Drivetrain Alignment Issues

[NylonAdmiral]

Hi guys, I'm trying to get my drivetrain alignment set and am finding that the tail end of my gearbox seems to need to be raised pretty high.

Here's the setup: '71 240z, RB26 DETT mated to RB25 DET gearbox, McKinney engine and gearbox mounts, R200 diff mounted in T3 rear end, 

 

Because the T3 moustache bar is solid billet and the R200 is solid mounted to that, there isn't really any way of adjusting the orientation of the diff, therefore the position of the engine and gearbox need to be adjusted to give the correct propshaft angles.

With the McKinney engine mounts, I have the poly bush on one side, then on the other side I have the poly bush plus two of the supplied spacers.  This seemed to be the only way to get the angle of the engine set correctly.

To match the angle of the gearbox output shaft to the same (or close) angle of the R200 pinion flange, I've set a digital inclinometer against each face and then looked to adjust the height of the gearbox, because the R200 is essentially fixed.

 

Here's the bit that seems odd though.  I have to lift the tail end of the box really quite high in order to get the angles even close.  If I just bolt up the McKinney gearbox mount then the angle of the gearbox is about 5deg out.  To get it close to being right, I'm going to need to make a spacer for the poly gearbox mount to space it away from the gearbox by about 20-25mm which will lift the tail end of the gearbox.  I can't lower the engine any further because one of the bushes has no spacers already.  If I take the spacers from the other side it will just rotate the engine without really achieving anything.

Has anyone else come across this same issue?  Is this just how this config sits or am I missing something?

Thanks for your input.

[260DET]

No experience but if you are sure that your calculations are correct then just go ahead and do what it takes to get the alignment right. Not all parts from an aftermarket supplier are always perfect.

[AkumaNoZeta]

No experience but if you are sure that your calculations are correct then just go ahead and do what it takes to get the alignment right. Not all parts from an aftermarket supplier are always perfect.

Even if all aftermarket parts were perfect, after 40 years of use and abuse, and rust, every car is going to be different too. I agree, do what needs to be done to get the angle of the dangle. Unwanted vibrations suck to have.