After having my differential mounts reinforced and replacing my rear axles, my differential front seal is now leaking. It shows up as a thin stream of oil dripping from the front of the differential onto the garage floor, and winding its way back on my nice epoxy coated floor. I will need to deal with the leak itself later. For now I need to keep the differential topped up. I am planning to check it once a year regardless of whether I see leaks, and I definitely topped it up when I first bought the car, before driving it any distance at all. Here are my notes so I remember details for next time:
1. Purchase Recommended Oil – I am using Brad Penn Multi Purpose GL4 80-90wt purchased from The Roadster Factory. It will not cause problems with any “yellow metal” components in the differential. (If there are any, this is a problem with transmissions).
2. Make an Oiler + 6-8″ Clear Vinyl Tube Extension – It is impossible to squeeze oil into the differential from the bottle. I made the following oiler rig from an inexpensive oil can purchased from Northern Tools, plus a piece of 1/4 inside diameter clear vinyl tubing from Lowes. I marked this oiler rig with a sharpie (80-90 wt Brad Penn GL4) to remember what oil is in it. I can use it for topping up both the differential and the gearbox.
3. Remove the filler plug – with car level on the ground, the plug is on the passenger side of the differential, and is square. Get on your back and wiggle under the passenger side from the rear of the car. Don’t jack it up, leave it level. There is room to get under it ok.
4. Fill the Oiler to a Predetermined Level – as a reference point, so you will know how much you added to the differential later
5. Insert Vinyl Tube end of Oiler Rig into Differential until it Turns Down – until it bends down, into the differential. This way you will know when you pump oil in and it leaks back out that it is truly full. At first I put the tube into the filler hole level, and didn’t turn it down into the differential. When I pumped oil in, it appeared to immediately overflow, as if it were full. I’d been wiping up oil for awhile now, and knew it had to be low. The oil was traveling back down the tube and dripping down as though it is overflowing when it was not. Pushing the vinyl tube down into the differential made a difference – I had to pump the whole can in before it overflowed.
6. Pump Until It Overflows
7. Make Note of How Much Oil Was Pumped In – open the oiler rig and make a note as to how much you used. This is a good way to keep track of the rate of the leak. The capacity of a TR6 differential is 2.4 pints (1.13 liters). 2.4 pints = 38.4 ounces. The oiler has about 8 ounces capacity. So for the last top up, it took almost the whole 8 ounces of the oiler. But that isn’t bad – I would have been concerned if it took more though, and wouldn’t want to drive it if it was more than 8 ounces low.
8. Replace the Filler Plug – its ok if it is still flowing out. Wipe down the overflow, and the nice epoxy coated floor!