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Old 11-07-2019, 06:27 AM   #1
Geerbangr
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Default Pinion angle situation

First off I’m working on my gasser, ladder bar car. Engine/Trans is a lot higher than rear. With that being said, is it acceptable to run positive angle on the pinion to achieve proper pinion angle?
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Old 11-07-2019, 10:52 AM   #2
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Default Re: Pinion angle situation

The pinion does not know where the ground is, it only cares where the tranny yoke is. You are heading in the right direction by mounting the engine with a downward angle and pointing the pinion up.
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Old 11-07-2019, 12:37 PM   #3
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Default Re: Pinion angle situation

Awesome thanks for the reply. So a stick shift, long ladder bar car with leaf springs. Should I set the pinion angle at 3* in the bottom hole front ladder bar mount and whatever it is in the top front ladder bar hole it is as long as it doesn’t go over center?
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Old 11-07-2019, 04:26 PM   #4
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Default Re: Pinion angle situation

Goal - engine and pinion angles are the same when loaded/power applied. This means they are parallel to each other. This demonstration explains why
The driveshaft operating/working angle is secondary although most would say < 3*, preferably < 1*. Check this out https://www.racingjunk.com/news/2014...-and-traction/
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Old 11-08-2019, 02:37 AM   #5
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Default Re: Pinion angle situation

I’ve watched that video. Very good explanation.
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Old 11-10-2019, 03:40 PM   #6
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Default Re: Pinion angle situation

Didn't mean to hijack thread, but no sense in making another thread for same topic. I checked the driveline angle in my car with it sitting on level ground, tire pressures where they need to be and this is what I got. And best that I could tell, I got 0 on the trans output, 0 on the driveshaft but 3 degrees on the pinion pointed towards the ground. Is that too excessive at the pinion and how should I adjust the ladder bars if so?
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Old 11-10-2019, 11:05 PM   #7
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Default Re: Pinion angle situation

Some good setup info.

Passmore, depending on diff setup, power, and tire 1.5 to 2.5 down is typical range. Any idea how far axle wraps under full power? You don't want to go past 0 under full power.
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Old 11-11-2019, 01:02 AM   #8
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Default Re: Pinion angle situation

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Originally Posted by tblentrprz View Post
Some good setup info. https://www.youtube.com/watch?v=uvvqVbuvDc8

Passmore, depending on diff setup, power, and tire 1.5 to 2.5 down is typical range. Any idea how far axle wraps under full power? You don't want to go past 0 under full power.
No idea, to be honest. First time putting a car together and drag racing is new to me. The video does help though. I have considered taking the car to a local chassis shop when the car is done to just go over a few things. For example, I noticed earlier in the year that the coilovers were both leaning at a certain angle... I quickly measured the ladder bars with it on the ground and one side was adjusted a bit longer than the other side. I was thinking that it was adjusted that way to get the car going straight but with the pinion angle and the coilovers combined, I'm thinking I might need someone to check it that's more knowledgeable than I am just to confirm, I don't know though. I'm sure I could get away without it the first few passes down, since this is only going to be around a 7.0 1/8 car but I like to know that something is right and won't throw me for any surprises on my first full 1/8 pass.
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Old 11-11-2019, 06:06 AM   #9
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Default Re: Pinion angle situation

Tremec offers an App for setting Pinion angle-you put your smartphone on each yoke and it does the math for you-give it a try, it works pretty slick-
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Old 11-11-2019, 10:57 AM   #10
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Default Re: Pinion angle situation

Quote:
Originally Posted by Passmore View Post
No idea, to be honest. First time putting a car together and drag racing is new to me. The video does help though. I have considered taking the car to a local chassis shop when the car is done to just go over a few things. For example, I noticed earlier in the year that the coilovers were both leaning at a certain angle... I quickly measured the ladder bars with it on the ground and one side was adjusted a bit longer than the other side. I was thinking that it was adjusted that way to get the car going straight but with the pinion angle and the coilovers combined, I'm thinking I might need someone to check it that's more knowledgeable than I am just to confirm, I don't know though. I'm sure I could get away without it the first few passes down, since this is only going to be around a 7.0 1/8 car but I like to know that something is right and won't throw me for any surprises on my first full 1/8 pass.
7.0 in the 1/4 I would be visiting an chassis shop.

7.0 in the 1/8, don't over-think it!

Few coil overs are completely straight up and down or side to side, don't worry about that.

My passenger side ladder bar is at least 1/16" longer than the driver side to get the car to launch straight, it could be up to 1/8" long, don't remember, but I go mid 1.3x in the 60ft and 9.4's in the 1/4, perfectly straight, and my coil overs are not 100% straight up and down, close, but not perfect!

The lower bar on my ladder bars point slightly downhill back to front in relationship to the rocker sill. I have gone 8.80's like that, as slow as 10.00 for Index Racing, I don't need to touch a thing on the car.

Pinion angle is -2*. My engine/trans points down front to rear, so my pinion has to point up somewhat. I can't lift the back of the trans anymore, already about on the floorboards already.

Pull the driveshaft out, put your anglefinder on the front pulley or balancer, get a reading. Now put it on the pinion of the rear, get a reading. Rotate the pinion so you get -2* to -3* down angle on that pinion. Sometimes you can lift/lower the back of the trans also to get things correct. But with ladder bars with adjusters on them, it's easy enough to rotate them equally to rotate the housing.
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Old 11-11-2019, 08:41 PM   #11
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Default Re: Pinion angle situation

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Originally Posted by Mike Beck View Post
7.0 in the 1/4 I would be visiting an chassis shop.

7.0 in the 1/8, don't over-think it!

Few coil overs are completely straight up and down or side to side, don't worry about that.

My passenger side ladder bar is at least 1/16" longer than the driver side to get the car to launch straight, it could be up to 1/8" long, don't remember, but I go mid 1.3x in the 60ft and 9.4's in the 1/4, perfectly straight, and my coil overs are not 100% straight up and down, close, but not perfect!

The lower bar on my ladder bars point slightly downhill back to front in relationship to the rocker sill. I have gone 8.80's like that, as slow as 10.00 for Index Racing, I don't need to touch a thing on the car.

Pinion angle is -2*. My engine/trans points down front to rear, so my pinion has to point up somewhat. I can't lift the back of the trans anymore, already about on the floorboards already.

Pull the driveshaft out, put your anglefinder on the front pulley or balancer, get a reading. Now put it on the pinion of the rear, get a reading. Rotate the pinion so you get -2* to -3* down angle on that pinion. Sometimes you can lift/lower the back of the trans also to get things correct. But with ladder bars with adjusters on them, it's easy enough to rotate them equally to rotate the housing.

I wanna say one of the ladder bars was 3/8-5/8 or so longer than the other taking a quick measurement of the bottom bar. I'll more than likely just not touch the suspension of my car until I drive it and see if it even needs anything. I was told by someone that they dialed in the suspension on this car and got it right for running 6.30s in the 1/8 before I bought it, so it probably is just best I don't even worry about any of it honestly..

I'll check into my angles a bit more closely. I'm not sure there's much I can really do other than ladder bar adjustments and/or different engine mounts, which I really wouldn't want to do the mount change. The trans is pretty close to the tunnel and my driveshaft is very close to the top of the driveshaft loop. Shimming the trans would only make it worse in my case. My biggest concern is just wearing out a u joint quickly or having failure , obviously. Something I'll just need to try and spend some more time on. Thanks for the info Mike

Last edited by Passmore; 11-11-2019 at 08:42 PM.
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Old 11-11-2019, 09:03 PM   #12
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Default Re: Pinion angle situation

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Originally Posted by Passmore View Post
I wanna say one of the ladder bars was 3/8-5/8 or so longer than the other taking a quick measurement of the bottom bar. I'll more than likely just not touch the suspension of my car until I drive it and see if it even needs anything. I was told by someone that they dialed in the suspension on this car and got it right for running 6.30s in the 1/8 before I bought it, so it probably is just best I don't even worry about any of it honestly..

I'll check into my angles a bit more closely. I'm not sure there's much I can really do other than ladder bar adjustments and/or different engine mounts, which I really wouldn't want to do the mount change. The trans is pretty close to the tunnel and my driveshaft is very close to the top of the driveshaft loop. Shimming the trans would only make it worse in my case. My biggest concern is just wearing out a u joint quickly or having failure , obviously. Something I'll just need to try and spend some more time on. Thanks for the info Mike
That is a big difference!

When you build a ladder bar car you bolt the ladder bars together on the floor to get them the same exact length, then adjust from there to get the car to launch straight.

So if your bars are actually that different in length, then something wasn't built correctly to being with, or something is really bent and the bar was adjusted to keep it going straight.

I found in my car years ago the drive side front ladder bar mount was bending up and forwards in the chassis, nothing was braced! Live and learn........

I made a new cross member for the ladder bar, triangulated them a lot! 45* bars going from the front side of the LB cross member to the subframe connectors. Then a pair of bars going from the top of the LB cross member to the cage. So it can not move forwards or up ever again.

The rear mounting brackets for the ladder bars are also braced a lot.

I have also bent the heim joints in the front of the ladder bars. They are definately a wear item. Chris Alston won't even sell his ladder bars with heim joints, only GIANT solid rod ends, just the the solid rod ends (but much smaller) on the rear of the ladder bars. That single from joint takes all the stress at the hit!

Anyway, take a look around to see if something is bending on you. Take it all apart over the winter to check it all out.
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Old 11-11-2019, 09:30 PM   #13
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Default Re: Pinion angle situation

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Originally Posted by Mike Beck View Post
That is a big difference!

When you build a ladder bar car you bolt the ladder bars together on the floor to get them the same exact length, then adjust from there to get the car to launch straight.

So if your bars are actually that different in length, then something wasn't built correctly to being with, or something is really bent and the bar was adjusted to keep it going straight.

I found in my car years ago the drive side front ladder bar mount was bending up and forwards in the chassis, nothing was braced! Live and learn........

I made a new cross member for the ladder bar, triangulated them a lot! 45* bars going from the front side of the LB cross member to the subframe connectors. Then a pair of bars going from the top of the LB cross member to the cage. So it can not move forwards or up ever again.

The rear mounting brackets for the ladder bars are also braced a lot.

I have also bent the heim joints in the front of the ladder bars. They are definately a wear item. Chris Alston won't even sell his ladder bars with heim joints, only GIANT solid rod ends, just the the solid rod ends (but much smaller) on the rear of the ladder bars. That single from joint takes all the stress at the hit!

Anyway, take a look around to see if something is bending on you. Take it all apart over the winter to check it all out.
I don't remember the exact measurement, but if memory serves right, it was somewhere in that area. Everything underneath looks straight and no obvious signs of something bent or off but we all know looks can be deceiving. It's possible that the ladder bar crossmember may not be exactly square but I think I could check that by measuring from a hole in the frame rail somewhere diagonally to the crossmember and that would tell me. I'll check it next time I get it up in the air just to be sure.
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Old 11-12-2019, 04:53 AM   #14
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Default Re: Pinion angle situation

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Didn't mean to hijack thread, but no sense in making another thread for same topic. I checked the driveline angle in my car with it sitting on level ground, tire pressures where they need to be and this is what I got. And best that I could tell, I got 0 on the trans output, 0 on the driveshaft but 3 degrees on the pinion pointed towards the ground. Is that too excessive at the pinion and how should I adjust the ladder bars if so?
Didnít mean to hijack the thread but you went ahead and did it anyway. Clown move!! Your situation is not the same. Iím dealing with a crazy setup old school gasser. Entirely different then what youíre dealing with but go on with your shit Iíll worry about mine in another thread, dickhead.
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Old 11-12-2019, 06:39 PM   #15
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Didnít mean to hijack the thread but you went ahead and did it anyway. Clown move!! Your situation is not the same. Iím dealing with a crazy setup old school gasser. Entirely different then what youíre dealing with but go on with your shit Iíll worry about mine in another thread, dickhead.

Yours is way more difficult/technical than my deal, no two ways about it. Figured I might've caught less shit just posting in a thread that's already up and similar to mine instead of making one in the same tech section but guess not. Sorry to ruin your day. If someone can tell me how to delete posts, I'll be more than happy to do it.
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