Changing Diff and Trans Oil
 

I'm not looking for a DIY as much as a bit of advice. Thus I'm posting here to get more views and hopefully help more people with general advice on the topic.

I'd like to swap out the diff and trans oil since Nissan won't do it for what seems like ages from now (I'm at 3300 mi). From the service manual, it seems easy enough to empty via the drain plugs.

Filling seems to be less clear from the manual. Is there enough clearance to just tip a bottle of trans oil with a small spout into the filler hole? Or do I need some special pressurized gizmo to refill the trans and diff? Also, the fill level is found by just putting my finger in the hole and feeling the level (essentially, fill until it spill out???).

I saw a thread where someone listed the oils they used for refilling both the trans and diff. I'd love any advice you have on this again. Also, where did you buy the gaskets which the manual says you can't reuse once you unscrew the plugs? A search didn't turn up any specific threads...just a lot of threads that referenced the diff or trans somewhere.

You will have to use a suction gun to put the fluids in - there isn't any room to just pour it. If I remember correctly about 3.2 qts for the MT and 1.8 qts. for the diff. Make sure the car is level and take the filler plug off first to make sure you can get it off. Just keep pumping the fluid in until it starts to escape out the filler hole. You can buy the crush washers at Nissan but they charge too much. I went to a Jiffy Lube and bought a handful for $5.00 because I wasn't sure of the size. All of them were too small and ended up re-using the old ones and watched for leaks for a couple of days.

Which oils did you use? I'd like to 'upgrade' to something better than Nissan uses...I think someone listed a couple from Redline that were good...

I purchased a oil pump from a marine dealership and fill my diffs and transmissions right from the bottle. I prefer to use a Shell full synthetic gear oil that is sulphur free for the rear diff and transmission.

I just reuse the metal gaskets and every once in awhile I'll replace them.

Fill them till the oil runs out. Try and keep the car as level as possible when filling.

Just be aware that gear oil stinks and will remain on your skin for quite awhile. It's advisable to wear rubber gloves to minimize skin contact.

I'm always leary of changing fluids more frequently than the manufacture who designed, engineered and tested the vehicle as well as being invested in the warranty of the vehicle not knowing how its going to be ragged on. Basically the manufacture is going to go to the extreme to cover themselves - they aren't paying to have the fluids replaced but they are covering parts if they wear prematurely. So its really in the best intrest of the manufacture to have the fluids replaced before they are questionable.

That being said - is there any evidence that these fluids need to be changed ahead of schedule?

What you saying does make complete sense but the manufacture just has to make sure the parts last as long as their warranty while at the same time not make it seem to the normal consumer that the vehicle doesn't require much upkeep.

Is not changing your oil now going to damage your transmission? No, but changing it now could possibly help with the longevity of the transmission. Am I going to do mine, ummm--no.

This ^^, the manufacturer is only going to do the bare minimum. Diff fluid looks pretty nasty after only about 10K miles of normal driving, trans fluid not so much. But why not put something in that will make it perform better (shift like butter) and wear less? Ill give the stock fluids about 5K before I swap them out with Redline.

I guess trying to figure out a balance is the trick. You would have the best fluids in the world with optiman protection if you changed them every 100 miles but that's a bit of a pain and costly....

when i changed the diff fluid in my IS300 it was horrible to see the metal shaving that came out!!!! i was at 20k miles, dealer said to do it at 30k.

If i get a Z i will change it every 10k miles. its relatively easy to do, but YES THE OIL STINKS!!!!!

I want to get the factory fill out and get some fresh oil in now that things are broken in. Then every 10k sounds good.

it would be helpful if someone post a DIY for both MT trans oil change and diff ;)

I'd be happy to but I have a couple thousand miles to go...unless I just do it next weekend :)

You know, engineers design things to fail. Sound crazy? If things worked 100% at all times, there would be no need for our services.

My friend's father works for a company that designs light bulbs. He was told that a light bulb his team designed had a lifespan that exceeded the limits. He had to make the light bulb more prone to failure. If they produced light bulb's that lasted forever, they would go out of business quickly.

That same mentality exists with all companies engineering teams.

The rear diff factory fill is a synthetic. I verified this by looking at the bottle that Nissan dealers use and comparing it to the owners manual.

However, I don't think the gearbox fluid is. The gearbox is also a weak point for our cars. Many already have trouble getting the car into some gears. For mine, from day one, I can't downshift into second gear without some hesitation or crunch.

Which Redline product should go in the rear diff? Here is my proposed order. I saw that the best plan for the transmission is to mix the MTL and MT-90 in a 50/50 ratio. For the rear diff, I was considering the 75W90 GL-5 gear oil but it's a little lighter than Nissan's recommendation for 80W90.