SOA + C&T + leaf perch angle

[fj40toycruiser]

I will try to keep this short. 1978 fj40 stock axles. STock body height. I am doing a SOA w/ rear fj60springs on the front and rear both ends flipped as to extend the WB. Stock 2f, sm420, rock box, 3 spd case, with shackle reversal. Sittin on 38". If I set the axle at the same height as the rear axle and I point the diff at the output of the t-case I come up with a leaf perch offset from factory of 18 degrees not factoring the knuckle turn of 3-5 degrees for my 38's. I have read of up to 14+ the 3-5 on the knuckle but degrees but 18 to start seems alot higher. That would make 18+3-5= 21-23degrees. I do know I may have to relocate the fill plug. Also some say to drop the diff housing from directly pointing at the t case output a couple degrees (some say 2-3, others say 6 degrees) to compensate for drive line angle changes under acceleration. so set leaf perch's at 16 degrees? I do plan on running a DC shaft. I could try to post pics but I am not sure it would help. Could I be doing something wrong?

 

[inkpot]

I do it with a lot less math. Bolt springs/shackles to frame. Put axle up on stands. Set fully loaded rig onto axle with perches loose between springs and axles. Rotate pumpkin up to get the driveshaft angles you need. Then cut knuckles loose if you haven't already, and set them at 3-5 degrees of caster. John

 

[Rock_Hugger]

I do it with a lot less math. Bolt springs/shackles to frame. Put axle up on stands. Set fully loaded rig onto axle with perches loose between springs and axles. Rotate pumpkin up to get the driveshaft angles you need. Then cut knuckles loose if you haven't already, and set them at 3-5 degrees of caster. John

^^^ This ^^^^


Who cares what the numbers are? Set the pinion to how you want it and rotate the knuckles to 4*-5*'s or whatever you want to run. I wouldn't worry about the fill plug, you are not going to drive it fast enough long enough with the front locked in to worry about it.

 

[reddingcruiser]

^^^^This X2^^^^
Or said another way, you're making it harder than you need to. I usually shoot for about 3º.

Just an FYI, the degree symbol can be had by holding the ALT key and typing 0186, like this - º

 

[BDSeff1fitty]

Just an FYI, the degree symbol can be had by holding the ALT key and typing 0186, like this - º

or buy a mac and its option 0 like this º

 

[pbgbottle]

X3 make sure your rig is on level ground also

I do it with a lot less math. Bolt springs/shackles to frame. Put axle up on stands. Set fully loaded rig onto axle with perches loose between springs and axles. Rotate pumpkin up to get the driveshaft angles you need. Then cut knuckles loose if you haven't already, and set them at 3-5 degrees of caster. John

Sent from iPhone

 

[fj40toycruiser]

I figured i was over thinking it but I am using the ruff stuff perches and I need to make the diff side fit for the angle and I don't want to screw it up. It also stops me form just bolting it up to get the right angle, Any thoughts about dropping the pinion a few deg. from pointing directly at the t case to compensate for drive line changes under power?

 

[sadam_husain]

Any thoughts about dropping the pinion a few deg. from pointing directly at the t case to compensate for drive line changes under power?

you don't want the pinion pointing directly at the t case you want the two flanges to be as close to the same plane as you can manage and you don't want the pinion pointing up too high or the bearing wont get lubricated properly but I guess you already know that bit coz you already mentioned shifting the filler hole up a bit higher

 

[pbgbottle]

i can't remember but doesn't the front pinion torque down under load ,so u might want to set it a degree or to higher i could be wrong..
and the rear pinion torques up , just thinking out loud here
i know the rear torques up for sure.

, Any thoughts about dropping the pinion a few deg. from pointing directly at the t case to compensate for drive line changes under power?

 

[pbgbottle]

also i was thinking everybody will have different measurements because there are too many variables when it comes to mounting perches because of spring choice .shackle reversal is the big reason the spring angle gets wonking on some shackle reversals .with out shackle reversal spring sits quite level ,long shackle up front. reversal depending on wether or not you sink the shackle mount into the frame or put it below the frame . this can cause the spring to sit at a different angle which means some will weld there perch on at a different degree than others may have . you really do have to get the weight of the rig on the axles to see where everything needs to be . u may have to make something up on the passenger side so u can get it all bolted up and see where u really need the perch it doesn't have to be bolted down super tight .even just bolt the perch on the driver side should get u a close visual ,