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Mon May 12, 2025 3:45 pm

1966 VW Beetle, stock.

Can I use 85w 140 gear oil in my rear transaxle?
Will it hurt anything?

Mon May 12, 2025 3:55 pm

That is too thick, 90 weight is the factory specification for most climates, 80 weight for artic type climates The 85W-140 means that the fluid acts like 85 weight when cold, but once warmed up it acts like 140 weight, which is much much too thick for our tranny.

The 90 weight factory specified acts like 90 Weight when armed up, and that is what she needs when warmed up, not 140

You also need to be assured this lube can work with Hypoid gears. So look for a hypoid oil too. And dont buy lube with friction modifiers added for use in Limited Slip applications, that is only for the limited slip clutches found in other cars, not our Bugs

Too thick an oil may not splash correctly, and splashing is needed to lube some parts of the tranny, as there aint no pump to do that job in there.

You will also see excessive drag in the tranny do to the too thick oil, which will result in loss of efficiency

Mon May 12, 2025 5:26 pm

Can you use 85w140 in your Bug trans? Sure you can.

Will it hurt it? Probably not.

The more important question is, should you use it? Also probably not, if for no other reasons than 1) it's not what the gearbox was designed to use so it can lead to difficult shifting or unnecessary excess drag in the driveline, and 2) there's no real benefit in doing so unless your transaxle is pretty worn out and you need the thicker lube to quiet it back down to a dull roar until you save enough pennies for a rebuild.

Mon May 12, 2025 6:11 pm

Thanks.
I am still in the process of locating an owner's manual that shows capacities, etc.
I read that it takes 4 quarts. Does that sound right?

Mon May 12, 2025 6:14 pm

DSVW wrote: I am still in the process of locating an owner's manual that shows capacities, etc.

Here ya go:
https://www.thesamba.com/vw/archives/manuals/aug65bug.php

Mon May 12, 2025 6:17 pm

Your transaxle oil capacity is 6.3 pints.

Mon May 12, 2025 7:21 pm

Thank you.

Mon May 12, 2025 8:41 pm

You can put anything in it, but VW recommended a certain weight, they could have given a wide range of lube weight, but they didnt. If 90 to 140 weight was ok, then I am pretty sure VW would have specified that. A tranny can be expensive to rebuild, why risk ruining it by putting in the wrong stuff?
The owners manual is very clear, 90 weight, except for arctic conditions, in which case 80 weight.

Refill is 5.3 US pints per below owners book... ( the prior post that mentions 6.3 US pints if for a dry tranny, since about one pint stays in a drained tranny, the refill volume is less, which is listed as 5.3 US pints. )***
https://www.thesamba.com/vw/archives/manuals/aug65bug/page75.jpg

And the factory recommended lube type here...
https://www.thesamba.com/vw/archives/manuals/aug65bug/page77.jpg

*** Proper fill level is when fluid level is to the bottom of the filler hole, it should be about 5.3 pints for a change after draining always drain when oil is hot after driving to assure the most gunk gets drained out. if it is a fresh build tranny that has zero oil in it, then 6.3 pints is required

Always assure you can open the filler plug BEFORE draining. sometimes the filler plug maybe stuck, and that is a big problem if the fluid has already been drained, as now the car cant be driven.
Always never over tighten the fill nor drain plugs, they are tapered, and can easily crack the soft magnesium transmission case if driven in too far, they only need to be snug, not tight. use of a thread sealer such as Teflon pipe tape will assure leak free service