Also posted in trans/drivelines, but nothing useful yet, so here again:


I've got baseline readings, but a bit confused because of contradictory recommendations from various sources (not really surprising).

Installed Currietrac adjustable rear upper and lower arms (johnny joints), and my car is lowered a bit as well. I measured the stock GM uppers, and for baseline set my JJ uppers at the same center to center distance.

The car is NOT perfectly level, but the angle measurements which matter are relative angles, not absolute "gravity" angles. As my 70 Malibu sits on ramps/jacks, I'm getting the following measuremnts:

Trans output shaft is DOWN 3 degrees
Driveshaft is UP 1 degree (running up to rear diff.)
Pinion shaft is DOWN 3 degrees.

As I understand how to add subtract these angles, I believe I have a front working angle (trans. U joint) of 4 degrees ; the rear Pinion U joint working angle is 2 degrees.

Now the confusion. Currie Enterprises recommends negative pinion angles of 2 degrees "pinion down".....Wolfe Race Craft recommends from -1.5 to -2.5 pinion working angle....it would seem I'm there or damn close now.

However, all other info. I've gleaned says that basically the trans yoke and pinion must be equal and opposite, i.e. parallel. Inland Empire Driveline goes to great lengths to make sure these are parallel. In fact, both of mine are currently pointing DOWN. Mark from SC&C recommended at most I run the rear diff. a half degree lower than the trans ( trans 2, diff -1.5) to account for the rotation during full accel. of the axle.....others have recommended a full degree down for suspension windup. I know that straight (zero angles in U joints) are no good and will beat the needle bearings flat.

Somebody who has BTDT please set me straight.....do I want my pinion down (almost mirrored angles as Trans down), or do I want them parallel with equal (or minus 1/2 degree different).

Thanks....heading out to buy a 1.5 inch box wrench so I can turn the JJ uppers.

Duane

If you want equal/opposite u-joint angles and no more than a 3 degree u-joint working angle. Try installing a 3/4" shim at transmission mount and rotate the pinion to a 2 degrees up angle. This should net Inland's recommended settings.

If my calculations are correct and you're using about a 60" drive-shaft; the end result is transmission 2 degrees down, drive shaft 1 degree up toward pinion and a pinion angle 2 degrees up.

You might want to take 1 degree out of the pinion angle for axle wrap-up so the pinion angle will end up being 1 degree up..............

If you want equal/opposite u-joint angles and no more than a 3 degree u-joint working angle. Try installing a 3/4" shim at transmission mount and rotate the pinion to a 2 degrees up angle. This should net Inland's recommended settings.

If my calculations are correct and you're using about a 60" drive-shaft; the end result is transmission 2 degrees down, drive shaft 1 degree up toward pinion and a pinion angle 2 degrees up.

You might want to take 1 degree out of the pinion angle for axle wrap-up so the pinion angle will end up being 1 degree up..............

Pat,

Indeed, your math sounds very close IF I want equal and opposite angles. Perhaps that is the main confusion for me. As posted by Currie and Wolfe Race Craft, they both are pointing towards negative pinion angles, not positive. Currie even specifically states that he is referring to street driven cars, not race cars (which may be Wolfes primary customers). Every thing I've read generically (not A bodys) states you want them equal and opposite, albeit perhaps at full accel / axle wrap up. I can certainly raise the tranny via the crossmember, and can adjust my UCA's to get the 2 or 1.5 positive pinion angle. What do you recommend, equal & opposite, or MINUS angles in the pinion as Currie recommends?

thanks.

I like the equal/opposite minus some for axle wrap-up but I don't have the experience of those companies..........the amount for wrap-up kind of depends on type of use and condition/material of suspension/bushings. My guess is 1/2 degree is probably enough for street use with good bushings...........

Is it possible that Currie and Wolfe are talking about building in some movement for axle wrap-up. When they say negative are they meaning less than the equal/opposite pinion angle?

I like the equal/opposite minus some for axle wrap-up but I don't have the experience of those companies..........the amount for wrap-up kind of depends on type of use and condition/material of suspension/bushings. My guess is 1/2 degree is probably enough for street use with good bushings...........

Is it possible that Currie and Wolfe are talking about building in some movement for axle wrap-up. When they say negative are they meaning less than the equal/opposite pinion angle?

I am in error! Just re-read the Currie article (carcraft) and infact he stands exactly with Inland.....equal and opposite. In fact, at the end the article they example measure a 70 Chevelle :D and he mentions Pinion UP. It was only a pro-stock chasis builder AND Wolfe Race Craft who are suggesting negative pinion....both must be targeting drag cars.

I will set my pinion angle at approx. 1.5-2 POSITIVE and shim the rear tranny mount to try for 2 degrees in the trans yoke U-joint angle.

FYI the Carcraft article:http://www.carcraft.com/howto/91758/index.html

thanks for the feedback. :thumbsup:

If you want equal/opposite u-joint angles and no more than a 3 degree u-joint working angle. Try installing a 3/4" shim at transmission mount and rotate the pinion to a 2 degrees up angle. This should net Inland's recommended settings.

If my calculations are correct and you're using about a 60" drive-shaft; the end result is transmission 2 degrees down, drive shaft 1 degree up toward pinion and a pinion angle 2 degrees up.

You might want to take 1 degree out of the pinion angle for axle wrap-up so the pinion angle will end up being 1 degree up..............

For the record, your calcs. were pretty spot on. I set the pinion at 2 degrees positive, have the driveshaft between 0.5 and 0 running uphil to the differential, and trans. output yoke pointing down 2.5 degrees, with a 3/4" spacer between the crossmember and trans. mount. I'll probably get a 3/4 and also 1" spacer made, fit check both to look for the 2 down, 2 up, driveshaft at 0 sweet spot.

thanks,

Duane

For the record, your calcs. were pretty spot on. I set the pinion at 2 degrees positive, have the driveshaft between 0.5 and 0 running uphil to the differential, and trans. output yoke pointing down 2.5 degrees, with a 3/4" spacer between the crossmember and trans. mount. I'll probably get a 3/4 and also 1" spacer made, fit check both to look for the 2 down, 2 up, driveshaft at 0 sweet spot.

thanks,

Duane

Thanks.........good to hear. :thumbsup: