Adjustable Rear LCAs and Pinion Angle

[richmeyer]

I'm thinking of getting the ToyTec adjustable lower control arms (or links) to hopefully fix the pinion angle that I suspect is causing some annoying driveline vibe. My question is this, how much longer should I extend them to get the correct angle? Right now I'm on the OME 891 springs with only a bumper so not much sag.

Also, thought the chart below did a good job at explaining correct driveline angles. Right now I think I fall into the third category, maybe the 4th, just not as exaggerated.

 

[Skidmarcx]

Normally you use the adjustable UCAs for locating... You shouldn't have to move them much I'd say go a 1/16" at a time? The factory arms should provide the correct geometry... You sure your issues aren't elsewhere?

 

[steezemcqueen]

Keep in mind, that chart is for single carden type driveshafts. 3rd gens use a double carden shaft which typically do not have the vibration issues that single carden shafts do. Pointing the pinion up and not being parallel with the T case output will reduce vibrations in my experience on these trucks even though that chart says not to.

Adjustable uppers definitely help reduce some vibrations after lifting for me.

Lowers will work too but you would have to shorten the LCA to reduce the pinion angle. Lengthening the UCA's is a better way to go IMHO.

 

[MStudt]

Technically the correct set-up for double cardan is keeping the rear pinion and drive shaft in a straight line. You can allow a slight degree on angle on the pinion side u-joint for flex and settling reasons. This picture shows the correct set-up for a double cardan. I ran this exact set-up on the rear of many jeeps with no drive line vibrations, and 4runners rear shafts are about 2x longer.

 

[richmeyer]

Normally you use the adjustable UCAs for locating... You shouldn't have to move them much I'd say go a 1/16" at a time? The factory arms should provide the correct geometry... You sure your issues aren't elsewhere?

I'm fairly sure its the driveline, I'm getting an oscillating type vibration thats coming up through the floor and can be felt literally by the seat of my pants. I can also feel/see it coming up through the gearshift (its a 5spd). I've had two different sets of wheels and two sets of tires on the second set of wheels and the vibe is about the same. So I dont think its out of balance wheels.

Unless anyone out there thinks it could be something else...

 

[richmeyer]

Technically the correct set-up for double cardan is keeping the rear pinion and drive shaft in a straight line. You can allow a slight degree on angle on the pinion side u-joint for flex and settling reasons. This picture shows the correct set-up for a double cardan. I ran this exact set-up on the rear of many jeeps with no drive line vibrations, and 4runners rear shafts are about 2x longer.

Awesome pic, had no idea about the different types of joints. Learn something everyday. Thanks!

 

[Andy in Pa]

Not sure if you have done it yet, but you may want to grease up the joints and the CV joint in the driveshaft to see if it changes the vibes. If that doesn't help, then remove the rear driveshaft, put it in 4wd and take it for a drive. If the vibes are still there its not the rear driveshaft. I have a similar issue right now, but its because the previous owner never touched my T4R with a grease gun. The ball/socket of the CV is worn and loose on my rear driveshaft, but I greased it up and its tolerable until I can change the CV joint in the next few weeks.

Also FYI... If you can hop under there and take a pic of your rear driveshaft installed, I am sure someone here can let you know if you could be getting vibes from your driveline. Mine has a 3" lift, and looks very close to the pic of the CV shaft above.

 

[MStudt]

Not sure if you have done it yet, but you may want to grease up the joints and the CV joint in the driveshaft to see if it changes the vibes. If that doesn't help, then remove the rear driveshaft, put it in 4wd and take it for a drive. If the vibes are still there its not the rear driveshaft. I have a similar issue right now, but its because the previous owner never touched my T4R with a grease gun. The ball/socket of the CV is worn and loose on my rear driveshaft, but I greased it up and its tolerable until I can change the CV joint in the next few weeks.

Also FYI... If you can hop under there and take a pic of your rear driveshaft installed, I am sure someone here can let you know if you could be getting vibes from your driveline. Mine has a 3" lift, and looks very close to the pic of the CV shaft above.

FYI. Changing the u-joints in the double cardan joint aren't going to be as easy as you think. The only place I know of that sells those u-joints is High Angle Driveline. Last I checked they only had a few left. Might be worth you money to have a shaft made that excepts standard u-joints that you can buy off the shelf.

 

[Andy in Pa]

FYI. Changing the u-joints in the double cardan joint aren't going to be as easy as you think. The only place I know of that sells those u-joints is High Angle Driveline. Last I checked they only had a few left. Might be worth you money to have a shaft made that excepts standard u-joints that you can buy off the shelf.

Yeah good call. I was reading that somewhere else on here, it probably is the best thing to do. I am a Jeep guy too, I have a few custom shafts around from my rock crawler Jeep (XJ), I could probably use some parts from that and build something custom. I'll check and see how close in length the XJ shaft is to the T4R shaft.

 

[MStudt]

Yeah good call. I was reading that somewhere else on here, it probably is the best thing to do. I am a Jeep guy too, I have a few custom shafts around from my rock crawler Jeep (XJ), I could probably use some parts from that and build something custom. I'll check and see how close in length the XJ shaft is to the T4R shaft.

Pretty sure the 4runner shaft is still going to be longer than the XJ. You might be able to cut the center section out and weld a longer section in.

 

[infamousRNR]

so how does one go about adjusting their upper and lower rear control arms?

do you want to lengthen or shorten these arms to compensate for a rear lift of ~ 4-5"

how do you correct the pinion angle? longer arms?
[MENTION=98153]MStudt[/MENTION]

 

[MStudt]

so how does one go about adjusting their upper and lower rear control arms?

do you want to lengthen or shorten these arms to compensate for a rear lift of ~ 4-5"

how do you correct the pinion angle? longer arms?
[MENTION=98153]MStudt[/MENTION]

Longer or shorter will do it. If you get longer lca's you'll push the axle towards the rear lowering the pinion, and raising the pinion if you go shorter. Having longer uca's will clock the axle moving the pinion higher, and lower if you have shorter arms.

As you lift the rear it's naturally going to pull the axle forward. Lengthening the lca's by only 1/2" to 1" will get is back to the stock loaction. You can do stock lca's with adjustable uca's, and be able to get some good adjustment that way.

 

[cruisercorner]

who's got a pic of the correct DC driveshaft alignment? The pics that were posted are now gone. I have adjustable rear control arms on our 3rd gen and trying to get this sorted.

 

[phattyduck]

who's got a pic of the correct DC driveshaft alignment? The pics that were posted are now gone. I have adjustable rear control arms on our 3rd gen and trying to get this sorted.

Plenty of info out there on the general internets:

Driveline Geometry 101 – Tom Wood's Custom Drive Shafts

If you have a 4WD, you have a double-cardan at the front end of the rear driveshaft. If you have a 2WD, you have two single u-joints. Align as needed for your setup...

-Charlie

 

[vegask]

If you are getting vibes after a lift, check your panhard angle. Your rear axle is more than likely 1/4" to 1/2" closer to the passenger side now. Adjustable panhard or eimkeith bracket will fix it.