pressure building and holding in front differential

[93 legacy]

Hey guys i was recommended here by legacy gt forms. i bought a 93 legacy 4wd for $950

noticed there was no front differential dip stick and a rag zip tied over the dip tube.
bought a new dip stick and flushed my front diff. ( it was filled with atf ) the new dip stick i blew off and is on the side of the road somewhere.

next dip stick..... i need to manually relieve pressure every so often and there is some atf fluid in the difff again.

what is causing pressure to build AND hold in my differential, where is the atf fluid coming from? how hard is this to fix and what is the risk of leaving it?

thanks for taking time to help me

[Legacy777]

Welcome to the BBS.

The seal between the trans and front diff is bad. To fix it, you'd have to drop the trans, separate the diff & trans sections and replace the seal between the trans and diff. I've never done this myself, but it's going to be a relatively involved process. Just dropping the auto trans is relatively involved process. Having a trans shop fix it will likely cost you more than what you paid for the car. If you can find a used trans, that might be an option.

[93 legacy]

so if m going to "learn to live with it" my best bet is to just always add tranny fluid to my trannmision since it selfbleeds

[Legacy777]

The dillution of gear oil with trans fluid will likely eventually cause the failure of the front differential. The differential gears require extreme pressure (EP) additives, which are found in GL5 rated gear oils. ATF does not have EP additives in it. Over time, as the ATF comes into the diff, as I mentioend, it will dillute the gear oil and the EP additives. The differential gears will start to wear prematurely and ultimately fail in some manner.

How long for this to happen is anyone's guess. It could be a couple weeks, couple months, or even years. So I would suggest if that if you're just going to live with it.....drive it until it dies and then swap another transmission in, or get another car.

[93 legacy]

I know this is an old thread but id like to update future readers.

50,000 miles and 3ish years later the transmission still runs great. never slips. but!!! and this is a big but, it sounds like it has a turbo spooling up in it. happens during all speeds acceleration and deceleration. it is the worst when accelerating.

not sure if its gears being ground down or if its a bearing that has failed. it gets worse with age. I tried to sell the car for 800 and no one would touch it after a test drive.

im going to put a used transmission in it. im nervous about it.

[Legacy777]

Thanks for updating the thread and the info, it's good to know.

The gears and possibly the bearings are wearing and making the noise. Hope the used trans swap goes alright.