Transmission, driveshaft, and differential alignment

[ThickCobra]

I have browsed all the techie guidance on how best to align the transmission, driveshaft and 2015 IRS for the mk4 roadster. As you may know, I have the 351w engine, tko600 transmission and the 2015 IRS. As I am working toward my first start, I'm rechecking my assembly - to - date and sometimes want to revisit things. So, I am inquiring as to how others with my same set up did their alignment. Both vertically and horizontally.

[mikeinatlanta]

Mine was lined up at bolting in with no adjustment required. You may want to measure and repost what misalignment you have, if any.

[GoDadGo]

Thick Cobra,

I'd check the manual once more or Jeff Kleiner, EdwardB, or Gordon Levy (Levy Racing) to see what the angle should be set at if any.
The big this is you need to make sure that your transmission output shaft angle matches the angle of the input shaft of the differential so that the U-Joints are in phase.
I don't have that set up (3 Link Instead / Which Is Set @ 2 Degrees) but the attached video may help you get things aligned.

https://youtu.be/gmV4qwLfOMY

In additions, the pinion angle on my 1995 C-4 Corvette, which is an independent setup, it is set at ZERO DEGREES from the factory with no adjustment possible.
On the C-4, there is a slight angle on that driveshaft that is kept static by the torque truss that goes from the tail shaft of the transmission to the Dana-44 pumpkin.
It has a slight angle built into it so that th U-Joints can cycle, but those two shafts are set at ZERO with maybe 1-2 degree of slop in it which won't cause vibrations.

Hope This Video Helps!

Steve

[ThickCobra]

GoDadGo, thanks for the responses.

As mentioned, I am revisiting several key components and settings performed during the build as I work toward first start. I believe I installed the drive train within specs during install, but have had an engine mount adjustment recently. As everything is in, including a 1" thick spacer beneath the transmission (want to revisit this also) and the safety hoop from Metro, I would like to take another reading of the pinion and operating angles. I watched your attached video and went back and re read the detailed posting by Karlos. Both very good. I have the Johnson Magnetic Protractor Angle Locator from Harbor Freight and need to know what surfaces to set it on to take measurements.

BTW, as the 2015 IRS differential is essentially fixed within the frame, (has rubber dampeners but essentially fixed) I believe the only adjustment available is raising or lowering the rear of the transmission.

Thoughts?

[mikeinatlanta]

By misalignment, I'm talking about angles. The eng and trans are offset, but they are supposed to be. If you don't have a good place to measure off the output shaft, the front pulley works just as well.

[ThickCobra]

By misalignment, I'm talking about angles. The eng and trans are offset, but they are supposed to be. If you don't have a good place to measure off the output shaft, the front pulley works just as well.

I knew what you meant and I appreciate it. And, using the front pulley is a great idea for getting my engine/transmission centerline.

[CraigS]

On my 2015 IRS retrofit I aligned vertically by measuring one of the pulleys on the front of the engine and then had a hard time finding something on the diff to measure. Tried to use the little bit of the pinion flange that is outside of the adapter but that is too thin. Tried using the surface on the diff case next to the pinion seal but same thing and it's cast not machined. tried using a pair of the diff cover bolts. Never found a really good spot to measure but I think got it to zero + or - 1 deg. by changing my washer stack under the trans. Then, laying under the car tried to look at horizontal alignment. Same crap, no real good reference points. Finally rotated the driveshaft so I had the u-joint cross horizontal and looked at the machined surface on each flange where the circlips are that retain the u-joint cups. As best as I can measure they are parallel. All in all it's damn frustrating having no good reference points but I think I am pretty close to parallel in both planes but not in line in either.

[karlos]

Since the IRS center section is for all intent and purposes non-adjustable, I'd suggest starting by measuring the angle of the pinion flange and use that as a baseline from which to proceed. There's probably enough of the edge of the pinion flange exposed to take a measurement as shown below.




Given that measurement, place a jack under the transmission and raise the back as required to achieve the ideal pinion angle of zero degrees. The TKO600 has a convenient cover plate that can be used to easily measure the output shaft angle. You'll find that you get the same reading when measured off the cover plate as you would from the face of the harmonic balancer.




Once the angle is where you want it, simply measure the gap at the transmission mount and create a shim of that same thickness.

Remember that pinion angle is the difference between the two operating angles. Because the IRS center section and the transmission are offset with respect to one another (center section sits higher than the transmission), you'll also have to measure the driveshaft angle to calculate the operating angles. You've got three objectives:

1. Maximum operating angle = 3.0 degrees
2. Minimum continuous operating angle = 0.5 degrees
3. Difference between the two operating angles (aka pinion angle) = 1.0 degree max

[CraigS]

Sure wish the 2015 diff had that much of the spacer available for an angle finder to sit on.

[ThickCobra]

With all the advice I plan on tackling this today, and post the results.