091 TRANSMISSION AND CV ANGLE.

[Nacho_Blanco]

What is the recommended alignment and or alignment limit for a 091 transmission with 3x3 trailing arms and 930 CV's? I was told that the transmission CV should align within 1 1/2" of the trailing arm CV. Is this correct? Should this be measured at ride height, full bump or full droop? I attached a quick sketch. "A" shows perfect alignment, "B" shows the transmission mounted behind the trailing arm CV and "C" shows the transmission mounted forward of the CV.
Which is correct and why?

Thanks

[FABRICATOR]

"Which is correct and why?" Is this a test?
“A” is OK for short travel and running around with low CV angle (Road racing). Must watch axle plunge.
“B” is good for nothing, super axle plunge, minimum travel.
“C” is the correct setup for long travel and can provide the most travel. Plunge can be nearly zeroed out.

[Billy_the_Kid]

Remember, you have to consider the angles working in two planes. Since the arms are swinging in an arc and gaining wheelbase as they compress... In that plane as you have it drawn (vertical view) I would want to set it up to be like your "B" drawing in full droop, and end up at the "A" drawing when at full bump.
Reason being full bump will most likely also be the point at which you have the most amount of traction and therefore would want the least amount of power robbing angular offset. Who cares about angular offset at full droop since you are traction limited at that point anyway.
Also, from a rear elevation view you would want to try and split that angle from full droop to full bump. Again, if you have to max out any angle, I would rather do it at full droop versus full bump.

Just my .02

[Nacho_Blanco]

No, this is not a test, I am trying to understand the geometry invloved in setting up an IRS. I am building a manx with a tube frame. (someone else started the project) The guy I bought it off of was very knowledgable, but I wanted to make sure that the trans was in the best possible position before I finished the mounting tabs and cage. I like the idea of keeping the maxed out angle (if present) at full droop, makes sense. Great info, thanks.

[1992f150]

another thing is, with B your transmission and motor are hanging further back off the chassis (weight distribution)

[powerbox_builder]

"A" is the one to keep in mind. That's how it should look at full drop. As your suspension compresses they will go towards "C". On a 3x3 car you will only wind up with about 1"-1.5" of trail when the CVs are strait across from each other. (0 down angle)