Tag Archives: Gear Oil

Mazda MX-5 Miata Maintenance Day

This father’s day my friend Bill and I decided to fix another issue both of our NC Miata’s were having… my rear stabilizer links were making a clicking sound ever since we installed the Bilstein shocks. His Miata seemed to have aftermarket end links where one of them was ripped out of it’s socket because of possible incorrect install to his massive Flyin’ Miata rear stabilizer bar. So Bill ordered the parts online, came over and as soon as we got the car up on the RhinoRamps it started raining… so we went to the Diner for breakfast. On the way we also stopped by at CarQuest to pick up some more new end link nuts because the old ones on my car were showing signs of wear and I didn’t want them to get stripped. He paid $3.30 apiece at the Mazda dealer… I paid $3.30 for a box of 4 Dorman aftermarket pieces. They looked the same.

Fast forward to some better weather and replacing the end links turned out to be a rather quick job. We did Bill’s car first. Taking them off was easy. But placing new ones on seemed to look weird because they went in on an angle when attached to the stabilizer bar… I was worried if we fastened them in this condition, it was possible that they might fail again.

Luckily we had my car nearby to see exactly what they were meant to look like in correct condition, as installed from factory.

So another idea was to take mine off. Replace them with new ones. And use my old ones as guinea pigs on Bills car to see if they would last. If no failure happens after a few weeks of driving we’ll go ahead and replace them with the new ones. So that’s what we did.

Ironically though, the clicking didn’t stop once we installed new end links on my car. Turns out they were not the problem I was experiencing. Instead it appears that the actual stabilizer bar was bending in such a manner that it was making noise when the chasis of the car twisted on various road conditions, particularly when going onto uneven surfaces, like up a driveway or into parking lots, or hitting pot holes.

I was disappointed that the problem didn’t get fixed, but as we were tinkering under my car I discovered that my differential was covered in fluid and grime. It turns out that the last time I did Castrol Syntrax flush to replace the Mobil 1 75W90, I did something wrong. It’s possible I didn’t tighten the bolts enough. Or that I overfilled the differential. Or that my car didn’t like the Castrol product. I was so concerned about it, I ordered another jug of Mobil 1 since it was proven to work well for a good 20k miles, and did the flush later on in the day. So far after the test drive the car feels smooth. There’s no whine at cruising speeds. And all is well. What I’m concerned about now looking at the old Castrol that I drained from the diff, is a bunch of small aluminum shavings. That doesn’t seem normal to me.

But I guess time will tell if there’s a bigger issue.

Today was a very productive Sunday!

Mazda MX-5: Diff Fluid Change With Castrol Syntrax 75W-90 Synthetic

Another unseasonably warm day this February with tropical like heat wave weather so I did some more maintenance on my Miata in preparation for the Road Trip to Florida next week.

Was the gear oil due for a flush? Nope… not necessarily. I was about 9k miles short of the scheduled change. However, I thought I heard a little whine coming from the rear end on a recent trip down the Jersey Shore for the Millenials Miata meet, so I decided to flush out the Mobil 1 I put into the diff at the end of 2015 and replace it with Castrol Syntrax 75W-90 synthetic.

As usual this was a two step process. Once I decided on the Castrol (and part of my decision was based on the engine oil I just started using – Castrol EDGE… not that engine oil has anything to do with the diff, I figured I’ll keep things consistent), I researched where I could buy it. First I found O’Reily Auto Parts sells it for about $14 bux but we don’t have any of those stores around here. Pep Boys and Advance Auto did not advertise it on their web site, Walmart could place an order for me for about $13 but surprisingly Auto Zone had it in stock for $9.99! I still wanted it cheaper, so I went on CardBear.com researched AutoZone gift cards and bought one from Raise.com saving about $3 bux! The gift card showed up in just a few days since I ordered it and as soon as it arrived I rushed out the door to my local Auto Zone to pick it up.

It was definitely convertible weather today!

It took no time to jack the car up and get it leveled to do this job, but once it was in the air I could not (for the life of me) find the necessary 23mm and 24mm sockets to do the actual job! Fucking hell…. I searched everywhere, wasted more than an hour looking to no avail. So I went to the local Lowe’s to pick up two sockets so I have them for the future. I stopped by my local Sears to see if they had Craftsman in stock since I have some Shop Your Way rewards points to burn but the 23mm socket is a high commodity only available for online orders… the price for the 24mm socket was $12 or $13, I picked up both sockets at Lowe’s for under $10! I think they were $4.88 each plus tax which seems very reasonable. (Though I’m sure I could have bought them for way less if I had the luxury of time).

Anyway, the job itself took no time. Very easy to undo the top bolt, then the bottom to drain the diff. Cleaned everything up. Put the bottom bolt back on. Jerryrigged a device to pump the new fluid into the diff, and then tightened both the bottom and top bolts. Surprisingly I was able to pump almost the entire bottle in this time, I think I pumped less with Mobil 1 a year ago, but I could be wrong.

So there it goes. Easy job. I’m hoping this one lasts more than 20k miles before the rear end starts making whining noises again. I should mention I was very surprised how dark the Mobil 1 gear oil got… many of you will remember I said the same thing about my Mobil 1 engine oil the first two oil changes I did. I just don’t know what makes that oil turn so dark so soon.

Some people claim that the oil is so good it takes all the dirt out of the system that’s why it turns so dark. And that the other oils I use are not as good and therefore not as dark when I flush them. But I call BS on that! There’s no reason why the rear diff fluid should be this dark at just 20k miles. I think it should have lasted longer. I guess time will tell when I flush the Castrol Syntrax for a direct comparison.

I took a short 2 mile drive down to the local Advance Auto to responsibly dispose of the used oil, and the diff feels just fine. Nothing to talk about… it’s smooth, there’s no noise. It’s good!

Will follow up again when it’s time to flush it in 30k miles.

Mazda MX-5: First Diff Fluid Change with Mobil 1 75W-90 Synthetic

Another maintenance project that I completed on my own, this time it was changing the rear differential fluid in the Miata. I actually practiced the fluid change on my Ford Explorer which badly needed this fluid changed, but this post is really about the MX-5. Now I won’t have to worry about this piece of maintenance for another 30,000 miles which should take me a couple of years to accumulate.

This project, like many others, started when I was reading Miata.net forums and saw what people were doing to their cars. Someone posted about doing the rear diff fluid change and how easy and quick it was and I decided to do it myself. At practically the same moment I was thinking that, a $5 off $10 purchase coupon arrived in my e-mail from Advance Auto Parts, so I went on their web site and ordered Mobil 1 75W-90 (listed for $10.99) which the Miata guys on the forums recommended. (Ironic because I’m not the biggest fan of the Mobil 1 0W-20 engine oil having used it for the past two oil changes, but whatever). The coupon from Advance came because I just spend over $60 buying Pennzoil Platinum oil & K&N filters. Had I known I’d get $5 off for every $30 spent, I would have split my Pennzoil order in half. Anyway, after I ordered the Mobil 1 for the Miata, I realized I might as well practice on the Ford Explorer but instead of buying the good stuff, I decided to buy cheaper Valvoline gear oil for the truck. Buying it from Advance didn’t make much sense because their version is marked up to $15+ while Pep Boys down the street had it listed for $12+ and offered a 20% coupon. Fast forward to today, when I went to pick up the oils from two of the stores, the job took no time in the Explorer. Miata was next.

mazda mx-5 miata rear differential fluid change 1

mazda mx-5 miata rear differential fluid change 2

mazda mx-5 miata rear differential fluid change 3

mazda mx-5 miata rear differential fluid change 4

The most difficult part of doing anything with the Miata, especially when it comes to the bottom of the car, is getting it elevated high enough so I could squeeze in under there. I recently purchased two more jack stands from Sears for a nice $21 bux out the door after a bunch of discounts, so this was a great excuse to use them.

mazda mx-5 miata rear differential fluid change 8

mazda mx-5 miata rear differential fluid change 9

mazda mx-5 miata rear differential fluid change 10

mazda mx-5 miata rear differential fluid change 12

mazda mx-5 miata rear differential fluid change 13

mazda mx-5 miata rear differential fluid change 16

Once the car was reasonably high in the air it was just matter of minutes of undoing two bolts and letting the oil drain. I left it sitting for a good 20 minutes so all the fluid dripped out, and then siphoned new fluid in via a small hose. Was pretty surprised that it took almost the entire Quart bottle, but eventually oil started seeping from the fill hole. And I was done!

mazda mx-5 miata rear differential fluid change 11

The bottom of the car still looks pretty good. No rust from the last winter which saw a lot of salt on the roads. And now my car is ready for another 30k interval. Easy peasy! Even dad came over to have a look at the progress…

mazda mx-5 miata rear differential fluid change 7

mazda mx-5 miata rear differential fluid change 5

mazda mx-5 miata rear differential fluid change 6

So hopefully this Mobil 1 product looks better with age then their engine oil does (I wasn’t too happy with how dark it got at only 5,000 miles especially since they advertise it could go 15,000).