switching over to synthetic gear oil...

[tjlboise]

Is this anything like when you change over to synthetic engine oil? Meaning that you really have to flush it all out, and get it all nice and shiny clean before you make the switch? If so, what is a good method for accomplishing this? Also, what is a good quality recommended brand, and weight?

 

[SteelHeadz]

That depends on the prior maintainance of the engine. High mileage engines that has used conventional oil from the past tends to have more build ups of sludge and other deposits that is sometimes stuck in the engine block walls. The new and advanced engine oils uses detergents that breaks down these sludges and build ups. In a way that's good but bad at the same token if you switch over to the synthetic. I have seen a few oil pump failures from the sludge and build ups that has been washed and broken down and accumulated on the bottom of the oil pan and eventually plugs up or causes a restriction on the oil pump sump screen. My best advise is to perform an engine flush and evaluate the fluid after you drain it and determine from there if its ready for the transition from the conventional oil to the synthetic.

 

[tjlboise]

That depends on the prior maintainance of the engine. High mileage engines that has used conventional oil from the past tends to have more build ups of sludge and other deposits that is sometimes stuck in the engine block walls. The new and advanced engine oils uses detergents that breaks down these sludges and build ups. In a way that's good but bad at the same token if you switch over to the synthetic. I have seen a few oil pump failures from the sludge and build ups that has been washed and broken down and accumulated on the bottom of the oil pan and eventually plugs up or causes a restriction on the oil pump sump screen. My best advise is to perform an engine flush and evaluate the fluid after you drain it and determine from there if its ready for the transition from the conventional oil to the synthetic.

I really appreciate your input, don't get me wrong, but I think you misunderstood my question. Lol. I understand the logistics of switching to synthetic engine oil. What I was asking about, was switching to synthetic GEAR oil, and the best way to go about that, what's a good brand of oil to use, weight, etc, etc.... thank you VERY much for your help though. Very thorough, and informative. 8)

 

[superj]

i think lots of people use royal purple but the other part of your question, i have no idea on

 

[tjlboise]

i think lots of people use royal purple but the other part of your question, i have no idea on

Any idea on the weight I should use?

 

[Jesse]

Depends on which gear box it is for.

 

[tjlboise]

I would like to do both the front and the back. Its a 90 YJ, so I THINK its a 30 and a 35?????? .....Im not sure exactly what they are, and I would go look, but its raining pretty hard out there right now. So I think im just gonna have to guess.

 

[Jesse]

If i remember correctly, 75-90 in both. But I am not 100% sure, so you might want to call any autoparts stores and they would be able to tell you. Or call any dealer, ask for the parts department, and they will be able to tell you. Also be sure to find out if you have any kind of Limited-slip in the rear, and if so add the appropriate additive.

 

[Utah_jeepster]

75-90 in the front and 75-140 in the rear, personally I use Lucas.
Since your going to need to pull the covers to drain them a can of brake cleaner will help get the rest of the gunk out of your diff. No need for gaskets just do a wet gasket with RTV and torque the cover bolts to 20 in-LBS.

 

[tjlboise]

Beautiful. That's exactly what I needed to hear thank you very much.

 

[JohnnyO]

I wouldn't worry about changing to synthetic. If the old lube is really gunked up and turned to tar or if there is water in the diffs, change it again after 5000 miles and they should be fine.