Drivetrain Angles

[IV_Joe]

Good Afternoon,
I’ve been trying to decide on a thickness for my transmission mount spacer, as is commonly used. I’ve got some driveline angle problems I’d like some advice on. So, my kit is a complete MK4 with FFR supplied IRS and the 302/351 SBF motor mount option. I have the Energy Suspension Motor and transmission mounts (part # 4.1122G) supplied by FFR. My engine, bellhousing, and Tremec TKX Transmission are all assembled. The problem is that I think my engine is sitting too high. I’m measuring my angles with a digital angle finder accurate to 0.1 degrees. I’m taking the differential angle off the installed driveshaft adapter plate, and it is almost perfectly horizontal within 0.1 degrees. My understanding is that with the IRS this is not movable. The engine and transmission right now is 2 degrees down running downhill from the front of the car to the rear. To find that angle I am using the Crank pulley and confirming with the small, exposed section of the driveshaft that attaches to the transmission. They agree with each other within 0.1 degrees. The studs and alignment pins on the motor mounts themselves are seated in their appropriate slots in the chassis. I have temporary non locking nuts on the studs that are tight. This combination puts my driveshaft at roughly 3-3.5 degrees downhill also front to back. I’m measuring off the flat on two yokes attached to the driveshaft center section and confirming with the actual round shaft section between the welds on the driveshaft. If I jack up the transmission more to try and get the rear end and engine/transmission parallel the driveshaft goes to more like 8 degrees downhill. From what I know about this the engine driveline is supposed to be parallel with the rear-end within a degree. And the operating angles on either end of the driveshaft should be less than 3 degrees but a minimum of ½ a degree. As it is now, I’m 2 degrees out of parallel and borderline on the differential/pinion to driveshaft operating angle. Everything is in line left to right PS to DS. I’ve read through several historical posts on this issue. I would like to hear your thoughts about my diagnosis before getting around to a solution. Thank you in advance.

[Jeff Kleiner]

Our ideal goal for pinion angle is to have the nose of the diff pointing 2 degrees down in relation to the transmission's output shaft. That's exactly what you have...run it!

Jeff

[IV_Joe]

Thank you Jeff. I was under the impression that the 2 degree difference you mention is only for a solid axle so that everything lines up as the suspension compresses under power. Mine is IRS so I thought it was a different situation. You know better then me for sure and if you say it's good to go I'll believe it.

[rich grsc]

Yes, only important on a solid axle. on the IRS, the differential isn't going to move