VW T25 T3 and Syncro Gearbox Oils
Gearbox oil gets a really hard life, engine oil has it easy. However when I ask people when was the last time you changed your gearbox oil replies often range from never to 5 years. Now what you say to someone who said that about their engine oil! VW in their wisdom 30 years ago stated that the oil doesn’t need to be changed for the life of the vehicle. Unfortunately, for us, VW classed the life of the vehicle as 10 years, they didn’t expect us to be still driving around in them 30 years later, Be kind to your van and change your gearbox oil like you would your engine oil.
Which oil to use in a VW T25 T3 gearbox?
One of the most frequently asked questions about the VW T25 T3 and Syncro Gearbox is which oil to use.
According to VW for the early 4 speed 091 4 speed gearbox VW recommend SAE 80/90W GL4 and 3.5 litres. The later 4-speed gearbox from 1985 091/1 (DU or ABD), one should use SAE 80/90W GL4. Petrol’s hold 3 litres gearboxes and Diesel gearboxes 4 litres. 5-speed gearboxes produced after this, use the same spec oil SAE 80/90W GL4 and 4 litres.
Which oil to use in a VW T25 T3 Syncro gearbox?
VW recommends SAE 80W GL4 for the Syncro gearboxes, and the gearbox takes 4.5 litres. 1.5 litres of oil are trapped in the gearbox so it is only possible to change 3 litres normally.
For the Syncro front differential, VW recommends SAE 80W GL4 and to use 1.5 litres.
VW’s standard manual gearbox oil is 75/90W GL4 so as such the current thinking is to use 75/90W GL4 for the standard syncro gearbox. Non-standard transmissions for TDI vans or those doing a lot of hard work have been recommended to use 75/140W GL4.
Most Motorfactors will have a relatively cheap 75/90W or 80/90W GL4/5 or GL4 gearbox oil which if changed every year should suffice.
Can I use GL5?
The VW T25/T3 and Syncro Gearboxes are not suited to GL5 spec oils. GL5 oils have a detrimental effect on brass components in the gearbox i.e. it erodes them! Therefore GL5 should not be used. Oils that are marked GL4/5 can be used.
Should I use Molyslip in my gearbox?
Molyslip GM6RA is a good additive to use to help extend the life of your syncro rings and to generally give the gearbox any help it can. One dose every two changes is probably enough.
Hope this information is of help Paul