I know you didn't but I'm asking you to because I don't understand how the pinion flange runout is even remotely related to pinion angle. Are you talking about radial or lateral runout?
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93SVTCobra said:I know you didn't but I'm asking you to because I don't understand how the pinion flange runout is even remotely related to pinion angle. Are you talking about radial or lateral runout?
Stitch said:Then you've never used them to adjust pinion angle on an IRS car.
As rotation of the pinion rises, the mounting points must be angled appropriately, flat washers are the same thickness on both sides therefore and uneven load is placed against the ears of the pumpkin. MM's kit are tapered to allow for this angle change. In other words, don't by the KB kit.
93SVTCobra said:There is another reason that this statement doesn't make any sense. If you change the front height of the Pumpkin as you have stated above you're actually causing the whole pumpkin to be put in a bind condition because the rear cover is attachment by two bolts that you've done nothing with.
93SVTCobra said:SO I'll ask again. Why would you EVER change the rear IRS pinion angle?
93SVTCobra said:This is what we did for the rear mount:
Doesn't look like much but on a road racing car you don't need all of the extra support that you would on a drag racing car.
serpentnoir said:Me like. What I really want is that KB modified cradle. But at $700 plus shipping it's a little stout.
93SVTCobra said:Changing the length of the transmission would not change the relationship between the two driveline angles. The physical numbers might change (but they would change at BOTH ends) but the actual difference between the two angles would not. How if the relative height of the transmission was different then you might have an issue but you can just shim the transmission mount to compensate for that.
Swapping out the front diff bushings shouldn't affect your pinion angle unless you don't replace it with a bushing , either urethane or aluminum, that is the same size.
Eric - You are correct. I forgot about the single mount on the back because we changed the rear mounting on my car to get rid of that excess weight.
This is what we did for the rear mount:
Doesn't look like much but on a road racing car you don't need all of the extra support that you would on a drag racing car.
Stitch said:A longer transmission will change the angle at the transmission to d/s point. therefore possibly causing unwanted vibrations.
I did not measure the pinion angle before the gear swap. What I can tell you is that the pumpkin is set at 90* now. The pumpkin is full secure. I'm not sure if the rubber bushings somehow collapsed but after replacing them with the kb aluminum pieces, pinion angle has to be set. As snake eyes pointed out, the rear mount of the diff cover is attached to the IRS frame via a rubber mount and a single bolt representing a pivot point. Normally I would say the pinion angle should be set at factory specs before and after install.
***Pinion flange runout has nothing to do with pinion angle so please stop saying I said that.***
Stitch said:If you install gears, the pinion flange runout can change and the whole pinion angle can change as a whole. My pinion was pointing down 2* which gave me a difference angle between my pinion and my crankshaft of 4*. Ford specs are for the difference to be less then 1*.
93SVTCobra said:But definitely worth it! :rockon:
93SVTCobra said:You are half right here. Both driveline angles (front and rear) will change and the net change will be zero.
If you're pumpkin is set at 90* then you DEFINITELY have a problem.
This is what you said:
Changing gears has NO effect on the pinion flange runout OR the pinion angle.
The pinion flange is the pinion flange and it's runout could be determined with it sitting on a table 100 miles away from your car. You then bring it back to your car and install it and it the pinion flange runout will not change.
Stitch said:That was a two part sentence. And yes, ask any mechanic who does rear end changes. Pinion flange runout will change once you tear apart a differential. That little yellow mark that the factory makes will no longer be the peak runout point.
What is your pinion angle set to? When I say 90* I am referencing the Pinion flange being 90* vertical. Most IRS cars I assume will be like this from the factory but could vary. Remember the goal is to have zero difference in angle for the pinion flange and the crank. If my Crankshaft is 88*, I want my pinion flange to also be 88*, difference is zero.
Without having rubber or MM's front differential mounts, you will not be able to change the pinion angle. KB's kit since its aluminum allow for no flex or angle change at the differential ears. Therefore all you can acheive is a 90* pinion angle measured at the flange.
Again, I do not know what the pinion angle is on a factory IRS car.
serpentnoir said:I looked at the pictures on your web site. Now I know what you mean. That upper arm should generate some decent camber gain.
93SVTCobra said:Please explain HOW the pinion runout changes when you change a differential. I have explained why it won't change and so I'd like to hear you explain why it would as I still don't see it.
You're also forgetting that you can change the crankshaft degree as well.
Come to think of it if you are changing the pinion flange by 1 or 2 degrees how much stress do you really think that is going to put on the snout?
93SVTCobra said:This will sound like a cop out but I'm not at liberty to say what our pinion angle is at but I can tell you that the difference from the front to rear angles is less than 1 degree.
So if you can change your crankshaft angle why do you need to change your pinion angle?
93SVTCobra said:Sounds like you need to index your driveshaft.