Driveline Angle

[JMD]

I know this has been talked to death, but I wanted to double check my findings.

I have a Blueprint 302 block with FFR supplied Energy poly engine and tranny mounts with the TKX and IRS. I initially used three 1/4" shims supplied by Forte on top of the transmission mount to lift the tail but had a noticeable vibration. I added two thick hardened washers on each side, raising it another 5/16" (total of 1 1/16") and the vibration was better, but still noticeable and increasing with speed. My driveshaft went from 2.5 degree up angle to 2.3 degree down angle with this adjustment. I removed one of the washers (now at a hair over 0.9" total shim) and it is a lot better. I'm not sure it's completely gone, but much better. I'm not quite sure what 'normal' vibrations for this car are yet.

My down angle on the engine is 2.6 degrees, my driveshaft is at 0 degrees, and my diff has a down angle of 0.3 degrees (all in relation to the frame). Total angle of diff in relation to driveshaft is 2.3 degrees but I think that's as good as I can get it without changing motor mounts. I wonder whether there's room to add a washer in front of the top diff mounts to increase the diff down angle...that would probably put me within the desirable 2 degree specification. I will take a look tomorrow to see if that's a possibility.

I did some searching to see what angles were working for others, but there's a lot of confusion about it and the terms up angle and down angle are often mixed up when referring to the diff. I would love to know other angle people are seeing with their FFR supplied IRS differential.

Here is a pic of where it sits now:

IMG_4187.jpg