How to set adjustable top rear links on an 80series?

[udm]

I got some adjustable top arms for the back of the 80, and cant seem to remember what to set them at. Was it something along the lines of 10 to 15 mm shorter than standard links?

Hoping that with shorter links the tyres wont rub the mudflaps as bad?

Info if needed: 36" et2 on 4" lift.

[Mr DJ]

Thought you adjusted the rotation of the housing so the pinion flange is exactly the same angle as the output flange on the transfer

[udm]

Thought you adjusted the rotation of the housing so the pinion flange is exactly the same angle as the output flange on the transfer

Well, that makes big sense i guess, especially if you got drivetrain noises and shit. But i got no noises and only bought the arms to see if it would pull the tyres away from the mudflaps even just a little bit. So will see how many mm to bring the diff forward then.

[georgey]

If you only got upper arms the diff will not move forwards or backwards,it will however rotate on the lower arm bolts,so all it will do is change the pinion angle.

If you get uppers and lowers you may be able to move the diff closer to the front although i wouldnt be going more than 10-20mm because it will change your shock and spring angles and may cause failure.

Id be setting the uppers so that the pinion angle is good.

Try finding a way to move or pull the mudflaps out of the way

[oldmate]

Id be setting the uppers so that the pinion angle is good.

Try finding a way to move or pull the mudflaps out of the way

x2

[lukethedork]

If you only got upper arms the diff will not move forwards or backwards,it will however rotate on the lower arm bolts,so all it will do is change the pinion angle.

If you get uppers and lowers you may be able to move the diff closer to the front although i wouldnt be going more than 10-20mm because it will change your shock and spring angles and may cause failure.

That's a lie.
When the diff rotates on the lower arm bolts it moves not only up/down but back/forward aswell. It is impossible for it to rotate around the bolt in only one axis.

It is true that changing the length of the upper arms will effect the wheelbase LESS than changing the lower arms. This is due to the lower arms being much closer to the center of the wheel than the upper arms.

Lukethedork.

[georgey]

So if you take the upper arms out and the weight of the car off the diff,then try and roll the diff it will somehow compress the steel lower arms,shorten the wheelbase and also miraculously the diff move up aswell?

Theres no way the diff can move up and down and defy gravity so "thats a lie" that the diff moves up and down

I mihgt be blind to the fact but,
I still fail to see how the wheelbase will be shortened when the lower arms are a fixed pivot point and are not adjustable or moveable on flat ground(which is when you measure your wheelbase).

Obviously when flexing the wheelbase may shorten because of the swing arc radius of the short arms,but we are talking about wheelbase so flex is irrelevant

Justin

[Mr DJ]

Agree with Luke, tho won't move axle centre line much.

If I understand what Luke's saying -
As the lower link diff mounts are below axle centre line, when the upper links are lengthened or shortened the axle centre line will change a small amount backward or forward, pivoting on the lower link bush bolt.

[RUFF]

So if you take the upper arms out and the weight of the car off the diff,then try and roll the diff it will somehow compress the steel lower arms,shorten the wheelbase and also miraculously the diff move up aswell?

Theres no way the diff can move up and down and defy gravity so "thats a lie" that the diff moves up and down

I mihgt be blind to the fact but,
I still fail to see how the wheelbase will be shortened when the lower arms are a fixed pivot point and are not adjustable or moveable on flat ground(which is when you measure your wheelbase).

Obviously when flexing the wheelbase may shorten because of the swing arc radius of the short arms,but we are talking about wheelbase so flex is irrelevant

Justin

Justin pull your head in. Your compleatly wrong on this one.

A very simple explanation that even you may be able to understand.

Stick your right pointer finger(if you have one) up in the air in front of you (you may need to take teh Golden Gloves off first). Now imagine the tip of your finger is where the top link mounts and the bottom knuckle is where the bottom link mounts. Now the centre line of the wheel is your second knuckle from the tip. Now move the tip of your finger forward as if you are shortening the top link. Notice the second joint also moves forward? And the further you move it forward it also moves down? Understand now how shortening the top link will shorten the wheelbase and in turn push the axle centre line down either raising or lowering the vehicle to some degree at the same time depending where the coils are mounted (for or aft of the axle tube)

In the case of the OP this solution will likely cause you drive train vibes as even slight adjustment in the arms will cause the pinion to rise or lower drasticaly as its so far forward of the centre line of the axle. Prefereably you want adjustable lowers as well but I can't recall ever seing them as generally you onl;y want adjustable uppers to correct pinion angles on lifted vehicles. Lowers are subject to a lot of abuse offroad from rocks and logs so its not allways a strong set up with adjustment in the arm.

[udm]

Still havent put the arms in Hopefully the next wkend is as good as this one so i can get stuck into again.