It's not what ya think, my garage floor has a 3 degree negative pitch to it. So my trans is at 6 degrees negative( -3 for floor & -3 for trans). Now my pinion should read at 0 degrees correct ? That would put the positive 3 cancelling out the negative 3 of the floor, shouldn't it ?
Man, I had to break out a pen and paper. I (finally) agree that you have neg 3 deg crank angle and pos 3 deg pinion angle. Your U-joints should be happy there. I would rather have the planes parallel myself, but as long as they are equal that is most important.
Ouch, math like this hurts my brain. First level the frame. The car can be setting on any incline and surface you can park the vehicle on. Start with a leveled frame, then measure for the trans. and pinion angle. It should be at 2 to 3 degrees nose up at pinion and trans output downward. No more angle that 5 degrees I am told.
If the transmission is down 3 degrees, the pinion should be up 3 is its a single piece driveshaft. If its a 2-piece there is some more math involved.
Exactly. The invisible lines of the pinion and crank centerline should not converge, but be parallel. The angles need to be equal or the u-joints will try to rotate at different speeds causing vibration.
It also depends on what kind of rear suspension you have (leaf springs, ladder bars, 4 link) how much horsepower/torque, drag set up, cruiser, roadrace, type of car/ weight / slicks or bias ply skinnys, etc. etc. Wil www.sakowskimotors.com
Heres a visual also. And as Sakowski said, the suspension type will play a roll in it too. Leaf springs wrap under a load and that needs to be taken into consideration. Whereas a 4-link has very minimal wrap.
If this is a drag only car I would set it up in a loaded position. (compensating for spring wrap) If not, i would measure the angles in the posion they rest at while at cruising speed. This is where the vibration issue will drive you insane. Twisted Minis...nice visual aid.
That is what I'm talking about, the crazy negative 3 pitch of the floor. There is no way to level the frame as the truck has a tire rake to it, this is not a bare frame type deal, fully put together truck that I'm putting new paralell leaf spring brackets on the housing. I know the angles need to be opposite and if wanted a slight negative pinion angle for the perfect alignment under acelleration. My sticking point is the pitched floor, should the rear be at positive 6, to match the negative 6 of the trans, or the zero I thought of before ?
You can still level the vehicle. You have jack stands? Put some under the rear axle, and some under the front of the frame. This way the rear axle is still loaded with weight and you can get an accurate rearing. Click the jack stands until the vehicle is nearly level, then shim it the rest of the way to make it level with the world. Then there will be no guessing on the matter.
I put it in at the opposite of the trans angle, positive 6, that way both are parallel to each other. When you take out the floor factor they are both at 3.
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