gq underbody knocks

Submitted: Monday, Feb 16, 2004 at 11:02
ThreadID: 10563 Views:1531 Replies:7 FollowUps:7
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Hi guys, just wondering if anyone has experienced underfloor thumping sounds coming from seemingly under the drivers and passengers feet in gq patrols. I have a 93 dx and the sound occurs during breaking on the tarmac and quite constantly while driving off road. A friend has a 97 dx and has the same thumping but to a lesser degree. Does anyone have any ideas and possible cures???
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Reply By: chrisfrd - Monday, Feb 16, 2004 at 11:16

Monday, Feb 16, 2004 at 11:16
G'day.

Check the following suspension components;

1. Swaybar bushes (top and bottom)
2. Swaybar lateral bushes.
3. Panhard rod journals and bushes (where the bar interfaces with the chassis under the drivers foot well)
4. The shock-absorber mounts and bushes.
5. If you are energetic, remove the shock absorbers and test their draw length and resistance.

There should be NO MOVEMENT by hand capable. A method I use is to jack the front of the car up using a trolley jack and "drop" (rapid decent) the car from 300mm or so. It normally shows any flaws in the bushes as you do this.

Another trick is to lift the chassis on either side to find any failures as above.

Many GQ's I've seen are now having the Panhard rod and sway bar bushes replaced, due to NVH problems. Banging is normally an excessive suspension wear problem, so look here first.

Chris
AnswerID: 46867

Follow Up By: Dirt - Monday, Feb 16, 2004 at 11:46

Monday, Feb 16, 2004 at 11:46
thanks for the ideas chris, however i have recently upgraded the springs and shocks and had the majority of the bushes replaced in the suspension which greatly improved the ride and handling and reduced the squeaks and creaks but the knock still remain. I will give your 'drop' test a go and see if it turns up something. I orginally thought it was the chassis knocking onto the body but i cant find any evidence of that at this stage
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FollowupID: 308874

Follow Up By: LBJ - Monday, Feb 16, 2004 at 12:22

Monday, Feb 16, 2004 at 12:22
they also had some problems with body mounts too. just something to check!
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FollowupID: 308876

Follow Up By: chrisfrd - Monday, Feb 16, 2004 at 16:21

Monday, Feb 16, 2004 at 16:21
Yup. That was the next step.

Speaking of steps.. Do you have ARB sidesteps with the barwork extending to the bullbar?

I've had the bleep s with these bars as they knock the body work when the car flexes.

Also, body mounts can be loose but vibrate. It's usually fairly visable.
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FollowupID: 308899

Reply By: Roachie - Monday, Feb 16, 2004 at 12:08

Monday, Feb 16, 2004 at 12:08
Dirt,
Have you checked the bushes on the leading arms? They are located right under the drivers/passengers footwell....ie where the arms come back from the axle tube and connect on to the chassis.
You may also be on the right track with the body/chassis connection. There is a body mounting point right near the same point I just mentioned and not much clearance, so if the rubbler body blocks have compressed a bit over the years, there maybe some intermittent contact occuring.
Cheers,
Roachie
AnswerID: 46873

Reply By: Big Trev - Monday, Feb 16, 2004 at 12:41

Monday, Feb 16, 2004 at 12:41
Just a thought. If you have side steps, make sure they aren't touching the body. They can be pushed up by big rocks, or climbing over humps. Mine do it every so often.
AnswerID: 46875

Reply By: Wayne (NSW) - Monday, Feb 16, 2004 at 13:32

Monday, Feb 16, 2004 at 13:32
Have a look at the leading arm bolts. Where the leading arm bolts to the chassis bracket. The bolt has to be 177nm(130lb-ft) at least.

Wayne
AnswerID: 46882

Reply By: Member - Luxoluk - Monday, Feb 16, 2004 at 13:58

Monday, Feb 16, 2004 at 13:58
Plenty has been written on this. I suggest you check front floor well for cracks and body/chasis rubber mounts for wear/compression. May look ok but!! Do a search on this forum and there's lots to find on these problems. Good luck!Butcher Country Track - Vic
AnswerID: 46885

Follow Up By: Eric from Cape York Connections - Monday, Feb 16, 2004 at 14:32

Monday, Feb 16, 2004 at 14:32
I think you are spot. On Peter had the same problem with his truck and found it was due to to much off road work 30 odd trips to the top and back.
Apparently the floor under about where your feet are gets a crack and sounds like a nocking sound.
From memory he got onto nissan and they know about it. I think they put a ute kit in it and it still nocks but wont now fall apart.

All the best
Eric

www.capeyorkconnections.com.auCape York Connections
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FollowupID: 308891

Follow Up By: chrisfrd - Monday, Feb 16, 2004 at 16:23

Monday, Feb 16, 2004 at 16:23
Gees... I've only ever seen that once!

There was a problem a while ago about 91-93 GQ's that cracked, but I thought they field-fixed that one with a reinforcing bracket.
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FollowupID: 308902

Follow Up By: Voxson (Adelaide) - Monday, Feb 16, 2004 at 20:33

Monday, Feb 16, 2004 at 20:33
Mine is cracked on the drivers floor and i have looked under several offroad GQ's and all cracked there also..___________________________________
Simpson trip 05/04 then turn left at Birdsville to Darwin via Lawn Hill etc
___________________________________
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Reply By: SupaMav - Monday, Feb 16, 2004 at 14:07

Monday, Feb 16, 2004 at 14:07
I had the exact same problem . . . . turned out to be worn chassis rubbers.
AnswerID: 46887

Follow Up By: tour boy - Monday, Feb 16, 2004 at 16:21

Monday, Feb 16, 2004 at 16:21
G'day, all the patrols i've done commercial tours with, have had bad body mount knocks and were replaced every 80,000km to prevent clients getting worried. Also as suggested the mounts nearest the firewall usually crack the body. I,ve had up to 18cm cracks in 3 directions .
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FollowupID: 308900

Reply By: Dirt - Monday, Feb 16, 2004 at 16:31

Monday, Feb 16, 2004 at 16:31
thanks for the ideas everyone, just looked thru the archives as well and it is certainly pointing towards the body mounts,

all i have to do now is to find the time and motivation to change them:)
AnswerID: 46906

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