When you measure the 3 degree angle at the u joint flange do you have the sub frame level on jack stands? I'm assuming this but wanted to see how others are doing it. Thanks

 

I used an electronic level that allows you to "zero" the device against whatever reference you like. So, it doesn't matter if the vehicle is perfectly level or not, close to level is good enough. Just be sure suspension is at right height.

If you want to measure the angle the engine/tranny sits at, zero the device on a frame rail or rocker panel. If you want to measure a U-joint angle, zero the device on the driveshaft. You just need to be certain that you have surfaces that are truly parallel output shaft of the tranny and the rearend pinion for using as proxies. Don't assume that yokes that hold U-joints have machined surfaces that are parallel to the caps. I found on my car as much as .7 of a degree difference between the yoke machined surface and the shaft it was supposed to be parallel to. Had to clean those up before I could get accurate measurements.

 

I would direct you to the Tremec site for good information on setting up your drive line angle. Also download the App.

http://www.tremec.com/anexos/File/TR...structions.pdf

How you have your subframe or frame can be misleading you on what you think your drive line angle will be. You car/frame needs to be sitting at ride height (can be on stands or a lift, but the rear wheel needs to be sitting at the right height as it would be sitting on the ground and weighted).

Hope this helps and gets you going.

BC

 

That app works very well. It shows green/red if it's good or bad.

 

Thanks for the tip on that Tremec app. Very handy

 

Maybe a stupid question.....

I downloaded the APP, and read the instructions, and watched the Youtube video.
Unfortunately I don't know what a 68-72 A-body (Olds Cutlass) driveline angle
should be at the end of the transmission, so I can determine if I'm too high or low. This has no driveshaft in it yet.

The Tremec video didn't really tell me what I needed to know as for what the measurement should be there. BRP rep told me that the Chevelle's had a 5 degree angle at the output shaft of the trans. I don't know if that's true or not, so trying to figure this out so I can finalize my LS install

 

If you search around a bit -- there are some general rules of thumb. 1) You want the engine/tranny angle and pinion angle to be equal and opposite -- so if the engine tranny is 3 degrees down (tranny lower than engine) then you want the rear end (pinion) to be 3 degrees up. This will result in the front and rear u-joint angles being equal and opposite. 2) Different size ujoints will tolerate different angles, also rpm dependent - more angle at lower rpm, less angle at higher rpm. Most folks shoot for U-joint angles of less than 2 degrees - equal and opposite. 3) All of that for a coil sprung rear end with control arms --- leaf spring set up is different because of the way the pinion angle changes under accel/deceleration. 4) With a swap, you often need some way of being able to adjust the pinion angle -- adjustable upper arms are what I used on mine. When I alter the length of the upper control up it moves the pinion -- longer arm = pinion up; shorter arm = pinion down. 5) Most folks shoot for engine/tranny at 3 degrees down --- but not all swappers can achieve this due to fitment issues. 6) If angles get extreme, often a CV joint on one end of the driveshaft can solve the problem - a bit pricey, but for some swaps there's no other way. 7) Often, engine/tranny angle can be adjusted with washers, shims and spacers placed at the motor mounts and the tranny mount to raise/lower one end or the other.

Without a driveshaft, you can only tend to measuring engine/tranny angle -- and trying to get it and the pinion set up equal and opposite. Can't measure ujoint angles until you get your driveshaft in, although if you get the engine/tranny/pinion set up equal and opposite and take some careful measurements from the floor to the center of the tranny output shaft and the center of the pinion - you can do some elementary triangle geometry and get a rough approximation of the ujoint angle.

 

Thanks for all the info

 

Here is what I posted on the Chevelles forum related to this questions:

"The angle of the car is irrelevant. What your looking for is the angle of the transmission output shaft relative to the driveshaft (front operating angle) and the angle of the pinion gear, also relative to the driveshaft (rear operating angle). In a static environment vibration free operation is achieved when the front and rear operating angles are equal, opposite, and as small as possible (definitely smaller than 3 degrees), without being zero.

In a dynamic environment, such as when a car is under power and the pinion rises, some compensation needs to be built into the rear operating angle to accommodate the movement. So some experimenting may be needed.

If the car is significantly lower than stock in the rear (front ride height makes zero difference in driveline angles) then it may be impossible to achieve smooth operation. The reason being is that when the car is lowered in the rear, the rear end is effectively sitting higher in the chassis. Eventually, the front operating angle forms a shallow V, which is not optimal. The stock configuration of the front operating angle is that of a shallow inverted V. No amount of fiddling with adjustable upper rear control arms will solve this problem. You'll be able to get the operating angles to be equal and opposite, but not below 3 degrees.

For instance, my 70 GTO front operating angle is 6 degrees because of the lowered rear ride height. I solved this issue by using a CV driveshaft (from The Driveshaft Shop), as many others have as well..

Please let us know what you come up with for measurements."

Andrew

 

Thanks for the input gents.

 

One other thing I'd add -- be careful with apps that use the level-finding ability of a smart phone. They're only as good as the data that gets input into them. I found it damn near impossible to get a repeatable/consistent angle reading on the driveshaft because of it's curve -- you don't have to be much off of perfectly parallel AND tangential to vary the angle reading by a significant amount relative to the size of the angles you're trying to measure. Even more important (at least to me) is that I could rarely figure out exactly what algorithms they were using to give me a "green" light - which means I didn't know if I was truly ok or just "lucky" with my measurements. I found results I thought were more reliable AND learned a lot more about what is actually going on geometrically by using a carpenter's electronic angle finder. And I made a fitting that's attached by magnets to the driveshaft that allowed me to get a correct and repeatable angle on the driveshaft every time I measured.