Rear end fluid ??

[Bennoel 10]

Just wondering what the membership thinks is best ? Changing out a rear 8 3/4 center section . What friction modifier do you like ?? Straight 90 weight plus modifier ? Like most things today too many choices.
Any suggestions greatly appreciated.

 

[4spdragtop]

I used the Mopar friction modifier, available at Dodge store. Can't remember what I used for gear fluid...80/90 I think....

 

[Dana67Dart]

Ford friction modifier available at Dr Diff and other places.

80/90 gear lube ( I got mine from O'Riley)

Be sure if it has new gears you break it in for 500 miles, then drain and refill with new friction modifier

 

[Big.J.007]

Ford Friction modifier and 85w/140 for me.

 

[Syleng1]

80w90 and Ma Mopar stuff in both my suregrips. No need (or advantage)to change what the factory did.

 

[Murray]

No modifier, I use Redline oil for these.

 

[RustyRatRod]

Pick your poison. Everybody has an opinion and you know what those are like. I'd just run 80w90 like Mopar called for and either use limited slip gear oil or put friction modifier in it as has been mentioned. This ain't the space shuttle.

 

[MoparLeo]

Never said LSD.

 

[Dana67Dart]

Never said LSD

What friction modifier do you like ?? Straight 90 weight plus modifier

OP did by mentioning modifier in his first post

 

[70SwingerGuy]

No modifier, I use Redline oil for these.

Royal Purple has it built in as well

 

[PROSTOCKTOM]

I always use the Ford version and I think you can but it at Summit Racing, or your local Ford dealer.

Tom

 

[Ottmundr]

Royal Purple has it built in as well

Just put it in my summit cart, and a little hand pump too for MY '16 392 Charger that my wife took. It's all good, since she took my car, I getting a motorcycle.
Ha! She sure showed me.

 

[Bewy]

I use Redline also, 85/140. I think they also have 75/140. It was sooooo good it quietened some slight coasting whine in the diff. It comes with the FM already added; so no need to try & guess mixing quantities for an outdated system.

 

[340six]

I use 90wt conventional in ooen carrier's.
And the Ford modifier if Dana PowerLock (clutch) / Borg Warner (cone) style LSD
Note)
The Ford stuff is better than the new Mopar.product. The old Mooar with Sperm Oil was best. Good luck finding some cheap.

 

[abodyjoe]

ford stuff is supposed to be the best.. https://www.amazon.com/dp/B0CPYR49PB?tag=fabo03-20

75/140 synthetic is what i run.. so many different brands.. i got what the local store had at the time. https://www.amazon.com/dp/B00ZRPL0WK?tag=fabo03-20

 

[Kern Dog]

Rear end fluid ??​

Any suggestions greatly appreciated.

13 year old ME was waiting for a thread like this one.....

 

[Newbomb Turk]

Torco 75w90 or 75w140 depending on gearing and tire size.

The lower the gearing the heavier the oil.

It is the ONLY GL-6 gear oil on the market. Since no other companies made a gear oil that could pass the GL-6 testing, API dropped the classification.

Torco still uses it because it passed those tests.

 

[mbaird]

Instead of filling thru the drain plug I use a funnel and a section of heater hose to fill it thru the axle tube before reinstalling the axle.

 

[4spdragtop]

Good point!

Never said LSD.

 

[glenn340]

I purchased a new clutch style sure grip from Dr. Diff. This is what he recommends, and what I used.

 

[Bennoel 10]

Never said LSD.

Sorry for not being specific enough. It's a 741 case with 3:23 gears and a clutch disc type Sure grip. It's a used unit so no need for break in worries.
Thanks to all for the input. Special thanks to 340sFastback , who gave me a great deal on the center section.

 

[70SwingerGuy]

So the general consensus seems to be either 90 or 140, since the factory calls for 90, what is the benefit of using a much thicker weight?

 

[Newbomb Turk]

So the general consensus seems to be either 90 or 140, since the factory calls for 90, what is the benefit of using a much thicker weight?

The lower the gear ratio (higher numerically) the faster the pinion and ring gear turn.

That makes heat.

Anything lower than a 3.9X gear I use 75w140.

 

[70SwingerGuy]

The lower the gear ratio (higher numerically) the faster the pinion and ring gear turn.

That makes heat.

Anything lower than a 3.9X gear I use 75w140.

Thanks for that info, I never knew the thicker oil would benefit more in a lower ratio diff, good to know since Ill be changing mine soon and I run a 3.55

 

[Newbomb Turk]

Thanks for that info, I never knew the thicker oil would benefit more in a lower ratio diff, good to know since Ill be changing mine soon and I run a 3.55

If you have a 26 inch or taller tire you can use 75w90 and be fine.