Changed gearbox oil now problems - update !

[quattrodave]

Changed the ' box oil on my 1990 1.6td multivan 5 speed today.
3.5 litres of old stuff came out that was very dark. New comma 80/90 gl4 oil from Wilkinson went in, 4 litres, now it's difficult to engage first 3 gears and 1st to 2nd has a bad crunch. Gears were fine beforehand.
Thinking back I wonder if the dark oil was due to molyslip
Or similar. The question is, is it worth popping an additive in the box or trying different oil altogether?

[MGP]

I would try it with the correct oil before putting additives in.

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[quattrodave]

I was under the impression 80/90 gl4 is the correct oil?

[ELVIS]

Did you take the linkage off at rear for axcess and put plate on wrong?

[quattrodave]

No nothing removed, only the filler and drain plugs

[MGP]

The correct specification is MIL-L-2105D

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[quattrodave]

The correct specification is MIL-L-2105D

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What gl spec and viscosity is that?

[300CE]

80/90 GL4 is fine, I've replaced mine with this twice in the last 3 years - Aidan is the gearbox guru and I'm sure he'll be along to provide some knowledge on the possible issue.

What did the magnetic drain plug look like upon removal of the old fluid?

[quattrodave]

A bit of swarf but just what I'd consider normal, no metallic pieces in the oil either.
It was fine before the change so it must be down to oil choice!

[bigherb]

GL4 is the correct oil, MIL L2105 is an equivalent US military specification.
Does the problem ease when the vehicle is driven and the gearbox warmed up? Some gearboxes the oil level was reduced to stop cold selection problems.

[Oldiebut goodie]

The correct specification is MIL-L-2105D

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Quick google says that that is GL5 whereas MIL-L-2105 (without the D) is GL4. (I thought that it was GL4 also for our boxes and Aidan said that straight GL5 shouldn't be used)

[quattrodave]

GL4 is the correct oil, MIL L2105 is an equivalent US military specification.
Does the problem ease when the vehicle is driven and the gearbox warmed up? Some gearboxes the oil level was reduced to stop cold selection problems.

Yes it does ease a bit when warming, the gearbox oil level might explain why only 3.5 litres came out!
I'll try reducing the level by 0.5 litres next weekend

[MGP]

My mistake drop the d from the specification, info taken from the owners manual
The mil specification is going to be harder to meet than the gl4 so will be the better quality oil.
Interestingly auto data says 75w90 synthetic oil should be used.
I went with Motul gear 300 after my gearbox rebuild, Aidan approved the use of the above oil.

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[quattrodave]

My mistake drop the d from the specification, info taken from the owners manual
The mil specification is going to be harder to meet than the gl4 so will be the better quality oil.
Interestingly auto data says 75w90 synthetic oil should be used.
I went with Motul gear 300 after my gearbox rebuild, Aidan approved the use of the above oil.

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Thanks for that

[Aidan]

80w/90 GL4 is fine but when cold all oil will slightly baulk the change on the lower gears for the first one or two changes, 80w/90 mineral slightly more so; 75w/90 is slightly more forgiving in the cold, fully synthetic to the old VW 501.50 spec, ie GL4+ is available again so that's what I have been using, Mannol is fairly readily available from fleabay at reasonable price and there are other similar spec oils from UK blenders at sensible money too, I spoke to one company I didn't know up in Co Durham this week and they checked their's is compatible with the MIL spec and VW 501.50 spec, Moore and Allan iirc, they have 20 litre drums on fleabay that's what I was looking at as I am down to my last half litre for assembly, but they also sell smaller containers; good to support UK blenders

yes Molyslip GM6RA is a worthwhile additive as our synchro rings are mostly moly coated and the additive does aid the slippiness and seems to protect the rings over time, add it every second oil change I reckon, especially as synchro rings genuine are now £50 a piece - £13 additive is a worthwhile investment

I think the factory fill had additive in it but VW refuse to confirm that, but don't deny it, just won't say

Don't overfill boxes, 4 litres in a 5 speed box is about 5mm below the overflow on a diesel, VW lowered the fill to 3.5 litres on the petrol box which is nose down to reduce the baulking but personally I'd go with 4. If you get 3.5litres out put 3.5 litres back in, you cannot fully empty the box in the vehicle

overfull boxes tend to blow a little out of the breather hole on the front of the box, damp nose of the gearbox is often down to that but on a 5 speed could be a sign of end case corrosion leading to perforation