What Gearbox and Diff Oil Viscosity do you use?

[Rally Pack 2000]

Ford Manual suggests SAE 90 for the diff and SAE 80 for the gearbox. Had been using up bottles of these I have had on the shelf for years but time for some new stuff but you cant seem to get it anymore. The most common offering being a 80w-90 but that somehow doesn't seem the correct replacement for both to me? But some companies claim it is a direct replacement for both. What do you use use in your standard diffs and gearboxes?

[colr6]

I put 75/90 semi synthetic in all my boxes apart from a t5 I’ll be using the same in a std diff

[katana]

19 minutes ago, colr6 said:

I put 75/90 semi synthetic in all my boxes apart from a t5 I’ll be using the same in a std diff

That's what Ford recommend for the T9 - GL4 or 5?

Only done that as it was stripped and refreshed. Rear didn't seem noisy, so as long as the level is right, its got what its got!

[colr6]

19 minutes ago, katana said:

That's what Ford recommend for the T9 - GL4 or 5?

Only done that as it was stripped and refreshed. Rear didn't seem noisy, so as long as the level is right, its got what its got!

GL 4

[DT36]

Think I put GL4 in my box and GL5 in my ATB. 

Was a while ago though... 😁

 

[Johnny Boy]

They are like multi grade versions of the old single grade oils, so better in all respects.

Some modern gear oils don't like some of the metals in old gearbox's. I'm not sure of all the implications.

Best do some research 😬

[Rally Pack 2000]

2 hours ago, Johnny Boy said:

Some modern gear oils don't like some of the metals in old gearbox's. I'm not sure of all the implications.

Best do some research 😬

It was doing that very thing which prompted me to start this thread. They mentioned the reaction with modern oils with some older diffs and gearboxes but nowhere did it say what reacts with what! So thought It best to discuss LOL

[Rally Pack 2000]

You know I never even took notice of the GL tags on these oils till you guys started quoting them on this thread I always just used the viscosity rating. Wasn't even sure it was used by local manufacturers but found an unopened multi-grade one in the shed, (who knows when I bought that!) and sure enough there as plain as day GL-5.

So use that one in the diff and get something with a 4 rating with a wider range for the gearbox? I dare say that one above is just a cheapy I bought in my travels so now that the old bomb is worth something should I take better care of it and upgrade to a better semi synthetic (or fully synthetic?) oil 75w 90 for both like Col suggests?

Always been a bit lax when it comes to getting the old fluid out, just a bit of a syringe to get some of the old stuff but then just topping it up. Now than Im changing the type of oil I should probably do a better job or extracting most of the old oil this time and the little syringe isn't going to cut it. Do you guys have reasonable home DIY oil extraction system?

[Johnny Boy]

All I do know is that, something in the modern oils, attacks the synchro rings and shims , that are made of bronze /bronze alloys.

 

[Johnny Boy]

As I am using a black line ATB in my car, and when they run in, by the nature of there construction, they can shed an amount of swarf, until all bedded in.

I put a magnetic drain plug in the bottom of my English axle, so I could drain and replace it , after 300 miles , and replace it easy whenever in the future.

[Rally Pack 2000]

7 hours ago, Johnny Boy said:

All I do know is that, something in the modern oils, attacks the synchro rings and shims , that are made of bronze /bronze alloys.

 

I got an email from a local oil manufacturer and they said that its something that affects pre-1960's cars so on the Escort front I should be fine.

7 hours ago, Johnny Boy said:

As I am using a black line ATB in my car, and when they run in, by the nature of there construction, they can shed an amount of swarf, until all bedded in.

I put a magnetic drain plug in the bottom of my English axle, so I could drain and replace it , after 300 miles , and replace it easy whenever in the future.

I have always wished there was a drain plug on both the gearbox and English axle in my Mk2 but alas there is none. Hence why I have been very slack over the decades in changing the oil and often just topping it up.