Rear yawing right when accelerating and yawing left.....

taroo · **Joined:** Sun Apr 27, 2008 2:14 pm **Posts:** 292

Help...

The rear end of my CRD is yawing right (right side seems to go back and rear pulls right) when I accelerate. When I decelerate the rear end seems to yaw back to straight and even yawing a little to the left (right side comes forward and left side goes back).

I have new lower control arms as the the others rusted through. Springs aren't broken. Stabilizer bar is not broken and is tightly bolted.

Is this a worn rear upper control arm? The ball joints on the existing really upper control arm look good but that does not mean they are good.

I welcome thoughts.

flash7210 · **Posted:** Sun Jun 26, 2016 10:16 am

If your lower control arms are bolted up tight and their bushings are solid, then the only other possibility is the upper bomerang.

taroo · **Joined:** Sun Apr 27, 2008 2:14 pm **Posts:** 292

flash7210 wrote:

If your lower control arms are bolted up tight and their bushings are solid, then the only other possibility is the upper bomerang.

Okay...bought a new Rear Upper Control Arm from Rock Auto. MEVOTECH - CMS25156 Control Arm $112.79

I assume it is straight forward to replace by following the FSM.

wilco549 · **Posted:** Tue Jun 28, 2016 9:58 am

Mine did that when the lowers were worn out. I'm not sure how the upper control arm can affect tracking (yaw) since it's a center point, pitch mount. In other words, the axle should only pitch forward, rearward if the top mount is worn, the lowers control tracking(yaw).

my $.02, let us know what you find.

WWDiesel · **Posted:** Tue Jun 28, 2016 12:45 pm

wilco549 wrote:

Mine did that when the lowers were worn out. I'm not sure how the upper control arm can affect tracking (yaw) since it's a center point, pitch mount. In other words, the axle should only pitch forward, rearward if the top mount is worn, the lowers control tracking(yaw).

my $.02, let us know what you find.

I agree, tracking is controlled by the lower control arms! The upper boomerang provides rotational control of the rear axle and also controls the angle of the rear axle while the tracking should remain constant during up and down movement. :roll:

I would be taking a hard look at the lower control arms! :wink:

69Hcode · **Posted:** Tue Jun 28, 2016 1:33 pm

The upper mount could affect it if one of the bushings where it mounts to the body is worn. If they are OK I doubt the ball joint would make it yaw. Probably just get a clunk.

taroo · **Joined:** Sun Apr 27, 2008 2:14 pm **Posts:** 292

69Hcode wrote:

The upper mount could affect it if one of the bushings where it mounts to the body is worn. If they are OK I doubt the ball joint would make it yaw. Probably just get a clunk.

So the lower control arms are new. The previous ones literally rusted through and I am in VA which is NOT a recall state. I replaced both and they are rock solid and new. I am getting a clunk and I checked the slip yoke and it is nice and smooth. I realize it could be the U-joints as well. However, I am not as concerned with the clunk as much as the rear tracking.

It is bizarre...I give the libby fuel and the rear heads to the right!!! I let off the gas and it heads to the left!!! I literally have to correct the steering (oversteer) to compensate for movement accelerating and decelerating.

bigE.94 · **Joined:** Wed Jul 01, 2015 2:00 am **Posts:** 48

Sounds like something Im facing right now. Except mine isn't as extreme.

wilco549 · **Posted:** Wed Jun 29, 2016 3:07 pm

Rear shocks and springs good? It's a long shot because the lowers are the real control.

taroo · **Joined:** Sun Apr 27, 2008 2:14 pm **Posts:** 292

taroo wrote:

Help...

The rear end of my CRD is yawing right (right side seems to go back and rear pulls right) when I accelerate. When I decelerate the rear end seems to yaw back to straight and even yawing a little to the left (right side comes forward and left side goes back).

I have new lower control arms as the the others rusted through. Springs aren't broken. Stabilizer bar is not broken and is tightly bolted.

Is this a worn rear upper control arm? The ball joints on the existing really upper control arm look good but that does not mean they are good.

I welcome thoughts.

Okay...I replaced the rear upper control arm. All is well !!! and the clunking noise is gone also. The middle joint was totally shot and darn near close to falling out. the ends were not bad but had play.

taroo · **Joined:** Sun Apr 27, 2008 2:14 pm **Posts:** 292

taroo wrote:

Help...

The rear end of my CRD is yawing right (right side seems to go back and rear pulls right) when I accelerate. When I decelerate the rear end seems to yaw back to straight and even yawing a little to the left (right side comes forward and left side goes back).

I have new lower control arms as the the others rusted through. Springs aren't broken. Stabilizer bar is not broken and is tightly bolted.

Is this a worn rear upper control arm? The ball joints on the existing really upper control arm look good but that does not mean they are good.

I welcome thoughts.

Okay...I replaced the rear upper control arm. All is well !!! and the clunking noise is gone also. The middle joint was totally shot and darn near close to falling out. the ends were not bad but had play.

Well Well...the clunk is gone but the yaw is still there. I had only taken it around the block last night and thought it was good. After driving on the interstate today and pushing and letting off the accelerator, it is clear it is back. I will look at the shocks at this point...aarrgghh!!!

wilco549 · **Posted:** Fri Jul 01, 2016 3:49 pm

when you replaced lowers, were the bolts worn? Holes elongated or wear at the attachment points either end? There should be a fairly tight fit-up of the bolts and mounts...I had to tap mine out and in. Are the bolts tight? I know it's elementary but......... I keep thinking it has to be the lowers.

Rear yawing right when accelerating and yawing left.....

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