MX5 Miata Manual Transmission Diff Oil temperature

[EddieCairns]

After hard driving the new ND Miata / MX5 via additional sensors fitted to them are showing transmission temperatures of 150C / 302F

The diffs are showing 160C / 320F and only has 0.6 litres/ 0.634 qtrs oil capacity.

Can anyone advise if these temperatures will cause any problems or are the found on other cars and which specific oils may reduce any problems if they exist.

Mazda give something like a 75W/90 recommendation.

 

[d00df00d]

Interesting. I'd be interested to know what exactly the spec fluids are.

Hard to imagine you'll get more than a few degrees of reduction with fluid choice alone. Going thinner might help, but that might be a bad call for obvious reasons.

I don't know if those temps are problematic, but if you want to reduce them, you'll probably need coolers -- a radiator and pump for the trans, and at least a finned cover for the diff.

 

[Cujet]

Spec Miata race cars regularly show 300+ degree temps in the differential. And 250-300 in the transmission.

They seemed to hold up just fine. My old Miata turbo was a spec racer for the first part of it's life. I put it back on the street, installed a turbo setup and went on my way. Never had a diff failure. However, I did use Redline Shockproof fluid and MT90, and change regularly.

Had a total of 6 transmissions over 175K miles. Each failure was due to the case breaking in half due to overloading. The transmissions never wore out. Even with considerable track and dragstrip time.

 

[zeng]

Gear oil operating viscosities at 150/160*C (a temperature caused by too low a viscosity grade oil in use) would definitely cause gear train problems.

The best thing that could happen is whines from gear trains (indicating wornout internal components), though irritating it stays serviceable for another 10-20 years........
but often it results in worn bearings , followed by wear gears and breaking up.

Plenty of gear oil types exist, to reduce or eliminate this problem.
My pick for now is SAE 80W140 for its high'ish KV@40*C for more assuredly components longevity.
For shear stability, do consider 85W140 or SAE 140, more so in my ambients.
JMHO.

 

[EddieCairns]

The owner’s manual specifies 75W/90 for the transmission and for the diff it specifies Mazda Long Life Hypoid Gear Oil SG1.

The opinion on the net is the diff oil is either a 75W/90 or an 80W/90

In the UK we are getting a good number of 1990 to 1994 cars with failed diffs but the early cars had small oil capacity diffs. How many cars have not had the diff oil changed and I would say most of them.
Problem with the later say 2002 to 2005 NB LSD diffs not the early ones on the NB
Very few NC diff failures.

 

[Jetronic]

Originally Posted By: EddieCairns
After hard driving the new ND Miata / MX5 via additional sensors fitted to them are showing transmission temperatures of 150C / 302F

The diffs are showing 160C / 320F and only has 0.6 litres/ 0.634 qtrs oil capacity.

Can anyone advise if these temperatures will cause any problems or are the found on other cars and which specific oils may reduce any problems if they exist.

Mazda give something like a 75W/90 recommendation.


Nearly all manual transmission cars see those temperatures if driven spiritedly or having a big torquey engine up front.

Frequent oil changes are key to keep things together.

75W-90 is the lowest I'd go but for the transmission, most likely requiring GL-4, that'll also be the highest viscosity you'll find.