Re: GL4/GL5

[alex.fadeev@xxxxxxxxxxx]

PeterSchop@domain.elided wrote:
> The car I just bought is a 1990 535i. I have the car at a shop that
> works mainly on European cars. I am having the trans and diff fluid
> changed. When I asked if they are using GL4 in the trans and GL5 in
> the differential, he said that they use the same fluid in both units.
> They use Valvoline 80/90 GL4/GL5.

Peter,
That's likely 80W90 (so far so good) GL5 fluid.
But if I were you I would call the shop to confirm.
GL4 and GL5 are two different standards that AFAIK should not be
interchanged. GL5 specifies about double the amount of wear resistance
additives over the GL4 level. If the gears were not designed to work in GL5
lube, they will corrode.

Here are some quotes from my past emails on the subject.
>From Penzoil:
If an API GL-5 gear oil is used in a application where API GL-4 gear oil is
called for, chemical corrosion of "yellow metal" components may occur, such
as bronze synchronizers, brass bushings, etc. This may lead to shifting
difficulties or shortened equipment life.

>From redlineoil.com:
Most manufacturers of manual transmissions and transaxles recommend an 80W
or 90W GL-4 lubricant. GL-5 gears oils which are required in hypoid
differentials are not used in most synchromesh transmissions because the
chemicals used to provide the extreme pressure protection can be corrosive
to synchronizers, which are commonly made of brass or bronze. Typically,
the use of a GL-5 lubricant in a synchromesh transmission will shorten the
synchronizer life by one half. The extreme pressure requirements of spur
gears and helical gears found in transmissions are not nearly as great as
found in rear-wheel drive differentials. A GL-4 lubricant provides adequate
protection for most manual transmissions, unless a unique design
consideration requires the extra protection of a GL-5.

> He said they uses it in all European cars they work on.

OK, if it's a GL4 lube.
Not OK if it's GL5 as BMW transmissions are designed for GL4 fluids only!

> When I told him that BMW recommends GL4 in the trans and GL5 in the diff,

You are correct.

> he said the Valvoline would work in both since it is a GL4/GL5. Is this
OK?

No.
I just hope they were bullshiting you about GL4/5 compatability are were
just trying to get you out the door.
Most likely, your shop is just selling you whatever fluid that had bought
in bulk. I'll take it a step further and suggest that they have likely
filled your tranny and diff with regular engine oil. A 70W80 GL-4 gear oil
is SAE 10W30 engine oil viscosity must be around 20W50, give or take (why
or why do we have to separate engine/gear oil scales!).
But I would call back to get to the bottom of this. If they had indeed put
GL-5 lube in your transmission you would want to drain it and refill it
with Gl-4 oil.

HTH,
alex f

------------------------------