Finally fixed my coast-down rumble ( "wub wub" noise )

[CP]

You're speaking spangrish to me.

Explain in Engrish please. Measure backlash how, and where? I've got lots of washers on hand, but need to know how to balance the driveshaft with them cuz mine needs help.

Sorry for the retard posts on this subject, but I've replaced everything else with new parts and the focker still makes lots of noise.

 

[Luke]

Hey man.. the backlash you described below is explained in the manual.

However, it is not the carrier shimming that adjusts backlash.
It is the differential gear shimming inside of the rear differential.

The carrier bearing is those rubber donuts that hold up the driveshaft.
There are two of them per car.
Where it bolts to the car, according to the manual, there are shims to adjust how high/low your driveshaft sections are.
That is the one we're talking about.

I know what you mean, CP.. I have replaced a bunch of stuffs also in my car in an effort to reduce this decel noise.
While I have succeeded somewhat, it's still there.

BTW, did you try the method I mentioned a few posts up in this same thread, whereby you twist the driveshaft back and forth and observe whether the play is from t-case or rear-diff ?

Good luck, all.. this is such a common problem on our car.


Quote:
I believe the idea behind the carrier shimming is to set backlash. Set a shim behind the ring-side bearing and then place a dial indicator against a ring tooth. You are required to be within a threshold of backlash. I don't know Mitsu's spec, but 5-7 thousandths seems to be a typical number on American cars. Then load up the other bearing shim to set preload on the carrier.

 

[CP]

My rear diff was just rebuilt by JNZ, so I'm looking for other things to tweak to fix this issue.

 

[CP]

Mine's still doing it. I found some grease on the bottom rearward section of my 2 month old front carrier bearing, which means the driveshaft is moving around enough to burp some grease out. It also has a hissy fit when beginning to move in reverse from a standstill. WTF?

I just found this video and it's very similar to what I experience...coastdown rumble that's both audible and vibrates the entire car.

I just installed all NEW rubber carrier bearing bushings and installed them as pictured on page 25-4 of the FSM. The "spacers" are what have me confused. I've got one for each stud, placed with the lip on the top (as in the picture). It's basically a metal sleeve that sits between the car stud and the rubber bushings/isolators. If this spacer was removed, that carrier bearing would be able to move around ALOT more since it will not be held tightly around the stud.

So basically what I'm saying is that you can't remove the spacers.

Has anyone with this problem actually been able to fix it?

 

[DailyDSM]

I have the same problem as the car in the video. I also have a different (grinding/rattling/vibration) noise at partial throttle while maintaining speed. This is most noticeable on the freeway while trying to maintain speed at 55-65mph but it occurs in every gear. One of the guys at RRE drove it around for a bit and said it could have something to do with a carrier bearing or the transmission/transfer case. For me, all the noises started after a clutch replacement so I haven't really been concentrating on the drive shaft area yet.

 

[Luke]

Hi CP:

I think there are two spacers.. One around the studs as you mentioned.

Then there are also washers that basically move the position of the carrier bearing up and down, so that the driveshaft sections have the correct angle throughout the three piece driveshaft sections.

I haven't reshimmed mine with washers, so I don't know if it does help.. But that's what I gathered from the manual.

 

[Luke]

Quote:
For me, all the noises started after a clutch replacement so I haven't really been concentrating on the drive shaft area yet.



When you replace the clutch, did you go from stock clutch to aftermarket / more-aggressive setup ?
An aftermarket setup would have more grip, and the dampening springs ( the ones on the clutch disk ) are also stiffer.
So, this would make any slack on the your driveline to be more pronounced..

 

[Luke]

Hey Cy, I just remembered something..

Did you check if you have the two dowel pins for where the transfer case mounts to the transmission.
I was missing one of the two dowel pins, and I believe that also caused some of my decel noise.

 

[DailyDSM]

Quote:
Quote:
For me, all the noises started after a clutch replacement so I haven't really been concentrating on the drive shaft area yet.



When you replace the clutch, did you go from stock clutch to aftermarket / more-aggressive setup ?
An aftermarket setup would have more grip, and the dampening springs ( the ones on the clutch disk ) are also stiffer.
So, this would make any slack on the your driveline to be more pronounced..



Actually it was just the opposite. I went from a 2900 to something lighter.

 

[CP]

Yeah, both dowel pins are intact. I switched to the lighter, aluminum rear t-case last year in an attempt to track down the noise/vibration, but that didn't change anything. How the hell do you determine the number of washers to use as "spacers?" Trial and error?

I ziptied a string to the front portion of the driveshaft and the other end to the rear near the diff, and pulled it TIGHT. This straight line from front to rear shows that the driveshaft obviously does't sit straight, but rather bends a bit from section to section. I guess I'll just start to add stacks of washers until something changes /ubbthreads/images/graemlins/dunno.gif

I have the same bad noises while cruising on the freeway that are mentioned above. This is NOT a case of an unbalanced driveshaft, as all noise and vibration goes away when the clutch is pushed in/coasting...basically when there's no load on the driveshaft. At steady cruise it's is mostly fine, but slight acceleration or deceleration causes vibrations that resonate throughtout the entire vehicle. I'll take some of you for rides on Sep 9th to show you to see if we can figure it out.

 

Yeah my car makes the same noise, when you let off the gas some times or coast down a hill. My friend said it sounds like a pod racer, whub whub whub whub whub... you get the idea. I think it's my diff, i want to get one of the nice 4 bolts anyhow once i have the loot.

 

[CP]

Quote:
My rear diff was just rebuilt by JNZ, so I'm looking for other things to tweak to fix this issue.



I doubt it's your rear diff.

 

[CP]

I tried a 1/2" stack of 4 thick washers in the front, in the rear, and in the front AND rear to move the carrier bearings away from the bottom of the car. No luck lessening the sound.

My t-case has also been leaking out of the vent on the top for 2 years now (happened with two different cases). It's not overfilled. I think this may be because the driveshaft is moving in and out of the t-case, causing the fluid to be pushed out...at least that's my theory. Ideas?

 

Cy-Is the center diff in your trans stock?You mentioned the car had problems backing up.Does it feel as if something is binding?If so it is very likely that your center diff is binding or seized.When I rebuilt my trans last year,I put a completely new center diff in(It had the Torrington bearing upgrade done also).I now have about 10k on the trans and I notice at times when I back up it feels as if it's dragging.It is also at this time that I have developed noises on decel like you have metioned.Maybe this is the source of the problem?

 

[CP]

I think it's the stock unit. But Shep said it looked alright when he rebuilt the tranny last spring. It did this with my other tranny too, so I don't think it's the center diff. I'm just gonna give up on trying to track it down for now and when it breaks, it breaks. I'm going to give a few people rides at the GTG in a month in hopes that someone will figure out what it is. Thanks for the reply.

 

[CP]

After 1000 miles in the last 3 days (175 of those track miles at speed), my car is almost undriveable due to the slop in the driveline. I'm going to try to get it up on a lift in the next few weeks to see if I can figure out where the noises are coming from.

In first gear at a creep the car feels like it has no carrier bearings (which were both replaced in the last few months), as I can feel slack in the system. Acceleration is no problem. Steady cruise and coastdown are a problem. I get grinding sometimes with my foot completely off the throttle. During a steady cruise, I get vibrations and resonation at certain speeds depending on what my throttle foot is doing. There's a sweet spot where this doesn't happen, which is 80-85 mph.

The tires were just balanced, so that's not it. As I said before, the carrier bearings are almost new. All this noise and vibration stops when the clutch is depressed and all forces are removed from the drivetrain, so it's NOT an unbalanced driveshaft.

I think this car's days in my possession are numbered. It will definitely NOT be coming to the Northeast meet in a few weeks if the problem persists.

 

[skivittlerjimb]

Worn out transmission mainshaft or countershaft bearings? I know you have a relatively new tranny, though. /ubbthreads/images//graemlins/dunno.gif

My vibration issue sounds similar to Cy's, but the car vibrates at certain speed ranges (15-35 & 45-60) whether the car is in gear or neutral. It happens equally with dd tires/wheels and track tires/wheels, so that's ruled out.

No traditional coast down wub-wubs and there's very little rotational play of the rearmost driveshaft where it goes into the rear diff., so for now I'm ruling out rear diff. slop. Also almost no play in u-joints so I'm going with new carrier bearings. We'll see. Right now driving the car at anything but full tilt isn't a whole lot of fun.

As a related issue, does anyone think the knock sensor could read heavy driveline vibration as knock? I've hear of severe lifter-tick causing it, but never vibration. Thoughts?

-Jim B.
280/1000

 

[OldHairyBastard]

I have this exact same problem and I have a new trans and transfer case--Brand New. I think it might be the center joint and not the carrier bearing or the U-Joints as all of mine are in good shape. I was also told that my wheel bearing might be going out in the rear as well so I will replace one at a time to find out what it is.

Doug
Quote:
After 1000 miles in the last 3 days (175 of those track miles at speed), my car is almost undriveable due to the slop in the driveline. I'm going to try to get it up on a lift in the next few weeks to see if I can figure out where the noises are coming from.

In first gear at a creep the car feels like it has no carrier bearings (which were both replaced in the last few months), as I can feel slack in the system. Acceleration is no problem. Steady cruise and coastdown are a problem. I get grinding sometimes with my foot completely off the throttle. During a steady cruise, I get vibrations and resonation at certain speeds depending on what my throttle foot is doing. There's a sweet spot where this doesn't happen, which is 80-85 mph.

The tires were just balanced, so that's not it. As I said before, the carrier bearings are almost new. All this noise and vibration stops when the clutch is depressed and all forces are removed from the drivetrain, so it's NOT an unbalanced driveshaft.

I think this car's days in my possession are numbered. It will definitely NOT be coming to the Northeast meet in a few weeks if the problem persists.

 

I doubt the knock sensor would pick up driveline noises as knock as it's pretty far away from all that. Now, pliers under the hood will make it knock on right hand turns, but that's another story. /ubbthreads/images//graemlins/rolleyes.gif On a bad 1-2 shift I'll get a few bars of knock, but that's pretty rare.

When you're cruising on the freeway in 5th, watch your gear lever/shift knob as you get on and off the gas a few times. If it moves more than a tiny bit, the nut on the end of (one of the shafts, I forget which) is backing off and your transmission guts are moving around all over the place.

And you shouldn't have to get the driveshaft perfectly straight to cancel out the speed variations caused by a U joint, as two U joints installed out of phase should cancel each other out, and besides there in there to allow for a few degrees of driveline angle anyway.

I've found that since I filled the transmission with the MTL/MT90 mix it's gotten incredibly noisy. At idle it sort of sounds like a washing machine on rinse cycle, but push the clutch in and it quiets right down. Maybe that's what you're hearing? I also get a wubwub/vibration, but I ruined at least the rear carrier bearing by letting the driveshaft hang (No Jon, bad Jon!) for too long.

 

[skivittlerjimb]

Quote:
I have this exact same problem and I have a new trans and transfer case--Brand New. I think it might be the center joint and not the carrier bearing or the U-Joints as all of mine are in good shape. I was also told that my wheel bearing might be going out in the rear as well so I will replace one at a time to find out what it is.



I'm beginning to think that might be my culprit, too. The "Lobro" or center joint is supposed to basically be a CV joint for the rear end, correct, so that no matter the angle of the driveshaft, the rotational speed remains the same front to rear. Has anyone ever had to rebuild or replace one? The one mechanic that's ever had a chance to comment on my driveline vibration issues said he thought the center joint was bad, but then it seems as if GVR4 owners rarely if ever talk about replacing them.

-Jim B.
280/1000