I have considered that Danny. Just figured I would wait until I add the lift to upgrade. Heading to Moab in 3 weeks so I need something that works for now.

 

Multi viscosity oils are made from oils that are the viscosity of the first number when cold. So 85w145 and 85w90 are the same viscosity base, and behave nearly exactly the same when cold. They then add polymers to the oil that keep if from thinning as much at higher temps. So 85w90 only gets as thin as a straight 90 would at operating temps. 85w145 only thins down to what a straight 145, etc.

When cold you shouldn't notice any difference.

 

Lets take a quart of 5w30 motor oil. Pour it into a cup and check how thin it is. Now take 85w140 and pour it into a cup, seriously thick oil. Run both fluids down to -17f and see how the viscosity changes.

 

Also make sure the ball joint on top of the rear diff isnt worn out causing weird pinion angles creatin more stress on the rotoflex. Also check all of the bushings on the axle and frame mounts.

 

So you went from 5w30 in your axles to 85w145?

 

Anyway, gear oil and crankcase oil aren't on the same scale. 80w90 gear oil is very close to 20w50 engine oil.

http://www.teamrip.com/viscosity_chart.html

 

Any good way to check this? I can see the joint is intact. Wanted to set one of my rack arms on the rear and tilt it up but think that is a bit dangerous!

Jafir, for the record I am a Audi tech. I know all about oil viscosity. I am comparing Cold gear oil to warm gear oil. To tell me that there is no difference between cold gear oil and warm gear oil is ridiculous. Sarcasm aside I do appretiate you trying to help.

 

Not to question your ability but did you install the rotoflex correctly? There should have been some sort of indicator as to the correct direction it should face. I ask because I, and others, have installed them backwards which can cause premature failure. Just throwing that out. Also when my first one failed it caused massive vibration at 10-25 mph. Good luck.

 

Please Question!! Being a tech I do know I can make mistakes!! When I installed it there were little arrows on it but no indicator which way it was supposed to point. Towards the rear or towards the front. Also I am not certain I got the bolts back in correctly. RE: my thread on the alignment bearing.

After I finally hacked that thing out I forgot how the rotoflex joint came out.
Anyone elighten me on the proper direction? I am picking up my new LR joint in a couple hours.

 

I think if you re-read you will notice that I said there is no difference between COLD gear oil and COLD gear oil. 85W-anything is the same 85 when cold. It doesn't matter if it is 85w90 or 85w145.