I have a question about the caster and pinion angles. I am doing a spring over and shackle reversal on my FJ40. My question is with everything mocked up, weight on vehicle the angles are the same as when started. My castor angle is -3 and the pinion is 86, the same as the transfer case. I did the spring over, with 2.5" old man emu springs and reversed the centering pin. My question is has anyone not cut and rotated the knuckles and what happens if I leave everything the way it is? Thanks in advance
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Yes it's been done but the pinion has to stay at factory setting so no pointing the pinion up. Neg castor is very dangerous to drive which is why the cut and turn
Not true, the pinion can be angled up for better clearance of the pinion yoke/drive shaft and easing the u-joint angle at full droop reducing possible u-joint binding or breaking, especially since you are using 2 1/2" lift springs to do the SOA. The pinion is pointed straight at the out put flange on the t-case, giving you a reading of 0* of u-joint angle on the pinion flange of the axle and a double cardan joint at the t-case. The double cardan angles cancel each other out (no vibration).
If you are not going to use a double cardan drive shaft, both the t-case flange and pinion flange need to parallel to each other, again each angle cancelling each other out.
I would run more caster, you are that far along, sucks to go back and do something twice, IMHO.
I run 4* of caster, it is super stable at highway speeds, nice not having to fight the vehicle down the road due to ruts or grooves.
Good luck with the build, throw some photos up of what you are doing, it helps with answers to your questions.
for the record an FJ60 pinion is set at about 84 deg , about 6 deg upward, while maintaining ~ 2+deg
positive caster. They only used a double cardon in some years
Not true, the pinion can be angled up for better clearance of the pinion yoke/drive shaft and easing the u-joint angle at full droop reducing possible u-joint binding or breaking, especially since you are using 2 1/2" lift springs to do the SOA.
If you don't rotate the pinion up, then you will run into U-joints binding up at axle droop when they exceed their operating angle. This is especially true with the 2.5 inch lift springs because you will be way up there.
That is why people cut and turn the knuckles, so they can have the pinion angle and the caster angle within the proper range. I know people that did a SOA without a cut and turn, but they didn't stay that way for long after breaking the U joint or the pinion.
Whenever you get Charlie aka (Pin Head) to answer a question in your post, do yourself a favor and listen to what he has to say. He is a great tech reference and has a vast working knowledge of cruisers.
cruiserjunkie and rockcod have it right. The relationship between the pinion and caster angles is FIXED. Using caster shims or cutting the perches loose will allow you to change these angles but their relationship to each other stays the same.
However, if drive line angles become an issue because of binding and you wish to resolve that but changing the pinion angle, then you have to 'cut and turn' the axle. Changing the pinion angle, and retaining a positive caster angle of 1 to 3 degrees, requires two actions - cutting loose the spring perches and turning the knuckles. If you want to point the pinion up to keep it out of harms way, it must point directly at the center of the t-case output shaft (0 joint angle at the pinion flange), in order for the double-cardan joint to work correctly.
Still a firm believer in not HAVING to cut and turn. Not only because mine works great, but mostly because guys like Mark W. have been doing it professionally for years with many, many, happy customers.
One does have to clearance u-joint yolks or find the rare 3 speed versions that are high clearance to make a no C&T SOA work, but it is a relatively easy job.
I have a link to my build thread in my sig with a more detailed write up in my sig line.
There is no comparison between a correctly set up front end and the stock 40 setup.
Driving manners are a night and a day difference with a correct arrangement. Stock works fine with no lift. Anyone that says 0 caster is fine for on highway driving will find themselves on the wrong side of the debate table with every automotive engineer on the planet
i am one such person who didn't do the cut-n-turn and ended up doing it all over again a few years later after a few twisted off pinion flanges .
a cut-n-turn isn't reallly very difficult and is well worth the effort in the end .
i would do it .
To answer the OP...C&T is not hard to do. But for an FJ40 with the spring reversal and the extra driveshaft length it gives you it is not required at all. I have done dozens of them this way. with no failures no problems and no complaints. No one has ever gone back and done a C&T on any of the rigs we have SOA'd without it.
I expect and achieve vibrationless 65-70 mph highway runs in 4wd and one handed steering at that speed out of any '40 I SOA.
If you do a C&T you can get a bit more stable high speed ride in terms of rut following by increasing the castor.
With 2.5 inch lift springs you will be getting into some extreme ujoint angles and will be seeing reduced joint life but for most people it will still be acceptable. You will want to clearance your Ujoint mounting ears and/or use some high angle assemblies too. Front and rear driveshafts.
Thank you everyone for the responses. I really appreciate it! I initially read my caster angle backwards (No surprise for me there lol). So today, sitting on its own weight, with everything secured, the caster was +4.
