Posts: 519
| Re: Propeller Shaft Dia
Very early 460 had smaller diameter shafts, same goes for tie
rod ends and transfer case output shafts.
Dont know when exactly, but by 84 the G received many improvements
to the drive line like bigger drive shafts with bigger U joints and
WARREN
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Frans
Date registered: Dec 1899
Location:
Vehicle(s):
| RE: Propeller Shaft Dia
Inkblotz - 5/15/2007 1:49 PM
RE your grease nipple. Is yours an innie or an outie (Needle or a ball type). I would think that any metric nipple of similar thread diameter would work for you. Just take out the remaining threaded piece and match it up with one from an auto parts store.
Mark
It's the outie type. Just after my post I got some info of a grease accessories place near me that I will visit today. Otherwise I'll get from MB dealer. Thanx anyway. |
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KERR
Date registered: Dec 1899
Location:
Vehicle(s):
| Re: Propeller Shaft Dia
Why do they call them "Propeller safts"?
Makes me feel like im looking for boat parts. |
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amzimmy
Elite Veteran
Date registered: Apr 2006
Location: South Africa/Italy
Vehicle(s): GD300 1981, Alfa GT 3,2 V6, Alfa Brera Q4 3,2 V6.
Posts: 850
| Re: Propeller Shaft Dia
KERR - 5/15/2007 4:28 PM
Why do they call them "Propeller safts"?
Makes me feel like im looking for boat parts.
Propeller shaft derives from = "to propel - from Latin 'propellere' - drive or push forward by twisting/turning motion - a shaft transmitting power from an engine to the driven wheels of a motor vehicle"
amzimmy  |
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Jonathan Joseph
Expert
Date registered: Oct 2006
Location: Charleston, South Carolina
Vehicle(s): 2004 G55
Posts: 1538
| RE: Propeller Shaft Dia
Hipine,
It seems to me that there would be a great deal more "traction" or resistance to the wheel turning( equating to load on the drivetrain) when the wheel was immersed in mud than when bearing on only a very small amount of surface area on hard tarmac with high tire pressure. I have no idea what sort of off-road/ on road duty cycle the MB engineers had in mind when they were designing this stuff.
Jonathan
Maybe I'm crazy, I realize tires spin in slippery situations but I can imagine them also being bogged down in the right off road situation |
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Frans
Date registered: Dec 1899
Location:
Vehicle(s):
| RE: Propeller Shaft Dia
We're talking about standard G's, but in the case of the Military LWB with the load body at the back, can one assume that the internal parts of such a G would be bulkier? Does it's specs differ?
 (290gdt.jpg)
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 290gdt.jpg (65KB - 1 downloads)
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