Might be a stupid question but I've got an 04 suburban, with 215k miles. I've only had it for about 5k of those miles so I'm not sure what kinda work it's had done. I've had some mechanics tell me to replace the diff oil, and I started to ask around and some others looked at me like I was crazy. Even saying things like: "Why the hell would you want to do that?" So I'm not sure what to believe here. Thanks for the help!
good idea to open up the pumpkin on a newly purchased vehicle.
The people who look at you crazy won't be so smart when their rear end grenades out.
I always thought it was better to know than not know. If there is any doubt at all, change the oil. You'll sleep better knowing it's good and that you did a good job.
You definitely should, I would take the cover off your rear differential and check the gears for wear and tear, clean the pan and the magnet that pulls shaved metal onto it and slap that b**** with new gear oil
I would at least make sure the level is good. I keep mine changed in my 07 Ford Ranger 4wd. Someone even told me that I should do my rear differential every 20-30,000 miles because it’s a limited slip and they get dirty from the clutches. And if it’s limited slip, you need to add friction modifier or buy oil with the friction modifier in it. But I only do them every 40-50,000 miles or so infact the last time I changed the front out, it looked clean. Rule of thumb I’ve heard from many people was every 100,000 miles or so is not a bad idea. The oil is not cheap. Probably $15-$20 per quart.
With that age and miles, I would do it. At a minimum to at least reseal the differential cover plate.
I have an '04 Mercury Grand Marquis with lower miles than yours that I bought from a snowbird here in AZ and it never had the diff fluid changed.
With my '03 F150 I did a full cover plate removal and fluid change and cleaned the inside; not a hard job to do at all....just follow the correct torque pattern and setting when putting the plate back on.
I felt lazy with the Merc (didn't want to drop the sway bar and less room to work there than the F150) so I did the method where you suck the fluid out through the fill port. Then shortly later I had a pinhole cover plate leak develop and 75% of the diff fluid leaked out while trucking down the interstate at 80 mph for a couple hundred miles. You have to figure that diffs get really hot and even the best sealant has limits on how many hot/cold expansions and contractions it can take. I spent $2,100 for a full rear end rebuild yesterday.......luckily the federal stimulus checks I got easily covered that. (Yes, that equaled the value of the car, but I really, really love this car for long haul highway cruising and I've put a lot of upgrades into it.)
A new $8 tube of sealant for a cover plate replacement is a lot better than $2,100 down the road.
You might also want to check your vehicles specs to see if there is a normal duty or severe duty gear oil. Depending on your driving and where you live you might want to go with the severe duty gear oil (no difference in price). I live in the desert southwest where roadway temps in the summer can be 130 to 150 degrees so I went with the fleet severe duty synthetic gear oil for the better heat protection.
