Traction-loc, chatter and Additive .....

[deanm11]

I did quite a bit searching but found little opinion or verdict. Here's my situation and query:

Got a new 2020 GT A10, total base car. Came with 3.15s.

Taking a shot with a boneyard 3.55 traction-loc from an Ecoboost. Supposed to have been under 30k miles and unit seemed good, smooth, seems like regular backlash. As with most yards, it was drained of fluid.

Put the complete rear in my car and filled with Mobil1 75w90 "LS" fluid. Supposed to have limited slip additive included. I've got a 4oz bottle of Motorcraft additive at the ready.

I've put maybe 10 miles on the car since getting it all together. I also put in Black steeda bushings and through bolts. So I fully expected and do get some rear end noise transmitted.

But while I hear a new baseline of noise (really only when the diff is 'working' in a material turn,) I'm getting occasional heavy chatter.

I called Mobil1 and they were not particularly helpful. They did say (obviously) that their inclusion of modifier would be an 'average' amount and that perhaps my application needs some more. Upon explaining the sump capacity of 1.5-1.6 quarts and 4oz of modifier, he said that's a heavy concentration. I'm thinking of starting with adding 2oz of Ford modifier.

I've spend a few minutes doing circles/figure 8s but I have little idea how much is enough of that .. I know that some would be required given the rear was dry for some time.

I welcome any thoughts.

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[deanm11]

Update: I decided to try so more tight circles first. It does seem to be improving. Also, maybe its just getting better but it seems to be a narrow situation where the chatter still occurs. Slow hard street turn, not typically. And when I did nearly full lock parking lot circles, if I kept it at about 13mph, it wouldn't chatter. More likely to chatter at 8-10mph. I'm going to hold off on the modifier.

 

[TeeLew]

It's a Trac-Loc, so it'll only chatter as long as as it works and that won't be long.

 

[deanm11]

Would you mind clarifying ? I do agree that some chattering basically indicates that it is 'working'. But do you mean that a quiet traction loc has lost most or all limited slip capability ?

 

[TeeLew]

Pretty much. The friction discs in the differential clutch pack wear quickly. What you're feeling presently is the preload from a fresh build. As the friction material wears, the differential will be more quiet, but it will also lock less.

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