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Gearbox oil selection for worn synchros. KM132


Poo

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Ok, first off my gearbox in the Eterna is mint around town, open road and everyday driving. 

But on the dragstrip 3rd gear is impossible to select without doubling the clutch. Once reved out in 2nd, I try for 3rd and its just not there. 

With the Oldschool Dragday coming up, I should really attempt to sort it. 

I am waaaaaaaaay to lazy to pull the box out and re-do the synchros. 

So I am tossing up putting some Redline MT90 or Lightweight Shockproof in there to see if that does the trick. 

MT90 seems better for synchros or would the Lightweight Shockproof be better suited?

 

If I sort this out, hopefully my car will run a quicker time than my scooter. lols. 

 

Thoughts?

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I've got MT90 in my gearbox and have found that over the last few months it's been a little harder to select some gears when changing in a hurry.

I'm not sure if this is because I've been expecting too much with gearshifts and wearing the synchros or the gearbox oil has been contributing.

 

But I do remember someone saying something about the redline oils being unfriendly with synchros over the long term?

 

Not sure if it's a myth / not sure on specifics though.

But I have been considering looking into it further and perhaps switching to something else.

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Ahhh looks like MT90 is fine, just not the shock proof

http://www.ingearperformance.com/archives/607
 

Over the Past few months I have seen a number of gearboxes coming to me with damaged Synchro rings and Hubs all using a common oil, that the customer thought was the best stuff to use for their application.

The Redline brand of oils are excellent, but the issue is people using the wrong type of oil for their application.

Redline Shock proof oils should only be used in final drives and dog boxes only! as it has friction modifiers that do not work well with synchromesh gear boxes.

If you are going to use Redline oil in your Synchromesh gear box, please use only MT-90 75W90 GL-4 Gear Oil.

 

 

Although I remember I had a different redline oil in my diff compared to gearbox, maybe it was MT90 in the diff... hmmm...

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Ahhh looks like MT90 is fine, just not the shock proof

http://www.ingearperformance.com/archives/607

 

 

Although I remember I had a different redline oil in my diff compared to gearbox, maybe it was MT90 in the diff... hmmm...

 

Weird, have a read here http://www.redlineoil.com/product.aspx?pid=43&pcid=7 they seem to think its mint for synchros. 

I so confused now. 

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Just run straight ATF dexron 3 or a GL4 75w85. Depends what the "shockproof" additive is thats in it, but half the time its LSD additive which makes shifting harder. LSD additive is slipperier = syncros not working so good. Use a GL4 not  GL5 for better shifting.

 

If you want the best oil for warn syncros go with a multi purpose tractor trans/hydraulic oil. Normally called an Agri super or somthing. It has a wet brake additive which bites in better. Just dont tell anyone you are using it on the road as its illegal apparently. Has no colour.

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They're are well known for poor hi revs shifting, I tried every brand available in my Starion some are better than others and it sometimes takes a few days before you get the benefits.

There was a Duckhams (SP?) that was good and Caltex easy shift 75w90, next time I will use what I do in Pajeros, a full synthetic Amsoil.

Gotta change the gearbox oil in Mitsis every second service when they are in full use.

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