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LH-UC The "double knuckle" (solid steering uni) conversion


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#1 LXCHEV

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Posted 29 September 2011 - 08:21 PM

Hi guys,

I ripped out my flexible coupling today (aftermarket nolathane type) which had been half fried from extractor heat, and developed a lot of slop. I couldn't believe the free play in it.

Anyway, I've now replaced it with a 2nd solid universal joint style knuckle. This just bolted straight in, the whole job took me 10 minutes. I swear I've heard other people say that modifications are normally required to one of the shafts?? Have I done something wrong since I didn't modify anything....

Would love to hear from others who have done this same conversion.

PS. I'm yet to drive the car, but it feels sharper, has eliminated all free-play, and has also provided more clearance. Great conversion in my opinion!

#2 Toranamat69

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Posted 29 September 2011 - 08:39 PM

I had to chop about 10mm from the steering rack shaft or the unijoint wouldn't even go on far enough to get the pin through as it hits on the centre of the Uni joint whereas on the rubber and poly ones, there is a hole in the centre that the 'extra 10mm' can poke through.

Hope I explained that. Surprised no-one has posted pics of that before as it has come up numerous times on here.

Did you use an original uni or an aftermarket one? Maybe they are a bit different - the aftermarket ones certainly look a bit different.

#3 LXCHEV

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Posted 29 September 2011 - 09:38 PM

I used a standard factory style Uni....

I don't have an "after" photo yet, but here's a crappy "before" pic...

Posted Image

#4 LXCHEV

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Posted 29 September 2011 - 09:54 PM

I had to chop about 10mm from the steering rack shaft or the unijoint wouldn't even go on far enough to get the pin through as it hits on the centre of the Uni joint whereas on the rubber and poly ones, there is a hole in the centre that the 'extra 10mm' can poke through.


So from my pic above, I assume you cut the 10mm from the bottom of the middle shaft??

#5 Toranamat69

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Posted 29 September 2011 - 09:57 PM

No, from the top of the shaft that goes into the steering rack. I seem to recal that little end bit that gets chopped off was actually smaller OD than the rest of the shaft but that was a fair few years ago I did this on mine. I don't have any standard ones here to check either.

Maybe your steering rack was already trimmed back.

#6 Statler

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Posted 29 September 2011 - 10:56 PM

No, from the top of the shaft that goes into the steering rack. I seem to recal that little end bit that gets chopped off was actually smaller OD than the rest of the shaft but that was a fair few years ago I did this on mine. I don't have any standard ones here to check either.

Maybe your steering rack was already trimmed back.

Correct!

The distance between where the cotter pin locates, & the length of the steering shaft [rack end] into the knuckle, dont line up. The rack end is too long.

The rack has a machined step at the end of the shaft which is easily removed.

I would definately be checking that the cotter pin is locating in the machined recess on the shaft!
Better being safe than sorry.

Edited by Statler, 29 September 2011 - 10:57 PM.


#7 76lxhatch

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Posted 30 September 2011 - 06:19 AM

Yeah its pretty obvious when you are looking at it due to the reduced diameter where it is machined as mentioned ^ , sounds like someone has trimmed it previously

#8 LXCHEV

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Posted 30 September 2011 - 07:41 AM

Yeah when I assembled it all, I was very careful to make sure the cotter pin went through where the recess was. It certainly seems that maybe someone else has previously trimmed it. Will have a closer look next time I'm working on the beast. Will keep you posted!

#9 LXCHEV

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Posted 30 September 2011 - 07:53 AM

Ok did some googling and found this pic of a UC rack (which I assume has the same shaft as an LH/LX rack). I can now see the stepped down end you're talking about.

So just to clarify, that stepped down end has no flat recess in it for the cotter pin? The flat recess is on the large part of the shaft. Therefore making it impossible to fit correctly without cutting off the stepped down section?

I don't remember seeing this on mine, but I'm still keen to check it out.

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Edited by LXCHEV, 30 September 2011 - 07:54 AM.


#10 76lxhatch

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Posted 30 September 2011 - 09:00 AM

Yeah you just cut that stepped down bit off flush and everything fits (can still go back to rag joint too)

#11 _76S.L.R_

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Posted 02 October 2011 - 01:45 PM

How much do those Uni Knuckles cost,mine has a bit of play in it and I'd like to replace it= Do rare Spares carry these???

#12 LXCHEV

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Posted 02 October 2011 - 07:50 PM

Brace yourself... new ones from Rare Spares are around $160. But that includes 2 new cotter pins. I've seen just the uni knuckle by itself on Ebay for around $130.

You can normally pick up good 2nd hand knuckles for $30 - $50.

#13 LXCHEV

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Posted 02 October 2011 - 08:08 PM

Apologies for the super average phone photos.... I gotta start taking the real camera outside again when I'm tinkering! Here's the double knuckle...

Posted Image

Posted Image

#14 _mick74lh_

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Posted 02 October 2011 - 09:54 PM

Why didn't they do them like that from the factory then? Would it have been just to reduce shock/feel transmitted into the driver's hands?

#15 76lxhatch

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Posted 02 October 2011 - 09:59 PM

Yeah just NVH stuff - the rubber bush mounted LH/LX steering rack was another (but was bad enough that it went back to being solid mounted in UC!)

#16 ls2lxhatch

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Posted 02 October 2011 - 10:07 PM

The rag coupler is purely there to absorb vibration, they are not used for direction changes. Holden could have saved money by just extending the steering shaft if they didn't think vibration was an issue.

Technically replacing the rag coupler with a uni is not legal although I doubt you would ever get pinged for it. If you don't care about vibration then you could probably just replace the rubber disk in the rag coupler with a steel disc.

Once the steering rack shaft has been cut for the "double uni" mod you can not safely go back to the rag coupler. The bit that you cut off the steering shaft for the mod is there to hold the rag coupler together should the rubber disc fail.

Edited by ls2lxhatch, 02 October 2011 - 10:13 PM.


#17 dattoman

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Posted 02 October 2011 - 10:18 PM

The double unit is a legit thing on many vehicles
Its actually used in place or a collapsable column on hotrods (though that might be changing)

#18 ls2lxhatch

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Posted 02 October 2011 - 10:59 PM

I thought I read somewhere in the NCOP that a vibration damper was required in the steering shaft. However after having another read of the NCOP I can not find any requirement for a vibration damper.

#19 rodomo

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Posted 02 October 2011 - 11:06 PM

VQ Statesman (and others I suppose? :dontknow: ) have like an spring eye bush with a dog in the column, virtually no give.
I'll take a pic if I remember.

#20 76lxhatch

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Posted 03 October 2011 - 05:18 AM

Once the steering rack shaft has been cut for the "double uni" mod you can not safely go back to the rag coupler. The bit that you cut off the steering shaft for the mod is there to hold the rag coupler together should the rubber disc fail.

Surely that would only hold the (now defunct) rubber piece from falling away? Its not long enough to extend into the second half of the joint and even if it was complete failure of the rubber (beyond the point where the two pins are any use) would still result in no steering...?

#21 MRLXSS

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Posted 03 October 2011 - 08:04 AM

Good Stuff Brett! It's an easy mod isn't it! You'll notice it the next time you drive the car... especially if the old coupling was a bit loose.

#22 ls2lxhatch

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Posted 03 October 2011 - 04:25 PM


Once the steering rack shaft has been cut for the "double uni" mod you can not safely go back to the rag coupler. The bit that you cut off the steering shaft for the mod is there to hold the rag coupler together should the rubber disc fail.

Surely that would only hold the (now defunct) rubber piece from falling away? Its not long enough to extend into the second half of the joint and even if it was complete failure of the rubber (beyond the point where the two pins are any use) would still result in no steering...?


There should be an explanation for why the steering shaft is longer than required. The intermediate shaft does not extend pass the cotter pin area so it does not appear to be part of the manufacturing process. They have gone to the trouble of machining the shaft down so it will slide easily into the joint. It appears to be there for a reason.

The two long pins on the rag coupler will make it difficult for the rag coupler to separate in the direction of the arrows.

Posted Image

There is however not much to stop it separating in this direction particularly if it kicks out on an angle.

Posted Image

However with the steering shaft extending into the rubber section the short rivets will hit the steering shaft preventing the rag coupler separating in this direction. They could just as easily used all long rivets

Posted Image.

#23 rodomo

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Posted 03 October 2011 - 09:03 PM

VQ Statesman (and others I suppose? :dontknow: ) have like an spring eye bush with a dog in the column, virtually no give.
I'll take a pic if I remember.

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#24 76lxhatch

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Posted 04 October 2011 - 03:19 AM

All the early Commodores are like that, still a little bit of give but they don't tend to wear out as easily as the donuts (have still heard of them separating occasionally though)

#25 _2wild4u_

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Posted 25 October 2011 - 11:52 PM

commodore ones still have a rubber insulator, theyre bonded where that shaft slides in




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