Setting up Transmission angle (LS1 related).

[trapin]

This is a transmission question but I felt because it was so exclusive to the LS1 conversion that it belonged in here.

I have my LS1 in with my S&P mounts and have my transmission bolted up to my S&P trans crossmember. All that is left to do is adjust the attitude of the trans with an angle finder for 3 degrees down, mark my holes and then drill them and bolt the crosssmember
in. My question is...has anyone ever attempted this? What pointers can you give me. For instance....do I just keep the car on the ground as it sits or do I have to level off the car? Is the trans being modified from 0 degrees horizontal? Thanks.

T.

[Rubes]

Tony...the absolute angle of the trans in my oppinion, is not so important...but the the angle thru the u-joint is. There should be more than 2 degrees, but less than 4 degrees between the input angle and output angle. This would need to be checked with the rear suspension loaded, but I dont believe you need to actually level the car. Dont forget to check the rear u-joint as well.

[TA219]

I am no expert but i did do some reading before making my crossmember and i beleive that 3* down is right for the transmission angle. I had my car on jackstands but i still checked the car and found that the car was actually sitting at a 2* angle so i had to take that in to account when making my crossmember. It would be ideal if your car was sitting perfectly level. I beleive that you want 3* at the trans and 3* at the rear end and no more than 10* total.


I found lots of info on the net and i am sure if i am telling you wrong someone will stop in soon to let us know!!

[trapin]

Thanks guys.

[Payton King]

put your angle finder on your subframe where it bolts to the car and get the reading. Then on the tail of your trans to get the 3 degrees down. Once you car is complete and at ride height take you can shim the rear to get the pinion angle right...still using the a mearsurement from the sub frame as a reference. Does that make sense?

They make or you can make wedge shaped shims that go between the mounting pad and leaf spring or use a set of DSE axle mounts and move them where you need them and tack them in place.

[trapin]

Payton...now you're scaring me. LOL!!! I certainly hope I don't have to shim my rear axle any. I'm having a hard enough time as it is with the transmission. But that is a good idea...I did not think of going off the arm of the sub-frame as a reference. What you're saying is, at ride height with the car sitting on the ground, find out what angle the arm of the subframe is at relative to zero and then set the transmission up off of that. At the same time, check the angle of the pinion shaft on the rear axle. Is the pinion angle also supposed to be 3 degrees down? Thanks Payton.

[Payton King]

I will slow down and try to give you a better description. With you car on jack stands or with the subframe out of the car...it does not matter. Put your angle finder on the arms. What you are trying to do is get a reference point. If while on the stands you subframe is pointing down 1 degree..add that to the 3 degrees that you want to achieve on the trans. So when you put the finder on the back of the trans, I found it easier to put it on the harmonic balancer (larger, flatter surface and the magnet will stick to it) You are looking for a total of 4 degrees of angle. The 3 down plus the 1 down from the sub frame. Get the point?

Once the car is together, you can check your pinion angle. You have already used the arms of the sub to set the trans angle to 3 degrees. With the rear at ride height take get the angle from the sub again and add or subtract that number depending on how your car is sitting, with the 3 degrees up angle you want on the rear pinion. It is best to have them equal..3 up on the rear and 3 down on the trans, but there is a small fudge factor. If you are running a rear set up for a first gen and leafs I am sure you will not need to do anything to the rear, it will be close to the 3 degrees up.

Shimming the rear is an old drag racer trick instead of having to re-weld the spring perches.

[trapin]

Well...I attempted this last night. I have the car sitting on 4 car ramps that are the same height. My subframe arms are actually pointing up (if going from the front of the car to the back) and there is a 2 degree difference between the arms. One arm reads +1 and the other +3. I then check the angle of the balancer vs. the output shaft and there is a 3* difference between the two of them. ARRRGGHHHHH!!!!!

So here's what I did. I split the difference between the two subframe arms and used +2, I then adusted the the transmission angle to 5* down (2* down + 3* down) and I marked the holes on my frame.

I don't think my angle finder is defective. I just bought it from Lowes and I experimented with it on other surfaces whose angles I already knew. It checked out.

So what do you think? Should I drill the holes and be done with it? How perfect does this need to be for a street car?

[Rubes]

Is there any play in the outputshaft?. I use the balancer...you KNOW that is perpendicular to the trans, unless it aint on straight or damaged. The rubber ring between the balancer parts could be giving you problems as well.

Dont get too hung up an a reference point. As long as the car dont move from where it is until your done, just use the same point for ALL measurments. The relationship needs to be between the trans outputshaft, driveshaft, and rear pinion. be sure to measure all those.

It may be easier to just measure the pinion angle and set the trans parallele to that. The danger there is that the motor/trans combo could be too high or too low and cause too much angle thru the u-joint. Thats t he problem I ran into with my Impala. I used the same mounts everyone else does, yet when I measured the angles, the u-joints were working thru 6 degrees. everyone else seems to be driving theirs without any problems, but I'm going to notch my cross member so I can lower the motor and get the right angle. mine is a bit more complicated due to the two piece driveshaft as well.

http://www.iedls.com/ptsetup.html

[Payton King]

that the subframe is in the car and you have it sitting on the tires and wheels. Difference in spring height or the way the suspension is sitting will give you that difference from side to side. Or you are using rubber bushings on the sub and one is tighten more or they may be worn.

I would either put it on jack stands on the frame or split the difference just like you stated. I would also trust the angle finder on the balancer more than I would on the back of the trans output shaft.

[70 Chevelle]

I started a similar thread and the guys from ATS graciously gave me a very detailed reply. This info was kindly given to me by Chicance67

Join Date: Dec 2002
Location: Lost Wages, Nevada
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Engine and Pinion Angle: There has been numerous "hear says" about what the pinion angle should or should not be. Hopefully this will clear up a lot of misconceptions. One of the biggest misconceptions is the engine angle is it is relative to the frame. Engine, pinion angle and ride height is all relative to the ground.

Most engines are set at 3 degrees, when you look at the side of the intake manifold on a carburetor engine you will notice the manifold has an angle in it. This angle is to allow the carburetor to sit level. I have heard many reasons to why this is done... but the main purpose of having an engine angle is for the u-joint misalignment and its associated rotation. I have even heard that it is to allow for more room in the passenger compartment by having a smaller tunnel... and this is why the car manufacturers build front engine cars with the engine at an angle. Many drag race cars have a 2 to 3 degree negative engine angle, (engine down in front.) Having this negative angle allow for better weight transfer to the rear of the chassis. The 3 degrees you keep hearing about is the recommended angle for carburetor cars with intake manifolds set at 3 degrees. With the engine and pinion set at 3 degrees they do not line up directly and requires you to make them parallel. This misalignment allow the u-joints to rotate on a street car. Personally, I believe that the requirement of being parallel has more to do for the suspension articulation/travel, as well as for misalignment for the joint operation. It provide's a range in which the joint can work without going into bind.

There is another misconception regarding the pinion angle on drag cars. I have seen many people advise that the pinion needs to be 2 - 7 degrees down. In relation to what? I disagree with this theory and set-up. The pinion needs to be "parallel" to the engine angle or in a straight line for the least amount of horse power lost. This following is a quote from Mark William's web site:

Quote:
"There is a general misunderstanding about "dropping the pinion down" several degrees. This is a practice that could be applied only to leaf spring cars without any traction control devices where springs can “wrap” and change pinion angle. This practice would not apply to 4-link, ladder bar or torque arm equipped cars. Failure to maintain matched and minimum operating angles increase erratic non-uniform output velocity from the drive shaft to the differential."
In a dragster, you can set up the engine angle at almost any degree just as long as the transmission is perfectly inline with the pinion yoke. However, when the engine and pinion yoke is in direct line, it does not allow for the rotation of the u-joints. This straight alignment is mostly used on drag race cars.

If you would crawl under your car and look at the pinion angle you will notice it is the same angle as the engine/transmission (they are parallel). A good example of having negative engine/pinion angle is when you lower a 1 ton crew cab where you lower the front more than the rear and there is quite a "rake". In this case you have to put a wedge on the back side of the spring perches to correct the pinion angle down.

If you are building a chassis you need to first determine ride height. This is the most important thing you need to do. Decide what wheels and tires you want to use before you pick up the welder. If a chassis builder does not ask you what tires you are going to use do not buy from him. How can he build your chassis without knowing the tire diameters? How can he set up the front end and engine angle? What they do is build a chassis based on what they want or think you should have and not what you want.

Now... determine the ground clearance you want for your oil pan. Set your motor mounts based on this and the angle that best fits your car. Try to set the pinion parallel to the engine angle. Before you weld the brackets on the rear end housing be sure that the rear end was set at "ride height" (ride height is where the rear end would be with the car done.)

If you find a chassis builder that says you have to have the engine angle at 3 degrees and there is no other angle you can set if at, find another cat to do the work. He apparently does not understand the principles of setting correct engine and pinion angles. Also, no chassis builder can build you a chassis with an optimum suspension geometry without knowing "proper" or the "designed" ride height.

Hope this might help...

[Payton King]

in your above post, which is excellent information they gave you, showing the trans and pinion angle need to be parallel. If you have a down angle of 3 degrees on the motor and up angle 3 degrees on the pinion...that makes it parallel.

Why I used and most use the 3 degrees is that what the factory set for a carb car. The first gen has/had a carb, so the if using a factory 10 or 12 bolt with the leaf springs, you should not have to adjust the rear pinion angle. I was under the assumption that Tony was running a stock rear and leafs.

I also assumed that a reference point is needed when setting this up, and if I am not mistaken, GM used the car as being parallel to the ground. That is what it appears to me when I look at chassis drawings from that era and why I said use the frame rail as the zero-ing point.

The most important point is they are parallel and that is checked with the rear at ride height.

[trapin]

I am using the factory 10 bolt and DS&E 3" drop springs.

I think what Payton outlined should work. Tonight I'm going to put some straps across the transmission and take the jack out from under the output shaft so I have the full weight of the engine and trans on the suspension. From there I will go off wherever the subframe arm angle is and adjust the attitude with the angle finder on the balancer. Thanks for everyone's help so far. This is a learning experience for me. I've never done this before.

[70 Chevelle]

I just want to make sure that no one takes my last post as my personal statement. That information can be found at the other thread. I want to make sure that the people who kindly took the time to give the information get credit. Here is the thread:

https://www.pro-touring.com/forum/showthread.php?t=32470