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I just installed a 3 Link Rear Suspension on my MK II roadster. The instructions state that they usually run about 2 degrees up on the rear axle, but you can adjust this to fit your particular set-up. If I am remembering right in the past when I helped out with some Hot Rods and Race Cars we always set the differentials to a positive (up angle). I read through a number of old posts in the Forum on this subject and a lot of members recommended a 2 degree negative (down angle). My Cobra is used mainly for street driving. I would like to hear from anyone that has an opinion on what I should set my differential at.
 

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FFCobra Craftsman
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The 2deg down is suggested because under acceleration the pinion tends to go upward. The 2 deg will hopefully have the pinion raise from 2 deg to 0deg. How much it actually moves depends on the bushings in the LCAs. The single UCA has rod ends which one assumes don't move while the LCAs range from rubber in oem donors to polyurethane in both FFR older and newer aluminum LCAs. So the LCAs may allow some movement which needs to be accounted for.
 

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this was a useful thread for me. the 2 deg down on the pinion is relative to the driveshaft. and keep in mind the terminology of up and down angles. if the pinion face is below the horizon, technically the pinion angle is pointed up. I just think of it as having the pinion face angled 2 deg down relative to the crank pulley angle.
 

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359835

Here's a drawing I made and posted about 10 years ago that may help visualize it. Notice that the front of the pinion angles downward in relation to the transmission output shaft. Doesn't matter whether the differential is above or below that output centerline, down is still down. Also note that there is no line for the earth or horizon because that doesn't matter (print this on a sheet of paper then turn or rotate it---2 degrees remains 2 degrees).

Jeff
 

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Discussion Starter #8
Thanks everyone for all the information and drawings. I guess I will go with the 2 degree down.
 

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Official OLD GUY
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Quote: "a lot of members recommended a 2 degree negative (down angle)"

That's because for some reason they throw all their training out the window when it comes to this issue.

ALL measurements and "orientation" are from the driver's seat, so why would they, all-of-a-sudden, stand behind the car and say the diff is pointed down???

The 2° angle that Jeff drew years ago is correct, the difference you need between the centerline of the engine / transmission and the centerline of the pinion shaft is 2° - which is pointing UP.

The junction between the engine / transmission and the pinion centerline should create a " \/ ", a very flat " V ", almost a straight line but with a difference of 2° from the left leg to the right leg.

IF you stand and look at your car from the side and say that both drive line and pinion angles are pointing down, you shouldn't be trying to set angles on your car, get someone that understands the geometry of things . . .

Rant over - let the flaming begin

Doc
 

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FFCobra Craftsman
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Jeez, relax a bit. No need to get nasty.
 

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Semantics fellas. That's why I posted the drawing above and whenever I speak of pinion angle I try to make sure that I clarify by saying "the front of the pinion angles downward" like I did in the earlier post. Without that it could be either. As I mentioned I made the drawing many years ago because there was a discussion going on and one poster was saying the pinion should angle up and the other was saying it should angle down. While they were busy telling each other that they were wrong it became apparent that they were both saying the same, just doing it using different terms. The drawing makes it clear; one might say that the pinion angles up and the other down.



Cheers,
Jeff
 

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Official OLD GUY
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Sorry guys . . . back on my meds.

Doc
 
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