can anyone walk me through this? i was under car but cant find plug to empty it. do i have to drop spare? what do i use and how do i drain? i posted problem about clunking noise in tech. per. but noone answered how to do this. thanks, nutsy.

 

I used that tool :



summit # WMR-W1145 , cost about $10.

 

but where is drain? can anyone explain how to? i know it cant be that hard if i know where to find plug. someone gotta be able to answer this.

 

You suck it out
Seriously--use the pump/suck tool Nutsy shows and suck it out thru
the fill hole.

 

This would be a good time to drill a drain hole, let the fluid clean out the metal, and tap the hole for a bolt. Then flush out the shavings, install the bolt, and fill it till it pukes.

 

How thick is the casting in that area??

 

I wouldn't tap it in that location though. I tap them back farther where it's thicker casting and easier to get at. I do it with the housing out so I can clean it out good.
For now you can use a vacuum pump through the fill hole.

 

The drain/fill plug is on the passenger side of the differential when you look at it from the rear of the car. Remove the plug and use a suction gun to suck out all of the old gear oil. Add one bottle of GM positraction additive and then fill with 75w90 oil from Valvoline or Lucas, your choice until it seeps out of the fill hole, You'll need 2 bottles of gear oil. Replace the fill plug and go out and do figure 8's with the car at a low speed to circulate the oil. Not a hard job at all, should take you about 30-45 minutes to do.

 

Yeah that about covers it.

BTW are you sure your clunk noise is not any of the U-joints?

At any rate, other than a little mess, there is no problem with sucking out your old oil and adding the new and some posi additive and seeing if that fixes the noise.
I think the additive I used was called Equa-Torque but it been a long time ago. Most auto parts stores sell cheap suction guns just tell them what you want to do.

 

There is no "drain plug"....the diffy only has a "fill plug". [How often do you change gear lube....once every 20 years?] An old turkey baster with a piece of rubber hose works just fine to get most of the lube out. It's easier if you have just driven it so the lube is warm and less viscous. Put half the {new} lube in, add the GM posi-additive, finish filling with lube till it starts to run out the fill hole. Button it up and go.

 

i dont have play in my u joints. i found fill plug but cant get a wrench on it because its so hard to get at and is a square bolt. any help would be appreciated. also to fill i have car on ramps so back end is up high so wont this overfill ? with car down i cant fit under it.

 

I bought a $5 siphon pump at Harbor Freight - sucked everything right out.

 

How often should the diff. oil be changed ?

is it true that if it's too old, you'd better add to it than change it ?

 

You could use a 8pt 5/8 socket or try a 11/16 12 pt to catch it. It's a 3/4 NPT thread. Use a little thread sealant on the plug when you install it back.
I usually tap the diff in the jobs I do. It sure makes it easy to change and most time I use new gears so the oil has to be changed at 500 miles.
I've opened up diff's with little oil left in them that were burnt black. changing the oil every 4-5 years or 30k miles would be a good idea but most don't do it.

 

I'm glad to see this subject. Mine seems to be leaking fluid as it has sprayed most of the surfaces around the diff. I'm guessing the seals need replacement as part of the job. Can anyone comment on this aspect?
Thanks,
greg

 

My recent rear "CLUNK" was a bad / wasted rear carrier bushing !!!

 

I replaced mine a few years ago but like yours...I've got a leak and need to replace the gasket.

I've not done it and perhaps someone can lead us through it, but it requires dropping the differential to get the rear plate off. I just picked up an aluminum floor jack and have a cast iron 3 ton...I understand you need this and more equipment to tdo the job.

 

I wrote a lot of procedures for this. Check this or other sites or pm me for the link.