[DonM]

About 3,000 miles ago, I had a brand new posi differential installed in my '17 because the previous owner partially grenaded the original unit (there were chunks of pinion ring coming out when the drain plug was pulled).

I had my preferred shop install the new unit ($3,100) and they said I should change the fluid after a thousand miles or so - but I didn't realize how much I was actually driving the car, so I hit 3K.

The shop wants $130 to change the fluid, but I have "rediscovered" doing the work myself and I bought 2 qts of the correct gear oil for just under $50.

I know ideally, the car should be on a lift, so it's level and you get the best drain of the old fluid, but that's not an option. I do have ramps that will fit under the rear of the car, but then that puts the drain plug higher than the bottom of the diff and won't let me get a complete drain. Am I just over-thinking it and will it be OK to have the rear end higher than the front of the car?

[buckwam]

I use the two piece race ramp wheel cribs. They provide seven inches of lift at each corner, which is fine for differential fluid change. Only need the front halves for oil changes.

[GreyGhost702]

Originally Posted by buckwam

I use the two piece race ramp wheel cribs. They provide seven inches of lift at each corner, which is fine for differential fluid change. Only need the front halves for oil changes.

You never get a 100% fluid swap, the same goes for engine oil changes and tranny fluid changes. With a diff, I think you get about a ~90% fluid swap, which is probably the better of all fluid changes. So don't over-think it. Just make sure you are safe under a raised vehicle. Wheel chocks if they are touching the ground.

When I do tranny fluid changes on my Auto's, I only get about 60-70% of the fluid swapped since fluid remains in the lines, cooler, and torque converter. Even with that level of swap, it makes a big difference.

[WhiteMale]

Make sure that you buy the hand pumper that attaches to your fluid bottles...otherwise the other guys are spot on.

[Vtor_ZL1]

Here's what I did on last Diff oil change:


1. Modified cap to fit hose into bottom of gear oil bottle and enough to reach diff housing
2. On same small, drill small hole to fit end of air compressor blow gun nozzle.
3. Set air pressure into low low end of scale, prob in 2psi range.


Slow add air into bottle, bottle will inflate a bit and will soon start to push gear oi out of the hose. Rinse repeat with both bottles. This method works best when gear oil is not frozen cold!

[DonM]

Originally Posted by WhiteMale

Make sure that you buy the hand pumper that attaches to your fluid bottles...otherwise the other guys are spot on.

I bought the 'flex fill' bottles of Valvoline Extended Protection 75WS90. Super easy to squeeze the gear oil into the differential.

[ctrlz]

Originally Posted by DonM

I bought the 'flex fill' bottles of Valvoline Extended Protection 75WS90. Super easy to squeeze the gear oil into the differential.

There are some ingenious ideas here.
I broke the bank and went all-in for the $10 pump kit from amazon.
Every few years I need something like this and now I finally own one!

[DonM]

Originally Posted by ctrlz

There are some ingenious ideas here.
I broke the bank and went all-in for the $10 pump kit from amazon.
Every few years I need something like this and now I finally own one!

I KNOW that feeling. I often "Get The Need" for a tool or whatever that I may only need once in my life, but it feels good just having it "in case" that same need appears again.

Like the set of sockets for rounded off bolts I HAD to buy because the last guy to change the oil in the wife's car made her oil drain plug into a wonderfully round, polished knob.

[ChibbMD]

If you want to be level (or closer to level than the ramps only) you could always put jack stands under the front half of the car.

[dpevans]

I have found you don't have to get the car that far up in the air to change the rear end fluid.

[Chutzpah]

Back car down an incline and onto ramps, until level. Easy peasy.

[TransamGTA350]

I would also jack up the front of the car to get is as level as you can. There will be a lot of limited slip friction material settled at the bottom of the housing that would be good to drain out. As others have said, get a cheap bottle pump with hose to get the new fluid into the fill port.

[keep_hope_alive]

investing in lift pads and four jack stands makes stuff like this really easy. Especially since we have a lift point between the two jack stands, you can get the entire car in the air in two steps. Having a pinch weld lifting puck also helps protect the lower skirt when using the lift point.

[Gunkk]

Originally Posted by DonM

I know ideally, the car should be on a lift, so it's level and you get the best drain of the old fluid, but that's not an option. I do have ramps that will fit under the rear of the car, but then that puts the drain plug higher than the bottom of the diff and won't let me get a complete drain. Am I just over-thinking it and will it be OK to have the rear end higher than the front of the car?

Another trick is to use a bit of the new fluid to flush out the old. After you drain and before you put the drain plug back in, pump a bit of new fluid in the fill hole and it will help flush out some of the remaining old fluid. And since you don't need the full 2 bottles to do the change, you have that extra bit already in hand to flush with.