Fg turbo ute rear knocking

Lithfkn · 17/08/19 11:10 AM

Hello ute gurus

Apologies for the long post but I figure it's best to be thorough.

I have a rear knocking noise coming out of my FG II XR6 Turbo Ute, 6spd Manual, 90,000ks.

When I'm just slipping the clutch out and using light revs to get it going it will go knock in the ***, mostly from the left, but sometimes knock knock on both sides. This also happens when going starting off a turn. Much worse on an incline. Never happens in reverse. If I give it more revs and slip the clutch more it seems to disappear or its not as evident. Also when the car is cold it hardly make the sound. Like if I warm the car up in the driveway and head out it will hardly make it but once everything is warm it will. Sounds clunky like someone is hitting the axle with a bit of wood. Also the odd clunk when changing from 1st to second. It has tramped sometimes, only in the wet, but I try to avoid it. Both tyres do kick so the LSD is working as it should. I drive it like an old bloke to be honest.

Other noises I've noticed is a kind of wobbling sound coming from the middle of the car between 20-40 kph but goes away after that speed. Also a little diff whine between 80-110.

I've done all the rear suspension, koni reds, superpro shackles bushes + front leaf bushes + pads. Triple checked everything is tight back there suspension wise. Also put in Penrite 80/140 and lsd additive a couple months ago. When I first changed the oil it didn't make any whining noises but on advice from a driveline specialist in Geelong, they recommended trying some additive to see if it will quieten down the knock. Seems to have caused it to whine. Is having too much additive a thing?

I've taken it to Pedders to have the safety check and all they could see is that the shackles look a little cocked, slightly twisted but shouldn't cause the knock. They said the centre bearing is slightly sagging which could be causing the wobbling sound but its not torn or flogged which wouldn't knock. Also mentioned that the knock could come from the little insulators being buggered in the leafs but I can't replicate the sound by bouncing on the ute tray or inside the tub. The car also does not knock or clunk when going over speed humps or rough road.

This has got me thinking it's something in the driveline.

I left it with the same driveline mob for the day to have a good look over it. They test drove it and could easily identify the noise and also the whine. They said the whine is a standard feature in the fg's. They had it on the hoist and checked everything thoroughly and couldn't replicate the clunk/knock. Mentioned the CVs and centre bearing were fine, although is has some "sag" and perhaps the slightest rip at the top but they said not to bother replacing yet. I feel like there needs to be load on the driveline to replicate it. Like remove the spare and lay on a creeper under the car and get someone to slowly creep forward to make the noise?

It's got me stumped what it is. I know there have been tonnes and tonnes of warranty claims on diffs from BA-FG, a lot in FG. I'm not getting any vibrations or clunks at higher speeds. I get the odd clunk when changing gears, after a good run with the car and everything is warm but its mainly at take off. Feels like there is driveline slack but could just be because its a manual.

I read a post here from a guy where the front leaf bush was over tightened and caused the bolt hole in the chassis to chew out, making it oval shaped and making it move. His symptoms are similar to mine but I can't contact him as he is inactive. Still, I can't replicate the sound via bouncing on the rear. Had another look under the car today and could tighten the u bolts a little but I was hanging off em with a breaker. The cv seemed fine on the diff.

I started a topic on ff.com.au and got some good replies. One good bloke mentioned the spring pack bolt might be too long not allowing the u bolts to clamp down properly. Haven't had them out to look yet.

Wondering if anyone here has had a similar issue and what did you do to fix it? Or a recommendation of a good workshop/specialist to check it out in Geelong?

Cheers

**JETURBO** · 17/08/19 01:11 PM

A picture tells a thousand words ......

( for people who don’t know what that picture is it’s the diff saddle block bushings held in by the big “U” bolts on each side of the diff/axels )

Lithfkn · 17/08/19 08:06 PM

Damn that's smashed.

I have new superpros in mine though so I'd be shocked if they already look this that.

**JETURBO** · 17/08/19 09:39 PM

Well there’s not much to the ute rear end then so check the leaf pack eye bushings as there’s not much left to cause the noises that you’re talking about

Lithfkn · 17/08/19 09:50 PM

I replaced the whole rear end with superpro. Shackles, pads and main eye bushes. It was knocking before I changed them, I was thinking it was a busted bush but clearly not after replacing everything.

**JETURBO** · 17/08/19 10:27 PM

Hummm weird, that said going off of what the AFF user mentioned are the superpro saddle blocks the same,thinner or thicker than OEM block bushes ? Is the crush more ? Are you out of tension ?