Determining Driveline Angles
 

I readily admit, my past projects have been drop & go w/o verifying the driveline angles. They were all mainly 1:1 final drive ratios so vibration wasn't an issue. I never had any issues to be honest & I've lowered almost every vehicle I've owned (GM trucks, ElCamino's, Malibus, Camaros, & 1 x-DPS Mustang). This time I'm trying to improve. I'm finishing up on a 'fresh' chassis for a 1964 pick-up/shop truck. I'm running a 700r4 w/factory style truck arms (2-link + Panhard bar) & understand the driveline angles become that much more critical for vibration free operation. So, I've been digging for info on driveline set-ups. What's correct, what's possible, 1pc, 2pc w/carrier, single u-joint, dbl CV joint, etc, etc.....

From what I understand, the angles @ each end of a 1pc d.shaft set-up should equal each other. I understand this as 3.0° @ the trans suggests I need 3.0° @ the rear end. Anyone want to confirm/correct this?

My reading also suggests these amounts/degrees @ each end of the shaft are to help cancel out the ocillation that occurs as the joint spins (speeding up & slowing down the shaft as it turns). By keeping the amounts similar, they help cancel each other out. Zero is not good either as the needle bearings won't lubricate/wear properly.... minimal (1-2°) difference is desired. Again, anyone that knows this stuff want to confirm/correct this?
If these statements are correct, it shouldn't matter whether the pinion is up or down, as long as the degree amount is similar.... Right??

Hoping this is correct, I played around w/the heights on my chassis until I could yield similar numbers (@ ride height). My starting point was: 4.8° @ the trans output shaft; 2.2° @ the drive shaft (climbing from the trans to the pinion; 2.0° @ the pinion). By slightly raising the trans tailshaft, I was able to achieve 4.2° @ the trans output shaft. I don't have room to raise it any higher for a lower degree.

I then swapped in some 2.5° shims & the new numbers were 4.2° @ the trans output, 1.6° @ driveshaft (again, uphill), & 4.5° down @ the pinion. The 4.5° @ the pinion is on the edge of acceptability from what I've read for a 'street vehicle'; the downside being increased wear on the u-joints. The plus side seems to be as the torque is transferred to the housing, I should remain within my 2° window. Is this correct?

If so, this is something I can live with. This also reduces the amount the truck arm drive shaft hoop must be raised by .500".

Allright experts..... chime in .

youre concerned about working angles (WA). the WA is a combination of both sides of the angle. so, if your ds was at 0* and your tranny at 2* you have a 2* WA. you want both of your WA's as close to 1* as possible, but not under (needle bearing issue you described). you also want both WA's no more than .5* different from each other. some will say 2-3* difference is ok, but like you said they help to cancel each other out.

if you really want it set up correct, dont fall into the camp that says "equal and opposite" when discussing the tranny and pinion. although that way will set it up correct 90%+ of the time it only takes a little time to measure your WA's and do it the best way possible.

It seems spacial concerns will hamper many targeting this 'ideal' range. What is the 'failure' if working angles cannot achieve that target range (as close to 1° as possible)? To ensure I understand this 100%, you add the sides together to yield the WA correct or how does it work (ex: trans output + d.shaft angle = 'front' WA; d.shaft + pinion angle = 'rear' WA)?

*EDIT* I did some additional reading of some GM tech-specs @ lunch & it stated: To calculate the working angle of each intersection subtract the smaller number from the larger to obtain the working angle.

So my set-up would yield 2.6° WA @ the trans & 2.9° WA @ the pinion. These are within the .5° range to be optimum. The spec sheet also indicates up to 4° is acceptable but not to exceed the range. It would seem I can leave things as is, or use a dbl CV style joint @ the trans & remove the pinion shim to put me closer to @ 2° down.

it depends on how you measure and if you have positive and negative numbers, but your method of subtraction is correct. i usually zero my digital on the ds and then there is no adding or subtracting needed. i just have to rezero every time an adjustment is made, but its a 2 second process.

what was 0*? i ask because if your trans was pointed down in the back, and your driveshaft was climbing up towards the pinion, then you have a 6.6* WA.

Tim

:censored:
The trans is pointed down, the d.shaft climbs up toward the pinion, & the pinion is now pointed down.

With a driveshaft sloping UP towards the rear, you add the working angles. A driveshaft that slopes up is no bueno...:rofl:

How is it different vs. a d.shaft sloping down?

Your driveshaft and driveline/pinion are on different planes with a driveshaft sloping up. Compare it to bending your arm at your elbow.

With a driveshaft sloping down, it's on the same plane as the pinion and driveline.

For instance:

Driveline angle/Pinion Angle of 4.2 degrees
Driveshaft slopes up 1.6 degrees
Your current front working angle is 5.8 degrees
Exaggerated example /\

Ideal:
Driveline/pinion at 3 degrees
Driveshaft slopes down 1 degrees
Your working angle is 2 degrees
//

With a working angle of 5.8, you are in jacked up 4x4 territory. I doubt the car will be happy at high speed. All my research calls for less than 3 degrees of working angle for high speed. 1-2 degrees is really ideal. You will need to chop your tunnel or compromise on working angles by running non conventional angles.

the problem with "is it sloping down or up" is what is that in relation to? if you zero the level on the tranny, your ds will almost always point up. if you zero it on the driveshaft then it brings things back into perspective a little. and its easier to tell what the trans and pinion are doing.

i would put a level on the driveshaft and zero it. i would then put it on the tranny and see what you have. i would next put it on the pinion and adjust it till it is the opposite of the trans. this will give you something like "\_____/" instead of the traditional "\_____\" and it will drop the back of the driveshaft down and improve your front WA. like todd said, you might need to raise the back of the tranny a bunch to make it all work.

let us know what you come up with......

It really does matter. If your front ujoint is higher than your rear ujoint, you must add the angles. The car could be on it's roof, the same math applies. I remember setting my car up 3 years ago and speaking with knowledgable people inthe industry. They said to subtract the angles. The were wrong then and still are today. :unibrow:

Inland Empire Driveline Service

"This booklet concerns the placement of power train components in the chassis. The engine/transmission, the third member and the drive shaft must be installed to work in harmony if driveability is your goal."

OPEN PRINTABLE DOCUMENT

you are correct. its a HUGE point. but, if the ds is zero there is nothing to add or subtract and therefore nothing to confuse. its the main reason i do it that way. you do have to rezero the level every time an adjustment is made, but that is quicker than doing the math and rechecking your measurements.

its funny how that works.

Yep, great document.....

I pretty much had the same scenario about a month ago with my trans pointing down over 4 degrees. As said earlier if you dont want to chop the tunnel you will have to live with it. In order to get my drive shaft level at 0 degrees I had to put a 5/8 thick plate of 304 stainless under my trans mount to lift it, then slice the tunnel from the firewall hump back about a foot and lift it 1 inch or so, make filler plates or a new hat and reweld(it sucked) but Im glad I did it now that its done. By getting the front drive angle minimum gives you more options/ wiggle room to steer your pionion angle where you want and still maintain very reasonable working angles. On these lowered cars be careful how high you go with the pinion, tunnel to yoke starts to get close.

I have to admit it was Todd who gave me the harsh reality of how much work I was in for, and I thank him for that(did I mention how it sucked). :rofl:

Rich

I did start to read that IEDS 'document' but missed the portion where it tells when to subtract for the WA & when to add. It also mentions the uphill d.shaft should be avoided & that it's a common issue with 'hot-rods'.

But, that's w/a standard single shaft & single u-joint @ each end arrangement. I'm waiting on feedback now about the feasibility of using a single shaft w/a double CV joint set-up on the trans output end of the shaft. I have confirmation from one trusted source that it will work but I'm waiting to hear from the driveshaft place for confirmation (since they're building the shaft, I want their 'buy-in').

Using the CV joint would require setting the pinion @ zero (or near).

I know that is done, my understanding is it won't hold much power. Let us know..

Could you elaborate? My understanding is these dbl CV joints are for larger, heavy trucks so I thought they'd be decent from a strength stand-point.

I got an e-mail from Greg Frick from Inland Empire Drive Line Service, he read this thread and asked that I'd post this on his behalf:

To do what Greg recommends, cutting the tunnel is the only option.

The compromise point in this thread is which each evil is worse. LARGE canceling angles or small unconventional angles. I found the small unconventional angles to be the smoothest alternative. When you lower these cars beyond what they were engineered to do 40 years ago, you find yourself in a less than an ideal engineering position.

Thanks for forwarding the message/info.

The truck is being built as a driver. That was the main reason behind raising the suspension mounting/pivot points (to keep them from hitting the ground). So while I won't be making any trips from Bangor, Maine to San Diego, CA, I will likely do the TX to Columbus OH or head the opposite direction out to Scottsdale AZ for some Good Guys shows.

I'm going to re-measure things & see what I get @ a 3° down trans angle. My next option is the 2pc shaft. I'll need to see if they suffer the same fate if that 2nd shaft slopes 'the wrong direction'.

If you lower them using the standard methods like dropped spindles, springs, or air bags w/o changing the pivot points, I could see that.

The front control arm mounting points for this project were raised 3" w/a R&P set-up to ensure correct steering geometry. I modifed the rear suspension & moved the location/mounting points of it up 3" to match the front & keep the consistency. I wanted to keep the drivetrain as low as possible within the frame so it's the only thing not raised the entire 3" like the suspension points.

The Truck
 

Hello,

Greg Frick from IEDLS here again.
Scott invited me to join in this discussion so here I am with some questions.

What kind of truck is this?

What is the distance in inches from the end of the transmission output shaft to the centerline of the pinion u-joint?

Will the shaft head down towards the pinion. be level of rise toward the pinion?

What is in the way of the driveshaft?

What will the engine/transmission bump into if you have to start juggling components to achieve angle changes?

Will the truck always be at the same ride height or does it have hydraulics or air bags ?

With this information in hand I might be able to suggest something to try.

Greg

Awesome.... I was going to contact you next week, you beat me to the punch. Answers above in RED.

A Suggestion
 

Good Morning,

What follows is unconventional but is less work than cutting up the tunnel and it MIGHT work for you. It has worked in some street rods with similar shaft lengths.

You could get complete u-joint angle cancellation by dropping the pinion to 3 degrees down. In this case you will have both mounts pointing down. If the angle made by the transmission/drive shaft is angle "A" and that made by the shaft/pinion is angle "B", then A - B = 0 with the working angles both on the same side of the shaft.

Why isn't this done all the time? I avoid going into this subject because it gets into very unfamiliar territory but you need to know the answer. Driveshafts are subject to forces called secondary couple loads. These loads operate at 90 degrees to the shaft. With equal and opposite angles these loads cancel out and are not an issue. When the angles are equal, but both on the same side of the drive shaft (the top in your case), they add up. The result of additive secondary couple loads is a shaking of the mounts: the transmission and the rear end. This shaking goes everywhere in the car and is very aggravating.

An odd feature of the secondary couple load problem is that the farther they are apart the less of a problem they seem to be. Unfortunately there is no rule on how far is far enough or how close is too close. What works in a '53 Studebaker will not work in a bucket T.

I suggest you raise the transmission end as much as is convenient and match what you get at the pinion end using shims. As someone mentioned earlier, less angle is always better. You can also leave the transmission alone and match the 3 degrees at the pinion end. Allow for revision later so you can "tune" the set up if it shakes.

The net result of this is the drive shaft being dropped somewhat and allowing additional clearance.
Good luck and let us know how it works out,

Greg

Thanks for this info. I'm currently waiting on some shims to dial in less change @ the pinion (I only had 2.5 & 3° sets). I do feel that if I match the motor/trans 3° angle @ the pinion, the shaft will be slightly angled down if not level. I'm assuming 3-3.5° will be acceptable as it cancels out w/o exceeding the >4° rule (since the truck arms are essenitially 51" ladder bars). I'm not sure how exact I'll be able to get it.

I've found that you must move the pinion around twice what the driveshaft angle will move. If you can get working angles between 3-4 degrees that cancel eachother out, that will likely make for a smooth ride. Less than 3 is ideal.

I'm a litte confused by what you are saying Greg. The way I read it, you are saying that he could drop the pinion down to where his working angles are both on the same side of the shaft and not equal and opposite or try it with equal and opposite closer to 3-4 degrees of working angle??? I'd certainly try the equal and opposite first in this situation. Not ideal but not huge angles either.

If I did the equal & opposite angles, I'd be back w/the d.shaft sloping up toward the pinion from the trans which is what I understand to be the greater of my 2 evils.

Clarification
 

You have it right.

Equal and opposite, less than 3 degree working angles is the perfect set up.
In some cases, especially with finished cars, it is worth the effort to try equal but not not opposite, small working angles as an alternative to major surgery. Sometimes it works if the u-joints are far enough apart.

You can see why I avoid this set up. It comes with built-in problems but sometimes works. If it doesn't work you have to start over trying to get equal and opposite. It is easier to get it right when in the building stage.

If at all possible, stick to equal, opposite small angles.

Greg

ive never heard it explained like that before. the program i used to set up my driveline lists that combo as a perfectly acceptable arrangement.

Scott, if you can achieve 3 degrees of driveline angle and say 2.5 degrees of pinion with a driveshaft less than 1 degree sloping up, your working angles would be between 3-4 degrees. Under acceleration and suspension compression, your angles would get larger. You could simulate that without springs and shocks. Raising the tailshaft another degree would probably get you in the money(2-3 degrees equal and opposite). Really depends on if you want to do surgery. If I was still in build stage, I'd have cut mine for small equal and opposites. Do you have a carrier bearing mid shaft? That could complicate things here. I'm so used to everyone having 1st gens around here.:D

The alternative is what I've done in my car. Lower the pinion angle below level to run the smallest working angles on both end of the shaft(2.5-3). That puts the working angle on the same side of the drivshaft as Greg said. Small angles but not canceling. My driveline angle is 4 degrees(Stock). My driveshaft would rise 2-3 degrees. That makes for 6-7 degrees with equal and opposite angles which is way to much for high speed.

Yes, this is where I'm currently at. 3° @ drivetrain, .9° incline slope to the pinion, & 2.4° range down @ the pinion. I didn't think to remeasure as it cycled through the travel so my next trip to work on it I'm going to measure the numbers @ 2" travel compression (to simulate normal driving compression) & @ maxed compression (on the bumpstops).

Thanks to all that have contributed toward a solution & for sharing their knowledge/experiences.

When you say down on the pinion do you mean \ or /(Looking from the drivers side of the car) We mean \ or same plane as the driveline.

The pinion is pointing down toward the front of the chassis (below level) or -2.4°. If the pinion is raised to the point that it is above level (+3°), the d.shaft would be @ an even greater incline slope (higher in the rear than it is in the front) from the trans to the pinion.

In that situation you would add the front working angle and subtract the rear. So you have -3.9 front and -1.3 rear.

Front: \/ Opposite planes
Rear:// Same plane

If it was me, I'd raise the trans or the ride height.

So you had a similar issue? What did you change on your set-up if you started w/4° @ the drivetrain & 2-3° rising slope on the shaft? These numbers are close to what I was starting with (4.2° down, 1.6° d.shaft rise, & 4.5° down @ pinion)....

You have to play with your own set up. You should be able to use washers or similar to mock it up and find the sweet spot.

My guess is another 1-1.5 degrees down get's you close to equal - numbers.

With the pinion moving 1.5 you should end up with approx. .2 up driveshaft angle.


That would give you -3.2 front and -3.7 rear.

Moving the pinion 1 degree shoud give you approx. .45 up driveshaft angle.

That will net you around -3.45 front and -2.95 rear.

I understand this.... was just curious what someone that went through a similar experience started & wound-up with.

The Program
 

It is a perfectly good mathematical solution and it is sometimes used in the real world.

Keep in mind that someone wrote that program and they got their information from a collection of formulae. These formulae were developed to explain, mathematically, what goes on in an ideal, distraction free environment such as outer space. It is impossible to quantify all of the real world variables and interactions of the components affecting the drive shaft.

Every text I have listing and describing the use of these formulae contains some version of this quotation from Rockwell: "The engineer must use trial and experience as a guide".

Always design some adjustability into your drive train set up. You may not need it but if you do you will be able to tune the set up without reaching for the cutting torch.

Greg

I sincerely hope this is not really aggravating everyone :_paranoid ..... & I apologize to those that easily see/understand the info here. I'm just trying to understand the 'whys'. We played around w/it again today. My buddy even came out to read & interpet the reference material from this thread from his perspective. I/we understand the optimum: 3.0° dn @ the drivetrain, a level d.shaft, & 3.0° up @ the pinion. Equal 'working' angles on opposite sides of the d.shaft canceling each other out.

The one question that we continued bumping up against because of our lack of subject knowledge (& that would be good to know in a situation such as this) is what are the options if that perfect set-up can't be achieved? Since several options exist when it comes to moving things, which option is the lesser of 2 evils? Is A) the incline slope of the d.shaft from the trans to the pinion w/equal & opposite angles better or worse from a physics perspective vs. B) equal angles on the same side of a d.shaft that's level or @ a slight (.1-.5) decline from the trans to the pinion?

I played around w/some settings & raised the front end an additional .500". I then checked the pinion angle as is (2.0° range pointing down toward the front of the chassis). Knowing the pinion angle, I raised the drivetrain until I achieved a similar angle (2.4° pointing down toward the rear of the chassis). This arrangement got the d.shaft just about level but the angles are on the same side of the d.shaft. I checked the pinion angle @ max drop in this configuration (just to know what it was) & it was @ 3.5°.

Greg, I'm going to try & give you guys a call tomorrow.

Driveline angles seem simple but they are confusing as hell!



Sounds like you have two scenarios:

Equal and opposite(Guessing at 2 degrees of upward driveshaft slope)

Driveline 2.4+2=-4.4 working angle at ride height

Pinion 2.0+2=+4.0

Unconventional

Driveline 2.4+or-0=-2.4

Pinion 2.0+or-0=-2.0

It's late and I'm tired, I'm assuming leaf springs?

I'd try one and if it doesn't work, change it to the other. Go by Greg's recommendation.