Differential Fluid Additive?

[TioSanchez]

I'm doing a tranny flush / filter / gasket job this weekend I suppose thats a no-brainer but in regards to the differential, what type of gear oil do you guys recommend and the previous owner said there was some type of additive to add to the gear oil, any comments on this?

[Ray H]

The additive is probably because it has a limited slip rearend (trac-loc). The additive is called a friction modifier, it helps the clutches in the limited slip.
As far as the tranny flush goes. Are you actually having it flushed or just dropping the pan and changing the fluid thats in the pan? If youre the one doing it, youre probably just changing the fluid in the pan. Nothing wrong with that, it gives you an opportunity to see what the filter and fluid look like. Besides, flushing a high mileage AW4 thats shifting fine has mixed reviews anyway.
Back to the subject, the filler tubes are notorious for sticking. they go into the pan on the pass side, there is an o ring where they fit into a tube just above the pan. The tube will come out but its a bear and will take some twisting a prying. I put just a small amount of antiseize compound on mine after the first time I pulled it and its been easy to remove since. Just a heads up.

[TioSanchez]

In regards to the flush, at first I was going to drop the pan, replace filter but as you already know you can't really replace all the tranny fluid as it doesn't all come out. I'm taking it to a place that actually has a tool to remove most of the tranny fluid, even whats in the torque converter, then I'll replace the filter and fluid, about a 100 dollar job.

And yes I've read and heard people talk about reasons why you shouldn't change the tranny fluid if it has been in there awhile and thats an interesting point in itself but I'm changing it because I have a few "mystery" sounds in the tranny and also some "clunking" sounds so I figured what the hell, the tranny fluid was last changed at 50K, I now have 125K on her...

[89ltd]

how does one determine if the diff's are limited slip or not?

[Mines69Olds]

Jack up the rear and spin one tire. If the other one starts to spin then it is limited slip. But if only one spins that it is an open diff.

[Ray H]

Actually, with the rearend off the ground and you spin a wheel and both wheels spin the same direction, its a limited slip, if they spin opposite each other, its open.

[Mines69Olds]

Sorry, my bad. If you have limited slip don't forgt to use the additive or it will make a god awful grind.