IRS set up

[JMortensen]

It's the angles that matter, not whether it's downhill or uphill. There have been some very clever people who have figured the angles using laser pointers. Search "pinion laser pointer" and I'm sure you'll come up with threads by Pop N Wood and bjhines among others who document what to do and how to do it.

 

John-You're a fountain of knowledge. Note to self: don't trust memory. 29 lbs... that's a lot of weight.

[240RR]

It's the angles that matter, not whether it's downhill or uphill. There have been some very clever people who have figured the angles using laser pointers. Search "pinion laser pointer" and I'm sure you'll come up with threads by Pop N Wood and bjhines among others who document what to do and how to do it.

 

John-You're a fountain of knowledge. Note to self: don't trust memory. 29 lbs... that's a lot of weight.

 

awesome...thanks, that is what I needed to hear! I have a digital protractor that I have been using.

[Trevor]

MY QUESTION IS HOW IMPORTANT IS THE ANGLE OF THE DRIVESHAFT GOING TO BE?

 

Operating angles in a driveshaft are the angles between the pinion, driveshaft and transmission centerlines. The optimal angle for any driveshaft to run at is 0 degrees, where many vibrational and frictional problems are non-existent. In order to minimize power loss and vibration in an offset configuration, the pinion centerline and the transmission centerline need to be parallel. In general, the largest angle for racing applications should 2 degrees and the centerlines should be parallel within 1/2 degree. With suspension movement the operating angle will increase, but should not exceed 15 degrees. If the centerlines are off too far, the u-joints travel at uneven operating velocities, causing vibration (this is the same problem induced by poorly phased end yokes). This vibration is hard to distinguish from an unbalanced driveshaft.

 

 

http://www.markwilliams.com/driveshafttech.aspx

Edited July 13, 2011 by Trevor

[240RR]

 

http://www.markwilliams.com/driveshafttech.aspx

 

thanks....that is good info!

 

So...let me see if I understand.

 

1) Driveshaft angle is at the top of the list and I need to get that right first and foremost.

2) Lower the diff to obtain the proper driveshaft angle

3) Halfshafts are gonna be OK running downhill to the diff as long as I do not go over 10 degrees and make sure shafts are not binding in bump and rebound?

[JMortensen]

I think you want to move the diff down to lower the CG. You can get the driveshaft angles worked out with the diff at the stock height.

Edited July 13, 2011 by JMortensen

[240RR]

I think you want to move the diff down to lower the CG. You can get the driveshaft angles worked out with the diff at the stock height.

 

With the diff at the stock height the halfshafts run at a proper angle but the driveshaft runs uphill to the diff...I think that is a big no no?

 

Forgive my denseness...just so important and do not want to do it over again.

 

So I should lower diff to get the driveshaft angles in check and the halfshafts will run downhill to the diff probably 4 degrees or so....and lower diff equalls lower CG

Edited July 14, 2011 by 240RR

[240RR]

The CV halfshaft angles are not important as long as they are kept in a reasonable range (<10 degrees). If it were me then I would lower the differential as far as possible with respect to ground clearance. I just lowered the mounting of my differential by one inch relative to the body for three reasons:

 

First, I wanted to minimize my drive shaft angle. The driveshaft was running uphill from the transmission to the pinion, but now it is level in the horizontal plane.

 

Second, I wanted the halfshafts to be at their minimum length at full droop. The reason for this is that I use 300ZX turbo halfshafts with the Modern Motorsports adapters. These axles were close bottoming during suspension motion when the axles were straight. By lowering the differential, the axles are always angled up toward the wheels even at full droop. I only have 2 inches of droop travel in my suspension.

 

Third, the R200 is heavy (and the R230 is really heavy) and should be mounted as low as possible to keep the CG as low as possible.

 

 

I somehow missed this post...or at least did not read it all. This totally makes sense to keep the halfshafts still running up to the wheel at full droop as that was one of my concerns that in travel it should not run through a 0 degree zone...THANKS!!