Driveline angle?

[midnightmoonlight]

I just need to clear something up. If my tranny points down 2.5 degrees and my diff points up 2.5 degrees my drive line will work well if the angle of the driveshaft is between 1 and 3 degrees?

 

Im confused because of an article posted here shows operating angles should be less then 3 degrees which is different then the actual drive shaft angle. Operating angle takes into account all of the angles. In the article the example shows tranny 3 degrees down, drive shaft 4.9 degrees down and diff 3.2 degrees up. The operating angle is 1.7 and 1.9 which is the drive shaft angle - diff angle or tranny angle.

 

So is the 3 degrees operating angle or drive shaft angle?

 

Then another article shows it different too. Engine 1 degree down diff 1 degree up drive shaft 2 degrees up. They refer to working angles engine+drive shaft=3 Diff+drive shaft = 3 and 3-3=0 and thats good. Which I now realize, is the same as operating angle above

[midnightmoonlight]

This is what Im refering too. The way I understand it is operating angle is what needs to be 1-3 degrees. Right now Im at 2.5 tranny 2.5 diff 1 driveshaft. So that gives me 1.5 operating angle isnt that going to work?

 

[getZ]

I'm not sure which write up you are talking about, because there are a lot of discussions about this.

 

The most critical angle or rather difference in angles is the transmission to the diff. To big a differance and you start to get driveline vibrations. I targeted less than 3 degrees difference between trans and diff. My transmission points 3 degrees down and my diff points 5 degrees up. For me it became an issue of ground clearance with the transmission rather that a perfect match in angles. I have no problems under hard acceleration. We shall see if that still holds true with the bigger sticky drag radials, but I can always change the diff angle if needed. Don't forget this also applies in the horizontal plane or side to side angle as well.

 

As far as the driveshaft having an angle, the only argument I remember on this was to keep the bearings lubricated. With no angle the universal joints don't move around, thus preventing the grease from moving around. How accurate that bit information is I can neither confirm or deny, but I don't think you have much choice on that part. It is what it is unless you want to cut out the whole transmission tunnel to make it perfect.

[midnightmoonlight]

The article is the picture I posted above. Ive read everything I can find here and everyone talks about the driveshaft angle being 1-3 and the diff and tranny need to be parallel. The way Im seeing it is the angle of the diff and tranny dirrectly effect the driveshaft angle and that just because the drive shaft has a 3 degree angle doesnt mean the ujoints opperating angle is 3 degrees because you have to take into account the angle of the diff and tranny.

 

With your set up your tranny and diff are not parallel. Which is supposed to be a problem because your ujoints are at different angles and should cancel each other out so there the same. Do you know what your driveshaft angle is? How long have you been running this set up?

 

When mine diff was 4.5 up tranny 2.5 down I only had about .5 degrees on the driveshaft.

 

Thanks

[getZ]

My transmission and diff are not perfectly parallel, there is a difference of about 2 degrees. That is the angle most posts are talking about, what they are saying is don't go beyond 3 degrees of difference, it does not have to be perfect. I've had my setup for a couple years now, but it has never seen freeway duty although I've had it up past 100mph with no problems.

 

My concern with the bigger tires is when they hook diff will try to point the diff up creating a larger angle. I'll deal with that when I get there.

 

As for drive shaft angles, I have no idea what my drive shaft angle is and I'm not sure you can do that much to really change it. If it was as critical as all that I'm sure you would see a lot more complaints about it.

[260DET]

Isn't the length of the tailshaft also relevant? The longer the shaft the more critical the angles are?

[getZ]

I would think it's the length of the driveshaft rather than length of the tailshaft. The longer the tailshaft, the shorter the driveshaft.

[trwebb26]

This is something I happen to know quite a bit about. There are only three rules when dealing with driveshafts:

1) Keep the angles small. Very high angles put a lot of stress on the U-Joints.

2) Don't line everything up so there is zero angle. There needs to be a little bit of angle at each joint so the spider will spin around in the needle bearings. If there is no angle - the spider doesn't turn and you will get surface fatigue - causing the spider to fail earlier than it would if it were spinning around on the bearings.

3) The one that everybody is most confused about - KEEP THE ANGLES EQUAL AT BOTH U-JOINTS and in the same plane for most of your suspension movement (ride height for instance). When there is a high angle from your transmission output to your driveshaft - and a low angle from your driveshaft to your diff - you will get an non-constant rotational velocity at the input to the differential - causing everything to shake.

 

To explain the third point further... Assuming that the rotational output velocity of your engine crankshaft is constant - as that rotation passes through a U-Joint - you will induce driveshat error (ie - a non-uniform output velocity at the exit of the U-Joint). It is like your driveshaft velocity "lopes" - speeding up and slowing down with every revolution. The higher your U-Joint angle - the worse the "lope". This may sound bad, but IF all of the driveline components are in the same plane - and the U-Joint angles are EQUAL - then the second U-Joint will cancel out the non-uniform velocity of the input and return the output from that U-Joint to being constant (no loping). It is when people get unequal angles, the driveshaft error gets high, and the speed of the driveshaft / diff changes with every revolution of the output of the transmission... This is what everybody experiences as shaking due to driveline vibration. It can get pretty severe if the driveline error is too high.

 

In short - follow the three rules and you should be good to go.

[midnightmoonlight]

So I should be good with tranny 2.5degrees down, diff 2.5 degrees up, tranny and diff lined up on the vertical plain, and my drive shaft at 1.5 degrees?

 

Im confused by #3 in that the suspension doesnt effect the rear end or tranny. So on a Z the suspension travel doesnt play a roll right?

 

Thanks for the help

[trwebb26]

Yeah... I forgot to make the distinction between a diff (IRS) and a solid rear axle. I deal with the solid rear axle the most (where the suspension does play a role in the driveline angles).

 

There are 2 ways you could set it up...

1) The tranny and diff are perfectly parralell - equal angles at each U-Joint.

2) To simplify - assume the tranny is at zero degrees (perfectly horizontal) and the diff is point up at 10 degrees from horizontal. The driveshaft must be at 5 degrees to the horizontal for the driveshaft angles to be equal.

 

Sounds to me like you've got it figured out... Just try to keep the angles as small as possible, not zero, and EQUAL.

[midnightmoonlight]

Thanks for the help and clarification. There really needs to be a sticky about the specifics of driveline angle and it sounds like your the guy to do it