how to determine proper rear end angle

[corpse]

ok, I got the u-joint and put it all back together..

I got the angles matched up between output shaft and yoke - the centerlines of them are parallel... the output shaft is ~ 2* down, and yoke ~ 2* up.

If the rearend was in its stock location, the angle between output shaft and driveshaft would be ~1.3*

However, I have 1" lowering blocks installed, and that brings that angle to ~ .2*
That's below the ideal, since I guess .5* is ideal for proper lubrication - but I guess if it cuts the u-joint life in half, I can live with that.

Attached is a drawing I whipped up to show where the angles are.. Anything look off, or does it show that I finally am graping these (easy) concepts? Unless there's any crazy problem, I should be getting the leaf spring mounts welded to the tubes tomorrow.

 

[1320stang]

Looks like the pinion points directly at the tranny output, is this right? Usually you have to go up the opposite of the tranny down angle, but if you draw a line straight out from each, they are parallel to each other but not in the same plane. So the angles of the yokes for each are the same, but opposite, but the driveshaft itself is at a different angle, like 2 or 3 degrees.

 

[corpse]

both angles are at 92*, both in the the _/ direction, its hard to tell in the picture I suppose cuz it is only about 2*

I did double check, and the centerline for yoke and output shaft are parallel...

 

[1320stang]

So the tranny is at a 2* down angle, the shaft is 2* more down, for a total of 4*, then opposite for the pinion end?

 

[corpse]

for the trans, on the left side there (like your drawing), I have the output shaft at 2* downward - the dimension for the output shaft is missing.. I extended the centerlines of the output shaft and yoke, and they are parallel.

The angle from the output shaft to the driveshaft is what is at ~ .2*
The 2.2* angle you see, is the angle of the driveshaft in relation to the ground - which I suppose really has no relationship to anything <g> other than to add and subtract it from stuff. Anyways, your diagram in autocad is the same that I have in solidworks, except my angles are different, but at least pointing in the right direction..

 

[1320stang]

Well, I'm showing the driveshaft at 3* down from the tranny's 2* down angle, the rear is 2* up and the driveshaft is 3* up from that. If what your showing is similar to what I have shown, I think you'd be okay. Optimal for what you intend to do with the car? I don't know, but for normal driving on the street I think it's correct.

 

[Jimmys66]

Sorry for skipping out for a couple of days. We're all hitting the same idea just verbalizing it differently.

The the drawing that I have, uses a centerline parallel between the pinion and the trans.

All the same concept were just finding the angle different.


The easiest way for me to explain it is....... if the driveshaft angles down from the trans at 2* and then turns back up 2* at the pinion you're good to go.

 

[1320stang]

Yeah, but ideally, in a street driven application, you want the pinion and trans to be parallel to each other and the driveshaft not more than 3.5* different from them. I guess one would think the ideal situation would be the pinion and trans to be directly inline with each other, then the driveshaft would be at exactly the same angle (0*) as well as the u-joints, but for some reason, I think I've read that this isn't ideal.

 

[corpse]

ok, from what everyone is saying, and from what I've read - I'm good to go!

As far as the angle between driveshaft and shaft/yoke, it *should* be more than 1/2* (based on what I've read), as that will create an elliptical path of force on the bearings, which greatly helps the longevity of the bearings, as it causes the grease to get worked thoroughly.

If it's under 1/2*, it shortens u-joint life, but for a car that shouldn't get more than 5k miles a year, I'm not too worried about it - I'll just replace the u-joints every 5 years

As for different angles, like with the rear end having an extra couple degrees, that is good for certain applications - like drag racing.. drag racing with some mushy leaf springs and killer lift bar would benefit from different angle because of all the travel the rearend will go thru.. I have stiff leafs on my car, thats lowered, so I shouldn't have more than 2 or 3 inches of travel, so the angle won't change much..

 

[Jimmys66]

Yeah, but ideally, in a street driven application, you want the pinion and trans to be parallel to each other and the driveshaft not more than 3.5* different from them. I guess one would think the ideal situation would be the pinion and trans to be directly inline with each other, then the driveshaft would be at exactly the same angle (0*) as well as the u-joints, but for some reason, I think I've read that this isn't ideal.

Correct.


A straight drive shaft is ideal, as it makes for the least amount of hp loss from the u-jounts. The only problem is the fact that as the ring gear climbs the pinion gear, the rearend rotates upward as it gets power, not just acceleration, but any power at all. Now the pinion is at a neg angle that causes bind.

Pinion angle is actually put into the car so that under power, when the pinion rotates upward, it makes as close to a straight line between the trans and the pinion.

The more the rotation the more the pinion angle. Leaf springs need more angle than a ladderbar or 4 link set up because they have more control of the rearend rotation.