Hello guys, just wanted to share my experience with Amsoil on my 1983 rx7 GSL with LSD diff. Last year, after purchasing the vehicle - I changed out my diff. and tranny fluid with 75w-90 Valvoline Full Synthetic *contains limited slip additive. I experienced diff. chatter right from the get go so I had to add the LSD additive. It helped with the chatter but didn't get rid of it completely. I also noticed that the car had a "whirlling" noise from the rear on highway speeds before and after changing the diff. oil. My mechanic inspected the vehicle as I suspected the noise was possibly a rear wheel bearing or sticking brake pad. He pin pointed the noise to the diff. and said I should advise with a shop specializing in differentials to see what a rebuild would cost. For now, him and I agreed that it could not hurt to change out the diff. oil to decrease or possibly remedy the noise. I changed out the oil this weekend and right off the bat noticed that the chatter was gone that I would experience when I reversed or took a turn from first. Today, on my commute to work on the freeway I turned off the stereo to listen for sound the whole 30 minute commute. The "whirlling" noise is still there but it was much more quite than before. Evidently it is way too early too tell but I can comfortably say that there is a big difference between Amsoil and Valvoline. For the record, Redline has always been my go to gear oil but decided to give Amsoil a shot for 2 reasons. Number 1, redline is very difficult to get locally now a days - has to be special ordered when Amsoil is available over the counter (along with Royal Purple but not a fan of it). Number 2, I read many threads in this forum and Amsoil was pretty much praised as being just as good as redline. I will be buying 2 more quarts of it for the transmission this coming weekend as I also learned in the threads that the Valvoline 75w-90 synth. is GL-5 and not recommended for our Tranny's. I checked their website and the fluid is GL-4+ so I am thinking I found my replacement go to gear oil going forward. Especially since they offer the fluid in their plastic fill quarts which made adding the fluid super easy and a lot less messy compared to having to use my fluid hand pump.

 

Which Amsoil did you switch to? 75W-90 Severe Gear?
It's also GL-5 but I thought they were all backward compatible. There was a transmission thread where I posted a better experience with GM Synchromesh over other oils so maybe it has different friction modifiers from other brands.

The only Amsoil I can find near me is ATF but they sell from their website.

 

Interesting. I also had persistent LSD chattering with Valvoline with friction modifier (Valvoline 70W90 mineral with LSD additive). It did not go away until I used Lucas 80W90 with 4 ounces of the GM additive, as recommended by @j_tso

Here's the thread with my experience with a lot of help from the guys here: https://www.rx7club.com/1st-generati...3-lsd-1166112/

 

Yup, that's the one. The website has it listed as GL-4 *meet and exceed. I can double check the bottle when i get home as well. GM Synchromesh is universal amongst car enthusiasts as that was also the top choice when I was part of the DSM forums with my awd eclipse. When searching, I also came across threads advising to mix 50/50 ATF with 75w-90 for the tranny. I do have an extra new left over bottle of Valvoline ATF synthetic but not sure I would be willing to experiment with my Tranny with it having 178k on the clock. The GL-5 was also an issue for the awd tranny's in the dsm forum as the synchros were made out of brass and the sulfur additive can corrode and degrade the material.

 

Good to hear you like the Amsoil gear lube.

We have always used Amsoil 75w 150 Severe Gear in our rear diffs without any kind of friction modifier because these are race cars. The 75w 90 should be great for a street car with just enough friction modifier to take car of chatter. Too much friction modifier allows the clutch pack to slip more than it should. Especially since slippery synthetic lube is already being used.

The Mazda diff does have some bronze material in it so it is important to use a lube that is safe for "yellow" metals. Amsoil is.

 

BTW, I ended up going with Redline MT-90/ MTL mocktail for the tranny. Here is the link for tranny fluid recommendations: https://www.rx7club.com/1st-generati...ou-use-937254/