IRS angled downward

[Real Time]

Hi All,
-for starters-thank you guys for ALL your contributions to this forum!

With the help of some great friends, I got my engine installed.

I leveled the frame to zero and its apparent my IRS is angled .8 degrees downward.
This seems to be in opposition to what others say it should be.

Before dealing with spacers (or whatever) to make adjustments with the tranny l'd like to know
-........is there anything I could/ or should do regarding the angle of the IRS?

....note: Tranny angles down around 1.7* resting on "A" bracket ,....Seems to be in the ball park of others.

......hope I didn't speak to soon the other day when I mentioned to someone about everything going pretty straight forward....lol

George

[Jeff Kleiner]

Hi All,


...I leveled the frame to zero and its apparent my IRS is angled .8 degrees downward....


Need clarification. Does that mean that the front of the pinion is angled downward compared to the chassis (i.e. nose is pointing down) or the opposite? Same with the transmission;do you mean that it angled downward front to rear?

Jeff

[Real Time]

Need clarification. Does that mean that the front of the pinion is angled downward compared to the chassis (i.e. nose is pointing down) or the opposite? Same with the transmission;do you mean that it angled downward front to rear?

Jeff

YES, IRS is angled down toward the front (.8*0), and Tranny, down towards rear-
-The chassis is level at 0*

George

[JohnK]

I can't tell you why, but it happens sometimes. Mine was angled downward at the front by 1 degree. Nothing you can really do about the IRS angle. You just need to factor it in when setting overall driveline angles. Here's my thread on the subject from a few years ago.

https://thefactoryfiveforum.com/showthread.php?40629-Pinion-angle-I-think-I-ve-got-it-but-please-check-me

[Jeff Kleiner]

YES, IRS is angled down toward the front (.8*0), and Tranny, down towards rear-
-The chassis is level at 0*

George

Then you're good. We shoot for the front of the pinion to be approximately 2 down in relation to the transmission output; you are currently at 2.5. If you shim the rear of the trans upward it will become less but really, it is not necessary. In the end it's kind of a moot point with IRS because the whole idea behind a couple of degrees down is so that as the nose of the pinion rises under hard acceleration the angle becomes less but with a rigid mounted differential that isn't going to happen. Short answer; run it!

Jeff

[rich grsc]

Guys with IRS need to stop worrying about pinion/transmission angle. The differential doesn't move, so the u-joints don't change angles.

[Presdough]

You NEED some angle in the driveshaft or the needle bearings will be stationary and will cut grooves in the bearing cap. When you get beyond 3 degrees is when you start flirting with vibration issues. The length and diameter of the tube also play a factor but the drivelines on these cars are so short that it's a non issue.

[JohnK]

Guys with IRS need to stop worrying about pinion/transmission angle. The differential doesn't move, so the u-joints don't change angles.

Driveline angle still needs to be set up properly, even with an IRS. You just have one less moving thing t worry abut with an IRS.

[CraigS]

It is very common to shim the trans up 1/2" to 1" which will bring your angles closer to parallel.

[cv2065]

It is very common to shim the trans up 1/2" to 1" which will bring your angles closer to parallel.

Agreed. I shimmed mine by 1" for the angle which also brought the pan above the frame rails.

[Real Time]

Need clarification. Does that mean that the front of the pinion is angled downward compared to the chassis (i.e. nose is pointing down) or the opposite? Same with the transmission;do you mean that it angled downward front to rear?

Jeff

-THANKS! so much for helping me feel comfortable about being "Good to go"!!!:)

[Real Time]

I can't tell you why, but it happens sometimes. Mine was angled downward at the front by 1 degree. Nothing you can really do about the IRS angle. You just need to factor it in when setting overall driveline angles. Here's my thread on the subject from a few years ago.

https://thefactoryfiveforum.com/showthread.php?40629-Pinion-angle-I-think-I-ve-got-it-but-please-check-me

Thanks for the link- yeah, looks like we're in the same boat. Glad to see a lot of members feel it's really a non issue but, also interesting to see the views on why parallel Trans and Diff-are important
-as of now, I have a 1" spacer under the tranny and still have about .9* out of parallel.

[M22_COBRA]

I have the same issue and trying to figure if I'm good. I'm the same +0.8 nose pointing down to the ground on the rear end ( low in front high in back), then the trans tail is also -1.4 pointing down to the ground (high front low in back). The drive shaft is in a state where it looks like a front to rear downhill check mark( is a small thing but that's the shape. This sounds like above but something doesn't feel right.??

[Waterman]

Like many have said you do not need to get angles perfect and can not but just within the limits published by several. These angles are discussed in my post where I did a spreadsheet on the affect of different shims under tranny. Around 3/4" is the norm for small block and tKX.https://thefactoryfiveforum.com/showthread.php?51776-Driveline-Vibration-Fixed-302-TKX-IRS-Early-2024-MK4https://thefactoryfiveforum.com/attachment.php?attachmentid=216377&d=1752582530

[M22_COBRA]

Ok so I have the angle front to rear at -.73 / -2.0 / +2.0
Seems fine but the oil pan is hanging down 1/8" below the rail. Do I put more angle in it and potentially irritate the angles and clear the pan or leave it. Don't feel great having the pan out in the open. Thoughts?

It's as if the engine needs to go up.

[rich grsc]

OMG. Stop worrying about the angles. If you want to raise the tail shaft to get a bit more oil pan clearance, then do it.
Crawl under a pickup truck and look at those angles, u-joints are designed to operate at angles

[gbranham]

I 100% agree with Rich on this. You IRS guys simply don't need to obsess over driveline angles.

Greg

[M22_COBRA]

OMG, STOP, just throw it in and go... Wont be doing that.

After a long think and evaluation here's how I worked around this, hopefully this helps someone else in the future here is what I did.
(1) I realize I can only control what I can control, and the rear gear angle is out of my control as I'm not cutting and rewelding.
(2) I Unbolted the rear DS, confirmed / re clean the mating surfaces ( no pebbles etc. ) / rotate it on it axis 180 degrees from the original position & re-fasten to the gear and torque it.
This worked many times at the tracks with high speed vibrations that you couldn't get rid of. Sometimes you just get a DS that isnt happy in the original position.
(3) Try to raised the engine till it cleared -> yielded a 7.5 deg DS angle.... NOPE! Cant do that, just accept it will hang down and work that problem with a chassis rub strip.
(4) Remeasured with the +3/4 spacer (maybe 7/8 total?) on the tranny and found it was the "best" I could get balancing engine height and respectable angles -> 3 deg up front / 4 deg in rear / 1 deg split
(5) The oil pan hangs the rear weld down 1/16" and the bell housing about 3/8" with this spacer. Cant / wont fix that. I'm going to bolt a strip material to warn me on the underside of the rails to protect for the speed bumps in town like the builder above. I ordered a set of 26" long 5/8" tall steel concrete forming stakes, the more involved version is to order a strip of A36 and machine holes. If something jumps up and hits me, well that can happen if it was above the rails too and without a massive redesign that wont be fixed.