2-piece driveshaft angles

[_Matt]

Hi, trying to figure out what angle to set my diff up and where to mount the carrier bearing in my Starlet. 
From research I’ve found, most seem to just set up the first half shaft at 0° to the gearbox, and then setup the rear section the same as if it were a single piece driveshaft. But from what I’ve heard u-joints aren’t supposed to be operating at 0°.
The other way is to make all the u-joint operating angles (O/A) cancel each other out. From my understanding and calculations I keep getting, the pinion angle degree always equal what the gearbox is set at - gearbox pointing down at 2.5° and pinion up 2.5°. To me that doesn’t seem right? But maybe it is?

The pen in the drawing is what I measured the angles at, with it sitting where I’d ideally want it mounted, but I can easily raise the carrier bearing up if needed.
The pencil is what I have come up with.

Anyone know how to set it up?

[Mof]

Pretty much right. Centre bearing flange should be around 3° off gearbox flange like you say to make the ujs work. This can be up or down btw (you drew down).

Diff angle should be the same angle as centre bearing flange, but some say to angle it slightly up to counter suspension twist when accelerating. Personally I think yes for a race car, most of the info I've found on the internet comes from Americans setting up drag cars. I'd be pretty much bang on for a road car.

[_Matt]

32 minutes ago, Mof said:

Pretty much right. Centre bearing flange should be around 3° off gearbox flange like you say to make the ujs work. This can be up or down btw (you drew down).

Diff angle should be the same angle as centre bearing flange, but some say to angle it slightly up to counter suspension twist when accelerating. Personally I think yes for a race car, most of the info I've found on the internet comes from Americans setting up drag cars. I'd be pretty much bang on for a road car.

Awesome thanks! Gonna raise the centre bearing mount up a bit more so the angles aren’t quite as much. Most of the info on google just came up with raised 4x4’s haha

[kpr]

going by your drawing.  can you  lift the rear of gearbox up  and  drop the pinion down   so  your angles are less aggressive ?   the hanger will have to be moved up as well obviously.
Or possibly leave the gearbox  where is.  run first shaft up at 2.5deg angle from the gearbox,    so  the flange on end of first shaft is at zero deg.   then drop the  diff nose down to zero deg also.  which should get you pretty close  doing some rough maths.       all depends if you can do that in your tunnel though

reason for running a very small angle on the first shaft, is because it has no 2nd uni to cancel out how the uni accelerates and decelerates the shaft when run on an angle.  sub 3 deg is fine.  running a zero best, but yeh, uni will wear fast since doesn't have and bearing rotation.   to much angle will cause more problems that running none.

as @Mof   says the rear shaft angles need to be matched.  ideally the less angle the better,  long as it  has enough angle to keep the uni's happy.  
the nose of the diff will want to rotate up  under acceleration.   but  from memory you are running rose joints on the 4 link?  if so wont get bugger all deflection.  so set up neutral  will be fine

 

[Mof]

Just now, kpr said:

the nose of the diff will want to rotate up  under acceleration

Quite right, my mistake 

[kpr]

Just now, Mof said:

Quite right, my mistake 

too many diffs aye. the front one will go down!

[_Matt]

21 hours ago, kpr said:

going by your drawing.  can you  lift the rear of gearbox up  and  drop the pinion down   so  your angles are less aggressive ?   the hanger will have to be moved up as well obviously.
Or possibly leave the gearbox  where is.  run first shaft up at 2.5deg angle from the gearbox,    so  the flange on end of first shaft is at zero deg.   then drop the  diff nose down to zero deg also.  which should get you pretty close  doing some rough maths.       all depends if you can do that in your tunnel though

reason for running a very small angle on the first shaft, is because it has no 2nd uni to cancel out how the uni accelerates and decelerates the shaft when run on an angle.  sub 3 deg is fine.  running a zero best, but yeh, uni will wear fast since doesn't have and bearing rotation.   to much angle will cause more problems that running none.

as @Mof   says the rear shaft angles need to be matched.  ideally the less angle the better,  long as it  has enough angle to keep the uni's happy.  
the nose of the diff will want to rotate up  under acceleration.   but  from memory you are running rose joints on the 4 link?  if so wont get bugger all deflection.  so set up neutral  will be fine

Sweet thanks man! I don't think there's going to be enough room to raise the gearbox up, could possibly drop the engine down a little if needed. I'll try and get the centre bearing mounted as high as it can, should be able to get it to 3° from the gearbox, and just have clearance for the handbrake.
Yeah the diff has rose joints on one end and urethane on the other, so I'll probably just set it up as neutral.