rear end angle - what am I doing wrong?

Built 4 cars in the last 10 years and everyone of them goes wur,wur, wur with a rear end or drive shaft vibration at 60 to 65 mph. I've read every artical I can find & talked to Inline Emp.
OK, here's how I set them up. First - Level the frame, with the front tires on ramps & the rear end on jack stands till the frame rails are level. Second - set the trans at 2.5 to 3 degrees down, Third - set the rear pinion at 2.5 to 3 degrees up. So simple, what am I missing?

 

Are your U joints in phase?

 

Yea I'd check to make sure the u joints are in phase had the same problem on a big rig one time till a buddy clued me in on it


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I've never had this problem myself, never worried about the angles, it always seems to have worked it self out for me. Thrust angle? subscribed....

 

I would let it sit on wheels at the height you want.Then level carb or trans oil pan,then set you rear end.

 

I agree with George. I set my engine first, leveling the intake manifold. Then set the rear end pinion to match the transmission tail shaft angle.

 

What are the U-joint working angles? They should be 1-2 degrees, not to exceed 3 for single cardon joints.

 

Get the desired trim height of the vehicle first then level the intake carb pad (to achieve proper fuel calibration). Take rear angles off this setup. Remember, rear axle angle changes as the suspension expands compresses.

http://www.clubfte.com/users/jniolon/drivelinephasing/drivelinephasing.html

 

And not to be zero degrees, they need some angle to lubricate.

 

I know this is not the same but when we did our circle track cars we were putting 9" fords under Monte Carlo's and always simulated the weight of the fuel in the vechicle by adding steel weights where the fuel cell was..at 8 pounds a gallon it will change the ride height and angel...just my 2 cents

 

What makes you think it is the driveshaft angle making the noise?
The driveshaft angles are the angle at the 'u' jont, has nothing to do whether the car is level or not. It is the anglar difference between the pinion yoke and the driveshaft etc - the car can be sitting flat or at a 45deg incline, it won't affect the pinion angle.
As far as the pinion goes, you do not want it pointing up..i don't care what inland driveshaft or anybody else says or how many technical papers and diagrams there are, what the engineers consider 'correct' may be entirely different than what we need. The pinion needs to point down just slightly so that under power it'll come back to level, when the driveshaft is spinning it wants to spin straight, level and true. Often, in a hot rod the engine is lower than the rear end and likely sitting close to or at level. In a factory car the engine is higher than the rear and angled rearward so factory reccommended pinion angles do not apply.
A few other things come to mind, do you hear the same noise under power, at cruise or at coast? If the noise varies then it might be a gear lash thing going on.
Did you weld or have somebody weld bracketry to these housings? If so, maybe the rear tires are toed in slightly.

 

we went around and around and around on my driveline vibration. turns out it WAS an out-of-phase (low-speed vibration) and unbalanced driveshaft (high-speed vibes). got a new shaft made. IT STILL VIBRATED but now only at high speed. had the shaft rebalanced many times. i tried attaching pennies at different spots. it got better but not great. it didn't go away until driveshaft specialists made me a nice, aluminum shaft. my driveline angles were not the problem. i will say though that i learned a hell of a lot in the process.

 

"As far as the pinion goes, you do not want it pointing up..i don't care what inland driveshaft or anybody else says or how many technical papers and diagrams there are, what the engineers consider 'correct' may be entirely different than what we need. The pinion needs to point down just slightly so that under power it'll come back to level, when the driveshaft is spinning it wants to spin straight, level and true. Often, in a hot rod the engine is lower than the rear end and likely sitting close to or at level. In a factory car the engine is higher than the rear and angled rearward so factory reccommended pinion angles do not apply."

Wow, I disagree with that hole paragraph, especially the "down" part......................
I should have said I disagree about this info on a daily driver.
OJ is race oriented and that info whould be great on the track!

 

I have heard that noise before,,,,,,,,, It turned out to be the way the rear gears were setup, Goes back to a previous post,,, backlash and pinion depth reset and the noise went away.

 

I have always had my drive shafts pointed straight at the pinion.In a desription easy to understand,crankshaft in a straight line with pinion.Never had a problem with u joint wear or vibration.If you want go look under any rear wheel drive factory late model and you will not see any "u joint angle".They have the crank pointed straight at the pinion.U joints are for bumps in the road and when the car leans in a turn.Why would you want the u joints working every revolution,when you dont have to?

 

So what you guys are saying is that I should set the engines carb intake base at level with the car sitting at ride height & not put the frame level to the ground first & than set the drive line up.. OK that should make the tail shaft of the trans at 2 to 3 degrees. Now the rear, some say up some say down.? Guess part of my problem is that I worked off my frame being level & not at ride height.

 

Agree, mine is set up for down a degree or two. No issues.

 

Hope this helps.

 

I don't know about factory cars but a lot of Hot Rods, because of appearance, center the pumkin in frame which in turn offsets pinion to one side or the other and is in itself another pinion angle. So maybe you can look under a factory car and think the motor/trans/rear pinion are in line "up & down" the rear might be offset making a side angle for the U-Joint..............

 

Yes, the carb needs to sit at or near level (not as critical for EFI motors), but think this step thru befor making your motor mounts as most all dual plane intakes have an angle built into them. If you use that intake to set the motor up and then switch to high rise (single or dual) those intakes do not have the angle machined into them. Just giving you a 'headsup' befor committing yourself to a particular intake design.
As far as getting the frame level to the ground, in real life it never is level to the ground is it? Having the frame level during construction is kinda handy for measuring and double checking purposes and to be honest with you, having it level and plumb bobs and centerline strings and lasers hanging from it do more for the observer than the experienced builder. For some reason people see shit like taht and they think you know what your're doing...i'll put my money on the guy that doesn't need a plumb bob!

 

Ditto..and That Guy With The Coupe is correct in the zero angle, not only will it not lube but it will flatten the bearings very soon to give that clunk we all hate to hear

 

I agree. That is meant for a competition vehicle where you are concerned about axle wrap-up on a hard launch, not everyday driving.

 

Readers- Please take this post with a grain of salt.

 

From ur post ur doing it backwards, tranny goes up 2-3 degrees and pinion goes down 2-3 degrees from drive shaft angle. I see where ur noise comes from

 

Pinion angle is figured off final crankshaft CL amount. It all depends upon the vehicle as to what crank CL you are going to finalize with (considering carb pad level). You then adjust proper pinion angle to the crank CL.

The theory is available in endless tech reports.

 

You guys dont get it. If the front joint is at 2 or 3 degrees angle up, the pinion angle must be 2 or 3 degrees down. or just the oposit if the angle is changed. The vibration caused by the front joint is cancelled by the angle of the rear. Any high speed shaft must be set up this way or the result is a vibration. Of course the lower the angle the better. The reason joints burn up with excessive angle is= the needles are forced to rotate to fast and cause a lot of friction and will burn out the grease! Any one with a lifted truck knows this if the DL angles are excessive you are putting joints in a couple times a year. So the man that said "you need angle for the joint to lubrcate" is incorrect.

 

Here is a very simple tutorial-

http://www.carcraft.com/howto/91758/index.html

 

woohooo free for all!!!!


seems everyone has an opinion on pinions.

heres how I do it, take it or leave it.

set angle finder against something (anything) that runs parallel or 90 degrees from the crank, (balancer, tailshaft, pan rails, sparkplugs, whatever is handy) write that number down.

set rear end 2-3 degrees down from whatever that number is at ride hieght. Yes, sometimes the pinion points up.

Pinion angle is set of crankshaft centerline and nothing else. frame doesnt have to be level, no plumb bob, levels, lasers or flux capacitors needed.

call me an idiot, marroon, whatever, your not changing my mind on how its done, built many many many MANY cars/trucks this way and NEVER had ujoint issues or strange thrumming vibs.

 

...no flux capacitors... ? ...really... ?

DAMN SNAP-ON MAN!...

 

Not that this post will do any good, but, the transmission output shaft and the pinion shaft must be parallel. The ideal angle is usually 3 degrees down and 3 degrees up with respect to level. This angle was chosen so that the fuel bowl in the carburetor sets level. The suspension is free to move up and down and both universal joint angles change the same and maintain equal but opposite angles.

You may get by with unequal u-joint angles in a rock crawler or drag car for a while, but you will soon destroy the u-joints in a street car. You can only get by running unequal angles by using a constant velocity joint which is basically the same as a pair of u-joints with identical angles.

From what you described, there is surely nothing wrong with your driveshaft angles if they are equal and opposite, the noise is caused by another problem...