GL4 vs GL5 gearbox fluid

[White Knight]

Hi guys, I read in a post that GL5 gearbox fluid was "as everyone knows" is a no no for our w5m33 gearboxes. Why is this? As allowed to GL4?
I ask as I have incidentally run GL5 spec in my gearbox for 6 months and after reading a thread or 2 have been worried and then dumped my fluid and went to a Nulon GL4 spec. Could I have hurt the longevity of my gearbox in the process?

 

[Benzo4gT]

Should be fine, I found this ↓

The gear oils of a few decades ago had lead additives that were effective at wear reduction, but not
very good for the environment. A long time ago they began to be replaced by gear oils with a
phosphorous additive (in itself a decent anti-wear additive) with active sulfur to grip hold of the gears
and create a very solid sacrificial layer of material that could be worn off, thereby protecting the gear
surface. Eventually it was discovered that the active sulfur was causing corrosion of brass and other
soft metals used in differentials and transmissions.
Somewhere around 20 years ago a deactivated or buffered sulfur was developed that would react with
the phosphorous to create the protective/sacrificial layer in the conditions created in the gear boxes
(temperature and pressure) without being corrosive to the brass, copper, etc. This additive system is
used in most gear oils today.

 

[MDK87]

How do you find that Nulon stuff Ian?
I've used it in a few cars.. none of which shifted smoothly with it.
Jacks transmissions recommend using E9 6sp gear oil. Might try to get hold of some of that next time.

 

[Benzo4gT]

How did it shift in yours Ian? I don't think any damage would have happened according to that writeup, so you can breath a sigh of relief, anyway I think I've had all the RVR bad luck for all of us, for a while at least

That stuff has the added bonus of your car being a little bit of E9 Mo, and that's good for 10hp at least :thumbsup:

Because it's designed for 6 speeds, it might encourage the 5 speed box to grow another gear A 6 speed would be perfect for our cars!

 

[White Knight]

You certainly have had our share hey benny. The shift action is as good as before, no real issues, actually selecting 1st on the go is actually easier. Like slowing down and entering the driveway deal. Mo, I am probably not the best indicator with shift action and notchiness, I am pretty easy on the gearbox, pause up the gears and match rev coming down.... What are you using mate?