Advise me on a GL-4 gear oil

[TijY_]

Why is Ravenol so hard to find…and so expensive

Because of this, why are you asking?

Impact on exports: German exports to the U.S. have declined significantly, with August 2025 exports dropping 23.5% compared to the previous year. This is attributed to the tariffs combined with a stronger euro.
Tariff rate: A 15% tariff rate is applied to most German goods exported to the United States.

You probably have plenty home made good oils to choose from anyway.

 

[Elkins45]

Why is Ravenol so hard to find…and so expensive ?

All GL-4 manual transmission fluids aren't easy to find. You can't walk into an AutoZone, NAPA or Advance and buy a bottle, with the exception of maybe Synchromesh fluid.

 

[Bob in Utah]

Because of this, why are you asking?

Impact on exports: German exports to the U.S. have declined significantly, with August 2025 exports dropping 23.5% compared to the previous year. This is attributed to the tariffs combined with a stronger euro.
Tariff rate: A 15% tariff rate is applied to most German goods exported to the United States.

You probably have plenty home made good oils to choose from anyway.

It was expensive even before the 15% tariffs

 

[Fabulous50s]

I have extensive knowledge on the SMOD Ford Toploader based transmissions. The TOD is a modification with the sheetmetal top cover replaced with an aluminum shift fork holding plate. This moves the shifter to the top TOD (top shifted overdrive) whereas the SMOD is a side mount overdrive like the 3 and 4 speed muscle car era transmissions but with an overdrive in place of 4th gear. So a TOD and SMOD are 3+OD.

The TOD was used in Jeeps and many Ford products before they went with the Mazda M5OD.

Here is the gearset I used in my SMOD I put in my 1959 Galaxie with 352FE. Colum shifted of course. This iron case transmission was out of a Granada.

 

[Lubener]

Good choice. Tell us how well it shifts now.

An update.. I had a couple very cold nights and my transmission shifts as smooth as butter. I wish I would have used this Redline MTL product years ago...

 

[CleanSump]

Why is Ravenol so hard to find…and so expensive ?

Because there is only one importer and distributor of Ravenol in the US.
You can buy direct
https://www.ravenolamerica.com/
Or get it here
https://www.blauparts.com/

 

[Japanese]

An update.. I had a couple very cold nights and my transmission shifts as smooth as butter. I wish I would have used this Redline MTL product years ago...

What gear oil and viscosity were you using until now?

 

[Lubener]

What gear oil and viscosity were you using until now?

Sta-Lube 80w-90 GL-4 which was conventional.

 

[Japanese]

There is big difference between 80W oil and 80W-90 oil.
My car MT calls for 75W by OEM and I put one time 75W-90. When the temp. dropped below 32*F I couldn't shift smoothly to 1st and 2nd gear. After 15-20 min. driving the transmission was shifting smoother but not as smoother when I put 75W oil in it. Both oils were high end synthetic oils.

For visual referrens 75W-90 is about SAE40 oil viscosity and 75W is like SAE20 oil.

 

[4wd]

There is big difference between 80W oil and 80W-90 oil.
My car MT calls for 75W by OEM and I put one time 75W-90. When the temp. dropped below 32*F I couldn't shift smoothly to 1st and 2nd gear. After 15-20 min. driving the transmission was shifting smoother but not as smoother when I put 75W oil in it. Both oils were high end synthetic oils.

For visual referrens 75W-90 is about SAE40 oil viscosity and 75W is like SAE20 oil.

It’s important to read across what it’s made for and what OEM’s credentials it carries. Like the D1 50 you laughed at is excellent for Mack heavy service …
Where I leave the farm on this is D1 GL5 because it’s used from Mack to track (Porsche) … practically all I have ever used in my 4WD axles …

 

[Japanese]

It’s important to read across what it’s made for and what OEM’s credentials it carries.

It was made for manual transmissions and it was GL-4, but was not the right viscosity.

 

[4wd]

It was made for manual transmissions and it was GL-4, but was not the right viscosity.

Pretty obvious from the label (didn’t Adam post a picture) …

 

[SureshR]

All GL-4 manual transmission fluids aren't easy to find. You can't walk into an AutoZone, NAPA or Advance and buy a bottle, with the exception of maybe Synchromesh fluid.

Most are now GL4 / GL5.1 (which is different from plain GL5 and backwards compatible to GL4 for old brass synchromesh etc gears)

 

[FordP3]

Most are now GL4 / GL5.1 (which is different from plain GL5 and backwards compatible to GL4 for old brass synchromesh etc gears)

If it isn't GL-4 rated ONLY.... I wouldn't trust it in a light vehicle synchro transmission.

Stay away from multi rated gear oils when it comes to GL ratings.

 

[SureshR]

If it isn't GL-4 rated ONLY.... I wouldn't trust it in a light vehicle synchro transmission.

Stay away from multi rated gear oils when it comes to GL ratings.

I totally agree especially for older vehicles. Just that the stock of available GL4 is going down all the time - either stuff that's been sitting on the shelf for years (not that it actually expires) or really boutique manufacturers.

 

[Fabulous50s]

I use Amsoil manual transmission & transaxle 75w-90 GL4 in toploaders/toploader based transmissions.

That said, they are in summer "fun cars" and never see temps below freezing. So something else may work better.

A lot of guys swear by ATF in their manuals, and having worked on many automatics with planetary gears and helical cut gears it seems ATF would be worth a try.

I use SAE 50 in many medium and heavy duty road tractor (semi) transmissions.

 

[Wheel366]

I use Amsoil manual transmission & transaxle 75w-90 GL4 in toploaders/toploader based transmissions.

I have this in the rear diff in my B5 S4. It might be in the front diff too but I can't remember if I went with that or the 75W-90 Manual Transmission & Transaxle Gear Lube.

 

[Japanese]

I use Amsoil manual transmission & transaxle 75w-90 GL4 in toploaders/toploader based transmissions.

That oil is too thick (higher viscosity) for car manual transmissions.
The equivalent of Amsoil oil he needs is 5W-30 Manual Synchromesh Transmission Fluid (it covers GL-4 too), which is much lower viscosity oil than the 75W-90 Transmission & Transaxle Gear Lube. This was mentioned in 1st page of the thread.

I don't know why Amsoil decided to use SAE 5W-30 motor oil designation for their manual transmission fluid, which in fact is about 75W-80 viscosity.

 

[burbguy82]

I use Valvoline synchromesh, you should also be able to use a 10w30 motor oil aswell, but would have to change it more often. GL4 is for yellow metal protection, Do not run a GL5

 

[SureshR]

I use Valvoline synchromesh, you should also be able to use a 10w30 motor oil aswell, but would have to change it more often. GL4 is for yellow metal protection, Do not run a GL5

Not gl5 but gl5.1 at a pinch is backward compatible to gl4. As others said stick to vanilla gl4 and at the weight specified in your manual if you can get it.

A heavier gear oil weight (90 instead of 80) would just result in heavier and notchier gear throws. Gets very noticeable when you have a light and slick MT with short, crisp throws like the usual golfball shifter in a MT Honda