Driveline setup during fab phase

[NorCal-SS]

I’m hoping some experts can chime in. Project details:
- 67 Chevelle with LS/T56 swap
- Hellwig Framefx brace kit
- Holley eng and trans mounts
- original 12 bolt with adjustable upper arms
- no driveshaft yet

I’m at a point where I need to weld in my transmission crossmember mounts and want to make sure I have the eng/trans at an acceptable angle. Understand the T56 will need to be raised substantially and the tunnel sheet metal will be cut. Problem I’m having is ensuring the transmission crossmember mounts are welded in at an acceptable height (especially with no driveshaft yet).


Would it be best to mock everything in place and measure for a driveshaft first? Or set the trans output angle and diff pinion at or near 3 deg?

Thanks in advance for an insight on proceeding !

[srode]

I set the transmission height and rear end where I wanted and used a straight edge to simulate where the DS would be with the rear set at the ride height I expected then used the Tremec phone app to check angles.

[NorCal-SS]

Great idea. Thank you!

[Alwhite00]

Is your pinion higher than the trans output? I lowered my 67 and ended up with that situation and ended up with a CV driveshaft to correct it.

[Alponcho]

I mocked up my 70 Firebird without a driveshaft. Got my driveline angles to where I thought they needed to be. A couple years later I installed the driveshaft and found I was off a bit. Had to make a couple small changes which were a lot more difficult/time consuming at that later stage of the build. If I had to do it again, I would have mocked everything up with driveshaft in place.

[NorCal-SS]

Is your pinion higher than the trans output? I lowered my 67 and ended up with that situation and ended up with a CV driveshaft to correct it.

Yeah my car is lowered and in almost certain the trans output is lower than the diff pinion. In the back of my mind I’m already preparing to go with a CV shaft but want to make sure I get the trans crossmember installed in the most ideal position now.

Do you happen to recall your pinion angles? I guess if I get these close to ideal the CV shaft should correct the rest, is that a safe assumption?

[NorCal-SS]

I mocked up my 70 Firebird without a driveshaft. Got my driveline angles to where I thought they needed to be. A couple years later I installed the driveshaft and found I was off a bit. Had to make a couple small changes which were a lot more difficult/time consuming at that later stage of the build. If I had to do it again, I would have mocked everything up with driveshaft in place.

Yes I definitely would rather only go through this once. Especially since the frame will be painted if/when I realize my setup will need more work

[Alwhite00]

I was 3 deg down on the trans but the problem is when the driveshaft heads uphill to the pinion it compounds the angle. I was at 4+ degrees.

Get the trans as high as you can.

[NorCal-SS]

Thank you for that insight. I may have underestimated just how high the trans need to go up. My biggest issue may be that I like a low ride height.

I take it the CV shaft took care of any driveline issues? Is the CV joint only on the transmission end? Or is there also a CV joint on the diff side too?

[dhutton]

Low ride height in an A body is a beeotch. Raise that trans as high as you can. Even then you are likely looking at a CV driveshaft or raising the whole tunnel….

Don

[Alwhite00]

Thank you for that insight. I may have underestimated just how high the trans need to go up. My biggest issue may be that I like a low ride height.

I take it the CV shaft took care of any driveline issues? Is the CV joint only on the transmission end? Or is there also a CV joint on the diff side too?

CV on trans end only. I can drive at 75mph on the superslab and have just a slight hint of vibration in the RV mirror. I don't feel it in the car. 67 Chevelle 6.0 LS / 4L60 / 9" 3:50

[NorCal-SS]

I appreciate the info guys. I’m going to plan to get the trans up as much as possible. Already have new sheet metal for the tunnel to raise it. I’m hoping I can keep the rear bench seat and not have to fan a tunnel running between to rear bucket seats. Sounds like I should just plan on a CV shaft from the get-go.

A quick search points to the driveshaft shop being the sole source for one of these, eh?

[dhutton]

I appreciate the info guys. I’m going to plan to get the trans up as much as possible. Already have new sheet metal for the tunnel to raise it. I’m hoping I can keep the rear bench seat and not have to fan a tunnel running between to rear bucket seats. Sounds like I should just plan on a CV shaft from the get-go.

A quick search points to the driveshaft shop being the sole source for one of these, eh?

Yes Driveshaft Shop is only source I know. Plan on a long wait once you order. Not sure what the reason is.

Andrew used one in his GTO without tunnel mods so it might be worthwhile asking him about it.

Don

[Alwhite00]

My CV shaft took 9 weeks. Due to Covid don't ya' know. ��

[NorCal-SS]

Thank you guys! I’ve got some work to do