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#2534323 - 08/10/18 04:35 PM Driveline vertical angles for custom chassis- opinions?
radar Offline
pro stock

Registered: 07/27/07
Posts: 1406
Loc: Philadelphia
Howdy!

I didn’t want to use the word pinion in the title but I’m building a street rod type truck and I have kind of a clean sheet of paper on how my angles all play together.

Here’s what I know- my driveline will be offset to the passenger side to match the pinion offset of my ‘70s ramcharger 9.25 axle. From what I can figure from book learnin’ I have two choices on pinion vs driveline angle. I know that I will want the pinion and driveline angles parallel. It seems like on a factory type build these parallel lines are vertically offset and don’t intersect so that the universal joints phase cancel but have to work enough to keep the needle bearings spinning and not galling and seizing. A true race car build has the transmission aimed directly at the pinion.

In a fast truck built for a fun weekend street driver which style do you think I should shoot for? I haven’t built motor or trans mounts yet and the leaf perches are not welded either. Whichever way I go I will get it perfect then tip the pinion down a touch to get it to line up under load. This truck might see the track like once a year but I’m not trying to be faster than anybody but stock mustangs haha

Thanks moparts!
Radar

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#2534336 - 08/10/18 05:06 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
Hemi_Joel Offline
master

Registered: 01/19/03
Posts: 5659
Loc: Minnesota
you want the centerline of the crankshaft and the centerline of the rear axle pinion parrallel under power. So you build it with the front of the pinion angled down 2-7 degrees in relation to the crank centerline, depending on the type of suspension and the power.

popcorn
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31 Plymouth Coupe, 392 Hemi, T56 magnum

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#2534362 - 08/10/18 06:18 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
radar Offline
pro stock

Registered: 07/27/07
Posts: 1406
Loc: Philadelphia
Joel-

Thanks I know that the pinion will rotate up under power. I am not asking about setting pinion angle. Under load the pinion angle and crankshaft angles will be parallel- that is a given.

My question is more about the driveline angle- in a production car a line through the crank and a line through the pinion will be parallel but the crank will be offset above the rear. The offset in only one axis (vertical) makes the u-joints work so the needle bearings get used and don’t get stuck, smashed , whatever.

In a purpose built race car the angles are also parallel under load but instead of being two lines that never intersect they are on exactly one line- the transmission is aimed directly at the pinion.

I am not another non search function dummy asking how to set my pinion angle. That’s easy and I have graduated to setting my driveline angle. I am building motor & trans mounts and setting the motor back some. I am engineering the angles not working with any angles or installed heights except the oil pan has to be high enough and the air cleaner has to be low enough.

Assume that under load in both scenarios the pinion is 3° up and the crank 3° down. In one scenario the driveshaft is also at 3° because I built the car more like a tube chassis race car and in the other scenario the driveshaft is at a slightly greater angle to make sure the universals actually do something.

At least that’s my understanding of how the angles work in production vs race cars? If I knew it all I wouldn’t be posting.

Thanks

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#2534364 - 08/10/18 06:21 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
radar Offline
pro stock

Registered: 07/27/07
Posts: 1406
Loc: Philadelphia
Is it just the issue of having to replace U-joints more regularly on a race car while gaining a tiny bit of power not used to work them so they stay free? Should I aim the trans at the pinion and let it eat? Or is it worth the half a pony or whatever to make the needle bearings spin enough to be happy in the U joint cups?

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#2534374 - 08/10/18 06:41 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 26872
Loc: Balt. Md
On a production car it looks to me that the eng/trans is usually higher in the chassis then the rear end so even if they are not offset from side to side they will still have some offset from the vertical. So they will both be on parallel centerlines under load but not the same centerlines. The eng/trans is higher then the rearend on a stock type car as far as I know. That's how they always look to me so the U-joints will still work and lube if the side to side is the same which it looks to be very close in some cars to me like GM and Fords. Most the Mopars look to me to be offset side to side. Ron
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My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#2534399 - 08/10/18 08:59 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
AndyF Offline
Too Many Posts

Registered: 01/20/03
Posts: 24628
Loc: Oregon
It just depends on the chassis design and where everything has to go. On some drag cars the rear end is higher than the crankshaft so the driveshaft goes uphill. You also have suspension travel to account for and you have to figure out what the pinion is doing during acceleration as well as suspension travel. The rear end usually moves in an arc rather than just straight up and down. You might want to mock up the rear suspension with light springs and move it thru the travel just to see what happens with the driveshaft and pinion angle.

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#2534531 - 08/11/18 10:19 AM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
Sport440 Offline
master

Registered: 01/20/03
Posts: 6585
Loc: Canton, Ohio
Originally Posted By radar
Is it just the issue of having to replace U-joints more regularly on a race car while gaining a tiny bit of power not used to work them so they stay free? Should I aim the trans at the pinion and let it eat? Or is it worth the half a pony or whatever to make the needle bearings spin enough to be happy in the U joint cups?



You seemed to be worried about one thing, the needle bearings not being rotated enough. Don't Worry about that. The Dynamic movement of the axel and driveline will always keep them moving no matter how straight you align them. Unless every driveline angle is welded made 100% solid, the needle bearings will see Movement, period, don't worry about it..

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#2534555 - 08/11/18 11:23 AM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
radar Offline
pro stock

Registered: 07/27/07
Posts: 1406
Loc: Philadelphia
Thanks!

Sport440 You are right I was basically only worried about not working the caps. I’ll stop worrying about it. And Andy thanks for chiming in!

I made some pretty big suspension compromises to get my 89 dakota chassis where I want it using only my welder and parts from around my garage. To get the frame dropped down from 9” of travel to 3 1/2” (plus the bump stop) plus switch to mancini xhd 6 leaf springs I had to move the front hanger up about 7” and back about 4”. The axle now moves 1.5” back through it’s full travel which is a lot. I decided I could live with it because I had these springs in my demon a long time ago and it was very stiff. This 1954 pickup on the dak rails should be 3000lbs (I hope) and trucks are light in the back anyway. So best case it rides a little hard, worst case it has more understeer than I want. Compromises. If I hate it once I get back on the road I can always do a 4 link and coilovers once my wallet recovers from the build. I will be careful to get the transmission yoke properly spaced so it won’t bind or lose spline engagement as the suspension works. My shackle angle is good so I should still get a little seperation on launch. My instant center is way high but I think it’ll be fine on the street.

I have a 400 block with a deep rear sump pan so I won’t be going very low like a dry sump tube car. I guess I’ll get the motor roughly in place for ground and hood clearance then start with the carb flange level and go from there. Sounds like aiming it at the pinion at ride height is a good bet and with 512 inches it’s also a good bet that my slapper bars will dictate the pinion angle under load. I could probably get by just using the short 20” front spring segment to fight wheel hop like a true mopar fanatic but I grew up seeing slapper bars and long shackles on muscle cars and can’t help myself!

Radar

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#2534569 - 08/11/18 11:43 AM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
radar Offline
pro stock

Registered: 07/27/07
Posts: 1406
Loc: Philadelphia
383 man

Thanks for the response too- I think you get what I’m talking about. I am definitely getting the crank aimed right at the pinion and parallel to the frame rails when viewed from above.

From what I’ve read ford and chevy have a consistent amount of offset but mopar varied it through the years and different models. All of them did it for steering clearance, weight distribution, or whatever reason.

I think when people build tube chassis race cars they have custom stubby axle housings that usually just go dead center with the pinion and motor but I’m doing a low buck driveway fabricated spare parts type deal. The journey is a lot of the fun for me- learning how things work and trying new things I haven’t done before. I just want to at least understand what the rules are before I break them and when I’m done I want my hotrod to be simple, safe, reliable, and easy to work on.

When I grow up I want a nice hotrod like yours I love that red car!

Radar

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#2534683 - 08/11/18 03:47 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
AndyF Offline
Too Many Posts

Registered: 01/20/03
Posts: 24628
Loc: Oregon
If you have a bare block and a bare transmission case you can slide a piece of roll bar tubing thru the engine and trans. That gives you an easy way to locate the engine and transmission to the rear end pinion. The roll bar tubing gives you a nice long place to measure the angle and to check that it is parallel to the frame.


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#2534684 - 08/11/18 03:54 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: Hemi_Joel]
WHITEDART Offline
top fuel

Registered: 10/06/11
Posts: 2417
Loc: bean town ....Ca
Originally Posted By Hemi_Joel
you want the centerline of the crankshaft and the centerline of the rear axle pinion parrallel under power. So you build it with the front of the pinion angled down 2-7 degrees in relation to the crank centerline, depending on the type of suspension and the power.

popcorn
iagree
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#2534701 - 08/11/18 04:35 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
radar Offline
pro stock

Registered: 07/27/07
Posts: 1406
Loc: Philadelphia
Man you guys are on shellshocked autopilot from years and years of trying to help people ask the same pinion angle question over and over!

Thanks for the responses anyway I know people’s time is valuable and you spent some trying to help me.

Andy gets my question- I’m making a custom driveline angle for a project that has no motor mounts or transmission crossmember yet. Obviously the pinion angle will change as power is applied, especially to a leaf suspension.

Andy that’s a slick idea but I already built my trans and no spare. I’ll have to go with good old tape measure, strings, and carpenter’s square. My build is so stone age that I don’t even have a level shop floor to drop a plumb bob.

Pretend the pinion is a magical ideal. No answers about passenger side driveline offset or dynamic pinion angle please. My question can be put the most simply: should the transmission point directly at the pinion like a tube chassis race car, or be vertically offset like in a production car. The relevant answer I seem to be getting is that it is mostly a packaging issue and it won’t matter as long as the U-joints only work on one axis and the dynamic pinion angles are well considered.

Any other helpful comments are welcome I really appreciate having this forum with so much collective experience. I have little experience but I buy all the books I can find that I don’t need a graphing calculator to figure out and my mom thinks I’m smart. My friends think I’m an a—hole though haha

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#2534735 - 08/11/18 05:55 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
AndyF Offline
Too Many Posts

Registered: 01/20/03
Posts: 24628
Loc: Oregon
When I did my Duster I pointed the engine and transmission centerline at the pinion. The pinion was 2 degrees down which is what Calvert recommends for their suspension. In theory that puts everything in alignment under acceleration. But of course the ride height can move around depending on weight so the driveshaft is constantly adjusting up and down. In my car I was able to do that without having to jump thru any hoops. In some cars you can't do it. The engine is either higher or lower than the pinion so the best you can do is make them parallel to each other.

I don't think it matters all that much. If it was me I'd be more concerned with header clearance, oil pan clearance, hood clearance etc. So put the engine where it fits best and then use the u-joints to connect to the pinion.

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#2534864 - 08/11/18 10:33 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
radar Offline
pro stock

Registered: 07/27/07
Posts: 1406
Loc: Philadelphia
Ok so just worry about packaging and get it as good as I can and don’t overthink it. Thanks for the thoughtful replies. Man I can’t wait to rip this thing around when it’s done!

I have a build thread on the dodge flathead site- it’s super easy to post pictures there so when I come in from the heat in my driveway to get a dry shirt and sit in front of a fan for awhile I post tons of updates on there. I just finally got the chassis shortened up and the body fitting pretty good this week here’s a link and apologies that I haven’t figured out how to get pics hosted so I can post them here.

Link to page 4 to see the stance of the old girl on the new chassis:

http://p15-d24.com/topic/47345-512-cid-c-series-on-dakota-chassis-build-thread/?page=4

Pages 1-3 have all the gory details of the build so far- remedial caveman stuff compared to the beautiful 1/4 mile rippers on here but I’m having too much fun and nobody called the township on me yet...

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#2534904 - 08/11/18 11:53 PM Re: Driveline vertical angles for custom chassis- opinions? [Re: radar]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 26872
Loc: Balt. Md
Originally Posted By radar
383 man

Thanks for the response too- I think you get what I’m talking about. I am definitely getting the crank aimed right at the pinion and parallel to the frame rails when viewed from above.

From what I’ve read ford and chevy have a consistent amount of offset but mopar varied it through the years and different models. All of them did it for steering clearance, weight distribution, or whatever reason.

I think when people build tube chassis race cars they have custom stubby axle housings that usually just go dead center with the pinion and motor but I’m doing a low buck driveway fabricated spare parts type deal. The journey is a lot of the fun for me- learning how things work and trying new things I haven’t done before. I just want to at least understand what the rules are before I break them and when I’m done I want my hotrod to be simple, safe, reliable, and easy to work on.

When I grow up I want a nice hotrod like yours I love that red car!

Radar


Thank you very much for the kind words. I do appreciate it. Good luck with your project and I hope it all goes well for you. Ron


Edited by 383man (08/11/18 11:55 PM)
_________________________
My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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