Gearbox oil

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Jonathancilia
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Gearbox oil

Post by Jonathancilia »

So today i changed my gearbox oil on the saxo diesel, i bought SAE 75W80, brand name is FINA, i noticed when putting the gear oil in it had a lot of bubbles in it, could it be this is an old bottle or bad batch of gear oil? Because now gears became very stiff. Tomorrow im going to buy the usual FUCHS stuff and see what happens. Clutch is fine i know because even when engine turned off gears are still stiff. And clutch is about 15k kms old only

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white exec
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Re: Gearbox oil

Post by white exec »

The bubbles shouldn't be a problem, if the bottle has been shaken up.
Gear oil does aerate, as can be seen when draining a recently driven car.

Check that the 75W-80 is GL-4, and not GL-5.
GL-5 has additional friction reducers in it, which interfere with the proper gear engagement and synchromesh action of PSA 'boxes.

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Re: Gearbox oil

Post by Jonathancilia »

I bought fuchs transmission oil, it shifts beautifully now, the other oil seems thinner, this took considerably longer to fill up, it was the same viscosity as this one on the bottle. Dont understand lol but the problem seems to have gone away

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Paul-R
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Re: Gearbox oil

Post by Paul-R »

If they're both 75W80 then they will be the same viscosity by definition. It's the additives that differ between GL-4 and GL-5 and the PSA gearboxes need GL-4 as described by Chris.

Can you confirm that you only have GL-4 oils?

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Re: Gearbox oil

Post by Jonathancilia »

The first one i used havent got anything written on it, only SAE75w80, its odd, it was considerably thinner than the FUCHS one. Which is gl4

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white exec
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Re: Gearbox oil

Post by white exec »

That first one might have been a mis-label; not good.
As Paul says, oils of a given grade will have the same viscosity at the same temperature.
There are gear oils out there labelled GL-4/5, which might be convenient for stockists and those marketing it, but the two specs are different.

At least you have the correct GL-4 now.
On a couple of occasions I've swapped PSA manual boxes over from 5 to 4, and the ease of gear engagement and changing improved.
_______

Long time ago, 90 grade EP oil was common in manual gearboxes. Remember when Rover first brought out their 5-speed box for the SD1 (in 1977)... Customer/service advice at the time was just to carry on using those heavy oils which had gone into the previous P6 4-speed (and which had worked well). Come the first winter, shoals of complaints about difficulty engaging gear - especially moving from 1st to 2nd.

The problem was ignored for a while, but eventually Rover modified their advice, and recommended ATF for those boxes instead! It solved the problem, and not long after Castrol came up with a "manual transmission fluid", first called MTF, then Syntrans, and later Syntrax (or something like that). It was bright red, and pretty much the same to look at and handle as ATF.

Somewhere in the late '80s, I fitted our P6 3500S with an SD1 5-speed box, and stupidly followed the service info in the old Rover documentation for the box, which said - guess what? - 90-grade gear oil. It was winter, and I remember driving the car with its new box gingerly away from my garage-workshop, and slowly out on to the road. She pulled away beautifully in 1st gear, but refused point blank to come out of 1st and into 2nd. Starting in 2nd was no problem, and 3-4-5 were managed, although a tad baulkily.

Made a few enquiries, and got reminded about the ATF recommendation. Read up about Castrol MTF, and switched to that. Driving was transformed, and the 3500S ran on that for the rest of its days.

Over the years, build tolerances in manual boxes (and autos) have become much finer, and a heavy oil is no longer needed to keep things quiet. Rover's 5-speed for the V8 incorporated all sorts of high-spec features, including its own oil circulation pump, and taper bearings. 5th gear was nicely high (1:1 in 4th, and a proper 'overdrive' 0.833 iirc in 5th), with the last of the V8 Vitesse SD1's had their 5th gear raised to produce 29.7mph per 1000 engine revs . . . Really leisurely cruising at 90mph!

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CitroJim
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Re: Gearbox oil

Post by CitroJim »

white exec wrote:
06 Mar 2021, 18:45
Somewhere in the late '80s, I fitted our P6 3500S with an SD1 5-speed box, and stupidly followed the service info in the old Rover documentation for the box, which said - guess what? - 90-grade gear oil. It was winter, and I remember driving the car with its new box gingerly away from my garage-workshop, and slowly out on to the road. She pulled away beautifully in 1st gear, but refused point blank to come out of 1st and into 2nd. Starting in 2nd was no problem, and 3-4-5 were managed, although a tad baulkily.
I've had similar experiences where EP90 has been mistakenly put in PSA BE3 'boxes Chris :D When hot it's not too bad but when cold on a frosty morning it becomes similar to your Rover, except it's getting it into gear in the first place, especially reverse!

Fina brings back some memories... Not seen ay Fina products for years now here in the UK...