So it seems that the Valvoline synthetic 75W90 I ordered won't be in stock anytime soon, so I'm looking for a replacement.

Does anyone have any good or bad opinions of Red Line's synthetic 75w90 or Royal Purple Max Gear 75W90?

Thanks.

 

I have Used Mobil 1, Amsoil, Valvoline, all of them, seem to get same performance. Even Wal Mart Brand does OK . Just needs to be GL5 synthetic. I am using Amsoil now and running the 75-110

 

Any Synthetic 75W90 that meets GL5 should be fine.

 

I like the Royal Purple just because it already has the limited slip additive in it, and I can find it at any autoparts store. You don't change the gear lube often so paying a bit more doesn't bother me.

 

That is correct. I use Mobil 1 75w90. Ghettozone usually has it in stock.

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I am a fan am the Amsoil 75w-90 or 75w-110... Extended drain intervals are nice.

 

I've used Royal Purple and M1 in both my GM 2500HD with the 11.5" AAM and now my Dodge with the 11.5" AAM axle.

I've even had M1 in the front and RP in the rear. None of the parts stores near me ever have enough of each to fill both diffs.

Close to 100k combined for both trucks and no issues.

 

Doesn't Dodge now suggest running 75W-110 instead of the factory used
75W-90?

 

Haven't seen that, but if you could find the reference that would be cool.

 

Happy with the RP.

 

There was a rumor at one time that dodge required 75-145 at one time if you towed heavy and that's all it was, a rumor.

Since 75-110 is a amsoil only fluid (can not get anywhere else) I highly doubt dodge/chrysler would say to use that instead of Dodge/Chrylers own 75-90.

 

I've had the best results with RP in the boxes. 75w140 minimum in the diff but the 85w140 has been even better on the UOAs and no downside to the 85w140 whatsoever. RP Synchromax in the 6sp. Craig

 

http://dodgeram.info/tsb/2004/03-001-04A.htm

Dodge recommends running 75/140 on certain axles on the 1500 Ram, Dakota, and Durango.

NOT on Ram HD 2500/3500 trucks. ONLY 75w90 GL-5 rated Synthetic.

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I'm a big fan of the Schaeffer lubricants. Buy in bulk ($300 order) and the shipping is free.

 

I put RP in my diffs at 15k as it was easier to get at that time, but at the next change I will put Amsoil Severe Gear in them.