Pinion Angle ?'s on an EM

[rbray]

Here is my setup:
EM with a four link / panhard rod ford 8.8.
Tremec 3550.

The angle of my drive shaft takes a downward slope to the transmission. Is this the correct setup? I'm concerned that with this initial angle I will run into problems when going over bumps.
In fact I do hear a cluck and get some feed back in the shifter handle when I go over bumps.

Any advice is appreciated,
Roger

[blykins]

Roger, I've been told that a Cobra with such a short driveshaft needs a little negative pinion angle like you're talking about to get a good stir of the driveshaft u-joints. Shouldn't cause any problems.

[392cobra]

Roger,
Maybe I am reading your post wrong judging from blykins reply.

Going front the front to the back of your Cobra;the trans angle is down and the driveshaft is up ? If so I would suspect your pinion then goes down ?

If so you are running positive which is not good.
I would head down to Sears and get a magnetic protractor,about $10.

What I now have is:

front u-joint operating angle - 1 degree

rear " " " - 1 degree

pinion angle neg. 1 degree



engine slopes down 1.5 degrees

driveshaft slopes down 2.5 degrees

pinion shaft slopes up 1.5 degrees (equal but opposite and parallel)

[rbray]

thanks for the replies.
I think I did a poor job of describing my situation so I will take another crack at it.
Starting from the front of the car and going back:
My transmission has a slight down slope.
the drive shaft points upward to the differential.

Here is what I am confused about:
The differential input is higher that the transmission output, which is what causes the drive shaft to have to slope up to reach it. Do I need to have the differential point down towards the transmission ( I can do this if necessary by adjusting the control arms ).

Thanks again for your help and sorry for any confusion.

[Tom Wells]

Hi Roger,

I think I see what you're saying

The important thing is this: the centerlines of the trans output shaft and the pinion gear should be parallel.

They don't need to meet or cross.

This is OK:

___ --------

Note that the first line (representing the pinion) is lower than the second (representing the trans output), but that they are parallel.

This would not be OK:

____ /

In this case the trans is pointing downward (way too much but can't find a gentle slope on the keyboard ) The opposite (pinion pointing down with trans horizontal) is also not recommended.

There's a little tolerance to this; the angles can deviate by a degree or so without hurting anything. If you have a live axle they'll change a little with load and car height anyway.

They don't need to be horizontal, either. If they each slope the same way and are parallel, it's fine (rotate your head in front of the screen if you don't believe me ). They can each slope up & to the right, for example, as long as they are still parallel.

You can measure these two angles with a protractor although you may have to be a little clever about how you do it. Like using vertical readings from the u-joint flanges instead of trying to find the horizontals

Have I added to the confusion?

Tom

[blykins]

In my Shell Valley manual, it says that the rear suspension kit comes with negative pinion angle built in....therefore the pinion yoke is pointing towards the floor (not literally but for reference)....the tranny has a little tilt in it also....pointing to the floor. They said this was optimal....and would help the ujoints stir.

[Bruce Edwards]

Roger,

Most production cars run about 3 degrees down angle. The idea is the when you step on it the pinion will rise to about level as the axle winds up. If it is straight to start with or pointed up when you go to start off and the axle starts it wind up the drive shaft angle can cause a bind in the driveshaft to rear yoke.
How much free space do you have on your slip yoke? If it is to far in it will bottom out on the output shaft.

[392cobra]

Rodger,
Below is some write ups on this often confusing subject.

http://www.drivetrain.com/driveline_angle_problem.html

http://www.go-fast.org/z28/pinionangle.html

[rbray]

Thanks for all the information.
I think I know what I need to do now.