Drive Shaft Angle

[burchfieldb]

I wanted to see if I could get some help with the driveshaft angle. I have an IRS setup with a TKX and a 351 Cleveland. These are the angles I have to make my pinion and transmission angle parallel or close to.

Transmission Output Shaft Angle: 0.2 up
Driveshaft Angle: 11.5 Down
IRS Pinion Angle: .5 up

This requires me to have a 1-1/8" spacer under the transmission mount. If I want to make my universal joint angle of 3-degrees and an overall driveline operating angle no greater than 2-degrees, I would have to make the transmission and pion angle opposing and not parallel. Has anyone else had issues with this and have recommendations?

[edwardb]

Something doesn't seem exactly right. I have no experience with a 351 Cleveland and don't know what you're doing with the motor mounts. But the typical installation (including mine over multiple builds) is the engine/trans points down. Not up. It's all relative, but you list the IRS as pointing .5 up. Which is about what I've experience with two IRS builds and the chassis level. So that suggests when measuring, your chassis is close to level as well. Adding spacers under the transmission will make the engine/trans angle even further up. And this just hasn't been my experience. How did you measure the engine/trans angle? The most reliable is against the harmonic balance on the front. My Coupe build, although with a Coyote and T-56, didn't require any spacers. Although that likely doesn't mean much to your combination.

[burchfieldb]

The Cleveland is the same setup as a Windsor, in terms of mounting. I used a digital angle guage on the u joint faces and drive shaft. I also measured the angle of the differential, on the mounting face, before attaching the driveshaft.

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My setup is like this image, where the transmission points up and the pinion is pointing down towards the ground.

Screenshot_20230402-210618_Chrome.jpg

[edwardb]

I'm a little lost with your response. Is your center section driveshaft flange pointing up to the top of the chassis or down? The actual measured angle could be just about anything relative to how level the chassis is.

The two IRS builds I've done the center section was pointing up as I described and it's not adjustable. Others have described the same. So with the engine/trans pointing down toward the rear (normal in my experience) and the IRS center section pointing up toward the front, it's possible to get an acceptable setup with spacers under the transmission.

[burchfieldb]

I'm a little lost with your response. Is your center section driveshaft flange pointing up to the top of the chassis or down? The actual measured angle could be just about anything relative to how level the chassis is.

The two IRS builds I've done the center section was pointing up as I described and it's not adjustable. Others have described the same. So with the engine/trans pointing down toward the rear (normal in my experience) and the IRS center section pointing up toward the front, it's possible to get an acceptable setup with spacers under the transmission.

Mine is doing the opposite. It is pointing down towards the ground .5 degrees relative to the frame. If mine was pointing as you describe, I would be good as well. Seems that the pointing down angle is the problem. I think the only way for me to fix that would be to lower the engine, which would cause me to go to a dry sump setup to get the oil pan clearance.

[David Williamson]

My IRS Coupe with a Dart 363 (Windsor block 302 dimensions) and TKO600 lined up with no spacers. I think you need to call FFR and find out what is going on with the IRS mounts it looks like something is off.
David W

[Alec]

Mine is doing the opposite. It is pointing down towards the ground .5 degrees relative to the frame. If mine was pointing as you describe, I would be good as well. Seems that the pointing down angle is the problem. I think the only way for me to fix that would be to lower the engine, which would cause me to go to a dry sump setup to get the oil pan clearance.

I am still building (kit delivered in Sept 2022), but for the sake of comparison: My IRS center section pointed down towards the front about .5 degrees (which cannot be adjusted). The trans also pointed down (towards rear) 4+ degrees using the kit-supplied poly mounts for the block and trans. This resulted in a V between the 2 angles with a relative angle of ~ 5+ degrees (which seemed problematic). I used the Levy hard mounts to lower my windsor block a bit and also about 3/4" of spacers under the trans and ended up with a relative angle of around 2 degrees; still a "V" when viewed from the side, but not nearly as severe.

[burchfieldb]

My IRS Coupe with a Dart 363 (Windsor block 302 dimensions) and TKO600 lined up with no spacers. I think you need to call FFR and find out what is going on with the IRS mounts it looks like something is off.
David W

I reached out and am waiting on a response. Something definitely seems off.

[burchfieldb]

I am still building (kit delivered in Sept 2022), but for the sake of comparison: My IRS center section pointed down towards the front about .5 degrees (which cannot be adjusted). The trans also pointed down (towards rear) 4+ degrees using the kit-supplied poly mounts for the block and trans. This resulted in a V between the 2 angles with a relative angle of ~ 5+ degrees (which seemed problematic). I used the Levy hard mounts to lower my windsor block a bit and also about 3/4" of spacers under the trans and ended up with a relative angle of around 2 degrees; still a "V" when viewed from the side, but not nearly as severe.

Good to know. I will have to go to a dry sump system if I lower it. I really need to go up, since as of right now I my oil pan dips below the frame.

[JohnK]

Just thought I'd provide another data point here. Granted my build is a roadster and not a coupe but I think the way the IRS mounts is similar between the two. My IRS was also angled downward in the front. You can read about my experience getting driveline angle dialed in here. Long story short - having the IRS angled downward in the front may be less common but not unheard of, and it will require additional spacers under the trans to get proper driveline angles.

[Ted G]

Thanks everyone..... Now I need to go re-check my angles..... LOL

[burchfieldb]

Just thought I'd provide another data point here. Granted my build is a roadster and not a coupe but I think the way the IRS mounts is similar between the two. My IRS was also angled downward in the front. You can read about my experience getting driveline angle dialed in here. Long story short - having the IRS angled downward in the front may be less common but not unheard of, and it will require additional spacers under the trans to get proper driveline angles.

Thanks, this helps. So how does it drive? How many miles do you have?

[LateApex]

This whole topic of drive shaft angle is interesting to me. I have a 3-link rear, which has the advantages of dithering drive shaft angle and lateral alignment of the differential with a twist of the wrist. I'll confess up front that I eyeballed my alignment.

The lateral alignment is largely limited by coil-over clearance. The clearance is a bit different with the staggered panhard bar mounting (interference) points. The car tracks straight and nothing is rubbing, so I am in the ballpark.

Driveshaft angle is also eye-balled, with a bias to how the angle changes as the suspension may be compressed over bumps. I tried to be a little more scientific than "eyeballing", but it is actually hard to find a surface on the Moser rear end that should be either perpendicular or parallel to the drive shaft, which in practice one can measure while under the car.

The notion of shimming the tranny or engine mounts is at present out of the question. 1) Those are installed. 2) Installing the combo at those mount points was very challenging - the tolerance stackup was not great, and involved a lot of grunting and leverage. 3) It looks well aligned, and I don't feel any vibration or hear any complaining.

I am now wondering if there is a better method than "eyeballing" - Haha! Or even with what precision should one apply to this alignment?

[burchfieldb]

I thought I would post an update to my solution for this. I decided to 3D print molds at work and make custom urethane bushings for the rear diff. They will have an off angle bore to make the differential point up instead of down. I will post pictures as I go.

[Mastertech5]

You can use a straight edge against the pinion flange as an extension to put an angle gauge on. Just hold it flat on the flange on put the angle gauge on it.

[burchfieldb]

I thought I would close out this thread with the solution I came up with. I ended up 3D printing a mold and casting some new 95 Shore A urethane bushings, which is about the same durometer as the stock ones. I hade to raise the front mounting points of the IRS and lower the back end. You can see in the picture how off center things had to be to get the transmission to point up at 0.6 degs, but there is still some material remaining to dampen vibrations. This solved the problem and all angles are in check now. It also keeps me from having to use engine lowering mounts and keeps the oil pan above the frame rails. Next up is to finish up making a Russ Thompson style turn signal. I will post pictures in my build thread as I go.

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