Diff Chatter with M1 75w90 LS.

[Gasbuggy]

My 2nd gen CTS-V has a stout Getrag diff in it. V Forums suggest drain and fills every 10k because these diffs run hot. Some have hit 300 degrees running on public roads in the summer.

My diff was in perfect working order. Frst drain and fill used Wolfs Head 80w90, I added TransX Limited Slip additive on my own. After that change, I gained diff chatter on the first couple turns whenever it was below freezing. I wasn't overly concerned about this because I only planned to have a 1 year run and I don't drive it much in the winter. I had gone a little light on the LS additive because my prior Gen 1 CTS-V with a different Getrag diff liked that.

I recently drained and replaced with Mobil 1 75w90LS and I have the same chatter issue. I thought maybe the additive needed a little time to work into the clutch packs, but even after a few 100 plus mile trips I'm still getting this cold chatter. I am slightly annoyed, I bought extra quarts of M1 to keep up with a yearly change schedule.

I can live with a little cold chatter, but I don't want to damage the LSD. Chatter is not an issue with these diffs usually. Some searching and I see M1 diff fluid chatter complaints scattered around the internet. Common sense would say change it for something else or put in extra LS additive Can you mix additional LS additives without issue?

 

[demarpaint]

I had a similar issue using gear oil that said an LS additive wasn't needed. A bottle of LS additive corrected the issue in very short order. There should be no problem adding it.

 

[njohnson]

I have used Valvoline, Mystik, and Mobil 1 gear lubes. On their websites, the companies say that the gear oils have friction modifiers already added, and adding more is not usually necessary. So, I tried the gear oils without adding anything first. On our two different vehicles, there was chattering and clunking. On our dad's 2006 Tundra, it was clunking slowing down to a stop, and accelerating from a stop. On the other vehicle, it only chattered going around corners.

I added Lubegard Limited Slip additive to both, and that has stopped the chattering and clunking.

I found the Lubegard Limited Slip additive at our local Napa, other auto stores in our area carry the transmissions additives, but not the Limited Slip.

In the last couple of years, Oreilly and Advance have now started carrying the Limited Slip additive.

 

[marc1]

Originally Posted by Gasbuggy
Can you mix additional LS additives without issue?


Yes. In fact my preferred method with LS differentials in performance cars I own and have owned is to use a non-LS fluid and then "tune" the formula with the additive. The LS fluids are not always formulated exactly correct straight from the bottle for all the possible LS diffs, sometimes there is too much additive, sometimes not enough (as in your case). Adding the additive adds cost, of course, so if that bothers you then when you deplete your current stash I would try a different brand. I am afraid I have absolutely no idea on the relative ranking of LS additive ratios by oil company i.e. does Redline have more additive than Royal Purple and more than M1 etc. so I can't suggest a brand that is better formulated for your diff. You did require more additive for the Wolf's Head as well so it just may be the nature of the beast that you need additional additive regardless of the fluid supplier.

 

[njohnson]

Originally Posted by marc1
Originally Posted by Gasbuggy
Can you mix additional LS additives without issue?


Yes. In fact my preferred method with LS differentials in performance cars I own and have owned is to use a non-LS fluid and then "tune" the formula with the additive. The LS fluids are not always formulated exactly correct straight from the bottle for all the possible LS diffs, sometimes there is too much additive, sometimes not enough (as in your case). Adding the additive adds cost, of course, so if that bothers you then when you deplete your current stash I would try a different brand. I am afraid I have absolutely no idea on the relative ranking of LS additive ratios by oil company i.e. does Redline have more additive than Royal Purple and more than M1 etc. so I can't suggest a brand that is better formulated for your diff. You did require more additive for the Wolf's Head as well so it just may be the nature of the beast that you need additional additive regardless of the fluid supplier.


I was talking to the gentleman at Oreilly's, and I was telling him about having to add additional additive to the gear oil. He said it was because the oil companies mix up huge batches of gear oil and the friction modifiers don't stay suspended well in the gear oil. He said they drop to the bottom of the containers. As a result, there are bottles that don't have enough friction modifiers in them. I thought it was an interesting explanation, don't know if it is true, but it was his answer about me having to add more additive.

 

[CT8]

Add more additive.

 

[benjy]

for hot running anything ester based lubes are best aka Redline, you can call + talk to a real person-tech for recommendations or use the on-line setup on their web site,

 

[dogememe]

Originally Posted by njohnson
Originally Posted by marc1
Originally Posted by Gasbuggy
Can you mix additional LS additives without issue?


Yes. In fact my preferred method with LS differentials in performance cars I own and have owned is to use a non-LS fluid and then "tune" the formula with the additive. The LS fluids are not always formulated exactly correct straight from the bottle for all the possible LS diffs, sometimes there is too much additive, sometimes not enough (as in your case). Adding the additive adds cost, of course, so if that bothers you then when you deplete your current stash I would try a different brand. I am afraid I have absolutely no idea on the relative ranking of LS additive ratios by oil company i.e. does Redline have more additive than Royal Purple and more than M1 etc. so I can't suggest a brand that is better formulated for your diff. You did require more additive for the Wolf's Head as well so it just may be the nature of the beast that you need additional additive regardless of the fluid supplier.


I was talking to the gentleman at Oreilly's, and I was telling him about having to add additional additive to the gear oil. He said it was because the oil companies mix up huge batches of gear oil and the friction modifiers don't stay suspended well in the gear oil. He said they drop to the bottom of the containers. As a result, there are bottles that don't have enough friction modifiers in them. I thought it was an interesting explanation, don't know if it is true, but it was his answer about me having to add more additive.


Haha I would never ask any of my coworkers about additives in gear oil. Every single one would give me a different opinion, some more ridiculous than others. That said, we sell LubeGard LS Additive and you should put that in. I'm not an M1 fan but I'm sure their gear oil is fine. Regardless of brand, the extra LS additive is usually required, even if the gear oil says "OK for use in LS diffs". It gets confusing on Chevys sometimes, the lockers used in trucks DO NOT need the LS Additive while the ones in the cars DO.

 

[joekingcorvette]

I know that a lot of GM vehicles had axle nuts that would come a little loose and cause a chatter. It happened on my 05 Corvette. GM makes a newer improved axle nut and you have to torque it to the correct specifications and also use the red locktight sealer to keep it from loosening. I don't know if your year of Cadillac has that type of axle nut or not. All you have to do on the Corvette is pull the center mag wheel cap off and tighten it up and put the sealer on it. It also helps to do a bunch of figure 8's to work the fluid around in the clutch packs. Then after the fluid is installed and the car is driven the level goes down and you have to fill it again to top it off. I couldn't believe how much of the fluid is added after driving for some miles then letting it sit overnight. I did this process on the Corvette myself.

 

[Gasbuggy]

My 05 CTS-V had that axel nut issue.

I will add a little bit more additive.