JulianH

Incidentally, it did wind up being the rear diff. Gears look fine, it must be a bad input bearing. Grabbed a lower mileage replacement down at the wrecking yard for $50.

Diff fluid was black, thick, and smelly, but no chunks of metal. There was a little bit of the normal "filings" on the magnetic plug, actually less than I've seen on some of the fluid change videos on YouTube. It might have also been a bit low - it's definitely leaking oil from somewhere, looks like maybe it's leaking past the axle shaft seals. I filled it up with fresh fluid and took it for a drive. No difference. I'll spray the diff off with engine cleaner to see if I can tell where it's leaking from. I had my wife drive past me a few times so I could get a listen from the outside, I'd say it's coming from the driver's side. So I'm thinking it's the rear driver's side wheel bearing at this point.

OK, yes, the diff is a bit warm. 2 mile round trip on the highway. Also, it feels like there is resistance when you start off - like driving through snow, or with your parking brake on. You hit about 30mph and it "lets go" - meaning the resistance/drag goes away until you stop the car again. The sound becomes audible around 20mph.

That's a good question... I'll go take it for a quick drive a mile down the highway and see.

I have a terrible hum/whine coming from the rear of my 91 Legacy(220K). I thought it was a wheel bearing, but when I pulled the wheels, calipers, and rotors there was no play or sound. I got in the back seat/trunk area to try to get a better idea of what it was, I couldn't definitively say it was from the left or right. When you take your foot off the gas, it does get an additional noise, what I would call a "gear" noise, which has me wondering about the diff. I recorded a short video... How can I definitely rule out a wheel bearing or the diff without tearing into the hubs?

OK, so I have to pull the differential to get to it?

I've seen a lot of mention of a seal that prevents ATF from getting into the differential and killing it, but no mention of where this seal lives, and what it's called. I'm swapping in a new (to me) tranny, and would like to get that taken care of while I've got it out so I don't have to worry about it. Any ideas where it is, how to get to it, what the part number might be, etc.?

How's your coolant level?

Auto? Manual? Sounds like torque bind in the center diff/MPT. In autos it's usually caused by a failing Duty C solenoid.

OK, problem solved. I guess maybe I did have a vacuum leak, because every thing I did to try to solve the problem dropped the idle speed a little more, and adjusting the TPS dropped it down to normal(750ish rpm). Thanks for all your help, everyone.

OK, all the pins on the main harness are straight and clean, and it's seated fully. The VSS is fine, and I should have known that, since a bad VSS throws it's own code. The AT code I'm getting is 31, which is a throttle position sensor problem! Apparently I'm having problems with my TPS reports... I'll test the wiring to make sure the problem's not there, but I suspect I must have damaged the TPS somehow when I put the engine back in. Does Delphi make a quality TPS?

OK, so the CEL was the same TPS circuit low, and front/rear O2 sensor(which I forgot to plug in ). When I drove it around to get it over 12mph, I noticed the speedometer wasn't responding(well, it moved a little, but not like it should), so that's probably the source of the flashing AT light. I'll take a look at the VSS in the morning when I can actually see. Could the TPS and fast idle have anything to do with each other?

I'm sure that they're all connected, but I don't know how I can be sure that there are no leaks beyond using a tester... I'm heading out to play contra with the TCU.

OK, I'm finally back... I've filled the coolant and connected the exhaust, it's now idling at 2500rpm. The CEL is on, right now I'm assuming it's the rear O2(which has needed to be replaced for a while), but I'll pull the code in a bit and see what's up. I picked up a vacuum gauge to check for a vacuum leak, I've got a solid -21 inhg, which I think is about what it should be. The AT Temp light flashes continuously, I stopped counting at 40 flashes. I'm going to check the TCM code in a bit, I can't get up to speed just in the driveway here so it'll have to wait till I can drive it. Thanks, Julian

Well, it shouldn't make any difference, this was at 9am on a cold start, the motor and CTS were both around 70-75 degrees. I just got home from work, so I'll fill it up and see where we're at. Thanks, Julian