rearend gear oil recomondations

Just bought a 87 xj ,4x4, standard transmission,130,000miles, what type of gear oil would you recomend 75-90 synthetic or conventional. Mostly in town driving not much 4 wheeling yet. How hard is it to change the gear oil. Just drain and replace? What else needs to be changed front axle and transfer case oil. Should i do it or take it to a shop. Ive changed the engine oil, filter, and air filter but never changed the gear oil before. Any advice would be helpful. What else would you do to give the jeep a once over. Spark plugs?

First, gear oil. I am using synthetic gear oil in both my differantials and using Mobile 1 Automatic synthetic for the NP231 Transfer Case. Changing diff. is easy. Have a tube of RTV on hand to reseal the covers,(Black works well) just remove the diff. cover, drain, clean out any metal. Reinstall cover, re-fill to the bottom of the fill plug. T-case, drain, re-fill to bottom of fill plug.

Using synthetic oil in any transmission is a good idea. In a transmission, the only source of heat is from friction. It is proven that synthetic oils will reduce operating temperature significantly.

Using synthetic oil in an engine is good because it will standup to the heat better than conventional oil- not that conventional oils won't do a good job too........

JD

A guy at Napa said to switch to synthetic that the transmission would have to be flushed? He said the same about the differentials.

Using synthetic oil in any transmission is a good idea. In a transmission, the only source of heat is from friction. It is proven that synthetic oils will reduce operating temperature significantly.

Using synthetic oil in an engine is good because it will standup to the heat better than conventional oil- not that conventional oils won't do a good job too........

JD

The tranny, just drian out the old fluid really well, I would run what everthe manufacture recommends, but offset it with a quart of LUCAS OIL STABILIZER. this will help lubricate things better.
As your differentials go, ALL the fluid will leave the tubes and ring gear area when you drain it. So flushing won't be nessacary. I drained mine and put in staight synthetic in both diff's, still running well after 50,000 since the change over of fluids.
Your spark plugs, recommend Bosch Platnuim (regular, not +4's) they work great in a Jeep. Also as far as your cap and rotor go, if they offer it go with the brass contacts, it cost allittle more, but worth it.

Oh, another BIG item, get your Jeep's radiator/coolant system professionally flushed. Over heating is the NUMBER 1 problem with the XJ's. Make sure they flush the engine, radiator, heater core completely. This will save you the added aggervasion later of trying to fix a HOT XJ.

A guy at Napa said to switch to synthetic that the transmission would have to be flushed? He said the same about the differentials.

I imagine that you mean an automatic transmission here.

Not really necessaary to flush as synthetics are compatible with the conventional dino oils. You would need to flush only to do a complete oil change and get the full benefit of the synthetic oil.

In a standard transmission or differential, like gtmud says only drain, clean up as necessary and refill with the synthetic.

I do not recommend any aftermarket additives for continous use in any lubrication system unless there is a specific problem with a component!!!

Aftermarket additives just mess up the original additive package that was formulated and balanced in precise proportions to keep things running smoothly. The components in an off the shelf additive can actualy negate the effects or produce the opposite effect in the lubricant and lubrication. With the formulated oils we have today, I don't believe they are necessary.

The only additive necessary is in a limited slip differential. There I would add 4 oz of the factory limited slip additive (half the bottle) to the diff oil.

In a 4wd, the diff and tranny oil should be changed every two years and if you off road, every year unless you do deep water. Then after each encounter.

Plug choice is also personal preference. I use the standard plugs. NGK or Bosch are good. I prefer to change them more often and for the cost of one set of platinums, I can make two sets of regulars go in. Just my take on plugs though. I'm not so sure about the benefits of the fancy plugs that are made. To me, a spark is a spark is a spark. It only takes one to get the fuel burning and changing the plugs regularly at a reasonable cost is the most important to me.

JD