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Moving an LC/LJ diff forwards

Started by orangeLJ , Oct 14 2011 04:32 PM

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62 replies to this topic

#1 orangeLJ

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Posted 14 October 2011 - 04:32 PM

Just wondering what solutions anyone else has come up with the fix the issue of the diff being off centre in the wheel arch.

Im planning to drop my LJ a bit more in the rear and as a consequence, the diff is moving rearwards.

I want to centre it up and get that sorted before I lower it anymore. See the picture for reference

Posted Image

I know from another members thread that chevelle adjustable upper arms are a straight fit, but I would also need adjustable lowers? to stop any adverse driveline angle roatation wouldnt i?

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#2 Potta

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Posted 14 October 2011 - 04:49 PM

I can't help but I have to say your car looks mint Chris.

Also, I think my mind has been made up as to whether flutes look good on a 4 door or not, YES, yes they do.

Are you moving the diff forward because of scrubbing or just to make it look a bit nicer??

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#3 dattoman

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Posted 14 October 2011 - 05:17 PM

Adjustable control arms

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#4 76lxhatch

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Posted 14 October 2011 - 05:56 PM

Given that the upper control arms are shorter I would think that most of the difference due to lowering is coming from them, so you'd expect that adjustable upper arms only would be adequate. You should measure the angles to be sure though.

It depends on where the upper arms are in their travel as to what further lowering will do - e.g. if they are currently level then further lowering would bring the diff forward again.

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#5 gtrboyy

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Posted 14 October 2011 - 05:58 PM

Either adjustable arms top & custom shorter bottom arms or have the diff brackets rewelded to move the diff forward(i think broads did this).

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#6 orangeLJ

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Posted 14 October 2011 - 07:49 PM

Bit of looks and to reduce the chance of scrubbing.

Does anyone do adjustable lower arms? Im going to order.the uppers at the end of the year.

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#7 orangeLJ

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Posted 14 October 2011 - 07:51 PM

ohh and thanks potta

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#8 _Macka_

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Posted 14 October 2011 - 08:26 PM

Yep go online and google full flight engineering. He did my upper arms and that was all I needed to lower car as you see it in my build thread nowand centre wheel nicely in guard. He can do uppers though if you want them.

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#9 _CHOPPER_

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Posted 15 October 2011 - 09:32 AM

If you bring the diff forward say 4", you may need to trim the tailshaft by the same amount.

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#10 _hutch_

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Posted 15 October 2011 - 12:54 PM

Interested in doing the same to my torrie,always thought it was just mine,if you did move the axle forward by 100 mm ?? what sort of effect would it have on the geometry,because the top bars are triangulated shortening them the angles are going to change.
I had thought of machining up the adjusters and the ends to take the original suspension bushes and using chrome moly bars and getting the welding done by a suitably qualified person of course,even then would it be legal ??
Phillip

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#11 _Skapinad_

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Posted 15 October 2011 - 12:55 PM

Wow 4 doors can look good, awesome car chris !

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#12 orangeLJ

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Posted 15 October 2011 - 06:12 PM

Exactly my worry hutch, im worried that shortening only one.set.of arms may "roll" the diff and have an ill effect on driveline angles.

There is a couple inches of tshaft yoke to take up some movement, but im not phased about having to shorten it if need be, ive got a mate.who does them.

Thanks skap! Its my favourite 4 door lol

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#13 _TorYoda_

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Posted 16 October 2011 - 12:19 AM

Just fill the holes in your existing arms with weld, grind them smooth and redrill them to the length you desire. If you plan to shift it forwards by 25mm or more filling the original holes will be unnecessary, simply drill a second hole in front of the existing one's and bolt up in that position. Safe, inexpensive and effective.

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#14 _shan620_

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Posted 17 October 2011 - 07:46 PM

mcdonald bros does the upper adjustable arms, i think they bout $300 a pair

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#15 Shtstr

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Posted 17 October 2011 - 08:28 PM

Mcdonnald brothers do both uper and lower arms. give them a call i think they are about $600 for a full set.

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#16 _CHOPPER_

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Posted 18 October 2011 - 08:21 AM

But they normally do NOT come with an engineers cert. Mine didn't, but then I didn't ask for one as it was for my drag car.

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#17 orangeLJ

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Posted 18 October 2011 - 08:45 AM

I know its going to give me greif, but to be honest, I dont really care if they come with an engineers cert or not, as long as they arent bits of shit (and seeing mbros other stuff I doubt they would be)

There are probably a lot of things on my car that arent exactly letter of the law legal anyway (i.e. the new front brake setup)

So now the only question is... rose joints?

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#18 _CHOPPER_

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Posted 18 October 2011 - 08:47 AM

The Mc Donald Bros. arms seem fine, I've had mine for over 5 years now.

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#19 orangeLJ

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Posted 18 October 2011 - 10:58 AM

Thanks chop.

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#20 _hutch_

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Posted 18 October 2011 - 07:59 PM

a piccie of a car with the axle moved forward would be good !!!!
Phillip

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#21 spaz

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Posted 31 October 2011 - 08:54 PM

Mate if i can get your email i can send you some photos of how i did mine Cheers!

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#22 _Macka_

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Posted 01 November 2011 - 04:25 PM

a piccie of a car with the axle moved forward would be good !!!!
Phillip

Mate check my build thread. Latest pictures have adjustable upper control arms. We didn't need to do lowers as it wasn't 'rolling forward'. I also have another 3-5mm of adjustment that I can do. I am also running 9 inch.

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#23 _Bomber Watson_

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Posted 01 November 2011 - 05:32 PM

But whats your pinion angle like???

Lets get a few things strait guys. Getting just one set of adjustable arms is MOSTLY to adjust your pinion angle. It will move the diff foward or backwards slightly

Purely cranking in a set of adjustable uppers untill your wheel looks nice and center will undoubtedly end in your tailshaft falling to bits, and probably flogging the pinion bearings and the extension housing bearing.

To actually move the diff foward or backwards like Chris wants to do and like im looking at, you need to be able to adjust BOTH the upper and lower arms. The method i would use is set the pinion angle correctly, measure how far forward/backwards you want to go, move the lowers in/out that distance, then re adjust the pinion angle.

Or in the case where im just looking at shortening my lowers do the same as above, but shorten them the measured amount.

Cheers..

Edited by Bomber Watson, 01 November 2011 - 05:34 PM.

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#24 _Macka_

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Posted 01 November 2011 - 06:10 PM

Bomber excuse my ignorance but what is pinion angle? I just dropped car off to guys a Full Flight Engineering in Melbourne and they did their stuff. They are well known and respected so l put trust in them to do it right. I am not exactly sure of everything they did but I know l only have adjustable upper control arms and said that it didn't need uppers.

Thoughts?

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#25 _Bomber Watson_

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Posted 01 November 2011 - 06:30 PM

Twice now you have said that you have adjustable upper control arms and you dont need uppers.

Which is it??

Im going to assume you have adjustable upperrs and stock lowers.

Pinion angle is the relationship of the diff pinion and the rear of the gearbox. The diff pinion should be parallell to the output shaft of the gearbox (and ergo paralel to the centerline of the crankshaft of the engine) but not in a strait line.

This sets the two universal joints (one on each end of the tailshaft) at the same angle so they cancel each other out, which is how everything is designed to work.

Cheers.

Edited by Bomber Watson, 01 November 2011 - 06:31 PM.