working on mt t want it low. Have center of pinon at 14" on center section. trans (350 turbo) at 10 inches so i need to raise my drive line up good 4 1/2, correct?
Huh? Pinion angle should be equal & opposite of drive line angle ,working angles of u-joints should be within 1-3° .
However if the angles are correct the driveline doesn’t care that it’s angled down towards the transmission. @gimpyshotrods, you called it!
I think he is measuring from the garage floor up to the pinion? If I am correct, the 4 1/2 inches sounds like it would get you close but it is not an accurate method or a correct one for that matter. I downloaded an app on my smart phone that digitally measures the face angle of the pinion and transmission. It is very accurate. Tremec also has a good app for checking pinion angels. The two angles need to be identical and opposite. ie: pinon up 3 degrees, transmission tail shaft down 3 degrees but you likely already know that. The rest can be found doing a search as this question comes up every month or so it seems.
at ride height your two u joints should be at the same but opposite angles as in "theoretically" with the car on the suspension if the front u joint angle was downhill 12 deg ( just a random number) then you would want your rear u joint angle to be 12 deg uphill , then the vibrations from the swiveling ujoints will cancel each other out and no vibration , on a leaf spring car i like to add a few extra degrees downhill to the rear pinion angle if ya plan on beating on it to have em line up better when the pinion lifts .. fabricator john miss you dad
As they said up/down doesn't matter as long as the output shaft and pinion shaft are parallell. Back in the 60's and 70's the ricky racer brigade had the misguided idea that the pinion had to angle down at X degrees to compensate for spring wrap at launch and acceleration and they where the ones who were always breaking U joints on the starting line.
In the top photo the needles in the bearing caps will not move and will develop flat spots on them. Second photo is the way to go.
A cheap $8 angle finder from Harbor Fright is a very useful tool for this, and many other things on a car build!
For you "equal but opposite angle" folks, think again. There is another configuration that works to cancel out the vibration caused by the ellipse formed when a U-Joint is rotated.
If you have a smartphone Tremech has a great app to insure you have proper angles. https://www.tremec.com/menu/tremec-toolbox-app/
The "W" setup does work however, it only works well when the angles are fixed. I've seen it on long wheel base trucks with multiple drivelines. It doesn't work well when one of the components moves up and down or tilts like a single drive shaft hot rod.
That is only true if you have a fixed-mount differential, such as with independent rear suspension. If you have live axle, suspension movement will be more than enough to move the needles, and circulate the grease.
The Jalopy Journal
