Front Diff Overfilled?

[PoisonousBeef]

2005 GT 5MT

 

This morning I decided to change my oil and diff fluids. I let the front diff drain for almost 20 minutes until it was barely a drip every few seconds. I poured slightly less than 4 quarts of 75w90 in. After I lowered the car and drove around the block, my transmission dipstick is reading WAY over the F mark. I'm the 2nd owner and the fluid that came out had never been changed (62k), smelled terrible and looked more like used motor oil. At first I thought I somehow didn't get the tranny all drained but the dipstick fluid is perfectly golden fresh fluid, even after a couple miles. Why would this be the case? My shifting feels 200x better but I'm sure that's just a reflection of going from totally trashed fluid to a good synthetic. I wouldn't be concerned about a LITTLE overfull but this looks like 2x the F mark. Anyone else run into this? Do I need to drain again and refill while measuring after each bottle?

[apexi]

I wouldn't worry about going from old beat up fluid to synthetic. The first time I did my tranny fluid, i overfilled a little bit too, probably due to residual oil leftover even though nothing else was dripping out. Now I do 3.5qt and go from there, its easier to add than it is to remove fluid. At 2x higher than the F mark on the dipstick, I would try to siphon some out. My worry would be foaming from too much fluid. I think you can get a ghetto fluid transfer pump for a buck or two that should do the job fine.

[bluesuby]

If you jack up the car under the rear diff, you will get most if not all the old fluid out. I don't think an overfill is a big deal because the lubrication is by splash rather than by pressure (pumped).

[PoisonousBeef]

I had the car on ramps in the front, which I'm guessing must have left some fluid behind. I've measured it a couple of times since my change and it is still rather high even though it's still light golden fluid on the dipstick and I don't see how any substantial amount of the old black sludge would mix in without being obvious.

 

I know we are talking splash lubrication so this is less of an issue than say overfilling the crank case, I've just been concerned about the degree to which it is overfull, since that suggests the gears are submerged much more than recommended and I'm probably increasing the likelihood of foam and lost lubrication (which I'm sure isn't catastrophic in the short term). I know a lot of RWD guys really try to avoid overfilling because it does seem to increase heat/pressure in the case and the fluid will start fighting with seals in their diff (typically axle seals I guess). I don't know enough to say with authority the kind of effect this would have on our combination trans/diff.

 

I picked up a suction gun last night so I'm gonna try to vac some fluid out, though I'm not totally confident I can get the tube far enough down the dipstick hole. If not, I might just go ahead and make a mess by popping the drain plug off for a second and trying to get it back in, then check and slowly fill back up if I went too far. I guess worst case would be not getting it back and having to spring for another 4 quarts.

 

I'm still blown away that I ended up so overfilled. I have started to wonder if the case is shaped in a way that causes a small amount to increase the fluid level a great deal once you get past the F mark.

[Max Capacity]

Yep, like the engine the oil level is hard to get a good reading on.

 

You need to fill it when it's flat.

 

You need to drain the tranny with the rear end jacked up.

 

You need to park on level ground pull the dip stick about a inch or so and walk away from the car for a few minutes, I do this at work, come out 8 hours later, wipe the stick, then check the level of the oil.

 

 

My boxer engine on my lawn tractor does the same thing, the oil stays up the dip stick.

 

Oh yea, the suction gun will work, mine does, you can buy a longer hose if you need. Tractor Supply Co has clear tygon tubing that works well.

[GTTuner]

I did the same thing, I drained my trans on a lift and added 3.6 quarts and it was overfull. I used a suction gun and sucked it back out of the filler tube.

 

IDK if this is my imagination but it shifted really gritty and tough when over filled. Ck the level cold.