Do I have 8.8 High Torque?

[skulldrinker]

My sticker says F6 which would be 3.73 limited slip 8.8". When I look up which fluid to use it has two for the 8.8 so How do I tell which 8.8 I have? The 8.8 non high torque or the 8.8 high torque version? just trying to know which fluid to use the 80/90 or the 75/145. I bought the 75/145 and some additive from the dealer but now I totally not sure if I should of gotten the 80/90. WTF this sucks. I should of just went to the counter and said give me some fluid for my truck and been done with it.

Thanks

 

[Curious Hound]

We'll, this might not be the textbook answer, but this is how I would treat that from a common sense mechanical viewpoint.

The torque being transmitted through the differential is a function of your engine and the load you put on it. So, if you have a wimpy engine like my 3.0 and you don't do a lot of heavy hauling and towing, then you are in a low torque situation. If you have a V8 or Ecoboost and your accelerator foot is heavy and you do a lot of heavy towing and hauling, then maybe go for the high torque option. It has to do with the load you put on the gears. Grandma, driving a turbo LS motor at 25mph on flat level roads to church once a week is still not putting high torque on her gears even though high levels of torque are available to her.

I feel sure that In most cases, our Rangers are fine with regular 80/90 weight oil in the diffs.

This message composed solely of recycled electrons. Go green!

 

[skulldrinker]

...and I think there is a 410 option. Maybe they consider that high torque. I already have the 75-145 oil and it leaves me wondering if that would be just as good or a mistake. I can always go exchange them to the 80-90 if my LS needs that only.

 

[scotts90ranger]

You're fine, they changed the oil spec over the years but didn't change the axles... there's only 2 8.8's used in RBV's the 28 spline and 31 spline, both use the same ring and pinion gears, same carrier bearings (I think, different carriers obviously), same pinion bearings, two different axle bearings... neither will hurt anything, the 75-145 is probably for better gas mileage (probably .5%, it upped the fleet average apparently or they wouldn't have changed), that drastic of a difference in viscosity usually means a lower useful life but there's nothing wrong with it.

 

[Captain Ledd]

It will be perfectly fine.

80/90 is more for general use.

75/145 is for more "heavy duty" (or high torque) applications, meaning that you tow a lot or that the gears are under that much more stress. It handles the heat a bit better and will break down at a much hotter temperature. It will not hurt a lower torque or general use application.

For all intents and purposes under general use, unless you live where there are wild temperatures (+ or -), and especially once there are some miles on the truck and the teeth wear on eachother and the tolerances open up a bit, just about any good clean "gear oil" of relatively close viscosity will suffice. The hypoid gear design hasn't changed much since the 1930's. It's easy to over think this stuff, I don't blame you. There's an almost overwhelming amount of (mis)information out there.

*edit: I just re-read that you have the additive already, but I'll leave the next bit in just in case.

HOWEVER, you do have the L/S version, which means you may need friction modifier. If it's full synthetic, you usually won't need it. The only thing the lack of F/M will do is make the clutches grabbier, and of course, potentially wear out faster. The good news is that if you feel your L/S is unnecessarily/unsatisfactorily "grabby", you can add the modifier separately afterwards.

Again, if there's some decent miles on the truck, the clutches may be worn out as it is, and it won't matter nearly as much.

 

[skulldrinker]

Thanks so much for the reply's and info. Yeah first time changing the fluid in this 2007 LS 8.5. I got nervous and returned the 75-145 and got Castrol 80-90 and it says Limited Slip on the front. So I'm guessing it has FM in the already?? I bought the 4 oz bottle from the dealer and paid $9 so I think I want to put it in there anyway. So this leads to another scary damn dumb question....

Is it possible to put too much FM in there and what harm will that do?

Thanks so much for replying.

Just got home from work so I'm going to do this in about an hour. Probably before anyone even reply's this. i hope adding it will be ok.

 

[skulldrinker]

Oh and thanks for explaining that high torque only meant hard use. I thought they made a full race Ranger at some point LOL