Non-EP, GL-1 gear oil - brass, synchros

[Nut124]

Shop manual calls for non-EP (GL-1) 80/90 gear oil. I'm having hard time finding any.

Supposedly the EP additives corrode the brass bushings(?) in the synchros and the modern EP oil is too slippery for the synchros to work properly.

Anybody else have this situation? What oil do you use?

[Krooser]

What application?

[piston guy]

GL4 spec gear oil is good for brass , GL5 is tough on brass. GL1 will be tough to find IMHO.

[englertracing]

Im pulling a kevin right now
Ive been reading up on the subject already actually

https://www.bobistheoilguy.com/forums/t ... 561/page-6

there is some fantastic information posted by a member by the name of molakule

on page 7 there is a list of GL4 manual transmission fluids by weight and CST values.

in any case GL4 is good in a transmission with yellow metal synchros, GL5 is not, howerver there are some GL4 oils that claim GL5 protection levels, which would aslo be fine.

you could match up the viscosity with the OEM oil and it should work.

[Nut124]

Thanks for the replies. I will get some synthetic GL-4 oil, "safe for yellow metal".

Krooser, this is for my Fiat 124 Spider -78, 5-speed manual. My old trans did have the 2nd gear synchro fail for what ever reason after a lot of hard driving and some missed up shifts.

[englertracing]

Heavier than oem for gear protection,
Lighter for possibly faster synchronization

[pdq67]

Back when I was with AP Green, I let my bulk fuel/lube distributor find it for me.

Imho, it is his job..

pdq67

[pdq67]

Sorry, double post.

My bad...

pdq67

[AC sports]

Just go synthetic.
Much better protection and shift quality and no issues with the bronze synchros in the fiat box. I'm using castrol syntrans in box and syntrax in diff. No issues.

[Krooser]

Thanks for the replies. I will get some synthetic GL-4 oil, "safe for yellow metal".

Krooser, this is for my Fiat 124 Spider -78, 5-speed manual. My old trans did have the 2nd gear synchro fail for what ever reason after a lot of hard driving and some missed up shifts.

I special ordered GL4 spec gear lube from a Mobil oil distributor back when I was messing with early Triumph roadsters. That was 10 years ago.

Since then I used GM Synchromesh fluid without any issues in early boxes... shifts real nice.

Ymmv...

[ClassAct]

Thanks for the replies. I will get some synthetic GL-4 oil, "safe for yellow metal".

Krooser, this is for my Fiat 124 Spider -78, 5-speed manual. My old trans did have the 2nd gear synchro fail for what ever reason after a lot of hard driving and some missed up shifts.

I special ordered GL4 spec gear lube from a Mobil oil distributor back when I was messing with early Triumph roadsters. That was 10 years ago.

Since then I used GM Synchromesh fluid without any issues in early boxes... shifts real nice.

Ymmv...

Is the syncromesh a GL-4 or GL-5 oil?

[Krooser]

Thanks for the replies. I will get some synthetic GL-4 oil, "safe for yellow metal".

Krooser, this is for my Fiat 124 Spider -78, 5-speed manual. My old trans did have the 2nd gear synchro fail for what ever reason after a lot of hard driving and some missed up shifts.

I special ordered GL4 spec gear lube from a Mobil oil distributor back when I was messing with early Triumph roadsters. That was 10 years ago.

Since then I used GM Synchromesh fluid without any issues in early boxes... shifts real nice.

Ymmv...

Is the syncromesh a GL-4 or GL-5 oil?

Neither...not an EP product.

light-truck applications that require synchromesh transmission fluid. Applications include manual transmissions and transaxles such as New Venture* NV T350, NV 1500, NV 2550, NV 3500, NV 3550, NV 5600, and Tremec* T4, T5, T18, T56, T176, TKO500, TKO600, TR 3450 and TR 3550. Replaces MTF-94 fluid for Land Rover*, MG*, and Mini Cooper*. Replaces Honda* Genuine MTF fluid for manual transaxles and Texaco* MTX fluid. Not for use in engines, hypoid rear axles, limited-slip or wet-clutch applications.

Years ago when I researched using this stuff I found only one refinery and blender made the product regardless of brand...Mobil iirc.

[RDY4WAR]

You will be fine running a GL-4 oil in an application that calls for GL-1. GL-1 is obsolete.

Some GL-5 oils will work in GL-4 applications if the additive package is adjusted to keep down the phosphorus and active sulfur content. These are rare however, and if you don't know what to look for or know the formulator, it's best to stick with GL-4.

Red Line MT-90 is an excellent GL-4 oil.

[naukkis79]

I do use synthetic ATF in manual gearboxes - it usually works much better than GL-4 grade oils. Redline MTL is one excellent product that have both GL4 and ATF grades but it's expensive, any thin synth ATF works usually also well.

[englertracing]

I do use synthetic ATF in manual gearboxes - it usually works much better than GL-4 grade oils. Redline MTL is one excellent product that have both GL4 and ATF grades but it's expensive, any thin synth ATF works usually also well.

My trans specs ATF
I'm going to give redline MTLV a try.
I hope and think it could/should work slightly better than atf.