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MG TD TF 1500 - Pinion-flange angle?

I'm trying to set up my rear axle, in advance of putting my engine and tranny back in the chassis....(At least as near as possible to correct).
I realize that it is best to make the rear-tranny flange and pinion-flange, as parallel as possible, so that the prop shaft is not at some strange relationship to the pumpkin, but I would like to know if there is an "ideal" flange angle?
I have attached an image , showing the current, un-set angle at 5 degrees to the perpendicular.
Thanks
Edward

E.B. Wesson

Edward - I thought that was the whole idea in having U-joints at both ends of the drive shaft - to compensate for changing angles between the transmission tail shaft and the rear axle pinion as the geometry changes as the result of the rear axle moving up and down with the springs. Cheers - Dave
David DuBois

Hello Edward. In looking at your photo it does not look like you have the diff attached to the springs. How they are arched will define what the static angle the flange sets at. And as David said it doesn't really matter what the initial angle is as it will change as the load on the rear wheels change. The universal joints have a greater working angle the the diff pinion flange will move even under extreme acceleration(?) and braking.

Butch Taras
VMG
R Taras

In "normal" operating position, the input (gbx) and output (diff) shafts should be parallel, hence the flanges will be parallel. The propshaft will have equal but opposite angles at each end. In a car, the "normal" would be at usual laden suspension position, and the geometry should be such as to give minimal variance over the suspension travel.
It is the geometric nature of the common (Hooke's or Cardan) u joint, that a pulsating velocity is produced when operating at an angle, so the propshaft speed is a sine wave when the input is constant. The opposite angle at the output end rectifies this to a constant velocity. This is why it is necessary to keep the UJs in phase, else the output velocity pulsates unacceptably.

FRM
FR Millmore

If you were setting up a jacked up mud truck or something, the angle would be of concern and you would have to change the diff angle with tapered spacers or something. The guys above are right that all will be fine when the weight of the assembled car is on the wheels. The driveshaft will be pretty much straight at rest. The joint and sliding yoke movement allow the rear end to move up and down with the springs, as well as some twist of the diff snout due to acceleration, etc. Unless you have cut the spring seats off of the axle and need to re-weld, all will be fine. George
George Butz

Thanks all, for the input....
I was hoping that I could find out where most owners found the final angle to be, after the suspension was loaded...I didn't know if there was an "optimum" angle,as there is with some chassis arrangements.

Edward
E.B. Wesson

Frankly, when I put my car together, it was what it was! I don't recall that I had any control over the angles and I didn't give it any thought. As mentioned earlier in the thread, this relationship is constantly changing as the suspension flexes and the components move around.
Steven Tobias

perhaps i am mistaken, but i had the same thought as steven..unless you are repositioning the welded platesor using some sort of shim pack, or having the springs re-arced..when the rear axle bolts in place it is whatever it is. no? regards, tom
tom peterson

perhaps i am mistaken, but i had the same thought as steven..unless you are repositioning the welded plates..when the rear axle bolts in place it is whatever it is. no? regards, tom
tom peterson

The only thing to be aware of is the possibility of the rear spring shackle plates being flipped over, but I think this would soon become apparent.

Dallas Congleton

Of course, now that it is all back together, I can see that there is no optional position, since the springs fix everything where it has to be....Sorry, for the stupid question, but this is what happens when you get too close to the forest to see the trees!...
Image attached
Edward

E.B. Wesson

Edward,

That was not a stupid question but a nice thinking excercise that happens when men with too much time and tools get together. Now I want an angle gauge too!

Willem
Willem vd Veer

This thread was discussed between 08/12/2011 and 12/12/2011

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