Possibly another solution for driveline decel noise

[Luke]

I know a few folks here, notably CP and myself, have been looking for ways to fix the deceleration noise that plaques many DSMs and GVR4s alike.

Last weekend, I adjusted my driveshaft angle with a magnetic angle-finder. Note that our driveshafts has 3 U-joints. When two sections of driveshaft are connected by a U-joint, the sections would actually accelerate and decelerate as they complete a single revolution. Therefore it is important to either minimize the angle, or have two neighboring U-joints setup in such a way so that this accel/decel cancels each other out.

More info on this is here.

Also note that the lobro joint on our driveshaft is a constant-velocity joint, so it does not accelerate/decelerate as it completes a revolution ( unlike a U-joint would )

So, what I did last weekend was adding shims ( actually a mitsubishi OEM parts ) to make the first two sections of my driveshaft to have the same angle. Before shimming, the angle was off by about 3 degrees. After shimming, it is within 1-degree of one another. This seems to reduce my deceleration/wub-wub noise tremendeously. Here are the pictures.








I would appreciate it if someone else with decel noise issue give this a try and let us know if this is indeed a fix.

 

[Terry Posten]

Thats cool. Never thought of that.

I just need to find a "angle thingy" to use. /ubbthreads/images/graemlins/grin.gif

 

[atc250r]

Great idea!

You can get that tool at Sears.

John

 

[Polish]

If it works you are a hero. /ubbthreads/images/graemlins/cool.gif

 

[curtis]

I checked this on my car years back and replaced one of the carriers and it helped just never got to do the other. Another thing to add to this is the pinion angle. It needs to be set, problem is with the bushings as loose as they are its hard to do because it constantly changes. When I replace the polyurethane bushings in the rear I plan on elongating the mounting holes so I can finally set up the angle.

This is a good idea... karma points awarded for sure.

 

[Luke]

You're welcome guys.
Now someone else give it a try, and see if this works in another car, and not just my car. /ubbthreads/images/graemlins/grin.gif

BTW, the amount of shims, and whether you shim the front or rear carrier bearing is very car dependent. So, I would suggest measuring the angle of the front-two driveshaft sections, and figure out which one of yours to shim in order to make the two angles equal.

I got my magnetic angle-finder from harbor freight.

 

[ktmrider]

Hmm, nice thought!
I have both the wub-wub and a cheapo angle gauge, will check it out later this week.

 

[CP]

Nice tip! So....does that measure the angle of the DS relative to horizontal (flat ground)? I'm going to attempt to replace the internals of my lobro joint next weekend and will report back in my carrier bearing install thread.

 

[Luke]

Hi Cy: No, I did not measure the DS angle relative to ground, or even relative to the car body.

In those particular pictures, my car was on an inclined driveway, with the rear jacked-up. I did not intend for it to be level with the ground at all. I simply want the driveshaft sections to be more or less parallel with each other, to minimize U-joint angles.

Let me know if that makes sense.

 

[CP]

It does.

 

[curtis]

If your checking angle relative to the driveshaft for the pinion angle just add 5 degrees pinion down. Not sure if 5 is the correct number for these cars but thats what we use to set Mustangs up at back in the day. If someone can verify the angle in a maintenance schedule it would be nice.

 

[jepherz]

I was just going to mention those square OEM shims when I read this topic. Good find.

I have heard that Kraut boxes call for lasers etc. to line up their drive shafts.

 

I thought it sounds cool!

 

[Hksvr4]

The noise plagued me for years! I always thought it was the downpipe hitting something. This is a great idea!

 

[Luke]

Yup, my decel noise is pretty much gone with this extremely simple shimming.

I thought this morning that I may still hear the wub-wub faintly, but as I listened more carefully, I realized that the noise is just in my head!!! I have daily driven my galant for 7 years, so basically my mind has been conditioned to hear the wub-wub whenever my right foot is off the gas pedal. /ubbthreads/images/graemlins/grin.gif
Strange, how the mind works, ain't it.

Note that the theory behind this shimming agrees with the carrier bushing fix in VFAQ ( which is filling with silicone ). Basically the carrier bearing keeps the three driveline sections angled correctly. So, you will need the carrier bearings to be both in good conditioned and also shimmed correctly. Both of mine were brand new replacement, but I still got the wub-wubs until I performed this shimming mod.

 

[Polish]

/ubbthreads/images/graemlins/worthy.gif /ubbthreads/images/graemlins/worthy.gif

I will not fear wub wubs anymore if I get another AWD crap box. Now if I get one and this doesn't fix it then I am going to beat you up, deal?

 

[G]

Nice what's the part # for the shims?

 

[CP]

I'm going to use stainless washers from Home Depot Racing. My wubs are felt way more than heard. The sound is just a by-product of the vibration.

 

[Armitage]

Thank you for posting this! I may not get a chance to try it anytime soon as I'm undertaking some other large projects right now but I do have some serious decel noise so I will check it out when I get a chance.

 

[GVR4ZUM]

Cool,somebody else pls try it and post some info.