Rear Differential fluid change. Synthetic?

[Mrneg9]

Hey guys.
I'm going to change out the stock fluid in my rear. Planning on using Synthetic rear oil. Do I have to use the GM additive with the syn oil. Or should I stay with the stock oil and additive? Thanks, D

 

[ngnowner]

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Hey guys.
I'm going to change out the stock fluid in my rear. Planning on using Synthetic rear oil. Do I have to use the GM additive with the syn oil. Or should I stay with the stock oil and additive? Thanks, D

It's been covered before but I think the consensus is NO depending on who's fluid you use. I put mobil one synthetic in, no addidtive, no chatter.

 

[LOLGN]

Amsoil 75w-90 with no additive. No chatter or funny noises.

 

[turbo nasty]

Eaton says NOT to use synthetic in their posi units due to it effects clutch operation. I think Eaton supplied the oem posi units
Based on that I use only dino in my GN's....
1 bottle of dino valvoline 75w90
1 bottle dino lucas oil stabilizer
1 bottle limited slip additive

No chatter, etc

 

[turbows6]

I would use conventional also. Add just enough additive to stop chatter on a street/strip car. Some hardcore street guys won't add additive because it is arguably better for the drag strip because there's less chance of slippage in posi unit.

 

[Mrneg9]

Wow! so many different answers.

Well so far everyone that has replied is running different type mixtures of oil in their rears. I though it would be one way or the other.

 

[HP Man]

A lot of new trucks use synthetic in the diffs. My rear end builder says "Never Synthetic" (Amsoil took out my inner pinion bearing, their losey tech support wouldn't do a thing, it cost me $1200 to do over with updates of course)Sorry but this left a bad taste in my mouth. My car was stored Winters but it was ran often with the wheels elevated, still it drains off the bearings and gears and causes a dry run until it re-applies. I always ran Dino with the GM Additive, no problem ever before using Syn. Gene

 

[scojack_2001]

I used Valvoline 75w90 when I changed my diff fluid. Also used two bottles of GM friction modifier. No problems since.

 

[LBNJWE4]

I better check mine, I used synth with GM additive, I think I hear my exhaust rubbing on my axle, maybe it's my gears!

 

[Mrneg9]

Thanks guys.

I will be going with regular gear oil with the additive. Thanks for all your input guys. D