1998 Rear diff fluid change

[chev]

I have a 1998 4.6 liter V8 mustang and I need to change the rear diff fluid because it's leaking from the bottom of the rear houseing. The issue is there is no drain hole. Ok, I can take the drain pan off because I have to put a new gasket on there anyway. I found the hole used for the suction pump on the top faceing the front of the car. The question is

1) I suppose I use the suction pump to also fill the rear?

2) What kind of fluid and how much?

3) What weight? Advanced auto parts told me 80/90 weight.

Thanks for any input

Joe

[RedFire281]

The 80W/90 was the factory fill and I believe the manual recommends 75w/140 when the fluid is changed. I would think that either one will be okay. Don't forget to buy a bottle of friction modifier unless the diff fluid already has it in the mix. You can use synthetic or fossil fluid; people swear by either one.

Once you remove the cover be sure to clean off all the old gasket remnants from both surfaces. Re-install the cover and torque the bolts down to 32 ft lbs. Also, rather than using a gasket, I recommend a 1/8 to 3/16 inch bead of RTV gasket maker. IMO, the gasket maker seals better.

Now, using the pump through the fill hole, empty the bottle of friction modifier into the pumpkin (don't forget or you will ruin the gears), then fill with diff fluid. It will take about 3.75 pints (1.75 quarts) to fill the pumpkin. Fill it to about 1/4" from the top using the pump. Clean off the plug (it has a magnetic base to collect metal shavings) and re-install.

It's an easy job and should take less than 1-1/2 hours.

Good luck and I hope this helps.

EDIT: BTW, for your own safety, please use jackstands under each axle and not just a hydraulic jack under the differential.

[chev]

That’s great, I went and bought the pump, and didn't know about friction modifier and I would have put the fluid back in there without this supplement, so thanks for that!

Anyway, did the job last night, clean it out as best as possible Refilled it, took it for a ride and did a few figure eights in a parking lot and everything seems good. The rear quieted down also, there was a slight tire sounding noise coming from it. Gone now. I used 80/90 synthetic because I already bought this before I posted.

Thanks again!
Joe