In order to diagnose a bang-clank, last night I put a floor jack under the diff and raised the rear eng.

I started the car, put it in drive, a tapped the accelerator to rev and release - just mildly, not a jolt, just a blip. I got some bang-clank...not the full monty but some. I grabbed a flourescent tube trouble light and jabbed the gas pedal while I looked underneath. When I blip it, the rear axle rotates just a wee bit - maybe 3/4". It rotates under torque then releases when the power application relaxes. Does the same in reverse - same motion, same distance.

I know that the torque from the engine through the driveline to the ring gear is going to want to spin the axle in the direction of rotation. I know the leafs are bolted solidly to the axle and to the shackles...but through a bushing.

So, the question is how much movement is normal?

Could it be worn bushings at the leaf spring mounts?
If so, are bushings difficult to replace?
Is it IMPORTANT...or OK to ignore?

Could it be related to Detroit Locker lash? (I know the Locker is noisey...but I don't have experience with them and don't know how much noise - how much bang-clank - is normal for a Locker.)

Would a wee bit - a wee bit - of play in the u-joints make a noticeable sound? By noticeable, I mean my wife might say "is that sound important?". It has been thirty years since I had a car with a worn u-joint...I've forgotten what they feel and sound like.

Any other ideas???

 

Is the noise generally noticable as you straighten up from coming out of a turn?

I've got a Detroit Locker in the Ford 9" in my Drag car. It is BRUTAL on the street.

No interior in the car so you can hear everything. When you go into a turn, it clunks a little when it disengages and then you hear the ratchet, clickety-clickety-clickety-clickety, until you straighten up coming out of the turn and the Click-BANG. it re-engages.

If you romp on it while in a turn it immediately goes to the Click-BANG as it locks back in.

That type of noise is normal from an honest Detroit locker.

 

Axle wrap is common with leave springs but with the rear up in the air it shouldnt really move. Could be your bushings are toast and making the noise. OR the rear DS ujoints are shot from the excessive axle wrap

 

I would check u-joints and u-bolts,then all the spring bushings.

 

Thanks. I have not noticed if it is more pronounced coming out of a turn. I'll check and report back.

I suspected the clank-bang is partly the Locker. I got the Locker manual out and did the complete buns-up test: Raised rear, rotate wheels forward, hold one and reverse spin the other, etc., etc. and it is set up perfect. Engages, disengages flawlessly forward and reverse. It is a very cool gadget.

I can hear it racheting outside but not when inside the car. Doesn't act brutal in driving...but it ain't no creampuff. Clank-bang, torque steer (very annoying because I think my shocks are junk and the body rocks when the torque applies).

I sure would like to know if anyone has raised the rear off the ground and watched the axle while blipping the throttle a bit. I'm really wondering if the movement I've got is normal or whether I've got to start swapping parts.

If it's normal, I'm willing to chalk the clank-bang up to the Locker. It's the axle wrap that worries me.

 

Mike&Jerm: How can I check the bushings?

I know the u-joints have a bit of play...just not bad enough to change out yet, IMO. The bushings have some cracking you can see but, other than that, I don't know how to judge if they're shot or not.

Would loose/worn bushings cause a feel like a worn out shock? I get a pretty good "rock" diagonally thru the car when I shift into drive or reverse with foot on brake. It feels like junk shocks...but the DPO put Gabriel Pro Comp's on five years ago and they don't leak and look "normal".

Something is not quite right. Not dangerous...but not right, either.

 

Sounds like your locker is making noise. Does it seem like you have to tense everything up and then go to get rid of the noise? With mine ( 5spd though ) i have to let the clutch out until my locker goes bang-bang and then it is set up so that it will go off the line with no more noise. This is, from what i have been told, due to the lockers backlash and that is what causes the noise. Hope this helps.

 

I barely hear my locker with a 5sp but it was used and well worn in. From time to time it bangs and i think i broke something until i remember i have a locker in the rear

 

Mine is an automatic...so I drop it into drive and get the clankbang immediately. But I can get why your 5 sp behaves the way you describe - seems perfectly normal for a locker with a manual.

When I did the Locker test specified in the manual for it, it tests perfectly and the backlash seems fine. It's been in there since 2000 and has 100k miles on it, easy.