Latest on Rear Diff additives? (Non-Limited Slip)

[RickM]

OK, I'm about to change the rear diff fluid on my non-limited slip unit.

Aside from the "upgraded"/higher viscosity Ford oil is there any additive I can use that may help with the whine? Past threads mention that Lucas didn't help.
Are there other additives alternatives to consider?

Even if I get temporary relief it's better than nothing.

 

[1AJeremyD]

Question to you is why are you adding higher viscosity oil to the rear end? I haven't seen any really good additives to the rear end. Lucas is just a masking product in my opinion but some people swear by it.

 

[RickM]

Question to you is why are you adding higher viscosity oil to the rear end? I haven't seen any really good additives to the rear end. Lucas is just a masking product in my opinion but some people swear by it.

Ford published a TSB on the viscosity change. Also, if one of these additives successfully masks the noise I'm 100% fine with that. It appears rare for the rears to self destruct. Therefore, my only issue is the noise.

Again, any improvement will be welcome.

 

[1AJeremyD]

From what I remember the rear end took either a 75-90 or a 75-140 fluid. I'm leaning more towards the 75-140 end. If your rear end is making noise you're really at the point of no return. Whats the mileage and when was it done last? I remember these things getting crummy at 15K and the ford interval was 100k to 150k for the rear ends

 

[RickM]

The rear end can take either but the latter (75-140W) supersedes the original, in part because of this issue. Ref TSB 05-23-3

 

[1AJeremyD]

Thought so. Really your best bet is stick the 75-140 syn and some lucas and call it a day. Hopefully all goes well with it.