New Gear Oil in Rear Differential & Check Engine Code PO420

[crowe47]

I have not serviced the rear differential in my 1998 Ranger 4X4 with a manual transmission since 2008 and about 25,000 miles ago - current mileage of 122,000 and owned since new and not leaking or making any unusual noises. How often should you service the differential, especially since it has not been driven a lot in last 12 years and mostly in town driving? Also, which is best - a paper or rubber cover gasket and is synthetic gear oil best option for differential or is it more likely to leak with the high mileage on Ranger? The fluid in transmission was drained and refilled with Dextron V conventional fluid in 2/17 with 115,136 miles.

Also, check engine light PO420 (Catalyst Efficiency Below Threshold on Bank 1) has been coming on and going off 3-4 times in last year and last 2-3 years. Turned off code in 8/19 and came back on 4/20 and went back off 8 days later, came back on week later and just went back off on 9/15/20. I replaced 2 precat oxygen sensors in 1/19 with 118,000 miles after PO153 code kept coming on and off and that code has not reappeared again. Will I be able to pass inspection when code disappears and before it probably comes back on again? My mechanic thinks I need a new converter. I do not want to have to replace the catalytic converter at this time, especially since the aftermarket cats do not last very long.

 

[Dirtman]

Question #1, I change my diff fluid every 50k or so. I think the owners manual specs it to be changed at like 100k but I think that's way too much. Synthetic is fine, if its limited slip don't forget to use the proper additive. I never use a gasket for diff covers, Black RTV works better.

Question #2, yes your cat may be on its last legs (or the downstream o2 sensor is starting to fail).

Whether or not your vehicle will pass inspection depends entirely on whether or not all the system monitors reset between the time you clear the code and the time its inspected. You cannot simply clear the code before showing up for inspection or you will fail. I don't know how it works in Georgia though, I'm assuming they just do an obd2 system scan.

 

[PetroleumJunkie412]

lubelocker gaskets on mine. Reusable and never leak. I love em.

 

[19Walt93]

P0420 isn't a sensor fault,it indicates cat failure. I don't know if that cat clean stuff works but it's possible to buy a used cat, you just have to get it from a place that can test them and guarantee they work.

 

[MikeG]

Ran some cata-clean through mine and picked up a couple of MPG. Found the stuff at the 'Zone....

 

[sgtsandman]

I'm partially drawing from memory since I no longer have a 1998 but I think the change intervals were similar to my 2011. The 2011 manual recommends 105,000 miles for the rear axle and 150,000 miles for the front axle.

As far as the code, I think I had the same code on my 2011. The fix was to change the catalytic converter. In my case, the driver's side was the bad one. After the cat was changed and the codes were cleared, it never came back. I installed a Walker brand from Rock Auto. It was cheaper than OEM and the discount for TRS members helps some too. It's isn't great (5%) but better than nothing. I did a bunch of internet research before I made the final decision on what the fix was for the code and multiple forums recommended the same course of action. Just make sure you are fixing the correct side and prepare for rusted and stuck fasteners.

 

[Snoranger]

I can show you a fleet of trucks that have been rode hard and put away wet... They never get the gear oil changed unless the diff cover rots out. We usually get rid of them around 200k miles with the original gear oil and trans fluid... Don’t buy an old fleet vehicle thinking it’s been well taken care of, it hasn’t.
So I’d recommend changing it every 75k - 100k miles.

 

[Dirtman]

I can show you a fleet of trucks that have been rode hard and put away wet... They never get the gear oil changed unless the diff cover rots out. We usually get rid of them around 200k miles with the original gear oil and trans fluid... Don’t buy an old fleet vehicle thinking it’s been well taken care of, it hasn’t.
So I’d recommend changing it every 75k - 100k miles.

My tax dollars at work!

 

[Snoranger]

My tax dollars at work!

We don’t waste money changing fluids that don’t “need” changing. We get rid of vehicles because of rot... not breakdowns. Generally we find rot holes in the frame after 10 years or so.