I'm new to subaru's I have a 99 forester front differential went. What interchanges? Also its an automatic.

Front diff is part of the trans.

If you need a new diff you need a trans.

Let me ask though, how was it determined it needs a new front diff.  That is extremely rare.  Other causes like broken CV axle or bad wheel bearing can make bad sounds, and mimic front diff trouble.  

 

Generally you swap the entire trans. It has to come out anyway and the front diff assembly is not sold separately by yards. 99 Forester uses 00 to 04 Forester and Outback transmissions. 

GD

Something snapped and all the oil came out of the differential. The passenger side CV axle at trans has a ton of play and the pin is gone.

 

I would definitely examine the CV axle and the stub first.

It may be just the broken CV axle and then the stub pulled out and drained the fluid.

Possibly I will check it out tonight ty.

It has play in the front differential. Alot of it.

4 hours ago, Jim P said:

It has play in the front differential. Alot of it.

Shaking the diff stub is not a test at all of diff condition.

The stub has play inside the spider gears, and the cup has play on the stub, and wiggle is normal.  they all have some play.

Did you check the backlash engagement of the teeth with a dial indicator?  Have you drained the front diff to look for chinks and large shavings?  

Seen to many junked subaru's for "bad diffs" I guess to trust anything but a conclusive diagnosis.  

Does the car still drive?

If there’s a lot of play I reckon you might have a collapsed diff bearing. Or a detonated auto - read on for more about that.

What colour/condition is the remaining oil like? 

I’m asking as the EA82 three speed auto was notorious for leaking the auto fluid into the diff and vice versa, the pinion shaft bearing would “dry out”, collapse and destroy the front diff - often leading to a front end lockup, sometimes at speed 

I reckon you’re up for a new auto. 

Throw up some pics if you can, specifically the loose drive shaft side that’s leaking the oil  

Cheers 

Bennie

check car-part.com for trans prices, then decide how deep into the diagnosis you want to go. Certainly not impossible for the diff to be shot, but odds are 90% axle vs 10% diff.(a very generalized statement)

If I wasn't dead-certain, I'd even consider taking the inner boots off my axles to inspect the doj before condemning a diff.

 

IThe car drives but slips all the oil came out of the differential. There is awhole lot of play. Something snapped. I willdrain the oil probley tomorrow.ty

I got a trans already. But got home and the trans has been changed. How do i look up gear ratios and center diff ratios? Hope I dont need the computer and rear from the car I got the trans out of. 

Rear diff - count how many times the rear driveshaft rotates for each wheel rotation by hand. 

Front diff - i believe you can do the same thing by peaking through the diff plug at the ring and pinion teeth.  Or, if the front diff is already bad just yank the axle stubs and look through there or bash the casing open with a sledgehammer and count the R&P.