drive shaft angle

I have a 2018 33 kit with 3-link suspension, moser 8.8 rear axle, koni coil over shocks, coyote and tremec tko600 transmission. I wanted to adjust the ride height so I could also set my pinion angle on the drive shaft including spacers on the tranny mount. As of now I have a 1 ¾” spacer at transmission. I originally had a 1 ½” spacer but the gap under the u joint to floor pan was only ¼” so I added another spacer to get a ½” gap. What is a normal gap here?
1. As of now I have ride height set at 5 ¼” in rear and 4 ¾” in front, allowing a ¼” extra since I don’t have body on or any other weight. In doing so I noticed the rear koni shocks are adjusted to max height, see picture.
2. I used the tremec app plus a digital level app to measure drive angles, I’m way off.
The tremec app shows .4/6.3/5.9 drive angle, the bubble app shows the trans angle at 3.6, driveshaft at 4.2 and differential at -2.8
In order to get the transmission and differential parallel to each other within acceptable u-joint angles I need to rotate the differential up but as you can see in picture the axle bracket is now hitting the rear shock???
Thanks in advance for any input you can give me.

Use a hole saw to relieve this area of the shock mount. I don't remember what size hole saw but select one slightly smaller than the ID of the part of the bracket that hits the shock. Mark down from the top edge of the bracket 3/16" to 1/4" and centered on the bracket. Start with a small pilot hole ~ .070" and incrementally step up the hole size until you reach 1/4". Carefully drill with your hole saw to cut away the part of the bracket causing the interference. Debur the edges and touch-up paint and it will look like OEM.

Attachment 107748Attachment 107749 Works like a charm.

Ahhh, so I'm not the only one, I thought I mounted something wrong, lol. I wish i knew this before i put everything together, well, off to H.F. to buy a hole saw bit.
Looks like i need to rotate my differential up about 4 degrees so this should do it.
Thanks guys!

If you are lucky like me, next you will find that the Moser rear end housing now interferes with the diagonal for the panhard bar anchor. Sometimes you can just cut and splice it but it will still be pretty close. I haven't decided yet how I am going to remedy that. By the way, I only have about 1/4 clearance between the u-joint and frame underneath but I think it will be ok. I am running an ls1 /tko 600 and had to raise the engine up about 7/8 inch to get the proper driveline angle but it also allowed me to rotate the electra steer motor up so it doesn't hang below the frame.

Interesting, I just checked mine, My electra steer motor does not hang below the frame and i just used the standard mounts they gave me for the coyote. in fact, FFR had already customized the steering motor bracket for me to rotate motor up. I also checked the panhard bar and i have plenty of clearance underneath the differential to the diagonal brace and about 1/2" clearance from the diagonal brace mount to the shock mount. After cutting out the axle mounts with a 3" hole saw as per Naz's instructions, the shocks no longer hit so that worked great but i found i had to grind slightly at the bottom axle bracket because it was just pinching the bottom of the shock also. All seems to fit nicely now. That 1/4" under the U joint just gives me the Willies since the trans mount is rubber, can that flex under hard load (400+ hp)? if that were to hit, It would be ugly. What do most of you guys have as a clearance under the u joint at transmission?

You can always shim it to increase the clearance. There is not a single correct angle the engine has to sit at -- you have some flexibility here. The critical angle is the pinion matching the trans output shaft angle UNDER LOAD to prevent vibration.

I think I have my setup complete but would love to hear from others to make myself feel better since I'm a newb at all this. I adjusted the panhard bar to align the center of the rear wheels with the center of the chassis. I set my ride height to 5 1/8" and 4 5/8". I wanted to go higher since the car is not loaded yet (body off, etc.) but the 5 1/8" is maxing out the rear shocks, I have the black sleeve screwed all the way up about 1/8" past top of shock. I have a 1 3/4" spacer at transmission mount which gives me about 1/2" clearance to frame under u joint. I purchased a Johnson digital angle finder and here are my drive line angles: 3 degrees down at engine/tranny, 3 degrees down at driveshaft and 1 degree down at differential. that gives me a 2 degree pre-load which from what i researched for 400 hp car is good. From what I've read a 3 degree down at engine is pretty typical but is having the same angle at driveshaft ok? I always thought you didn't want the drive line to be perfectly in line with u joints? I used the Tremec app and it gave me 3 green lights but I am skeptical of the readings since it hard to get a good position with a large cell phone. I appreciate any and all comments, thanks

Dan,

You need your drive shaft to be at a little bit of an angle so that it cycles the U-Joints needle bearings or they will prematurely wear.
It doesn't need to be much of an angle, just a few degrees to get those needles moving around.
Also, here is a U-Joint phasing video which many of us have found to be helpful.

https://youtu.be/Idk3BVDVHq4

Good Luck & Hope This Helps!

Steve

My thoughts on your set-up.

RIDE HEIGHT: "5 1/8 is maxing out the rear shock"... The first issue I see is the rear shock topped out. That will give a poor ride and cause handling issues as the tire will lose traction on rebound. The shock being topped out will cause the tire to unload as the chassis tries to lift it off the road. The suspension's job is to keep the tires planted to the road surface and transfer weight properly. If you need to run this ride height you also need longer shocks. But also be advised that your ride height adjustment also affects other suspension variables such as instant center front & rear, rear roll steer, front & rear roll center, front camber gain, and anti-squat. These all affect handling, traction, and weight transfer.
DRIVESHAFT ANGLE: Yes it is better to have the u-joints working through a minimum of a couple degrees to keep the needle bearings lubricated. When your trans tail shaft angle matches the driveshaft angle the needle bearings will not rotate and this can lead to premature wear as the grease will tend to be pushed away from the bearing contact surfaces. The relatively stiff suspensions FFR provides will limit suspension movement which in turn limit driveshaft articulation.
PINION ANGLE: The purpose of setting the static pinion angle X number of degrees less (down at front) than the tail shaft is so that under load the pinion will match the tail shaft angle. Mismatched angles will cause vibration and the vibration is worse under load. Is 2-degrees the correct amount of angle offset? You will get a lot of opinions out there but unless you have measured the amount of pinion angle change under load for your specific set-up you're just guessing. I used science to determine mine but that's way more involved than most folks will want to deal with. 2-degrees for your set-up sounds reasonable so try it and see. If you don't feel vibration under heavy load (acceleration) you're probably close enough.

Thanks for the help guys, i really appreciate it.
I've seen the video which helps but still a little vague. So first things first.
1. If i have my rear shocks adjusted to the max height which is not a good idea, then i can only assume FFR gave me the wrong shocks and i need to order longer ones? Not the end of the world but a little frustrating.
2. I think i understand where i was wrong with my preload setup, i thought it was 2 degrees from pinion to the drive shaft so when under load they lined up, but now i see its so when under load the engine/tranny drive line angle is parallel to the differential pinion angle.
my current setup with 1 3/4" spacer at tranny is -3.0/-3.0/-1.0 (engine/d.s./pinion), if i go back to the shims FFR specified (1 .5") i have -3.5/-2.3/-1.5 which gives me u joint angles of 1.2/0.8 which is better but still not ideal.
i'd rather keep the engine at -3 degrees but i guess i would have to have less preload in order to get the d.s. angle to not line line up with engine??? i dont have many options here for adjustment

Dan,

Your drive-line angle needs to be the same angle as the pinion to be perfectly in phase; however, the pinion needs to point downward between 1 and 2 degrees as your preload.
The assumption is that you'll be at ZERO degrees under hard acceleration as the axle tries to rotate upward so it's pretty simple deal when you think about it.
Any vibrations, assuming your drive shaft is balanced, would then come from an out of phase condition.
H O P E....T H I S....H E L P S !

Steve

it does thanks, but my problem is i'm not sure how to get there. the best setup i can come up with is -3.0/-2.7/-1.0 (trans/d.s./pinion) which gives me a 2 degree preload but u joint angles are only .3/1.7, its almost like my drive line is too much in line to get any kind of angle on the u joints???

Do you have room in the trans tunnel to raise the trans higher? Just as a point of reference, I set my engine in the chassis at 1.0-deg incline (output shaft slopes down at the rear) in relation to the chassis. At ride height my engine / trans sit at a ~2-degree incline (sloping down at front -- yes counter intuitive to most folks idea of normal) by design. You have more leeway than perhaps you realize.

I can raise trans up to about -2.5 degrees by hand without forcing it, I've walked around engine and it seems like it would work, not hitting anywhere, i could try to go higher by jacking trans up but would really have to look at everything to make sure i don't have an interference issue, i have a coyote and as all know, its stuffed in there. Those results are: -2.5/-3.4/-1.3 which gives me a 1.2 degree preload and u joint angles of .9/2.1, getting better
ill try a trans angle of -2.0 tomorrow, its about all i haven't tried to see if it helps, thanks again!

Good luck, and don't fret too much about hitting any particular u-joint angle. Do the best you can on u-joint angle and pay close attention to pinion angle, you'll be fine.

BTW, some drag racers tend to lean toward zero u-joint angle because there is some incremental power loss as the u-joint cycles through angle changes -- but they also don't worry about u-joints lasting 100,000 miles.

After experimenting with a bunch of different transmission angles I've discovered I can get into 2 different scenarios with the pinion angle. "A" has the drive shaft steeper then the pinion, "B" has the driveshaft shallower than the pinion. I would assume scenario "A" is better or does it matter?
Attachment 108022

As far as driveshaft angle is concerned, makes no difference. Mine is angled like "B" and I'll guarantee you that mine gets a work out and never complains.