lowering springs and DL angle?

[BALLSS]

is the DL angle between tranny & rear end changed when installing "lowering" springs?

considering the Hotchkis springs if that makes a dif.

[RJI]

Yes it will change the DL angle, but and I think most will agree not enough to be a factor. I noticed very little change when I went from Caprice springs to SS springs. I did notice a big difference when I went to extended trailing arms.

It's easy to check with an inexpensive digital gauge so you may want to check it and be sure you are within limits.

http://www.1finecaprice.com/chassisandsuspension.htm

[1slow96]

You may be thinking about pinion angle,which does not change. Unless one changes the effective length of the upper trailing arms,typically.

[BALLSS]

thanks guys

by "DL angle" I mean both pinon and front yoke/tranny angle

yes I know 'extended" trailing arms effect DL angle due to moving rear end back. Was not sure if changeing height (lower springs) also effected either pinon or front yoke/tranny.

RJ. I did measure back when I did the T56 swap and had to add shims under T56. Will measure once I get the car up (with suspension loaded) before I pull the old springs and then after new ones are in to see if it is the same.

My concern is I don't have any more room to raise the tranny should I need to due to the lower springs.

[1slow96]

We seem to be talking about very different things. Pinion angle is strictly about the relationship between the upper,and lower trailing arms. Moving the rear end up,or down,or even straight back does not change the pinion angle. What I think you're referring to are the comparative angles of the front,and rear universal joints. They should be the same (within a degree) to be what is referred to as "in phase" Is this what you mean?

[Mr pogo]

changing the height might cause issues if you were at the vibration borderline previously.
magnetic angle finders are cheap at harbor freight, sears etc and there are plenty of threads on the procedure so Im not going add to that.

as far as being in phase, that refers to the relationship of the front and rear yoke to each other.
stock b-bodies use a one piece driveshaft with no slip joint so being out of phase is not possible.

[1slow96]

Perhaps I used improper terms myself. What is the term that compares the angle of the front u-joint,to the angle of the rear u-joint?

[Fred Kiehl]

The U-joints are there to allow for misalignment between the output shaft of the transmission, and the input of the differential. they are not affected by the pinion angle or the transmission angle. For example, look at a jacked up 4WD truck with the extreme angles for the driveshafts. The universals allow them to have up to 20-30 degree angles exiting the transmissions and/or transfer case and entering the differentials.

The main concern is the amount of movement in the universals themselves. The more they move, the more wear on the bearings in the universal. With the minor amount of misalignment you will encounter in lowering a B-body, the lifetime of the universals will not be adversly affected. The lowered position is still within the allowable suspension travel that the car was designed to have. The optimum position is to have no misalignment, but every time you change the weight, or go over a bump, the angle changes. Even front wheel drive cars have the same situation with the individual front wheels.

The reason for having 2 universals is to neutralize intermediate shaft acceleration and deceleration. If you only had one universal, the output shaft would transmit a sinosoidal output to the differential, varying in amplitude with the angle of displacement. This would put undue strain on the gears, and universals. (old VW beetles and Corvairs ignored this issue in the axles, and allowed the tires to absorb the strain).

The transmission is in a fixed position, and the axle can move up and down in an arc that is determined by the control arms. Any time the suspension moves, the axle to transmission distance varies slightly. The output shaft of the transmission has a splined shaft, which allows the drive shaft to slip slightly to adjust for the minor distance changes between the transmission, and the differential.

You should not worry a lot about the angles when lowering the car. It will not make a noticable difference in either the performance or life expectancy of the parts.

[Mr pogo]

most peeps call it pinion or driveline angle for short.
the thing is that the pinion angle changes as the axle moves up and down thru its suspension travel.
the upper and lower control arms are different lengths and travel in different arcs from each other causing pinion angle to change.
during normal suspension travel this minute change happens only momentarily but when you lower the car, it becomes permanent and vibrations can be noticed due to the angle change of the pinion.
Eaton makes a few driveline analyzing hardware tools including an computer driveshaft analyzer you punch in all the angles and u-joints in and it tells you what angles need to change. I used it when I worked at Freightliner, mainly needed for multi-driveshaft setups.


actually while in a perfect world no driveline angle would be perfect, in RL you want some angle so as to prevent wear on the u-joints.
zero angle will lead to needle bearing wear and indentation in the crosshafts and the u-joint eventually seizing from lack of lubrication being circulated.
a degree or two allows the torque load to be spread among several more needle bearings as the driveshaft turns and grease inside is circulated.
whenever I drop the driveline on my car I spin the rear u-joint caps and move the u-joints thru their travel to spread the grease, I use sealed u-joints without grease zerks because they are stronger than greasable joints.

basically as far as a one piece driveshaft, you want the drivetrain and pinion centerlines to be parallel to each other without pointing at each other.

[94MI9C1]

A Caprice or an Impala output from the trans and rearend pinion are not parallel from the factory, they are close, but not that close. I think that FSM states a front working angle (comparison of driveshaft angle and output shaft angle) to be 1.3 degrees and the rear working angle to be 2.5 degrees or something along those lines. The optimum differences for these working angles (subtracting the two) should be 1.0 degrees or less for a highspeed one piece driveshaft.

Pinion angle will change with the motion of rearend unless the geometry of the upper and lower control arms is perfect, which our cars are not, there is going to be slight degree changes. At least this is what I have seen. They are very very minor, but they do change.