Adjustable Rear Control Arms

[JeremyH]

What are you guys doing for adjustable rear control arms (both upper and lower). After adding my 3" lift, I noticed that the WB is a bit shorter and I'm assuming that the pinion angle isn't right either. To correct both, I'll need adjustable uppers and lowers. One option is gathering parts (heims, busings, threaded inserts and tubing) to make what I need, but, being as lazy as I am, I wanted to know what other options (bolt on) are out there.

Thanks!

Jeremy

 

[shawkins]

Spidertrax will make whatever length links you want. They are heat treated 4130 chromoly. I'm using one for my panhard currently.

 

[Pikeman]

ok i am running the LC coils on my 98 which is about 4.5 inch. having a 4 link helps maintain Pinion angle throughout the arc of the swing. As you go full droop it swings forward and at full stuff it moves backward.

In both those pictures you can see how it travels along the path of an arc. I have looked at my pinion angle when it has been full stuff and it isnt bad. Hopefully it answers or gives some insight to your question and concern.

 

[JeremyH]

Shawins, thanks for the reminder. I forgot that places like Spidertrax and Branik will make whatever length links you want.

Pikeman, I'm assuming you have a double triangulated 4 link....got any pictures of the link setup? Yeah, I am familiar with the 4 link setup, but this 4Runner is a street queen (I've got another offroad only toy:cheers and sticking with the 5 link should be fine for this truck. I just needed a a way to adjust pinion angle and set the wheelbase. BTW, when you installed your lift, how much did the pinion angle change? I am used to a short wheelbase vehicle with short driveshafts where a small amount of lift results in a rather large pinion angle change.

Thanks!

 

[Pikeman]

Jeremy-- I am running the factory set up with an adjustable Panhard bar. Short wheelbase leaf sprung vehicles yes you have to worry about pinion angle because with a spring the pinion angle stays flat (nose stays parrellel to ground) as the spring droops thereby increasing angle on the U-joints. With the 4 link that our trucks have it keeps the pinion angle more relative to the drive shaft (nose rotates up) as it moves through the arc. You can spend money on adjustable links and end up with much stronger links. If the few main lift manufacturers that have been making lifts and researching them for the past 10-14 years have not felt a need to create longer or adjustable link arms then it is not a big enough issue to worry about IMHO. Wouldnt it make sense that if they could make money on another product or it was a safety concern they would do so?

Jeeps have long arm kits that help a little bit but those are also the 5 or more inch lift kit and not a 3". However you look at almost any leaf spring kit 3" or more and they all come with Pinion adjuster shims to put between spring pack and spring plate.

 

[JeremyH]

Yeah, I was referring to my 3" suspension lifted, short arm, coil spring jeep. Anything over 2" on a coil sprung jeep will require adjustable uppers at a minimum.

However, the reason that I ask about this on my 4R is because I now (just after the installation of these new 906 coils) feel a slight vibration at about 60mph. It only occurs when you let off the gas. I am assuming that this is the result of the pinion rotating to point back downward when decelerating. When accelerating, it should rotate upward and lessen the angle with respect to the drivehsaft and tranny output.

I didnt think I would have this problem since the DS on these vehicles is quite a bit longer than what I've worked with in the past, but it seems to be....

 

[theizzardking]

good conversation guys, tuned in.

 

[techno]

I'm trying to think logically about the changes in geometry that occur with lifts and longer control arms, and am now wondering about the effects on the coils and shocks if the wheelbase is modified slightly as mentioned.

From the factory, I assume that the rear suspension is probably close to being centered, meaning that there is equal travel distance available up and down when the vehicle is just sitting there. I would also assume that the shock absorber upper and lower mounts are now close to being perfectly 'lined up' so that when wheel travel occurs the shock bushes will flex an equal amount in both directions during compression and extension. That being said, if the control arms are now lengthened, the shock bushes will now need to flex beyond their 'normal' range, so will this have an undesirable impact on the shock mounts and cause premature failure/excessive wear?

I doubt it's anything to be overly concerned about, just throwing it out there for thoughts...

 

[JeremyH]

Techno, I have run quite a few different types of suspensions on my jeep and have NEVER noticed a shock bushing failure. IIRC, the rear shock mounts on the 4R are positioned to rotate freely (without bind) as the suspension cycles. Just for reference, here is the rear shock setup on a highly lifted 4R: http://www.4x4wire.com/toyota/minutemods/4rrearshock/rearsusp.jpg. I see that he has adjustable uppers, but that looks like a LOT of lift.

BTW, just to clarify what I posted earlier, I installed the rear coils only a few days before I did the front and this is when I noticed the vibration. I was thinking that after I installed the front coils, the tranny output shaft would level off and reduce the angle difference between it and the driveshaft, but I suppose that did not happen.

Usually, when I set a pinion angle, I like for it to be between 1-2* below the angle of the driveshaft, to account for the fact that during acceleration, it will rotate upward.

I really just need to get under there with my angle finder and check the pinion and driveshaft angles to see what the difference between the two really is. Just gotta wait for the weather to clear up...it's been crappy these last few days.