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'72 280SE: Dumb driveshaft nut question
The (giant!) 46mm wrench came in from Northern Tool, and so I'm making another run at getting the transmission out of the car.
The clamp nut on the driveshaft is well and truly stuck, and it's not clear from the documentation which way is loose. Am I trying to move the 46mm nut towards the front of the car, or the rear? Thanks! -Zandr
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1972 280SE "Babe" 1968 250S 4spd |
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I had to think about your question for a bit. Counter-clock-wise to loosen the nut which equates moving the front most edge of the nut towards the "front" of the car
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Quote:
Got it, thanks! back to the garage... -Zandr
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1972 280SE "Babe" 1968 250S 4spd |
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don´t forget to mark the driveshaft! and when you tighten the 46mm nut please do it only by hand!
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´64 W111 220seb coupé ´66 W113 230sl pagode ´67 W110 230 6cyl ´69 W111 280sec coupé ´71 W115 250ce coupé ´72 W108 280se 4.5 ´73 W108 280se 4.5 ´79 W123 300d auto ´80 W123 230ce 4cyl |
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[QUOTE=Housecrew;1895596]don´t forget to mark the driveshaft! and when you tighten the 46mm nut please do it only by hand!
No way.. that clamping nut has a Factory Torque of 20 mgk [ 145 ft/lbs] ..and it is only tightened After every thing is reassembled and the car is let on the ground and pushed back/forth a few times to set the shaft length .
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A Dalton |
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Quote:
EDIT: The rear clamp nut on a 3pc driveshaft is indeed 20.0 mkp. But this a 108.018, I only have a 2pc driveshaft. Still can't budge the nut, though. As to marking it...as I'm replacing the transmission, what am I marking it relative to?
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1972 280SE "Babe" 1968 250S 4spd |
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Mark the driveshaft halves. They were originally balanced as one unit.
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WorkShop Manual
Two piece propeller shaft Clamp Nut. Job 41-1-5: Clamp nut and screws for bearing attachment should not be comepletely tightened until the car is standing in curb position and pushed back/forth several times for shaft to adjust to proper length. Torgue settings -Job 41-0:- Bearing atttachment bolts - 4.3 mkg Clamping Nut at front propeller shaft - 20 mkg
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A Dalton |
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Got it. I'm not planning on separating the driveshaft, just compressing it to get the transmission out.
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1972 280SE "Babe" 1968 250S 4spd |
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Quote:
From 'Passenger Cars starting 1968 - Service Manual' Page 41-0/2 (Early Model Years CD: Volume 3 - Disc 2\pdf\WM\280\grp41\41-00.pdf) Code:
Tightening Torques in mkp 2-part universal shaft clamping nut 3.0 + 1.0 3-part universal shaft clamping nut front 3.0 + 1.0 clamping nut rear 20.0
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1972 280SE "Babe" 1968 250S 4spd |
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I see that
Pre '68 - 145ft/lbs '68-72 - 22-28 ft/lbs. You will note also that '68 and on they want the rear of the 3 piece torqued at the 145 of the earlier versions.. I believe that is so one side of the intermediate shaft is locked tighter than the other b.c they want the shaft to stay centered. [ they require equal distant on each end at installation]
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A Dalton Last edited by Arthur Dalton; 06-27-2008 at 09:28 PM. |
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Man, this one is fighting me. I've mangaged to move it about one flat (1/6th of a turn) and it's not getting any easier. We're sure it's counterclockwise as you face the rear of the car, right? (pull the wrench towards the left side of the car...)
I'm beginning to think that I was wrong about this transmission having been out of the car...and factory torque really was 145ft-lbs. (factory and service being different in this case) Going to give the liquid wrench a little more time and get a cold one.
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1972 280SE "Babe" 1968 250S 4spd |
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The nut is threaded onto the front shaft. It is an angular wedge inside and as it tightens, it compresses the spline surfaces to facilitate zero backlash.
When you state "Facing the rear " ..you can be facing it either from the rear of the car or from under the car...so your orientation discription is the problem. Alway state direction as "Direction of Travel" And right/left side on a car is always from the DRIVERS POSITION..thereby eliminating confusion for RHD and LHD vehicles and if you are in front or in back of the car. This eliminates any mistakes and is normal orintation procedure. Look at the threads that the nut turns on ..It is RH Thread and turns as any standard nut does ..you tighten CW and loosen CCW. So, looking at the driveshaft in "Direction of Travel".[ Looking Foward from under the car} You loosen the nut by turrning it CCW. That will release the tension on the splines . You are turning the nut the wrong direction, if I understand your R/L orientation discriptions correctly. By turning the wrench as you state "to the left side of car'", you are tightening the nut and moving it foward. The more foward the nut goes , the tighter it gets. You have the CD...look at intermediate bearing assembly and you can see the wedge shape design of the slide nut right in the diagram. You tighten the nut, you tighten the backlash..you loosen the nut, you loosen the backlash...simple...
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A Dalton Last edited by Arthur Dalton; 06-28-2008 at 08:44 PM. |
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Quote:
Quote:
Thanks again! -Zandr
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1972 280SE "Babe" 1968 250S 4spd |
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Once apart , you will see that the outer surface for the splines is tapered, so as the nut goes up the taper [ tightening the nut] , it closes the outer splines inside circumference size smaller ..thereby tightening on to the inner spline shaft [which has a fixed circumference size].. it is a CLAMPING device employing a wedging force principle. And that force is calculated by the designers to be a specific and exact force for that application. So, they have calculated that at a specific rotational torque on that nuts threads, the wedge design will exert the required force thay want to get the proper backlash specs on the splines that they have decided to be appropriate for that shafts input .
It is specific and handtight does not make it....I have seen plenty of worn splines b/c they were not torqued for proper backlash ..same goes for the rear tranny flange nut. Guys just smack em down with a punch amd hammer [ ouch!!] and a few miles later, the speedo doesn't work [ first bad sign] b/c the clamping force of the tailshaft helix is lost and a little later the flex disc goes , along with the splines on the rear flange, etc..... Doesn't take any longer to do it right.
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A Dalton Last edited by Arthur Dalton; 06-28-2008 at 11:10 PM. |
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