Does Drive shaft angle really matter?

As a forward. I have spent the last 3 days reading all the posts and every bit of info online. I havent found anything relating to this issue.
Im working on getting the pinion and tailshaft angles in parallel lines. The problem is that the rear end is higher than the tailshaft.
What im dealing with is a 7 degree uphill angle on the drive shaft. If I make the parallel work I will be at an even greater angle. So know alot of reading and what not came up with.... It doesn't matter at all what the driveshaft angle is as long as you have your tailshaft and rear pinion angles set the same..
True or not?

 

If you get it too steep you'll start eating U joints. There is an article on pinion angle and minum driveshaft angle needed to keep the u joint loaded and maximum angle before U joint failure becomes a problem in a recent hot rod magazine.

It addresses the problem of the rear being above the ****** as I recall. it would have been within the last 6 months.

No time to look now but I'll find it this evening for you or at least try so you'll know where to look.

 

This is probably the article he's talking about.

http://www.streetrodderweb.com/tech/0203sr_drive_shaft_angles/index.html

 

true! as long as the angle at the tail shaft is equal AND OPPOSITE to the angle at the pinion, then you wont get bad vibes.

Unless the angle is severe enough to test the limits of the joint as the suspension cycles.

The driveshaft can run up hill or down- doesn't care- as long as the pinion and tailshaft are parallel.

The whole " 3 degrees down " thing is misinterpreted alot. It comes from the need to SOMETIMES set the pinion angle 1 to 3 degrees down from parallel to compensate for axle rotation when on the gas. In these cases, the axle rotates under load (suspension deflection, etc). and the extra down angle lets the pinion rotate INTO a parallel relationship with the tailshaft when on the throttle.- so experimenting may be needed to dial in your car.

I hate it when people think 3 degrees down means from the ground horizon- the car could be upside down and still be fine- it's relationship to the tailshaft is all that matters....

rick. good luck and tell us how it goes.... take pics.

 

The tailshaft and the pinion don't have to be parallel. You need the angle in the u-joint to be the same on each end and in phase. In a case like yours, you can probably tip the pinion down to achieve this. This will help the driveshaft angle. Kind of a trial and error deal, as you tip the pinion down keep checking the u-joint angles. At some point they'll match. Depending on what you're runnuing for suspension and how it's driven you may want to add a bit more to compensate for the pinion rising under acceleration.

 

^I don't have any experience in messing this part up but what 69fury says is valid.


The angle doesn't matter to the drive shaft. I've seen cars where the entire drive line is parallel to the ground.

 

Yes!

 

I don't read street rodder I actually wouldn't read hot rod but they send it to me for some reason beyond my understanding. But that article is pretty close to the same one.

I think that the one that I was reading was a little more technicle as far as u joint loads etc. But that one will get you there.

I tried doing a quick search of the hot rod site but no luck. probably using the wrong terms. The article I'm thinking about would have been in Pit Stop.

 

Look at my Avitar. My rearend is a good 4 in above my trans and it works fine because the angles are correct. Since it is buggy sprung and ladder bar controlled there is little or no wrap up. I think you will be fine

 

This is right on, I'm sure others have said the same thing already.

I wanted to add that the maximum angles for the u-joints them selves is 4 degrees and no less than .5 degrees. Both must either be the same or no more than .5 degree difference. This is text book stuff from the manufacturers them selves and the engineers who designed them.

IF the angles are too great and the engine/trans and rear diff planes are parallel then you must either raise or lower on of the planes to make the crossing driveline's angles withing the limits.

Don't forget spring wrap, in the case with my car I need some ladder bars or to go with a 4 link as my rear will wrap and bring my diff plane way past parallel under heavy accel. I have it set 3 degrees below the parallel plane to accommodate, but it still is too much wrap.

 

Well, it's been over 40 years since I was in any kind of geometry cl***, but if I recall correctly, I believe that your statement "the angle in the u-joint to be the same on each end and in phase" means that the tailshaft and pinion shaft WOULD be parallel. Are you saying otherwise? If so, could you explain, please?

 

69fury has it right.
The extra 3 deg down was (is?) an old drag race item. We liked to have just a little bit of wrap-up before the pinion hit the snubber and this worked well for us.


.

 

For instance; the tailshaft could be down 2* to the rear and the pinion down 2* to the front with the driveshaft level. Not parallel but equal angles in the u-joints. Since the angles match, no vibration.

 

That is the other side of the coin. No more than .5 degree difference.

 

Anybody know how this same case would work in a car with a torque tube. Say the car had been lowered 5 inches in the rear. I can't see how I could change the angle in the rear. Will a car with a torque tube get the same vibrations?

 

Torque tube only has 1 joint so there is no problem as long as you do not exceed the joints max. operating angle.

 

My understanding is that this example is a combined angularity of 4 degrees and would vibrate.

Pretty sure they need to be equal, yet opposite to have a net measurement of 0 degrees (or close to it)

LeSigh..... I'm at work and dont have it here- someone post the damned chart. - the red one with all the examples,lol.... oughta be a sticky...

-rick

 

By nature a u-joint at any angle other than zero causes the driveshaft to speed up and slow down slightly twice per revolution. The greater the angle, the greater the variance. As long as both ends of the drive shaft try to speed up and slow down the same amount at the same time ( within reason ) everything's happy. When the ends are trying to do something different you get a vibration. This is what happens when the phasing is off. As long as the angles are the same and timed correctly (phasing), parallel or not, both ends of the driveshaft speed up and slow down at the same time. And everythings happy.

 

True, but the theoretical ideal is to have the two be what's called "alternate interior angles". That requires the output shaft and pinion be parallel to one another.

 

Granted that the phasing of the joints helps this problem it still creates premature wear in the joints themselves.This is why so-called,"constant-velocity"(CV) joints were invented for front wheel drive applications.There was also an attempt by General Motors(I think) to try and alleviate the problem in drive shafts by using a double Hooke joint setup on the front yoke.It consisted of two standard U-joints about 3" apart which provided a bit more deflection without undue wear.Around the 1970's on Cadillacs and other large GM vehicles.

 

Engine - trans down 2*
rear axle pinion down 2*
And if the tailshaft and pinion are at the same height, the drive shaft would be level.
Level to the ground.... so what?
The ground as nothing to do with it.
The statement is absolutely wrong.

if the tailshaft is down X*
the pinion should be UP X*

 

If your building a Rodent Rod it doesn't. HRP

 

Would work with IRS but not live axle as it goes up and down.

 

This is a great point. We are talking u-joints on drive shafts and not taking into account suspension movement geometry.

Remember the usable rotational degrees of a u-joint is only 270 out of the 360. The closer the u-joint is to 0 degrees, but not at 0, the easier is is on the joint to make the flex keep from binding.

 

This is my understanding as well. They need to be at equal, and opposite angles to cancel. Think about it from the tailshaft back. Let's say there is a 2° down angle from the tailshaft to the driveshaft. As the front u-joint reaches one of it's acceleration phases, the tailshaft velocity remains constant, and there is an ever so slight acceleration of the driveshaft. The rear u-joint is at the same angle as the front u-joint, another 2° down from the driveshaft to the pinion shaft, so is also in the same acceleration phase as the front u-joint. So the slight acceleration of the driveshaft at this point is accelerated further at the pinion shaft. X+X=2X. They will not cancel. You can't argue with geometry or algebra, they are both based on hard facts.

It wouldn't work on an IRS either, for the same reasons.

If you want to set up a driveline in your prescribed manner, you'd be better off having the u-joints 90 degrees out of phase. It'd buzz like the red-hat ladies at lunch, but the vibration wouldn't be as bad as if they were in phase.

 

i didnt wanna start any battle between all the geometery majors on here. I was just looking for a simple answer to lets say I have ****** down 2 deg and pinion up 2 degrees...Parallel now Yes? how much is it gonna affect the vibration side. if the drive shaft is say 8-10 degress up?

 

First the actual angle of the shaft to the ground has NO bearing on anything. What we are after are equal angles at each end of the shaft from trans to shaft and diff to shaft. And contrary to what some believe the center lines of the trans and diif do NOT have to be parallel . They can also make a intersecting angle which is fine as long as each end of the shaft is equal. This means that both the trans and diff can point down OR up and the end result is the same as parallel.

 

8 to 10 degrees up from what? If it's from the ground, that's irrelevant. If that angle is the relationship of the driveshaft to the pinion or tailshaft, then you're in dicey territory. The vibration you'll feel will not be from any phasing or mismatched angles, just that when you get beyond a few degrees there is a fairly significant acceleration/deceleration of the driveshaft twice each revolution. The bottom line is you'll probably feel some vibration, and your u-joints won't last as long as they would in a less angular installation. U-joints can operate at some pretty severe angles. Take a look at some of these hi-jacked 4X4 P'sOS driving around. Some of those driveshafts look like they're at 40-45 degrees.

 

Weird as it seems...Norfab IS correct.

It's called "broken back" style or sometimes "W" configuration.
It's often seen on farm equipment, certain 18 wheel tractors and some Landrovers had it as well.

I had to look it up to be sure but remembered seeing it on a 4x4 site.
Apparently it can be hard on parts if things wear but if you keep up maintainance it will last AND work.
In a situation where you HAVE to use it...what choice do you have!?!?

I'm wondering if it might be possible to use a Double-Cardan style CV joint and simply have the rearend point directly at the trans output.
Thats how the 4x4 guys get driveshafts into steep angled drivelines and have them last.
The angle is compensated for at the D-Cardan CV.

Such a setup seems to use a fixed output and a slip joint in the shaft itself. Not sure how hard it would be to make it work in a car. Guess it would depend on the transmission being used.
Some larger luxury cars had this CV joint from the factory, so the needed parts are out there for some vehicles...

 

The double carden joint (considered to be a constant velocity joint )is a perfect example of why this works. If you look at one, the center portion is nothing but a very short driveshaft. As you put angle into it the two u-joints maintain equal but non parallel angles cancelling the acceleration and decelleration. Hence, constant velocity.

I'm not saying this is the only way to do it, just an alternative in certain situations. If the OP is going to wind up with a driveshaft running uphill at 7* and the tailshaft down 3* ( included angle 10*) , it may work better by pointing the pinion down, thereby taking some angle out of the driveshaft.