Rear Diff Leak

I changed out my fluids in both front and rear differentials last weekend. As usual nothing more satisfying than doing it yourself so you know it's done and done right. :grinyes:

Anyway I found next to nothing left in my rear D35. I mean what drained out could have fit in a shot glass. I really don't relish pulling this thing apart to replace a seal. I'm not even sure if I have the means to do something like this. My recently aquired FSM has this looking like it will require specialized tools. Not something for a shadetree mechanic to attempt in the driveway.

And then I remembered FredJacksonsan talking about this stuff called Auto-RX and I recall the claims the product was a leak stopper. So I did a little research on the web site and they claim it can be used in differentials.

So this morning I popped the plug and put 2 oz in and the test is on. If it ain't snakeoil it's going to save me a real pita of a job.

I changed out my fluids in both front and rear differentials last weekend. As usual nothing more satisfying than doing it yourself so you know it's done and done right. :grinyes:

Anyway I found next to nothing left in my rear D35. I mean what drained out could have fit in a shot glass. I really don't relish pulling this thing apart to replace a seal. I'm not even sure if I have the means to do something like this. My recently aquired FSM has this looking like it will require specialized tools. Not something for a shadetree mechanic to attempt in the driveway.

And then I remembered FredJacksonsan talking about this stuff called Auto-RX and I recall the claims the product was a leak stopper. So I did a little research on the web site and they claim it can be used in differentials.

So this morning I popped the plug and put 2 oz in and the test is on. If it ain't snakeoil it's going to save me a real pita of a job.

If the leak is coming form the pinion seal, then I doubt the Auto-RX is going to work, the pinion is turning constantly while driving and I don't see this stuff work on that type of leak, a stationary leak - like a leak coming form the cover, maybe.

The pinion seal isn't too hard to replace, unbolt the driveshaft from the rear-end and remove the yoke from the pinion, make sure to mark the relationship of the yoke and pinion. using a screwdriver or seal puller (easier done with a seal puller) remove the pinion seal. now just put the new seal in, good idea to find a socket big enough to fit on the outside edge of the seal and tap it in. This job is a lil easier with the pinion gear removed from the rear end, but that involves a teardown of the rear end.

Your version sounds a whole lot better than what I saw in the FSM!

I took a good look at the RTV all around the cover to see if I could see an obvious failure when I had it off but no way am I that lucky. I have to believe it's the pinion seal. I can see oily discoloration further forward where the yoke enters the diff.

I'll give this stuff a fair shot and we'll see what it can do. But maybe while I'm driving around with it doing it's thing back there I'll stop a few places and price a seal puller. :wink:

Yesterday I put the Auto-RX in, this morning I topped off the diff with gear oil. I was 12 oz down this morning.

I'm not down so much as a drop this evening, had a little seep over the edge as I pulled the plug and a flashlight shows the fluid right up to the lip of the fill hole.

I could tell I was leaking after my weekend change because it started to get flung around underneath and as it hit the exhaust it was burning off.

There's a distinct lack of that smell this evening.

I changed the rear pinion seal a few weeks back on my 95 yj with dana 35, like the man says, remove the big nut, it will be very tight, helps to have someone hold the brakes when you remove and put it back on. Pry out the old oil seal, tap in the new one, put the yoke back on in the same place , use some medium duty thread lock and torque the nut back on. I guess it took me ten minutes to do the job. The seal is around $6. A rebuild, around $800 if you take some where.

I tossed the rest of the container of Auto-RX down the oil fill Saturday morning. Drove 142 miles that day. My ticky lifter, on a 4.0 liter with 202K miles was the original reason I was looking at this stuff. It was gone Sunday morning when we went out to find some breakfast. My oil pressure at warm idle is running higher than it used to. But I drove it less than 20 miles yesterday.

I was down 10 oz in the differential Sunday morning and I topped it off again. I may be losing too much gear oil too fast for this stuff to have a real chance of doing anything. What I want to see is a definitive slowing of that loss rate.

I'm going to go through the procedure for doing the engine so I'll need a second bottle for that. I'll order two this week, one I'll reserve for the engine for the second cleaning after I've run it 1500 miles on the first treatment. The other I'll get and keep tossing the stuff in the rear until I use it up and see what happens.

I'm glad to hear the seal isn't such a deal to do though, and probably because I have that to fall back on is why I'm willing to keep experimenting with the snake oil for now.

650 miles

Down 18 oz in the diff case refill using 4 0z Auto-RX and 14 oz gear oil.
No Lifter tick has been heard since the first trip with a 12 oz bottle in the oil and
now at about 900 miles I definately see 10 lbs higher oil pressure idling at a stop light or parked.

1500 Miles

Drained and changed oil in the engine per instructions. Put a Motorcraft FL-1A filter back on with fresh dino 10W-30.

The needle hits 60 lbs oil pressure when I start up. NEVER not once ever have I seen the needle hit 60 in the 2 years I've owned the vehicle.

I finally got to the pinion seal last week. I also wound up doing the seal on my NV249 T-case since there were drips. Pretty sure they were Timken 2506 and Timken 3946 respectively. If not it's the other way around.

No joy from Auto-RX sealing that rear yoke seal. But very possibly an unfair trial from the condition the seal was in. A very obvious gap could be seen.

But as stated previously, after running a cleaning cycle through my engine my oil pressure is astounding. I don't drop below 40 lbs at idle and at highway speed am seeing probably 62lbs with an FL1-A oil filter.

Pressure is over-rated. Flow is more critical. The 4.0L should have 37psi of oil pressure at 1600RPM. High pressure usually means low flow.. Engine bearings(especially worn ones) need flow. Higher pressures also reduce fuel mileage. Mopar says additives are a no-no, too.