Pinion + Engine Height/Angle Question

[Bradfords_garage]

Hi Guys,

I figure this belongs here since it pertains to pinion angle, but sorry if it doesn't.

I'll start by saying that I've read as much as I can find on setting engine angle and pinion angle. I'm building a custom chassis for my Falcon, which will be primarily used for road racing and street, but not a DD by any means. Not likely to ever see drag racing or hard launches.

Things I know:

Ride Height
Wheel and Tire Height
Pinion C/L height from the ground (at 0 deg), which is 10.55"
With a dry sump, I can set my crankshaft C/L to match it.
Rear suspension will be a 3 link setup with rod ends or Johnny Joints + Panhard

My question is this- everything I read says you tilt the engine to aim at the pinion, whether positive or negative, but no-one talks about if the C/L of the crank, output shaft and pinion are at the same height. If I'm designing the chassis and have the option to set the crank C/L at the same height as the pinion and run them both level, with a level driveshaft, is this a bad idea? I can't find a shred of information of having them lined up straight. So, I'm either way over-thinking it or its not something I should do, haha.

Thanks in advance for any help!

Brad

[Motobrewmaster]

Read this. It should get you to where you need to be.

.https://www.iedls.com/uploads/files/Power%20Train%20Setup.pdf

Also handy for a quick reference is the Tremec app. You can download it for free.

https://www.tremec.com/menu.php?m=154

And lastly make sure to put some thought into your drive shaft and u-joints. Dana/Spicer has some good info for that too.

https://spicerparts.com/calculators

Do your homework. Learn a bunch and show us on here what you do!

Cheers, Steve

[Bradfords_garage]

Thanks Motobrewmaster for the links. I read the article and glanced at the calculators. The article seemed helpful, though I don't know how you go about determining what the harmonics will be for a given driveshaft length, rpm, gear ratio, diameter, angle...etc. Though, as an instrument builder I find it interesting.

Luckily, my uncle stopped by today to have a look at the project and he cleared it up for me. It could be level and in-line, but the misalignment is what causes the needle bearings inside the u-joint to spin inside the cup. As soon as he said it I understood something I'd read earlier, but didn't quite get at the time.

I have some drafting and figuring to do, but the links you provided were helpful, so thank you!

Brad

[andrewb70]

...If I'm designing the chassis and have the option to set the crank C/L at the same height as the pinion and run them both level, with a level driveshaft, is this a bad idea? ...

Brad

Brad,

If you have the ability to do this, I see no reason not to do this. Remember, under dynamic load conditions, the pinion will rise and fall some, even with johnny joints. What you might ultimately end up doing is pointing the pinion down just a hair, so that under load, you have a level driveline. Also keep in mind that to achieve smooth high speed operation, you want to keep the front and rear operating angles under 3 degrees. Some will say level is bad because the needle bearing in the u-joints don't move around, but I think that is BS...

You can even set the engine a little lower than the pinion centerline, which will be give you a better center of gravity. Your limiting factor there will probably be the bellhousing ground clearance, unless you plan on using a small diameter racing clutch.

http://www.markwilliams.com/servicebull/sb0049.pdf

Andrew

[Motobrewmaster]

Glad the links helped you out Brad. I agree with Andrew on what he said.

I have a 4-link in my car and set it up equal trans angle and diff angle. Like Andrew said there is always some movement in the system so I would not worry about wearing out your u-joints. It is also true that under load your pinion will move up and a slightly down pinion angle compared to your trans angle is OK, that said I would only go down a little (a few 0.1 th's of a degree). Remember there is also braking load which will drop the pinion angle as well, if you are going to road race the car you will have that too, hence my choice to leave them equal.

Make sure to have a good drive shaft made up. Once you have everything all setup and the car fully loaded on it's tires measure up what you need for the driveshaft. I have used both Inland Empire & Denny's and both are great. Give them your application specifics and they will recommend the right driveshaft for you. For me Alu DS's work fine and I have no harmonics cruising above 100 on the highway. Carbon fiber DS are awesome but $$$$$$.

Good luck on the project, the learning is half the fun!

Cheers, Steve

[andrewb70]

Lastly, you can use a driveshaft with CV joints on both sides, like I have in my Cougar, and not give a f@#k about any of this...lol

Andrew

[Bradfords_garage]

Thanks, Andrew! You've given me some things to think about. You hit the nail on the head with your bell housing comment. I cannot get the engine as close to the ground as I'd like due to the bell housing. That was an overlooked detail on my part. So many details to work through and consider! But now that I know where the engine has to sit for bell housing clearance, this should be much easier to figure. Thanks for your help, I appreciate it!

Brad



Brad,

If you have the ability to do this, I see no reason not to do this. Remember, under dynamic load conditions, the pinion will rise and fall some, even with johnny joints. What you might ultimately end up doing is pointing the pinion down just a hair, so that under load, you have a level driveline. Also keep in mind that to achieve smooth high speed operation, you want to keep the front and rear operating angles under 3 degrees. Some will say level is bad because the needle bearing in the u-joints don't move around, but I think that is BS...

You can even set the engine a little lower than the pinion centerline, which will be give you a better center of gravity. Your limiting factor there will probably be the bellhousing ground clearance, unless you plan on using a small diameter racing clutch.

http://www.markwilliams.com/servicebull/sb0049.pdf

Andrew

Thanks, Steve!


Glad the links helped you out Brad. I agree with Andrew on what he said.

I have a 4-link in my car and set it up equal trans angle and diff angle. Like Andrew said there is always some movement in the system so I would not worry about wearing out your u-joints. It is also true that under load your pinion will move up and a slightly down pinion angle compared to your trans angle is OK, that said I would only go down a little (a few 0.1 th's of a degree). Remember there is also braking load which will drop the pinion angle as well, if you are going to road race the car you will have that too, hence my choice to leave them equal.

Make sure to have a good drive shaft made up. Once you have everything all setup and the car fully loaded on it's tires measure up what you need for the driveshaft. I have used both Inland Empire & Denny's and both are great. Give them your application specifics and they will recommend the right driveshaft for you. For me Alu DS's work fine and I have no harmonics cruising above 100 on the highway. Carbon fiber DS are awesome but $$$$$$.

Good luck on the project, the learning is half the fun!

Cheers, Steve


Lastly, you can use a driveshaft with CV joints on both sides, like I have in my Cougar, and not give a f@#k about any of this...lol

Andrew

[andrewb70]

Good luck! You ha e some decisions to make.

Andrew