Drive line angles

[RamblerRob]

Ok folks I've twisted my brain into a bit of a knot trying to sort out my driveline angles as I go about figuring out the engine mounts.

I'm trying to figure out what angles are relevant, where the best places to take measurements from are and what effect things, such as the slope of the garage floor (1/8 to 1/4 inch per foot) or the weight of engine etc on the ride height and therefore angles, might have.

Currently I'm using ratchet straps to compress the springs to bring the tide height to where it was with engine weight on the chassis however I'm not sure how much more weight will be added nor how much effect that will have.

I'm taking my angle measurements vertically off the rear pinion flange and the drum of the parking brake on the lt230.

The best I can do while being able to close the hood is about 2 degrees difference between the two angles

 

[chris snell]

The angle of the garage floor is irrelevant, since you're really only concerned about the relative angles of the pinion flange and t-case outputs. Ideally, the angles should match but they never do. The difference in the flange and pinion angles dictates what kind of driveshaft you want and what other corrections you will want to do.

In general, anything over a 2" lift necessitates a dual-cardan front driveshaft to avoid vibrations. I don't have exact angle difference figure for you so you'll just want to drive it. You'll often notice vibrations when you let off the gas at highway speeds but you may get harmonic vibratons at certain speeds as well.

Proper driveline angle (Tom Wood's Driveshaft):

Another concern is steering angle. You'll know if you have a problem here when you drive it at speed. You have a few options to correct this. You can install "cranked" radius arms to rotate the front axle back towards factory position. If you're happy with the pinion angle but not with the steering angles, you can also buy drilled swivel balls to rotate just the swivel housing back. With more extreme lifts, you may want both corrections.

Finally, when you lift the truck, the panhard arm will force the front axle to one side, messing up the vehicles tracking and sometimes forcing a radius arm to rub against the side of the frame. This can be corrected with an adjustable panhard arm.

 

[RamblerRob]

That was my thought about the level of the ground as well but wanted to confirm.
I'm actually not lifting it from where it was. None of this is stock though. It's a series rig on a range Rover classic chassis with stock defender springs (as best I can tell)

My immediate concern is getting my engine mounts in such a place as not to f@#k anything up down the road.

Ill need to either modify my current drive shafts or get custom ones as my lengths are different. The downside of that is I won't be able to drive it to test for vibration before I set to getting new shafts

 

[RamblerRob]

So I guess my best bet is to let the hood clearance determine the mounting height of the engine for now and worry about drive line implications later.

 

[javelinadave]

What motor?

 

[RamblerRob]

Chev 4.3 v6

 

[ezzzzzzz]

It depends on whether you're going u-joint or double cardon. U-joint will require the equal opposing angles (transfercase output yoke/ differential yoke). If not, the u-joints will oscillate out of speed and destruct over a short period plus cause vibration issues while driving. Double cardon requires the differential pinion pointing directly at the output yoke of the transfercase. I don't recall specifically but if using a u-joint I'd try to keep the u-joint angle <3 degrees, but not 0, as it requires some oscillation to provide good lubrication. So, focus on the rear diff pinion angle because it's easiest to leave it where it is. Fisrt, determine engine height in the bay so the hood while close. If using a u-jointed driveshaft tilt the engine to match the rear pinion angle at an opposing angle (example: 2 degrees up at rear then 2 degrees down at transfercase as seen in the drawing shown earlier). If using a double cardon then focus tilting the engine to point the rear pinion directly at the trasfercase output yoke and keep the total misalignment <5 degrees. When you've got the engine tilted to accommodate this then you're ready to weld in the engine mounts. Don't worry about fluctuations while driving or offroading as you can't account for those variations. You could install the transfercase mounting brackets and tilt the engine up or down to meet the required driveshaft angles then weld in the motor mounts. I've welded in engine mounts to accommodate height for hood clearance then raised or lowered the transfercase to set driveshaft angles and welded in those mounts too. Don't overthink it. It's simple limits of angle operation for a u-joint or double-cardon ensuring long life.

 

[RamblerRob]

The problem being that there is little to no room to lower the transfer case or raise the engine in order to achieve the steeper angle that I need. I can get a little bit extra height if I can find an air intake that is lower profile.

Also I won't really know the angle of the rear pinion until all the weight is on the front springs

 

[ezzzzzzz]

Run a double-cardon to work with harsher angles. The rear pinion angle isn't going to shift enough, with or without the engine weight, to be of major concern as the whole truck will rotate downward at the front on the centerline of the rear axle.

The driveshaft angles are constantly changing when driving so don't get fixated on that alone. The 2 degree difference you mentioned in the first post is more than adequate for either u-joint or double cardon.

I'm assuming you're putting this into your 109? I did this in a '71 88" but had to convert to a Defender hood and rad support to gain room for a radiator. While a radiator clearance issue may remain for you the extra length of the rear driveshaft is a blessing.

Are you running a carb'd, throttle bodied or vortec V6?

 

[RamblerRob]

Yes it's in the 109. Radiator clearance is ok the way I have it mocked up currently. It's a 2006 mpfi version. I did find some lower profile air intakes but they were for engines with 5" or so necks. Mine is only 3.5" or so.

 

[ezzzzzzz]

It appears you've got a deluxe dished hood for the spare. You may have to go to a flat one to gain intake clearance.

 

[RamblerRob]

I was really hoping to keep a stock look, but that wouldnt be the end of the world. Do you know how much height that gains?

 

[ezzzzzzz]

I'd have ride out to a buddy's house to measure. I'm guessing about an inch. That isn't much except on maps or in the bedroom but it could be what gets you over the potential clearance problem.