I told my math teacher in HS I wouldn’t use most of the stuff she taught. Then I became collision tech that specialized in frame/unibody repair. I use this experience with chassis work now. We set a build we are doing at school on its wheels this week. We set up the chassis without the body on it. Used measurements from the body to make modifications like stepping the frame down in the front so the front bumper was on the same plane as the body. Modified the rear bumper to fit tight to the body. Installed an off topic from suspension by using the chassis dominions from the donor car. When we set the body on the chassis the bumpers fit perfect and at the height we figured with weight on the suspension. We have lowered this and at ride height the suspension is unmodified and has correct alignment.
Vibration or bind wouldn't be the issue. It would have the speed up and slow down reaction of out of phase u-joints. The steering ratio would be constantly changing. It may not even be noticeable, but would be better to be in phase.
This thread is timely for me, as I am mounting the engine in my RP project. Since it will be a street/strip application with Injectors and Carbs, depending on which engine is in the chassis, I am make minor adjustments to the engine angle. The chassis ride angle will be level, or slightly nose high, these 2 photos show the difference. I am also building some flexibility into the trans mount. BTW, I always agree with V-8 Bob, a no nonsense hot rod builder !
Let's be thankful that everyone seems to visualize the driveline schematics with the front of the vehicle on the left. (Except maybe the English who approach and enter vehicles from the 'wrong' side. ) That's half the battle over confusion. But the problem is the rear, right side visualization of the driveline. The 'rule' of left to right, though it is the superior way in an academic situation for determining whether a slope is up or down, breaks down in a workshop situation. It's just too persuasive for most mechanical types to think of the engine/crank/trans as an individual pumpkin with the trans tail being its pointer, and the differential a separate pumpkin with the pinion being its pointer. So if the pointer(s) are clocked above 0 degrees horizontal, it's considered up. Pointed below horizontal is down. Right or left? Who knows? It's usually a secret. Now comes the supervillain in our tale of woe. Simply saying "pinion up X degrees" or "sloped up/down X degrees" is useless and isn't communicating squat. If a post doesn't specify whether the slope is following our rule or is contrary to the rule, it's garbage, a coin toss. A sketch does help usually, even if it makes up new rules never seen before because a sketch tends to trump the written garbage.
Examples In the real world, in the parallel example above, Both are pointing down. In the real world, in the opposing example, Left is pointing down and right is pointing up. The angles are indeed opposite. Also Resembles a wide U In the hamb world the opposing example pictured above supposedly is not compromised of opposite angles. It’s perfectly acceptable to build a driveline in the opposing configuration provided the ujoint working angles are relatively equal. It’s useful on low slung vehicles
That’s all great speculation and I bet every individual can express it differently in their own way. Which sort of just perpetuates the confusion. I certainly didn’t make up these terms, write out their definitions, nor did I disregard them. I never had any part in discovering the wonders of angles nor developed the common ground to work with them. In all respects it’s a technical subject and to discuss it the terms shouldn’t be eviscerated and definitions ignored. But fuck it that’s what today’s world is all about right? As far as these so called academics ( not school work) getting lost in the shop,, well who the hell decided righty tighty lefty loosy Any ways? If you want it loose you need to follow that rule. And sorry but that 1/2” wrench is not going to loosen up a 1/2” bolt, it should right they are both 1/2”. Fight it all you want. Oh there’s no telling if that’s true or not. Maybe they are on their back looking up at the damn thing when they start explaining it. You’ve got no idea what’s going on in the shop nor what’s getting lost, as you say.
Question: When measuring for a new driveshaft, will not having the final pinion angle correctly set have any significant effect on final driveshaft length, when factoring in slip yoke protrusion? Since there is no driveshaft installed, there is no easy, positive way to correctly calculate final pinion angle...or is there?
Yes there is. You can get pretty darn really really close,,, close enough that any more changes won’t effect the driveshaft length. You’ll be within the 1* variant You will need some parts for mock up, like the trans yoke mostly. Any bolt on flanges as well. Anything you need to get the u joint cups established.
This has been a very rewarding discussion. Everything became somewhat crystal clear when I read 'parallel lines' and 'you read slope like you read a book, left to right'. Those two items helped me alot Mr. 31Vicki, thanks.
Thanks for answering my question 31Vicky! A straight edge centered at the u-joint cup bores to establish driveshaft slope angle, then twist the pinion to accommodate the calculated angles, then measure for driveshaft length....got it! Some really good info in this thread
Plus she’s cute! Wish my math teacher looked like that. I doubt it was viewed by many - but just getting to about the 0:30 mark and pay attention because it’s quick.
Yes, math class would have been more enjoyable with her as a teacher. But the problem I see with most of us hot rod type guys is that we had/have with math is associating the abstract concept of most mathematics to the 'real world' we live in. Just think if your math teacher had said, "Today we're going to show you how to determine the correct way to set up your transmission, driveshaft and pinion angles. First we always look at the car with the front to the left. What we are trying to do is determine the slope of the drive shaft. If the transmission end is lower than the differential end, it has negative slope." Would that have peaked your interest? My somewhat dated experience is that teachers of most of the stuff we deal with (math, physics, chemistry) are not good at relating the concepts to tactile (hands on) learners. Back in the day we had 'Shop Math' and although it taught students things like reading micrometers, it was treated as a class for low level achievers. This is getting WAAAAAY off topic! But actually, it's right on topic because it shows that how hard it is to explain things to others if you don't have the common ground of language. We don't want to get started on your English teacher (unless it's Miss Zimba, my 9th grade E teacher). Soap box put away!
There’s good and bad teachers with everything. My algebra teacher was honest - he was a great teacher but a hard nosed fucking prick. A real mother fucker. Honest though,,, he said “I’m probably the toughest teacher you will ever have, you’ll probably hate me some sooner than others, you’ll probably not use the algebra I’m going to teach you in your life other than helping your children with their algebra homework and you will remember. The sole purpose of this is to teach your brains how to think, that’s it. Nobody actually cares what the value of X is, but they do care if you can figure it out because it shows an absolute ability to figure out other real life problems and solutions. Some day you’ll thank me, some sooner than others, the hard part for you will be thanking me and still hating me later in life. My boys were bitching about their “stupid” math and fractions and ratios and percentages. I’m never gonna use this they said.... I told them I use math every day. Then i marched them into the shop and I taught them about “pedal” ratios. How to mix paint - even 6:1 ratios when it’s not on the cup. 2% by weight What 5/16 and 1/4” and 1/2 inch plates stack up to. Then they said ,,, ok but what if we don’t do what you do. Back to the house- Mortgage rates vs APR Check books Profit /loss statements Capital gains Got momma cook book and split or doubled recipes. Tips on restaurant bills Sales flyers- with 15% off shit. Stuff they absolutely have no need for now but they will for sure!
Now throw a wrench into the discussion and u-joint angle is also affected by the offset from centerline of the transmission output vs the pinion yoke. On many rearends the pinion yoke is not in the exact center of the housing. In other words the driveshaft is not parallel to the car longitudinal centerline. This is also part of the u-joint included angle. So even in the case of the trans output and rear yoke being parallel (both slope same), and the driveshaft being at 0 degree u-joint angle when viewing from the side, you may still have 2-3 degrees of u-joint angle due to offset pinion from centerline. Sent from dumb operator on a smart phone
Yep that’s true. Now we have a 3D slope with an X,Y AND Z axis work out. Think about it like this,,, Make a wire model of including both, the angles seen in vertical and the offset pinion in 3D, then rotate the model to 2D. Calculate from there and That will give you what you seek.
I just happen to be starting work on a new driveshaft for my latest project. It has a factory configured 8.8 rear and the pinion offset has been on my mind. From what I've been lead to understand, it's not an issue, but I'm not totally sure if it needs to be factored into the equation or not. I do know, I'm not smart enough to figure it out if it does
31Vicky with a Hemi, I hope you didn't think I was throwing all teachers under the bus. I taught high school Auto Shop and found that I was the one pointing out the uses for the academic classes that they were required to take. What I realized was that very few of those teachers knew how to apply their subject area to my students. No fault of their own, just the way it is. Doublepumper, Just look at the offset between the transmission and the rear end from the top view, front of the car to the left. All the same rules apply.
You need a few points of measure first- In top view From chassis center line to Trans output shaft and then to pinion and relative distance between them. In side view - elevation difference between the trans out put shaft, and lastly the most adjustable still movable pinion. That’s where you start
One more thing on drive shafts. Make sure you have room for movement at the yoke. I have seen transmission and crankshaft damage from driveshafts beating on the output shaft after a vehicle has been lowered.
The Jalopy Journal
