SYE without adjustable control arms

[Jmr17320]

Has anyone ever installed a SYE without adding adjustable control arms? I have done the 2.5” OME lift and want to do Adj CAs with the SYE, but can’t swing the cost all at once.
Would I get any benefit with the SYE even though I can’t fully rotate/align the rear axle ?

any issues with doing it in stages?

 

[mrblaine]

Has anyone ever installed a SYE without adding adjustable control arms? I have done the 2.5” OME lift and want to do Adj CAs with the SYE, but can’t swing the cost all at once.
Would I get any benefit with the SYE even though I can’t fully rotate/align the rear axle ?

any issues with doing it in stages?

Here is the perfect way to do things in stages. Buy the SYE, toss it in the closet. Buy the upper adjustables, put them next to the SYE. Buy the lowers, put them next to the uppers. When you have saved enough for the Double Cardan driveshaft, install the rest of the stuff. Works perfectly every single time.

 

[jazngab]

Here is the perfect way to do things in stages. Buy the SYE, toss it in the closet. Buy the upper adjustables, put them next to the SYE. Buy the lowers, put them next to the uppers. When you have saved enough for the Double Cardan driveshaft, install the rest of the stuff. Works perfectly every single time.

Is it necessary to have BOTH adjustable uppers and lowers? From my understanding only adjustable uppers arms were needed. I ordered the Currie double adjustable upper arms but I actually bought all new stock arms for the other 6 CAs.

 

[mrblaine]

Is it necessary to have BOTH adjustable uppers and lowers? From my understanding only adjustable uppers arms were needed. I ordered the Currie double adjustable upper arms but I actually bought all new stock arms for the other 6 CAs.

I'd like to kick the idiot that started that shit right in the taint until they promise never to utter or repeat that crap again. You can not adjust the lower or upper arms without changing wheelbase and pinion angle at the same time. The only way the uppers could adjust the pinion angle without changing the wheelbase is if they were mounted to the center of the axle shaft.

 

[jazngab]

I'd like to kick the idiot that started that shit right in the taint until they promise never to utter or repeat that crap again. You can not adjust the lower or upper arms without changing wheelbase and pinion angle at the same time. The only way the uppers could adjust the pinion angle without changing the wheelbase is if they were mounted to the center of the axle shaft.

Not the answer I was hoping to hear.....
So all the people running just adjustable upper CAs, how is it possible they are adjusting pinion angle with fixed lower arms?

 

[JMT]

I'd like to kick the idiot that started that shit right in the taint until they promise never to utter or repeat that crap again.

Just about everyone on here perpetuated that myth at one time.

 

[JMT]

Not the answer I was hoping to hear.....
So all the people running just adjustable upper CAs, how is it possible they are adjusting pinion angle with fixed lower arms?

You can, but just think about what is happening when you just lengthen the uppers to rotate the pinion, but leave the lowers the same length.

 

[Goatman]

Depending on component selection you can get away with stock lowers in the FRONT. You may need to adjust the FRONT a degree or two.
With a SYE you are now aiming the pinion like a howitzer to point up to the transfer instead of parallel to it.
Even if you are not installing a SYE then you would still be best to use adjustable upper and lower in the rear because you have a lot of stuff (fuel tank shocks) located close together. That way you can avoid having to drop the transfer to get DS alignment.

 

[jjvw]

Not the answer I was hoping to hear.....
So all the people running just adjustable upper CAs, how is it possible they are adjusting pinion angle with fixed lower arms?

Many of those setups are leaving suspension travel on the table and very likely have interference issues with the track bar, gas tank and diff cover.

 

[mrblaine]

Not the answer I was hoping to hear.....
So all the people running just adjustable upper CAs, how is it possible they are adjusting pinion angle with fixed lower arms?

I didn't say it could not be done and I didn't say don't do it. What I said was you can NOT change the pinion without also changing wheelbase and the inverse is also true, you can't change wheel base without changing the pinion angle. If your axle is far enough forward that when you raise the pinion and it clears, then you don't need adjustable lowers. If the lowers are adjusted to raise the pinion angle and the axle stays out of trouble, then you don't need adjustable uppers.

If you raise the pinion with adjustable uppers and the axle moves too far back, then what will you do?

 

[89grand]

I'm trying to understand how the wheelbase can change from just adjustable uppers and rotating the pinion up or down. If the lower control arms are fixed, they can't be pushed further forward or back, they can only move in an arc as they go up and down, so the wheel base certainly changes as the suspension travels, and a lift kit causes the arms to be angled down at the axle end, which shortens the wheel base, but for some reason I can't see how the wheel base is effected by adjustable uppers.

I'm sure I'm wrong, but thinking of this mechanically in my head, I don't understand how the wheel base would change with just one set up adjustable arms, whether they be uppers or lowers, while the other two are fixed.

I can see the other problems that are caused by the axle rotation, such as the springs mounts and bump stops not being in proper alignment, but the wheel base thing is stumping me.

 

[jjvw]

Aren't the lower control arm mounts below the center point of the axle tubes? If the lowers are a fixed point, imagine what happens to the center point of the axle when the upper mounts get moved one way or another. It moves.

 

[mrblaine]

I'm trying to understand how the wheelbase can change from just adjustable uppers and rotating the pinion up or down. If the lower control arms are fixed, they can't be pushed further forward or back, they can only move in an arc as they go up and down, so the wheel base certainly changes as the suspension travels, and a lift kit causes the arms to be angled down at the axle end, which shortens the wheel base, but for some reason I can't see how the wheel base is effected by adjustable uppers.

I'm sure I'm wrong, but thinking of this mechanically in my head, I don't understand how the wheel base would change with just one set up adjustable arms, whether they be uppers or lowers, while the other two are fixed.

I can see the other problems that are caused by the axle rotation, such as the springs mounts and bump stops not being in proper alignment, but the wheel base thing is stumping me.

The rear lower links attach below the axle center line. You can't raise the pinion without the axle moving back.

 

[89grand]

I was thinking about this after I wrote it. I guess when you change the length on the upper arm, you are changing the angle of the lower arm, which in turn does make the wheel base slightly shorter or longer. I was picturing it being fixed, and not able to move forward or reward, but the angle does change, and therefore the axles position changes with it.

I think I get it now...or do I?

 

[mrblaine]

I was thinking about this after I wrote it. I guess when you change the length on the upper arm, you are changing the angle of the lower arm, which in turn does make the wheel base slightly shorter or longer. I was picturing it being fixed, and not able to move forward or reward, but the angle does change, and therefore the axles position changes with it.

I think I get it now...or do I?

Has zero to do with angle. The lower mount hangs down below the axle. If you make the upper arm longer, what does the axle react against to raise the pinion?

 

[89grand]

Has zero to do with angle. The lower mount hangs down below the axle. If you make the upper arm longer, what does the axle react against to raise the pinion?

Thinking about this off and on today, it seems if the lower arm is fixed, when you make the upper longer to raise the pinion angle, you're rotating the top of axle back CW because you're pushing against the lower arm, and if you made them shorter, you are pulling against the lower arm rotating the top of the axle CCW.

So, rotating the top of the axle CW (looking at it from the drivers side) to raise the pinion makes the wheel base slighter longer, rotating the axle CCW makes the wheel base slightly shorter. If you have just one set of adjustable arms, all of the adjustment has to happen there, which may put the axle in an unfavorable position, whereas if you have both uppers and lowers, one could use them both, while maintaining the same axle position, i.e 50% top, 50% lower or whatever combination works.

Am I getting it at all?

 

[mrblaine]

Thinking about this off and on today, it seems if the lower arm is fixed, when you make the upper longer to raise the pinion angle, you're rotating the top of axle back CW because you're pushing against the lower arm, and if you made them shorter, you are pulling against the lower arm rotating the top of the axle CCW.

So, rotating the top of the axle CW (looking at it from the drivers side) to raise the pinion makes the wheel base slighter longer, rotating the axle CCW makes the wheel base slightly shorter. If you have just one set of adjustable arms, all of the adjustment has to happen there, which may put the axle in an unfavorable position, whereas if you have both uppers and lowers, one could use them both, while maintaining the same axle position, i.e 50% top, 50% lower or whatever combination works.

Am I getting it at all?

Finally. Also be aware that due to the coarser thread pitch in lower adjustables, 1 turn will move the pinion further up or down that the same turn on the upper. That is added to by the fact that the lower mounts are closer to center of the tube than the uppers.

Basically we set the wheelbase with the lowers (approximately) set the pinion with the uppers and then use both to move the axle back and forth, up and down to dial it in. I wouldn't even try it without both being adjustable.

If we have to move the axle forward or back, we always have to readjust the uppers to reset the pinion.

 

[LukesfirstJeep]

Blaine, any idea of how much the wheelbase changes if upper only control arms are lengthened or shortened? The example I'm thinking of is when the upper control arms are adjusted one to two full revolutions.

Looking at Savvy's website, their jam nut is 1"-14 pitch. If my math is correct, one revolution is about 0.070". If wheelbase changes an equal amount, are small changes that critical? Or does it become critical when you make a 10 turn change, changing wheelbase 3/4"?

 

[mrblaine]

Blaine, any idea of how much the wheelbase changes if upper only control arms are lengthened or shortened? The example I'm thinking of is when the upper control arms are adjusted one to two full revolutions.

Looking at Savvy's website, their jam nut is 1"-14 pitch. If my math is correct, one revolution is about 0.070". If wheelbase changes an equal amount, are small changes that critical? Or does it become critical when you make a 10 turn change, changing wheelbase 3/4"?

That's a numbers thing. I neither know or care. I let the rig tell me what it needs and go from there. This is getting back into the "what length do I set my arms?" bullshit and I don't go there.

 

[89grand]

I appreciate being made to figure it out myself. I've never adjusted an adjustable arm, so I was having to visualize it in my head, but it makes sense now.