<VV> Finding manual transmission oil locally?

Hugo Miller hugo at aruncoaches.co.uk
Sun Jun 30 10:36:21 EDT 2019

Thank you, but I wasn't actually suggesting putting ATF in a diff. I 
went to some lengths to explain that (hypoid) crown wheel & pinion gears 
(ring & pinion if you prefer) require a different oil from the standard 
Extreme Pressure stuff, and I explained why hypoid oil was unsuitable 
for synchro cones. It has less to do with the oil attacking the soft 
metals (in fact I've never seen a sybchro cone corroded in this fashion) 
and everything to do with making the cones slide over one another 
instead of biting, which can literally make a vehicle un-driveable, on 
commercial gearboxes anyway.
But I've already said all that - the confusion arose because my car has 
separate oil for gearbox and transmission and I didn't realise that a 4 
speed shared trans oil while a PG didn't. Not that this affects the 
validity of my arguments of course.
PS I just noticed you say that diff gears are designed for GL4. That is 
putting the cart before the horse if I may say so. Hypoid gears are 
designed to work with whatever lubricants are available at any one time. 
At present, that would be GL5 rather than GL4 I think?
I have an old 1927 Lagonda that runs its axle and gearbox on castor 
oil. It is a crash gearbox (sliding spur type) with straight cut gears, 
and believe it or not, the best oil for these boxes is still reckoned to 
be good old castor oil. With the added bonus it is an effective cure for 

On 2019-06-30 15:17, Charles Sadek wrote:
> Hugo,
> Private
> I doubt the differential gears will survive with ATF. They are not 
> designed
> for that. They are designed for GL4. The transmission and 
> differential share
> the same fluid on a manual transmission car. Since they share on a 
> manual
> trans and do not on a PG - there are seals, it should suggest to you 
> that
> ATF is NOT used in the differential. To suggest using it doesn't make 
> sense.
> Your own cars do not use ATF in the differential.
> If the fluid between the two was the same, would there be different
> dipsticks? If there is a common path between them? Since the fluids 
> are
> different on your car, it says they must not be common.  Of course 
> there is
> a dipstick for the engine oil. The gearboxes are not common to the 
> engine
> oil sump nor are they on most cars.
> The only reason GL4 is preferred over GL5 is due to the brass (yellow 
> metal)
> synchronizers which are not used in modern cars in the last twenty 
> years or
> so.
> With all due respect, you need to get a manual for your cars.
> Chuck Sadek
> -----Original Message-----
> From: VirtualVairs [mailto:virtualvairs-bounces at corvair.org] On 
> Behalf Of
> Hugo Miller via VirtualVairs
> Sent: Sunday, June 30, 2019 9:56 AM
> To: Bryan Blackwell
> Cc: virtualvairs at corvair.org
> Subject: Re: <VV> Finding manual transmission oil locally?
> My Corvairs are 2 spd PG. At least one of my cars has three 
> dipsticks;
> one for engine oil, one for axle oil and one for transmission oil. 
> How
> does that work if axle and transmission are combined? Or is that on
> manual gearboxes only?
> If they are combined, it's going to be a trade-off. You want hypoid 
> oil
> in the diff but not in the transmission. I guess that GL4, which is
> 'slightly' hypoid as I read it, is as good a compromise as any.
> But what happens in all the modern FWD cars that have automatic
> transmission in a combined housing with the differential?
> I originally come from the UK and used to work on Minis when they 
> came
> out - they have the transmission gears and differential effectively
> living in the oil pan, all running in the (dirty!) engine oil. The
> differential gear is not hypoid on those however, it is slightly
> helical. Never had any issues with them.
> On 2019-06-30 14:43, Bryan Blackwell wrote:
>> Corvairs share the lubricant between the trans and diff. You 
>> *cannot*
>> use ATF, and you *should not* use GL5. I'd suggest finding a place
>> that carries GL4, pretty sure Amsoil has one that meets the specs, 
>> or
>> just order the stuff, there are quite a few vendors who carry Amsoil
>> products.
>> --Bryan
>>> On Jun 30, 2019, at 8:00 AM, Hugo Miller via VirtualVairs
>>> <virtualvairs at corvair.org [1]> wrote:
>>> As a general rule, synchromesh transmissions run best on ATF. What
>>> you want to avoid is hypoid oil, as this will allow the synchro
>>> cones to slip & slide without biting. I have known commercial ZF
>>> transmissions become almost underiveable when filled with hypoid
>>> oil.
>>> The problem is that in the good old days, we had hypoid gear oils
>>> and we had EP (extreme pressure) gear oils. So you had EP 90, which
>>> was good for synchro transmissions, and Hypoid 90, which was not.
>>> The two were quite different.
>>> But today, through the magic of modern chemistry, we see EP/hypoid
>>> oils, which serve both functions. I would avoid these and use ATF
>> or
>>> EP 90 if you can find it.
>>> I'm not up to speed with the GL numbers - Google will tell you more
>>> than I can. Just steer clear of anything with 'hypoid' on the
>> label.
>>> On 2019-06-30 12:11, John Gull via VirtualVairs wrote:
>>>> Well not having any luck finding 75w90 gl4 gear oil for my 65
>>>> 4speed
>>>> tranny! I can find gl5 oil but according to Richard Widman
>>>> website it
>>>> is not recommended to use. Any suggestions where to find locally
>>>> will
>>>> be helpful. Thanks John Gull in Asheville NC
>> Links:
>> ------
>> [1] mailto:virtualvairs at corvair.org
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