Oil on back window... Main seal?

[DeviousPsycho620]

Hi all. I was driving home tonight and i noticed speckles of something on my rear window. When i got home, i ran my fingers across it and realized its oil. Do i have a rear main seal going out?

 

I have a 76' 620 with an 89' 240sx motor and i believe its an 83' 280z tranny.

[bonvo]

main seal is at the back of the engine not transmission only thing i can think of is possibly the output shaft seal but that is still to far forward as for your transmission unless someone swapped the bellhousing it is not from a z car it might be a z series transmission for a nap z engine however

[DeviousPsycho620]

Could my rear diff sling it from the pinion seal? It seems kind of far and going the wrong direction, but i did see some shiny, fresh fluid around that area.

 

I may have forgotten to mention i have a large hole in the bed.

 

[datzenmike]

Get under and look for wetness. Could be diff or trans. Better find out before it goes dry.

[mike]

That hole in the bed could cause a neg pressure/vacuum and weird turbulence that could pull oil spray from anywhere and it doesnt take a whole lot of oil to make a mess on a window... Check EVERYTHING. 

 

If its gear oil from your diff or trans you should be able to smell the difference.

[72240z]

Ya gear oil is going to stink and engine oil is going to have a petrol smell. 

You have to bite the bullet and search everything in depth. If you find a general area but cant pin point then make sure you clean up the whole area well so you can see for sure. 

[datzenmike]

Park on cardboard for the night.

[72240z]

Ya, def a good way to find the area. 

[DeviousPsycho620]

Went searching this morning and found a leak in the rear diff where the drive shaft meets the diff. Thanks for all your suggestions guys. Very helpful.

[datzenmike]

That would be the pinion seal. Most auto parts stores will have it just use the Nissan # 38189-P0101 to cross reference it.

 

Before going any further grab the pinion flange where it bolts to the driveshaft and try to move it to the sides or up and down. If there is any movement other than turning the bearing is shot and a new seal won't help.

 

Mark the flange/driveshaft relationship and remove drive shaft. Block tires so they don't move, place in 5th gear and have someone hold the brakes on hard! Now you should be able to loosen the pinion nut. Tap the back side of the flange with a hammer and drive it off the pinion. It will take a while but it will slowly move forward and off. A gear puller will also work if you have one. Do not disturb the pinion. You should be able to carefully pry out the old seal and equally carefully hammer in the new seal. Use a block of wood. Grease the flange so it does not tear the new seal when installing and also so it does not start up dry. Tighten the pinion nut to 100-123 ft lbs.

[DeviousPsycho620]

Thank you. Great instructions. Seems easy enough. Guess I'll give it a shot.

[datzenmike]

I had one leak from using synthetic gear oil. It's a risk you take when using that stuff on an old seal. It's so slippery it will get past. A new seal usually fixes it.

[DeviousPsycho620]

Found one for 12 bucks. It's not a horrible price. A lot cheaper than i thought. Guess i have plans for this weekend.

[metalmonkey47]

I had a grease seal on a U joint fail that didn't drip, so that's one thing to consider. It slung grease all over under my bed, but I didn't notice until it was too late. 

 

EDIT: Nvm, looks like you found it.