Gear Oil Question

[Magnum5.9]

About to take the diff cover off and replace the diff fluid on my dana 44 and 9.25" and ran into a potential issue.

I believe I don't have a limited slip because the dealership told me I didn't and when I burn out in dirt, one tire leaves a big burn out while the one leaves a small burn out. I also lifted the rear, put it in park and spun the tires and they spun in opposite directions. So I think I have an open diff.

But I can only find 75-90w(for the rear) gear oil with limited slip additive. Is it ok to use limited slip oil in an open diff??

Second question: manual says if used for heavy duty or towing applications, use 75-140w instead of 75-90w. I do very little towing of a small trailer and the typical couple hundreds pounds of lumber in the bed often, should I use the 75-140w just because better protection? Or will it just mean worse MPG for me

 

[dodge dude94]

If you're worried about gas mileage, you can use 75W90. LS additive won't hurt anything at all.

 

[BBartow]

75W-90 is fine. Don't worry about it saying safe for LS, doesn't even have enough additive for them anyway.

I run 75W-140 f/r.

 

[Magnum5.9]

75W-90 is fine. Don't worry about it saying safe for LS, doesn't even have enough additive for them anyway.

I run 75W-140 f/r.

Did the 75-140 make any difference in the mpg or us it very minimal and better to have it for the protection?

 

[BBartow]

Don't know. I've always used 75W-140 since the front takes it. Rather carry one type of gear oil.

 

[Magnum5.9]

Went to the dealership and for a 1500 with a Dana 44 in the front, it calls for 4.8 pints of 80-90w of GL-5...

You guys use 75-140 up front?

 

[dodge dude94]

Went to the dealership and for a 1500 with a Dana 44 in the front, it calls for 4.8 pints of 80-90w of GL-5...

You guys use 75-140 up front?

75W140 is what the manual calls for. lol
Service and owners.

 

[1SilverBullet2]

I use 75w140 up front and 80w90 in the back, never had any issues

 

[Magnum5.9]

75W140 is what the manual calls for. lol
Service and owners.

All my owners manual talks about is the rear diff which is total

 

[dodge dude94]

All my owners manual talks about is the rear diff which is total

Well then.....

 

[Magnum5.9]

Well then.....

So I guess my front diff gear oil is good for life!!!

 

[dodge dude94]

So I guess my front diff gear oil is good for life!!!

lol I suppose so.

 

[BBartow]

According to to the manual, front calls for 75W-140 and rear 80W-90. 80W-90 is conventional so go with 75W-90 since its synthetic. 75W-140 is synthetic as well. Either is fine for rear. 75W-140 up front.