Transaxle Lubrication

From the Mid-America Mountain Motor Works catalog -

Filling your new transmission or changing the oil in your old transmission is essential for the longevity of your gear box. When installing a rebuilt transmission, its a good idea to change the oil after 300 miles. This preventive measure removes the possibility of any debris that might be left in the transmission after assembly. After the initial break-in period, the oil level should be checked every 10,000 miles and changed every 30,000 miles. When you check or change your oil, be sure to lift the rear of the car with an appropriate jack and secure the car with jack stands. The oil filler plug is located on the left side of the transmission. Using a 17mm Allen/Hex head tool, remove the plug. Insert your finger in the hole; the oil level should reach the edge of the opening and be on your finger tip. The vehicle must be as close to level as possible to check the oil accurately.

When changing the oil, remove the two plugs under the transmission. After all the oil has drained, thoroughly clean the plugs and reinstall them. Fill the transmission using SAE 80W90W hypoid gear oil. The transmission’s oil capacity is approximately 6 to 7 U.S. pints. Fill the transmission slowly; if you fill it too fast, the oil will overflow as if the transmission is full when its really not. After you have reached the correct level, clean and reinstall the filler plug.

Rob wrote -- The gearbox holds 2.5 liters of Hypoid 90 (or Hypoid 80w90 is good for colder climates). The gearbox fluid should be changed about every 30,000 miles. If you just purchased your Bug and don’t know its history, replace the transmission fluid in preference to topping up. It often gets forgotten by owners, and can come out looking rather disgusting. Hypoid gear oil is a mineral oil. Any good brand of 85W90 or 80W90 hypoid will work well, and good oil definitely makes for smoother gear changes. (See our Transmission Fluid Check/Replacement procedure.)

Regarding gearbox lubricant, someone wrote - You need GL4 type for old Volkswagens. Most folks will try to sell you GL5, which is the present-day standard. So be sure to use the right stuff. Every two years.

Rob responded - GL must be a U.S. specification - I'd never heard of it until I started talking on the newsgroup. I think it originated with the U.S. military. My Owner's Manual says to use "SAE90 Hypoid" generally, or "SAE80 Hypoid" in low temp areas, or "ATF (Dexron 11)" in arctic conditions. I use Castrol SAE 85/90 Hypoid all year round.

If you don't have a suitable 'giant allen key' (17mm) for the plugs, I made a tool from a short (about 3/4 inch) bolt with a head which fits inside the plugs (17mm) I welded the shank of the bolt to a piece of flat steel about one-inch wide by 15 inches long. This homemade tool fits both filler and drain plugs. The bolt need to be fairly short so the tool will fit between the gearbox and the engine yoke running past the gearbox.

You mentioned that your tranny has two drain plugs -- the second plug will allow the last liter of fluid to drain, so don't be surprised if it takes most of that gallon, instead of the 2.5 liters.

To fill the gearbox, I use a 4-foot length of plastic tube (e.g., Tygon) about 3/8 inch ID (has to fit in the filler hole). Poke one end into the filler hole on the side of the tranny, then bring the tube out under the left rear wheel arch, and poke a funnel into the other end (the tube should be 'down hill' all the way to the gearbox). Put the oil bottle in a bucket of hot water for a time (to thin it a bit). Then stand next to the left rear wheel, holding the funnel, and slowly pour the warmed gearbox fluid into the funnel. When the oil spills out of the filler plug, it's full (put some newspaper underneath to catch any spill). Not hard -- just takes a little time.

Dave wrote - We do have a slight leak of transmission fluid -- just a drop or two now and then. Any comment on that?

Rob responded - I wouldn't worry too much. A drop or two will take a long time to go below minimum.

I guess just check it when your son brings it back from school and top it up then. That will give you a quick indication of the loss rate, so you can check it appropriately another time. Only a leak from the seal around the gearbox input shaft (inside the bell housing) would be a problem -- possible oil on the clutch, so if this ever starts to slip -- guess you'd need to check it then.

Dave asked - During refilling or topping off, how do you know when it's full? A mate under the car watching for it to spill out?

Rob - Start with 2.5 liters in the filler bottle -- that's how much it takes. I also place a drip tray under the tranny, and then add a drop or two more until it just starts to dribble out the filler hole -- pour a bit -- have a look and repeat.

Dave - We still have a problem occasionally shifting into second. I think we're looking at transmission repair/replacement, not right now, but down the road.

Rob - Glad it's much improved. And I guess it's just getting close to the time an old gearbox got some internal attention. If you can find it, try getting some Teflon (TPFE) oil for gearboxes. Slick50 and Nulon make it for engines, but this is no good (dilutes the gearbox oil). Nulon also make it in a tube of about 100ml for gearboxes, and this stuff has kept my weak synchros going for 5 years after they started showing signs of wear. I don't know if Nulon is sold over there or not, but I'm sure SOMEONE makes it there. And I forget if you've changed the gearbox oil itself since you got the car -- if not, this can sometimes help too. Castrol make a very good 85/90 geabox oil (or is it 80/90?) Anyway, the multigrade type gearbox oil is very good, especially in colder climate winters like yours.

Dave - I went to the auto parts store and bought a gallon of Valvoline Gear Oil, 80W90. Also bought a bottle of Slick50, "fortified with DuPont Teflon PTFE," and a Valvoline fluid lubricant pump.

Note: The lubricant pump Dave purchased broke after only one or two uses. Dave reverted to the gravity drain fill method as shown in the picture above with very good success. Dave wrote - It's so much easier to fill the tranny by gravity than trying to pump the fluid up with a cheap pump (I couldn't afford the more expensive ones). And with my long piece of electrical conduit anchored into a coffee can with concrete, then a chemistry lab clamp to hold the funnel, it's duck soup!