greetings from Las Vegas. Just picked up my 2nd HHR this time an SS. Got lucky with the "performance package" with LSD and Brembos. My Silverado SS with LSD calls for the GM " additive" for LSD along with the gear oil. I couldnt find it anywhere in my owners manual. Should I add the additive when i change my Manual trans gear oil?
thanks!

 

Some information for you

https://www.chevyhhr.net/forums/ss-s...nny-oil-27204/

And here

https://www.chevyhhr.net/forums/hhr-...-change-19592/

 

No additive needed if you use the correct fluid.
The rear wheel drive LSD rear end is different than the HHR SS front wheel drive transaxle with LSD quaife. The rear wheel drive normally has a clutch pack system in the rear end that does require the friction modifiers to be added when changing fluid. Changed my rear end fluid a couple years ago in my 98 Dodge truck. It was "popping" on low speed tight turns.
The G85 LSD system on the HHR SS is, I believe, a geared type LSD and has no clutch pack.
There are some old threads on the Cobalt SS forum that discuss that and fluid change options.

 

great response and right on the money... no additive necessary!
thanks!