1997 Ranger Differential (open 7.5") Leaking

[CAJones]

I noticed oil spots on the ground under the differential a few weeks ago and as I am learning about car repair as I go so I have some basic questions. From the pictures attached, you can see how the entire bottom side of the diff is wet (the diff gasket, pinion seal, and both axles driving the rear wheels). This truck has about 300k miles on it and consumes about as much oil as it does gas. In the three years I have owned it, I have driven it 7,000 miles so not a daily driver.

1) In order to find the leak, should I clean the oil off everything (brake cleaner?) and then check again to see if leak is only from one spot?
2) Do the drive axles (not sure on the correct term) leak oil or is that just a nearby leak confusing me?
3) The owners manual doesn't list what type of oil to use but it seems like it should be 80w90 gear oil?
4) I haven't been able to find torque specs on the diff gasket, anyone know what it should be? I found one site that said ~75 ft-lbs, but that seems like a lot for those little bolts.
5) As this is a slow leak and I don't drive it much, I could just continue to refill the diff to make sure it doesn't run dry until I get a chance to fix all the leaks?
6) On the driver side axle, there is a rubber hose coming out of the top of the axle but it is completely torn off, what is this?

By the way, this forum has been a great help, I put a new head on my engine about 1,000 miles ago with your help!

 

[scotts90ranger]

Pull the fill plug (the one with the 3/8" square drive you can see in your last picture that takes a ratchet to take out) and see how low it is, it should be about 1/4" below the hole, it takes 80W90 gear oil, some say 75W140, I say whatever...

Speaking as someone with a Ranger that consumes a lot of oil, that could honestly be engine oil... judging by how oily the driveshaft is it looks to be coming from the front... before I fixed some of the oil leaks on the '90 the rear mud flaps would get spatter, and the rear axle was always wet...

If I were to bet on where on the axle it was leaking I would say the pinion seal. It's not hard to do but to do it right isn't easy... If you drop the driveshaft then pull the big nut you can see then (parking brake on, maybe impact to get it off), the seal is right there after you pull the flange, pry it out, put in a new one. Reassembly is the iffy part, to do it right you should pull the pinion bearing and put in a new crush sleeve and set that, but there's a way to use a new pinion nut (or red loctite) and only torque it down so far... I don't remember the specs...

 

[RonD]

The axle/differential has a VENT port on top of one of the axle tubes, it will have a rubber hose attached, hose goes up and is attached to the under side of the bed, should have a small filter on it
If the Vent hose gets clogged up then when axle is used and oil heats up pressure builds up inside and.................leaks start

This bring us to the differential cover, there should be no pressure inside the differential, see above, so...........doesn't take much to seal it up, torque spec on the bolts is "snug" which is 20-25ft/lb
Ford didn't use a gasket, just some RTV, but you can buy gaskets, and also use RTV, lol


The pinion seal requires full disassembly of the differential, and re-shimming, I wouldn't bother unless differential is making a noise

 

[scotts90ranger]

Now that you mention the vent hose, it's on the right side of the third picture and broken off/missing, chances are it might be plugged too... the vent hose on my F350 was missing and the fitting plugged, the axle seals leaked and lubricated my rear brakes...

 

[RonD]

On my first car, Willys overlander, I put on new brake shoes all the way around, and the brakes squeaked, so I oiled them..................................we learn more from our mistakes than our successes

The smoke and the smell was worth it.........................NOT

 

[CAJones]

Thanks guys!

It certainly could be engine oil. Cylinder #1 has a scratched wall (from overheating) so the crankcase gets pressurized and blows oil out of the dipstick. I think I will just make it a point to regularly check oil and the diff gear oil level. Didn't know about the vent on the axle, that is certainly not how it is supposed to be. Not much of a shock considering how I have come across other "repairs."

 

[don4331]

I'm betting the rear cover isn't leaking - or at least not badly. Leak from the pinion seal will flow back/down as you drive coating everything behind it.

As RonD identified the vent hose is AWOL - you can just see the remnants of it kind of inline with driver's side shock.

So, your 1st action is to: clean the axle tube, pull the vent, unclog it, then reinstall, with new hose that goes up to the frame (you might find the end of the hose still clipped there with the dust cap.)

2nd action is to check/add oil (truck needs to be sitting level when checked). Then clean everything spotless. If you're driving into interior Washington with its >110F, 75w/140 would be recommended, if you're staying by coast, the 80w90 is fine.

Then you will be able to determine in you have a leak in pinion seal or not.

 

[CAJones]

Pulled the plug and gear oil started coming out right away, so it was engine oil fooling me. So awesome! The devil I know is far better.

Got it on the vent, thanks for the instructions! I can see the open end of the old hose but the end is just open with no covering.

 

[RonD]

Google: Axle breather caps