I have a 03 grand cherokee limited and want to know which gear oil I should use 80/90 or 75/140 I never off road it's my wifes car just got some TFC fluid from the dealer he reamed me for $13.25 a quart and $9.92 for the additive. I want to change the diff fluid as well and want to know wich I should buy. I also bought 2 additive bottles for both diffs will I need to use them as well with the fluid change. I had read somewhere I don't need to and then read I should??? Thanks in advance

 

ment 80/90 or 75/140

 

ment 80/90 or 75/140

 

First of all, Welcome to the forum

Second, do you know what axles you have? I have an 01 Grand Cherokee Laredo with the 4.0 so i have a Dana-30 up front and a Dana-35 out back. Since I dont know what axles you have I'll give you what I know from my Jeep.

My front axle took just under two pints of 80w/90 (75w/90 will also do fine). The front axle does not require the limited slip friction modifier additive, only the rear axle as it is a limited slip axle. Since it being your wife's car, I suspect that you will not be doing any heavy duty off-roading. I think I would go with a heavier oil if that were the case. For everyday driving and light playing in the dirt or some mud you will be fine with the 75/90 for both axles if yours are like mine. Just add the additive to rear axle.

Also the fluids will be cheaper at any typical auto parts store, like Pepboys or Autozone, here in El Paso I use O'reilly's Auto alot.

 

the dealer looked up my trucks vin and said it has lockers in both front and rear not sure what lockers are as far as dana numbers

thanks for the welcome and your answering my post

 

Yes both front and rear will have "Limited Slip" Differentials (lockers) on some Cherokees like yours. Some gear oil will have the additives you bought from the dealership so it all depends which oil you buy.

What the additive does is let the "Clutches" engage and slip properly so the front axles "lock" for traction and "slip" to go around corners as needed - being the wife's car my suggestion is put in the Dealer Fluid to avoid any concerns with strange engagement and releases banging around in the axles, yes cheaper stuff will probably work but is it worth the chance.

The safe answer is use the stuff from the dealer, if you don't I would look at getting some good synthetic gear oil.

Regarding what weight gear oil, it depends on how you will be using the vehicle, as well as what the temperatures are like in your area, I would get 80/90 unless as said above you are doing heavy towing.