Transmission oil recommendations for worn synchros?

[hks_kansei]

Also bear in mind the viscousity will have an effect on the slipperyness

The thinner stuff (ATF) may well be a lot more slippery, but also a lot more likely to not stay where it needs to be for lubrication.

At the other end of the scale, bearing grease doesnt feel slippery, but it's that thick it stays wherever it's put, so may be more slippery in use.
(obviously not suggesting to use bearing grease, just using it an an example of the extreme end of how thick a lube is)


Personally I'd be concerned that the ATF wont provide the lubrication needed to keep stuff from wearing prematurely.

[Ross]

Using Castrol VMX-M in the daughters daily and it seems fine.
I'm about to change the weekend toys over to the VMX-M also as I've been getting the occasional baulk going into fifth, but it's more likely operator error than the box,
I'm unsure what's in the box currently, it was full when I got the car 2 years ago and have only done 5K Kms since.
205k kms on the box currently
Will report back when it's done.

[manga_blue]

Time to report on today's work.

First I tried cutting the old Redline MT90 50/50 with Redline Lightweight Shockproof and that made no difference.

Then I drained the lot and filled it with Penrite Pro Gear 75W-90 (GL-5 full synthetic) and the improvement is dramatic. Previously 1st, 2nd and 4th were sort of OK, 3rd was a bit slow and crunchy and 5th was really bad. Now 1st, 2nd, 3rd and 4th are almost as good as new while 5th has had about 90% of the crunch taken out of it. Very happy about it.

[hks_kansei]

I might give it a go when i'm due to change mine.

the VMX-M has been fine for me, and hasnt made the 2nd gear whine worse.

But hey, if the Penrite may help (plus I like to support them, Aussie and all)

[DTH]

93_clubman wrote:
"Phil, interestingly (I think), many including myself run a Dexron III automatic transmission fluid in their Toyota T50 5 speed manual gearboxes."
Back in the 80s a mechanic who ran an Elfin Mallala recommended i use Dexron ATF in my Nota Major (Morris Major/MGA) gearbox. It worked very well except for the leaks.....

[Tony]

Then I drained the lot and filled it with Penrite Pro Gear 75W-90 (GL-5 full synthetic) and the improvement is dramatic.

I'm glad to hear you've made some headway Phil. Many people make the mistake of putting oil that's too slippery in their gearbox and then wonder why the synchros loose their effectiveness (I've mistakenly done it myself in the early days).

If you're going GL-5 you could always think about Redline NS (non-slip) oil as another option. Following a recommendation from a Spec Miata transmission expert in the US, I've put NS oil in my Torsen with great results.

https://www.redlineoil.com/75w90-ns-gl-5-gear-oil

[manga_blue]

[I'm glad to hear you've made some headway Phil. Many people make the mistake of putting oil that's too slippery in their gearbox and then wonder why the synchros loose their effectiveness (I've mistakenly done it myself in the early days).

If you're going GL-5 you could always think about Redline NS (non-slip) oil as another option. Following a recommendation from a Spec Miata transmission expert in the US, I've put NS oil in my Torsen with great results.

https://www.redlineoil.com/75w90-ns-gl-5-gear-oil

Hi Tony, good to hear from you again. I somehow overlooked the non-slip Redlines when I was trawling through their site, otherwise It sounds like it might have been the best option. Redlines have been very good for me until I used MT90 in this gearbox which absolutely hated it. As it is though I'm happy to have bought something that seems to work and that's cheap, locally available and locally made.