Rear axle noise

[txtoolman]

I have a 1978 Scout II that I'm working on. I have had the rear end worked on. He replaced the bearings on the outside of the axles and the seals. Now he says that the posi-track unit is shifting causing a noise that sounds like trolls with hammers. It does not change when I turn and it makes it when I’m driving 20 mph or less. It seems to go away when the temperature is blow 40 deg. Which does not happen very often in Houston. I’m using 80/90 weight. Has anyone had this problem and could I use a thicker fluid to get rid of this noise. I being told that it isn’t causing any damage but I’m not so sure.

[Dana Strong]

I would pull the cover off and clean the differential and case insides so I could look at things clearly and get a gear tooth contact pattern, just to make sure things are adjusted properly. The manual has information about this, the amount of preload, etc. and I suppose some of it is available online too.
Do you know what type of differential you have or if the axle assembly is stock? If you don't know its history, it might be good to look just to find out what you have, its condition, and so you can refill it with what you know is the proper lubricant w/ correct amount of friction modifier additives.

[timscout1]

It sounds like you have a limited slip diff. and it needs one or two tubes of the special additive added even if the ep 80-90 is rated for limited slip. Cheap to try and usually fixes it unless it is completely worn out.

[txtoolman]

Thank you both for the information. I'm not sure but from the history I received about the truck it is the stock rear end. I'm being told that it is a posi track so would the limited slip additive apply?

[timscout1]

Thank you both for the information. I'm not sure but from the history I received about the truck it is the stock rear end. I'm being told that it is a posi track so would the limited slip additive apply?

This is when it does apply!! it is called limited slip additive by some

[txtoolman]

So even if I have posi track I need to add the limited slip additive? I thought that if this was the issue I would primarily hear the knock while turning either right or left? This noise is continuos while driving straight or turning

[Dana Strong]

The only way to see what is causing the problem is to open it up and look at it; anything else is just a guess. Things like bearings do wear out, stuff can get inside and cause damage to others, etc.
The additive is to change the friction characteristics of the lubricant so parts which mate don't wear each other out but still have the necessary drag. If differential action is not occurring, lack of the additive is less likely the cause of any noise present.

[txtoolman]

It seems to get worse on warmer days, which is most of the time in Texas. Then it will go for weeks and I don't hear it at all?