Trex evolution radius arm install question and caster/driveline angle

[steelworker77]

For those who have installed these.

Regarding the lower bushings in the head unit. I have a large gap between the radius arm and the head unit when installed and just see if im supposed to simply suck up that space when I torque to spec. Wandering if i pushed the bushings in to far when I installed in the vice. I didnt go crazy on them and they call for a 150ft so I would think that would push them as far as I did.

Regarding caster and pinion angle-

I got my hands on a Dana 44 mag front end from toms for a good deal. It has 4* of added caster and 2* added pinion.

With the trex arms with the caster backed all the way off with 2* bushings im getting 7* caster and my front driveline angle (what im calling the difference between the front driveshaft and pinion angle) is 9*.

Do i leave as is or rotate the 2* bushings for -2* so i am at 3 and 5 then use the caster bolts on the arms to go to say 5 and 7.

Wasn't sure what was an acceptable front driveline angle since not using it all the time as well as best caster * for 34" tires.

Might see 40 mph in 4wd and that would be driving snowy roads. Besides that its in the sand at the beach or some trails out in the woods. Nothing to crazy.

 

[DirtDonk]

Just checking here, but what’s your ultimate goal? Caster, or pinion angle?
Unfortunately you can’t have both using these methods.

That 9° doesn’t sound like as bad as some have had it, but it’s still just a static measurement.
You can rotate the driveshaft by hand to feel if there’s any binding at certain positions, but that only tells half the story.
Since the suspension cycles up and down, it’s hard to tell if it’s going to bind this way. You could jack the frame up and let the suspension hang to see if the driveshaft still turns.
If it turns with no perceptible binding, then other than a vibration at higher speeds in four-wheel drive, you are probably not in danger of snapping a joint or yoke right away.

 

[DirtDonk]

I didn’t really pay attention to the 44 Mag part.
They’ve reduced the pinion angle by 2° compared to stock? Is that what it is?
Sorry I haven’t studied it so curious about the details.

 

[steelworker77]

I didn’t really pay attention to the 44 Mag part.
They’ve reduced the pinion angle by 2° compared to stock? Is that what it is?
Sorry I haven’t studied it so curious about the details.

 

[steelworker77]

Just checking here, but what’s your ultimate goal? Caster, or pinion angle?
Unfortunately you can’t have both using these methods.

That 9° doesn’t sound like as bad as some have had it, but it’s still just a static measurement.
You can rotate the driveshaft by hand to feel if there’s any binding at certain positions, but that only tells half the story.
Since the suspension cycles up and down, it’s hard to tell if it’s going to bind this way. You could jack the frame up and let the suspension hang to see if the driveshaft still turns.
If it turns with no perceptible binding, then other than a vibration at higher speeds in four-wheel drive, you are probably not in danger of snapping a joint or yoke right away.

Really wasnt sure what front driveline angle was acceptable. I dont get any bind at full extension but wasnt sure if that amount was a major issue.

Plan as of now is to rotate my 2* c bushings to pull 4* of caster and pinion angle out of it making 3-4* of caster and 5* of driveline angle. Then use the adjustable cam bolts on radius arms to set my caster at 5* which should put my driveline angle at about 6*.

Assuming it should drive fairly well with 5* of caster? Was at 1* so figured anything more than 4 should be great.

 

[DirtDonk]

That’s a logical assumption. And it’s correct for most people, I’d say.
However, in recent years, several members here have reported they weren’t happy until they got into the six and above range.
But because five is so close to that, I think you should be fine. Crossing fingers anyway!

Are you measuring all this at ride height? That differential set up is slick, with its added 2° pinion angle.
But with already built in extra caster, plus the caster of the radius arms, plus the bushings, plus the better pinion angle, are you sure your measurements are consistent?
I’m thinking you should already be in the caster range with all of you’ve got. Seems strange that you would have to settle for a 4 to 5°, with already 8° or more of built in compensation.
And still have to deal with a slightly wonky pinion angle.

Speaking of which, you are measuring the difference between the centerline of the driveshaft and the pinion angle itself. I think you said. Correct?

 

[steelworker77]

That’s a logical assumption. And it’s correct for most people, I’d say.
However, in recent years, several members here have reported they weren’t happy until they got into the six and above range.
But because five is so close to that, I think you should be fine. Crossing fingers anyway!

Are you measuring all this at ride height? That differential set up is slick, with its added 2° pinion angle.
But with already built in extra caster, plus the caster of the radius arms, plus the bushings, plus the better pinion angle, are you sure your measurements are consistent?
I’m thinking you should already be in the caster range with all of you’ve got. Seems strange that you would have to settle for a 4 to 5°, with already 8° or more of built in compensation.
And still have to deal with a slightly wonky pinion angle.

Speaking of which, you are measuring the difference between the centerline of the driveshaft and the pinion angle itself. I think you said. Correct?

Correct measuring everything at ride height. I have a 2 1/2" suspension lift but the rear measures 3" and the front actually measures 3 1/2" (thinking I may have received the wrong front coil springs when I installed the lift 2 years ago. I have a winch on the front and am fairly loaded down.

Yeah pretty confident in all measurements. Plan was to cut and turn the original rear but after inspecting it someone had done some pretty hack work cutting and welding on it and pretty sure the axle tube is slightly bent on the one side.

Correct what I am calling the driveline angle is the difference between the driveshaft and pinion angle.

 

[steelworker77]

Something that just hit me and I guess I need to call toms to verify. The new rear has 3" axle tubes. I just saw duffs offers C cap spacers for the radius arms for the larger axle tubes.

Toms doesnt mention anything on needing them but when I was installing the bushings I definately had to crank down the last 1/4" or so much more than normal to suck everything up tight and the 2* bushings are squished out much more than I normally see especially only being 2*.

 

[DirtDonk]

Yeah, could be a thing. But many of the C-bushings nowadays squeeze out like nobody's business. Been dealing with it for years at our end.
So that, in itself at least, is not a big indicator of anything amiss. However, it still could be, so is worth keeping it in mind while figuring all this out.

You're using the standard 7" in front and 6" in back, stock height measurments, as your baseline for figuring out your lift?
It's not unusual for the rear springs to lift higher than expected, but it isn't common for the front coils to have that characteristic. So yes, you may have gotten higher springs. Especially when you take the winch into account!
Unless they happen to be BC Broncos coils, which can be ordered in "winch" versions to carry the extra weight.

Paul