Trans output shaft and pinion NOT parallel?

I'm working on a driveline swap at work. To get the engine and trans to fit, it would solve ALOT of problems if I could set the engine & trans in the chassis at an angle(when looking from the top down). This means that the trans tailshaft and the pinion won't be parallel. I've researched a bit, but haven't come across anything conclusive other than "they should be parallel." Provided the offset is small enough so that the u-joint angles work out alright, what problems would we encounter doing it this way? Can you suggest any solutions to those problems? Thanks for the help.

 

You can't just offset the engine?

 

I always heard that the drive shaft should be offset

 

If the angles work out, I can't see a problem....
(If someone shows I am wrong then I have learned something...)

edited to add: but what allsteel said is the usual solution.

 

I can tell you that it will be absolutley fine. I installed a new ring and pinion and a spool in a Dana 60 rear. Well after everything was done and right before I installed it I realised it was an offset rearend from an early Jeep J-truck. Wow, what a set back! So I thought.

I installed it in a 110" wheelbase offroad vehicle with a steeper driveline, 5.13 gears and 44" tires. It was offset by almost 6". I never thought it would work.

All I can say is that I was never gentle with the truck and never once did it act funny or shake. Not once.





You shouldn't have any problems.

Good luck.


BloodyKnuckles

 

Offsets in either rear or tranny/engine isn't the issue (as I read the original post)...in effect, I think his engine and tranny are not parallel with the frame.

 

A lot of the early Chrysler products with the Hemi (Hemi Dart, etc) had the engine offset to the right about an inch or two. They seemed to work.

 

That the way I understood it as well. You should still be ok with a slight angle.

 

Offset rears will still have the pinion and output shaft parallel. Though offset to one side they are still in the same plane.

 

Imagine if your pinion was was lower that the transmission by a bit - like any standard pick up. The pinion being lower (or higher) is the same as the pinion being offset, the U-Joint cannot tell the difference as long as the pinion angle is acceptable.

 

I'm sorry. When I read the post the first thing I thought of was my situation.

To answer the correct question you would possibly need a CV joint in the shaft. A CV joint is designed for different trans and pinion angles and have been used for many years for front drivelines on four wheel drive vehicles.

Personally, I would try without one and see how it reacts to the different angles. If it is smooth at all times especially under hard accelleration then I wouldn't see the need for one.


BloodyKnuckles

 

One should NOT confuse the idea of engine/trans "offset" with what the OP's paragraph describes. As others have posted, "offset" usually means the engine/trans centerline is offset to one side an EQUAL amount front and rear. That is, in effect, the same as an eng/trans being higher or lower the the pinion centerline, and follows the rule of keeping the extended centerlines of the pinion and eng/trans parallel.

What the OP describes is a horse of another color.He describes offsetting the front of the engine a geater amount than the rear of the trans, causing the eng/trans centerline to be at an angle to the centerline of the chassis, and the pinion of course. Without the use of a CV joint, that is considered incorrect and will have the u-joints on either end of the driveshaft operating at different angles. Not a desirable condition.

What isn't clear is WHY the engine trans cannot be offset an equal amount front to rear, which of course would eliminate driveline issues.

Ray

 

You should not have a problem if the angle is not too crazy.
The u-joint will take care of the angles, up and down and left or right.
On our Busch car we would move one side of the rear forward or back for set up reasons and cause what you are talking about and we had no problems at 190 MPH

 

Ever see CLOCKED ujoints (as in something OTHER than 90 degrees) from a FACTORY DETROIT SETUP??? Wonder what they are for...

 

When the transmission output shaft and the pinion are not parallel, it results in a driveshaft condition known as "out of phase". It may be tolerable on a rock crawler or a drag car, but it can be very undesirable on a street car.
Go here and read the posts made by patrick2965, he knows driveshafts.
http://www.jalopyjournal.com/forum/showthread.php?t=445498&highlight=out+of+phase

 

Thanks for the replys and suggestions. We can't offset the engine/trans far enough to get the space we need. We're stuck with either a slight trans/pinion missalignment or running an electric water pump. The boss is concerned with the reliability of the electric pump setup(and the customer probably wouldn't notice if it went bad until it was to late).

 

It I understand Patrick2965's posts linked above(and it's entirley possible that I don't), as long as I can get the angles on either end of the driveshaft to be complimentary, the shaft vibrations will cancel reguardless of the angles. The issue then would be u-joint wear if the angles are to great or to little.

That leads me to another question. As the rear end moves up and down, the angles change. With the output shaft and pinion parallel, the angles stay complimentary. But, if they are not parallel, the angles WON'T stay complimentary as the axle moves. Is that correct?

 

Yes complimentary angles cancel out the speed variations.

Oops - I missed your second question. Yes to a degree, but that also happens during spring wrap up. Small variations most often go unnoticed. There IS a certain amount of forgiveness in the joint itself. Plus the speed fluxuation (is that a real word?) curve (positional accuracy versus driveshaft rotation) looks almost like a SINE WAVE. Meaning that at the beginning of the curve not alot is happening - it gets ugly fast - THAT'S when you need to get your ducks in a row. I also suspect there's a relationship between the ujoint phasing and the input /output angles - but I don't understand the relationship enough to know fo rcertain if it's a 1 to 1 relationship or not - instinct says yes, but that's only a guess.

 

Very well stated! I'll definately second this one. If there is no way of offsetting the engine/trans evenly , front to rear, then a CV joint at the trans is the best fix.

 

+1 on the cv joint. just dont "aim" the tailshaft at the pinion yoke, because the needles in the joints wont turn and you'll wipe out the joints sooner than normal.

It really would be best to look at moving what you have to move to get the mill offset, but parallel.

 

Had followup thought to the issue of axle wrap up on acceleration and the presumed accommodation of this temporary angle change by the u-joint. If the 'wrap up' is sufficient to cause an angle change that would "put the u-joint in a bind" the stress in the u-joint, it seems to me, could force the pinion angle downward against the torque force of the axle and rotate as needed. In any case the wrap up is usually brief and not sustained.

In the example of the OP's question, the incorrect angularity is constant and not "correctable" by the driveshaft/u-joint moving the offending yoke into alignment, even temporarily. The stress would be continuous and likely to cause vibration at least and u-joint failure at worst.

I suppose the actual effect will depend on the degree of misalignment. Maybe 1 or 2 degress would be hard to detect, I don't know, but regardless, the principle applies, in my opinion.

Ray

 

I never meant to suggest there is a mystical "accomodation" of angle changes by the Ujoint. Let's back up a few steps...

When you use a Ujoint to transmit power there is a DEFINITE CHANGE of positional accuracy. What I mean is that at any given rotational position the second shaft is not in 100% sync (positionally) with the first shaft. They are PERFECT EVERY 90 degrees and "off" varying amounts inbetween those 4 positions. The amount they are OFF is maximized as the working angle is increased.

So in a standard type drive shaft - it goes like this: The input (transmission) is rotating at a perfect (constant) speed. The driveshaft itself is NOT at a constant speed - it is forever speeding up and slowing down during each of 4 "quadrants" of rotation. This positional error is a result of the working angle. So now when we hook up the driveshaft to the rear axle with the SAME working angle - we reserve the situation and we now go from speed variations o fht edriveshaft BACK to perfect or constant speed ot the rear end again. There are of course limits to how much speeeding up and slowing down a driveshaft can do before we feel a vibration. I suspect this is from the driveshaft's mass. If you were to plot the relationship between position and degrees of rotation - it is THAT graph that looks a bit like a sine wave. Meaning at low operating angles there is alot of forgiveness.

So back ot the OP question - it is NOT necessarily a CONSTANT condition - that's what I mean by COMPLIMENTARY angles - that means you DO NOT have to have the trans and rear PARALLEL to achieve teh exact same math as what we consider normal (meaning parallel) so long as those angles are complimentary they speed fluxuation is cancelled out. The working equation does vary from ideal during suspension travel - if kept to a minimum you'll probably never notice it. BTW when the angel are not complimentary - that's when the clocking comes into play.

 

Hemirambler........I agree with everything you said in the above post.......with one possible reservation....because the OP is discussing installing the eng/trans at angle to the centerline of the vehicle, not parallel, I fail to understand how the "complimentary angles" can be achieved under that circumstance. It seems to me the angle at the front will be less than the angle at the back, in this scenario, and therefore not fully cancel each other. There is where I see the problem, theroretically at least. Not trying to be argumentive, just wanting to be sure I correctly comprehend the geometry involved. If I missed something here, I am open to enlightenment.

Ray

 

Bugman,

Do you have a sense of how many degrees out of parallel the trans tailshaft and the pinion will actually be?

 

Hnstray, I don't think your being arguementative!!! ;-)

Forgive my poor "drawing" below, but it is an example of complimentary angles without having parallel input/output:


/-------\

in.........out


That works because the 0-180 degrees of rotation (graph) is identical to the 180-360 degree curve. The ujoints "see" the same set of parameters - as does the driveshaft.

Above same as:

/-------/

 

OK...........I still don't get it. Let me lay out my mental vision here.

Starting with the vehicle centerline (VCL) as a reference........and using representative angles to illustrate since I don't know the OP's actual figures, but taking him at his word that the eng trans in not parallel.............

The pinion centerline in this scenario should be parallel with the VCL, whether it is a 'centered' pumpkin or not.

If the eng/trans centerline is at, say 3 degrees to the VCL, and whether or not the trans output shaft is on the VCL or not, the angle between the driveshaft and the trans output shaft, whatever that angle is, is not likely to be the same as the angle between the driveshaft and the pinion. Therefore, it seems to me, some remaining "uncancelled" angularity would result.

I did some drawings with various possibilites, i.e. pinion same as VCL, eng angled 3* with tailshaft at VCL: same as described but with pinion offset from VCL and so on.

I can see it would be possible, in particular with an offset pinion, to "match" the angles with careful measuring and placement of the eng/trans centerline. It would sure look funny but could be geometrically correct.

edit: you will notice, as have I, that later in this post I 'conditionally' contradict the statements in the first paragraph or two. Just my learning curve...........

Fun exercise and stretches the brain........mine anyway

Ray

 

Ok, I may be missing something, but, here goes. I am viewing the relationship between the output shaft C/L and the pinion C/L from above.
If the output shaft C/L is not parallel to the chassis C/L, I dont see any way to "match" the angles to compensate. Wouldnt this result in a rear axle that is not square in the chassis (one rear tire ahead of the other)?
I was always taught that the 2 shafts had to be parallel (offset is OK) to prevent unwanted harmonics.
Just my 2 cents!

 

Agreed in general. However, if you read my post carefully, I can only arrive at the pssoibility that you are questioning when the rear axle pinion is offset from the vehicle centerline. Not 'crooked' in the frame. As you know, not all pinions are in the center of the car, though they are parallel.

Using your method of viewing from above, start with the center line of the vehicle as a reference. Now imagine the pinion offset to the right (pass side) a couple of inches.
Now visualize the eng/trans angled with the front of the engine offset to the right but the trans output shaft on the VEHICLE centerline. Say this angle is 3* variation from the VCL. In this situation, viewed from above, the eng/trans is angled to the right, the driveshaft angles from the VCL to the right as it extends to the pinion.

Now, depending on driveshaft length, the actual amount the pinion is offset from the VCL, it seems it should be POSSIBLE to match those angles, creating correct u-joint geometry.

Now, let me make this clear before the flaming starts; I DO NOT ADVOCATE THIS SCENARIO!! It is too complicated. I am merely trying to reconcile, in theory, the claims made by others this is doable without adverse u-joint issues. Personally, I am firmly in the camp of parallelism in driveline parts.

Ray

 

BUGMAN...I think KNUCKLES is right. most trivelines are not streight, but if the offset isn't extrime you'll be fine. and considering there are 2 universal joint's just go for it brother...POP.

 

If you use a driveshaft with a CV joint on both ends you can have any screwy angles you want, no problem. I know 70's Cadillacs had them. They can be custom made for whatever you want.