Another IRS question
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Posting Guru
Joined: Jul 2007
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From: I live in Leitchfield, KY
Another IRS question
Hey guys,I know we had a LONG thread on this but................. I forgot what was said about pinion angles on IRS's? I know that the pinion on the IRS dosent move, but I'm assuming that there is still a need for a slight "Z" in the drive shaft to work the needle bearings on the U-joints? Assuming I'm right in this, is this completely different than setting up a solid axle? Or do I set them about the same? The reason is I'm considering using an old Cougar IRS I have for one of my project trucks?? I'm not sure yet?
Thanks guys!!
Thanks guys!!
Senior User
Joined: Sep 2006
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From: Winters Ca
Yes you set it up just like a solid Axel. It does not have anything to do with frame rake but has everything to do with Motor angle and that gives you your tail shaft angle. You will want your pinion angle to be just opposite of the tail shaft angle. +5 on one -5 on the other kind of thing. So as long as your 5% engine slant or level intake surface is set then you should be good to set your pinion angle as well. If I remember right you can shim down the IRS pinion angle a small amount so lean toward the up hill side of things if anything and shim down a small amount as needed.
Kevin
LFD Inc.
Kevin
LFD Inc.
I'll have the Roast Duck
Joined: Jul 2002
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From: Northshore, MN
Out of curiousity, I wonder if a measurement from the CL of the pinion nut to the attachment points (to the frame/body of the car) would be the same on both sides? I assume the car's pinion is centered on the axle, unlike a truck's. That said, if your engine is offset a little to the passenger side, then the needles should get lubed, and only the up-down will need to be figured, like Kevin said. ( of course still keeping the engine in a straight line with the frame)
Thread Starter
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Posting Guru
Joined: Jul 2007
Posts: 2,344
Likes: 11
From: I live in Leitchfield, KY
Yes you set it up just like a solid Axel. It does not have anything to do with frame rake but has everything to do with Motor angle and that gives you your tail shaft angle. You will want your pinion angle to be just opposite of the tail shaft angle. +5 on one -5 on the other kind of thing. So as long as your 5% engine slant or level intake surface is set then you should be good to set your pinion angle as well. If I remember right you can shim down the IRS pinion angle a small amount so lean toward the up hill side of things if anything and shim down a small amount as needed.
Kevin
LFD Inc.
Kevin
LFD Inc.
Thanks Kevin, that's what I thought.
Lead Driver
Joined: Aug 2006
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From: Brentwood, TN
Corvettes have a bar that bolts the nose of the differential to the tail of the driveshaft. This locks the two together at a constant angle that keeps the tail shaft at 1 degree off from the pinion. This is necessary because the transmission is on the same plane as the differential...that is, the tailshaft of the trans points in a direct line to the pinion center. If the engine sits higher than the differential then you don't have to worry, just make the pinion and the tailshaft angles match, the difference in height between the two will take care of the needle bearing rotation for lubing purposes.
