Why 75w-140 in 9 1/4 AA Rear Diff?

[MojaveJoe]

My son has a 1500 Hemi (2005), and asked me what the front and rear diff oil spec was supposed to be. I checked my 2004 manual and it shows (instead of 75w-90) 75w-140 for the rear axle (9 1/4 AA) Im almost sure this is what his 1500 has?

Anyone know why the AA 9 1/4 rear diff uses 75w-140 instead of the 75w-90 all other listed diffs use, including the 9 1/4 front diff and the C205F front axle axle?

If he has limited slip, he needs LS additive also, right?

He's visiting us tomorrow and I need help to look smart

All advice and experiences welcome,
Joe

 

[Matt400]

From the 05 manual-

75/140 full synthetic for the 9. 25 rear axle, the change to the 140 may be for added protection in a unit that has a smaller capacity.



LS additive is used in the Trac-Loc.

LS units with Track-Rite / Trac-Rite EL do not require the additive



From the manuals layout it appears The Trac-Loc's were in the 9. 25's while the Track-Rites went in the 10. 5 and 11. 5s



Your son does have a 9. 25 as the 10. 5's went in early 3rd gen 2500's

Hope this helps. .

 

[amsoilman]

My son has a 1500 Hemi (2005), and asked me what the front and rear diff oil spec was supposed to be. I checked my 2004 manual and it shows (instead of 75w-90) 75w-140 for the rear axle (9 1/4 AA) Im almost sure this is what his 1500 has?



Anyone know why the AA 9 1/4 rear diff uses 75w-140 instead of the 75w-90 all other listed diffs use, including the 9 1/4 front diff and the C205F front axle axle?



If he has limited slip, he needs LS additive also, right?



He's visiting us tomorrow and I need help to look smart in front of his new gf



All advice and experiences welcome,

Joe

Hee is a "Link" that shows what your son's truck requires. Just put in the year and make of vehicle, and follow by putting in all the info.



http://www.amsoil.com/scripts/runisa.dll?amsoiloaf:index

 

[HEMI®Dart]

Wayne,



Do you agree that 75w-140 in a top of the line synthetic lube is overkill? Maybe if you are towing 15,000 lbs through the mountains in 100° heat.

 

[MojaveJoe]

Great info guys.

1 more question. If Jiffy Lube put 75w-90 in his rear diff instead of 75w-140 is there a way to drain most of it to replace with 75w-140 without removing the diff cover?

Probably have to put in 4 oz of Trac-Loc LS additive too.

Thanks,
Joe

 

[amsoilman]

Great info guys.



1 more question. If Jiffy Lube put 75w-90 in his rear diff instead of 75w-140 is there a way to drain most of it to replace with 75w-140 without removing the diff cover?



Probably have to put in 4 oz of Trac-Loc LS additive too.



Thanks,

Joe

I beleive the only way to get the fluid out, would be to remove the cover.





Wayne

amsoilman

 

[HEMI®Dart]

I beleive the only way to get the fluid out, would be to remove the cover.





Wayne

amsoilman

That's the best way. This way you can wipe out the bottom of the housing ( see pic) and use brake cleaner to really clean it up if it's bad. When I change lube, I like to get all the old stuff out.

 

[d90boy]

You can use a suction device to draw out the fluid if taking the cover off is out of the question.

 

[steved]

I will only add the 9. 25Corp (used in the rear of 1/2tons since 1974) is built by Eaton, not AAM. It is something completely different than a 9. 25AAM currently used in the front of the 3rd gens...

They use different fluids because they are different differentials.

steved

Edit: 1874 to 1974...

 

[MConyers]

My son has a 1500 Hemi (2005), <SNIP>

He's visiting us tomorrow and I need help to look smart



All advice and experiences welcome,

Joe

This maybe too late based on the time that you had posted this, but... I helped my cousin change the front and rear fluid on his '03 4x4 1500. It took longer for two of us to change his fluid than it took me to change the fluid in my truck by myself.



The 1/2 tons don't have the replaceable gaskets, so plan on some time to clean off the sealant and reapply. The front bolts are a bit more difficult to get to than the AA. If it has the skidplate on the front, IIRC that has to come off also. And the front cover has the vent tube integrated into it.

 

[MojaveJoe]

Exactly what is a 9. 25Corp rear end? That name doesn't ring any bells. What does Corp stand for?

These 1500 rear diffs have been the same since the mid 70's? No wonder they need LS additive and heavy oil. Must be bullet proof though.

Thanks all for your input. Jiffy Lube used 75w-90 syn w/ additive. We're going back for a refund.

 

[steved]

Exactly what is a 9. 25Corp rear end? That name doesn't ring any bells. What does Corp stand for?



These 1500 rear diffs have been the same since the mid 70's? No wonder they need LS additive and heavy oil. Must be bullet proof though.



Thanks all for your input. Jiffy Lube used 75w-90 syn w/ additive. We're going back for a refund.

Corp = Corporate... at one point, instead of calling axles by their manufacturer, they called them "corporate" like it was some secret design. GM did the same thing with their AAMs... the Corp 14-bolt is nothing more than a version of the 10. 5AAM.



And yes, the 9. 25 Corp has went through very little in the way of changes since the 70s... the overall design is the same.



I would not worry about the 75w90 synthetic... it will protect as well as 80w90 dino. Unless he tows heavy and would benefit from a heavier oil, the 9. 25Corp is not finicky with oil. I have ran them on everything from SAE90 to 75w140... not one lasted longer than another.



steved