I changed the Diff oil today 75w90 lucas and im still getting the "diff engaging and disengaging "chatter. Under car looks good no typical rust on other components . I have been driving on essentially unsuitable oil for a season. My question is not about my diff specifically but more so on the cobsequences of driving on substandard fluid and what the symptoms would be from healthy to dead. Its much less frequent after this change and typically happens while the transmission is shifting in 1st to 2nd . Its an automatic. Also when I did the tie rod end check (grab the middles of the tire with both hands and push and pull horizontally) both wheels moved the steering linkages looks stable and the notorious idler arm bushings looked taught. How can i further assess my cars suspension chassis concerns Mods and admins sorry for the multiple edits and what sections should this be in if not here

1984 GSL "Berlinetta "

 

I put Lucas 75w90 in a LSD that I swapped into my 79. Everything was in spec but it also chatters. I was going to try a different brand oil. I know some people advocate adding an LSD additive even to oils designed for LSDs.

Edit:
Found this in the FAQ section

https://www.rx7club.com/1st-generation-specific-1979-1985-18/lsd-shot-248523/

 

Thanks Joe. as long as it has spec LSD fluid in it, regardless of quality of the oil the damages to the plates is minimal? The fluid I replaced was dark and less viscous. Probably aged. This car is more like a barn find with me changing novel stuff like exhaust hanger rubbers and small easy stuff. Original heat shields are falling off. That will go when I upgrade the exhaust

 

Mazda calls for a very specific GM LSD additive be added to ANY gear oil that you choose to use, and I wouldn't trust 'LSD Oil' to have it in there. The bottle of LSD lube is about 3-4 ounces, and is added to the gear oil when it's changed.

Any kind of chatter felt or heard from the LSD is probably an indicator that you don't have the right LSD additive in there, and I've never had the issue. Mazdatrix sells it, as does Racing Beat in their LSD sections.


http://www.mazdatrix.com/G8DiffMnt.HTM

 

Sweet! I will look for that GM additive to add to the Lucas 75w90 I put in there saturday. thanks dudes. i'd hate to think im destroying this car by being slow to maintain it! this boston winter kicked my ***

 

Crazy, I didn't know there was a specific additive that needed to go in our LSD's - thanks for the tip!