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Weird vibration and whirling/humming noise only under decel? HELP!

cupajoe

Well-known member
Joined
Mar 1, 2010
Messages
343
Location
Cocoa, FL
Ok, under decel my car make a whirling/humming noise and vibration under decel, mostly in 4th/5th gear. But once I press in the clutch the noise and vibration both go away instantly. Its coming from the backseats/rearend and definetly from the drivetrain. Anyone have experiance with this?

Quick question, what drivetrain parts are interchangle between the awd 1g and galant. Driveline parts interchangable?

Any help would be appreacaited. Thanks.
 

mooserage

Staff member
Joined
May 17, 2004
Messages
1,293
Location
Seattle, WA
Okay, lots of info to give you here. Almost all of your answers can be found by searching, but I will help out a bit. It sounds like your rear differential is having some problems. This may be that it just needs some shimming, but its probably a good idea to get a new/good used one and just replace it. If your problem gets any worse I highly recommend not driving the car, as the bad diff or drivetrain part can lock up (this is VERY dangerous) and is known to happen on these cars at 50-80 mph (ask me how I know...).

As for what is interchangeable, 1G DSM with a manual transmission has the same ratios and is therefore interchangeable. (this should be confirmed by searching or a knowledgeable member)
Options:
-3 bolt open diff (Stock on VR4, direct bolt on)
-3 bolt viscous lsd (Needs the lsd axles, otherwise direct bolt on with axle replacement)
-4 bolt viscous lsd (Needs the 4 bolt axles and cups)

All of these will work, however, if you want to use the 3 bolt lsd or 4 bolt lsd you need the axles as well because they are all different from each other. For the four bolt you will also need the cups.

If its not the rear diff, and it may not be, hopefully someone can help you out. I'm sure we will get other members in here to confirm my info and hopefully give some insight on how to check to ensure it is your rear diff that is the problem. Thanks and good luck.
-shamus
 

cupajoe

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Joined
Mar 1, 2010
Messages
343
Location
Cocoa, FL
Thank you very much for the info, I apprecaite it. I guess I'll start looking around for a rear diff and start there.
 

Muskrat

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Jun 13, 2004
Messages
2,107
Location
Lexington, KY
Does it still have working 4 wheel steering? and/or the dif w/ pump attached?
 

cupajoe

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Mar 1, 2010
Messages
343
Location
Cocoa, FL
Yea, car is pretty much all stock. aws and pump all still intact.
 

Muskrat

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Jun 13, 2004
Messages
2,107
Location
Lexington, KY
The 4ws pump is driven off the dif. If you get a dsm dif, and want to retain 4ws you'll need to swap everything into the galant housing.

At that point it's worth it to actually investigate the issue, instead of just throwing parts at it. Potentially cheaper too.

start with checking fluid levels in trans, t-case, and rear dif. Maybe drain the fluid and check for any foreign objects that could indicate a problem (metal particles, etc..). If everything checks out, and you feel comefortable pull the cover to the rear dif and inspect it. I'll bet the fsm has instructions for performing an inspection.
 

cupajoe

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Mar 1, 2010
Messages
343
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Cocoa, FL
Damn, fluid was going to be my next step. I already did the trans, i'll be doing the tcase and rear dif soon. I doubt that its just the fluid if anything it will only mask the problem and wont be a fix.
 

Muskrat

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Lexington, KY
Checking fluid is just a step in figuring out what's wrong, not a fix.
 

cupajoe

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Mar 1, 2010
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343
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Cocoa, FL
Yea I understand was just saying. Would have like to get to it today, but it just snowed a good 5 inches. blah. As soon as I can ill pull the cover off and inspect it, once I read up on what im looking for. Anymore input would be appreicated, thanks again.
 
Last edited:

broxma

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Joined
Nov 16, 2009
Messages
911
Location
San Antonio Tx
The exact location of the noise may be masked by vibration and acoustics through the body of the car, that is to say, what sounds like it is behind you may be in front. Usually having a secondary receiver(Person) listening away from the car(Going down the road) will pin point the source better than you inside the car, where acoustics are terrible at best.

If pressing the clutch makes it go away, I'd check the part most likely to be at fault near the clutch first and work away from that point. In this case, that would be the throwout bearing.

/brox
 

brisvr4

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Joined
Feb 13, 2004
Messages
955
Location
brisbane australia
Exactly what clutch are you using?
Once you change from a clutch disc that is able to absorb the harmonics from the crankshaft to a more aggressive type of disc your driveline noise will increase.
I run a QM twin plate clutch and my car sounds like it is going to explode on hard decel.
That is one more thing for you to consider.
 

cupajoe

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Mar 1, 2010
Messages
343
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Cocoa, FL
I just bought the car >month ago, it has a Act 2100 in it. Another idea, could a possible bad u-joint cause this?
 

cupajoe

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Mar 1, 2010
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343
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Cocoa, FL
Ok I changed the rear diff and tcase fluid and no metal or anything unusual. The tcase fluid was very dark in color and diff fluid looks much fresher. While I was under there I checked on u joints and all checked good.
 

cupajoe

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Joined
Mar 1, 2010
Messages
343
Location
Cocoa, FL
Ok well I think th fluid did it. I have only drove about 20 miles so far but much smoother and Noe noises or vibrations. Idk if the tcase fluid as just that broken down and it was binding or what. But we will see how long t last. Any ideas?
 

mooserage

Staff member
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May 17, 2004
Messages
1,293
Location
Seattle, WA
If it was the t-case, you may consider rebuilding or getting a newer one pretty soon. That's just what I would do, I've had one lock up and I never want it to happen again. Glad to see it helped though!
-shamus
 

cupajoe

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Mar 1, 2010
Messages
343
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Cocoa, FL
Thanks for all the help. I actually have two good dsm tcases in the garage so I'm set, pretty sure there the same ratio.
 
Last edited:

mooserage

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May 17, 2004
Messages
1,293
Location
Seattle, WA
Just remember, depending on the year it may have 22 or 23 teeth for the input shaft, so if you switch them just count the teeth. A sharpy helps with that too /ubbthreads/images/graemlins/wink.gif
 

cupajoe

Well-known member
Joined
Mar 1, 2010
Messages
343
Location
Cocoa, FL
Yea hopefully the I need a 23 spline, if I remember corectly that's what my spares are.
 

MellowVR4

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Jul 25, 2009
Messages
1,662
Location
Milwaukee, Wi
you know i have this exact same problem , trying to pin point out. I am changing out my diff to an lsd so maybe that will get rid of the vibrations at deceleration? /ubbthreads/images/graemlins/dunno.gif all i know is, it sounds horrible and feels horrible. /ubbthreads/images/graemlins/banghead.gif defently it sounds like its coming from my rear but then again it sounds like its coming from the front.
 
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