Hi all, story is, 6-7 weeks and 1200 miles ago I had an Auburn 3.42 posi installed in my 12 bolt.

The shop that installed it put Valvoline and additive in. After 700 miles I changed the oil but could only get Comma LSD oil 80w-90. After this, if I've driven at high speed for a long distance and then do slow driving with turns, turning makes horrible cracking noises!

I've read up on this diff and know it known for being noisy but these noises scare me. I can almost feel the chassis shudder. Is that right?! Should I add some more additive? And is it safe driving with this? I'm going away next weekend but I'm not sure I can get additive before then.

Thanks for any advice

Volvo240GLT

With the posi unit, you need to add the additive to the rear end oil. Stop by your local parts store and tell them that you need some posi diff additive. They should have it.

I have a posi in both my truck and car, and with every change I add the additive. This is even when the fluid says that it already has it. I have found that adding it helps keep this chatter down.

In a turn, usually slow speed, it can shake the whole car. The posi unit feels one tire moving faster than the other, so it will try to engage. This will cause the chassis shudder. Add some more additive. I would feel safer getting more additive in as soon as possible. It might cause some long term heat damage to the unit and take some life out of it.

Bill