lemans1

iTrader: (4)

Well I dropped my lq4 into my 67 Sportwagon for the first time and have a few issues. The only one that concerns me is the angle. I have not put am angle finder on it yet, but visually I call see the front of the engine is sitting high. Now my oil pan is touching the crossmember on the back corner. What I would like to do is space the tall of the transmission up about 1/4" to fix both issues. My question is how much angle is too much? Am I likely to have vibration issues our wear out U-joints by doing this?

John McGraw

This is a widely misunderstood subject. The angle of the engine and transmission is actually of no importance. What is important is the angle of the front and rear u-joint, to the driveshaft. The front and rear angle should be opposite each other and approximately equal. Ideally, the angle should be no less then 1 degree and no more than 3 degrees, but there are people who run 4 degrees or more with no problems. If the engine is angled down in the rear 3 degrees, the rear end pinion, should be angled up 3 degrees, but the angle between the yokes on either end and the driveshaft, should fall into that 1-3 degree range.

To state it a different way, the centerline of the rear pinion, and the centerline of the transmission shaft, should be parallel to each other, no matter the driveshaft angle. The reason for that universal joints accelerate and de-accelerate as they rotate, when operated at an angle. Having the angles match at both ends, will allow the two to cancel out the vibration each other. Angles above 3 degrees will result in shorter U-joint life, but 4WD guys regularly run u-joints at 5 degrees or more. The life is just shorter. You do not ever want to run a u-joint at 0 degrees angle, because the rollers will brinell because the rollers will not rotate and keep them lubricated.

If it becomes impossible to keep a reasonable driveshaft angle, you can get a driveshaft made with CV joints. A car that has either been lowered or raised substantially, may not be able to stay within the 1-3 degree range.

You will want to adjust the rear pinion angle to compliment the engine angle. With leaf springs, this can be accomplished with tapered shims that go between the rear end and the springs, and for Coil springs, you can buy adjustable upper control arms, that will allow you to dial the angle in perfect.
Unfortunately, you will really not know what the driveshaft angle will be until you get the front and rear angles set correctly, but if you fall anywhere in the 1-4 degree range, I would call it good.
Since you are setting the engine and trans now, I would measure the rear pinion angle. and set the trans to be opposite it, as long as the trans can be moved that much without causing other issues. If not, just adjust the rear pinion angle to be opposite the trans angle, when you get it where it works.


Regards, John McGraw

John McGraw

Here is a really good article on this issue:

http://www.hotrodhotline.com/md/html..._harmonics.php




Regards, John McGraw

lemans1

iTrader: (4)

Wow, thanks for the info and insight. Now i know what to shoot for as well a what's relevant.

soundengineer

iTrader: (16)

I just went thru this process on my 93 mustang project...I'm using a Motor plate and Midplate....
started with the rearend in the car... Jumped up and down on the bumpers to settle the suspension.....
used some motorcycle ratchet straps to secure the rear in resting position, lifted the car up...(suspension stays at normal compressed resting ride height)
dropped my motor and trans in..
the motor plate on the front is strictly there to hold up the engine...
the midplate is used to set the angle of the motor.
I bolted the midplate to the motor, and bolted the midplate chassis brackets to the midplate.
I actually used a laser finder against the flywheel with a special adapter I made to bolt it to the flywheel....centered on the crank and flat with the crank/driveline
pointed the laser towards the rear... put a jack under the back of the motor and moved it around until it aimed just a hair below the center of the pinion in the rear....

then I climbed out from under the car, tack welded the midplate to the chassis, pulled the motor back out, welded the midplate brackets in and then dropped the whole combo in the car.

my old driveshaft from my camaro is a bit shorter than what I need in the mustang, but it was good enough to jam the yoke into the transmission, and hold it up to see that I was indeed dead in line with the pinion on the rear.

Total pinion angle is the important #... the motor/transmission driveline angle really doesnt matter at all... its all about how it connects at the rear.


my motor actually points 3.7* downhill towards the rear...
my rear will point approximately 1.7* uphill towards the front... making a total pinion angle of 2*

bmf5150

Great info guys

John McGraw

Actually, the pinion angle and engine angle should be the same angle, but opposite, for the most vibration free operation. If the engine points down at 3.7, the pinion should point upward at 3.7. That being said, for a drag car, the pinion should be a little less to accommodate axle wrap-up under acceleration. If you raise the pinion angle with tapered shims, you will also see the angle at the transmission U joint will decrease as well. The point here, is that you have to know what the angle is between the yoke and pinion and the driveshaft, as that is the angle that is critical for u-joint wear. You can have have the engine angle and the pinion angle identical, and still have 10 degrees of U-joint angle. There are two components of proper driveshaft geometry, the engine and pinion angle, and the U-joint angles.

Opposite but equal engine and pinion angles will yield the most vibration free ride, and the amount of this angle is irrelevant, as long as it yields a driveshaft angle that falls within acceptable norms. The driveshaft angle is what gives you strong drive lines and long U- joint life. Low driveshaft angles will yield long U-joint life and U-joints that are less likely to break under severe use. Zero driveshaft angles will also yield short U-joint life, because the rollers will not rotate, so they will not lubricate

C2 and C3 Corvettes are perfect examples of this. If you jack the rear off the ground on these cars, you often can't rotate the tires. This is because the u-joint angle increases enough to make the U-joints bind. The yoke on the rear end and the axle yoke are still the same and are reasonably parallel with each other, but the angle between halfshafts and the U-joints has increased enough to prevent the shaft from rotating. This is why modern cars use CV joints and no longer use U-joints.

Regards, John McGraw

John McGraw

I have a 67 Chevelle wagon with a LS drivetrain in it, and I had a real tough time with driveline angle on this car. By the time I got the stance where I wanted it, the U-joint angle ended up at 3.5 degrees. I could have gotten better if I had lowered the rear a little, but I really like the stance of the car as it is. I only got it this good by lowering the rear of the trans slightly from the stock location, so I would guess that raising the trans mounting point, will only aggravate the U-joint angle issue.

Of course, If you are willing to run a stock ride height in the rear, you may be able to get away with it. I ended up slicing the top rear edge off of the front crossmember and then welding a plate back over it. This gave me the pan clearance I needed. Since your wagon is identical in dimension to the Chevelle wagon, I would bet that you will have the same issues.

Here is a pic of the crossmember modification:



Here is the stance of the car:






Regards, John McGraw

74modified

I agree
Good information John, well explained

Pop N Wood

iTrader: (1)

If you had put a second laser pointer on the rear pinion than you could have done the alignment perfectly by just making sure the two lines are parallel. Just measure the distance between the two laser lines at the trans and at the pinion and when the measurements are equal, the front and rear angle cancel exactly. A piece of lined notebook paper or graph paper works perfectly for this.

This two laser pointer method has the added advantage of checking the left-right alignment as well as the up down, a measurement that is just as important but seemingly never checked. Having the front of the motor not perfectly along the car centerline is no different then excess engine tilt.

I made a set of driveshaft alignment tools with cat toy laser pointers I got at Petco. Made the actual alignment part a 10 minute job.

lemans1

iTrader: (4)

John, nice looking wagon. My car has a very similar stance. Cutting the crossmember may be the best way to go. Her is a shot of my car before dropping it an inch. Thanks again for your help with this.

John McGraw

The other thing you have to be concerned about when raising the trans mount. is interference between the driveshaft and the body reinforcement that runs under the floor right behind the front seats. This was such a concern for GM, that they used a stepped driveshaft for clearance. I removed the support on my car because I used the huge 6L80E trans, and had to cut a bunch of the tunnel away to make it fit. The seat belt bolts stick through this support, and it is fairly common to cut the driveshaft in half when these bolts rub against the driveshaft. I used a 3" aluminum shaft, and fabricated new seatbelt mounts in the new tunnell. I have loads of clearance for the driveshaft now.

Here is a shot of the underside, showing the removal of the brace and the large tunnel. I was going to put a Air Ride suspension on it, and wanted to be able to drop it in the weeds. Compare this pic to your stock floor, and you will see clearance is really tight at this brace.





Regards, John McGraw