Diff Fluid Question!!!

[wpurple]

I use 80W90 Mobil 1 in my Mustang's LS rear w/o Friction Modifiers and never had a problem even after 130K. No chatter of the clutches either.

I also use Ford's 75W140 Synthetic on my X's rear as the manual states but it is not a LS.

 

[vbtruk]

Yeh i will be doing the Front and rear diff oil and tranny and transfer case myself!!! So i was thinking of puting the AMSOIL universal ATF in the transmission and transfer case and then the AMSOIL synthetis 75W-140 gear oil in the front and rear diff with an aditive! DOES THAT SOUND RIGHT???
Thanks

by the way guy's over here the AMSOIL synthetic lubes are cheaper than Ford's motocraft LUBE's!

 

[dogfriend]

Originally posted by vbtruk
Yeh i will be doing the Front and rear diff oil and tranny and transfer case myself!!! So i was thinking of puting the AMSOIL universal ATF in the transmission and transfer case and then the AMSOIL synthetis 75W-140 gear oil in the front and rear diff with an aditive! DOES THAT SOUND RIGHT???
Thanks

by the way guy's over here the AMSOIL synthetic lubes are cheaper than Ford's motocraft LUBE's!

Trans and Transfer Case - I am using AMSOil Universal ATF in my transmission and my transfer case. I have approx 7k miles with this combination and everything seems fine. The AMSOil meets Mercon V specifications which is important for the 5R55E. The engagement of the transfer case seems smoother than before, but this may be a placebo effect - no drastic changes.

Rear axle - You should be fine with 75w-140 because that is recommended in the owner's manual. AMSOil says that friction modifier is not required, but it is okay to add it (it is compatible with AMSOil) if you feel it is necessary. I would probably try it without and only add the friction modifier if I was experiencing "shattering" of the rear while going around corners.

Front axle - I believe that 75W-140 should be okay (I bought some for my front axle, but haven't changed yet) but the owners manual calls for 80W-90. You do not need friction modifier for the front axle because it is an open diff (unless you have changed it ) The friction modifier is only required for limited slip (rear) axles.

 

[vbtruk]

Thanks "dogfriend"
What is the difference between the 75-140 and the 80-90? Also if i do use an additive is it ok to use the friction modifier paste that comes in a tube???
thanks.

 

[dogfriend]

The numbers refer to the viscosity ranges of the gear lube. The first number refers to the "winter" rating (viscosity at low temp) e.g. 75W. The second number refers to the hot (100degC) viscosity.

Here's a chart:Dead Link Removed

Comparing 75W-140 to 80W-90:

At low temps, the 75W will flow better than 80W;viscosity for 75W is the same at -40C as 80W is at -26C.

At high temps, the 140 is thicker at 100C than the 90 will be at 100C.

My interpretation is that the 75W-140 will flow better at low temp (good) will protect better when hot (good) but will probably not be as fuel efficient as 80W-90 overall (not as good). Since I live in an area where summer temps are high, I think it is worth giving up some fuel efficiency for more protection. The syn gear lube will still be superior in flow at low temp compared to dino no matter which grade you choose.

Most of the friction modifiers I have seen come in a tube. The type that I used was thick, like a grease if I remember correctly.

 

[vbtruk]

So dogfriend what do you think?? As i will be using the AMSOIL either way and over here it doesn't get below-5 deg C or above +40deg C so what would be the best application for me?

 

[dogfriend]

Advantages of 80W-90:

1. Its what Ford calls out in the Owners Manual for the front axle, so you know its ok to use.

2. May get better fuel economy compared to 75W-140.

Advantages of 75W-140:

1. You need it for the rear axle, so you can buy just one type for both front and rear.

2. May protect the front axle slightly better under heavy loading (probably not necessary though).

Its safest to stick with Ford recommendations, but my opinion is that either one will work ok

 

[vbtruk]

OK SO IF I GET THE AMSOIL 2000 75W-140 AND PUT IT IN BOTH FRONT AND REAR SHOULD BE FINE THEN? THIS FUEL ECONOMY YOU MENTIONED, IS IT THAT MUCH DIFFERENT?

 

[dogfriend]

No need to shout, I can 'hear' you fine

Its like the difference between putting heavy syrup in your diff or putting molasses in your diff. The syrup will be slightly easier to turn; theoretically the syrup will give better fuel economy than the molasses.

How much better? I really have no clue since I haven't done any tests on this. It depends upon how you drive, where you drive (hiway or urban stop&go), the average temperature, the phase of the moon and many other factors.

The only way to know would be to try one, drive for several tankfuls to get an average fuel economy, then drain it, try the other one, drive the same several tankfuls and compare mileage.

Or just use what the manual recommends and forget about it

 

[vbtruk]

sorry my cap's lock was accidently on. Thanks heaps Dogfriend i'll do it and let you know!

 

[vbtruk]

Hey Dogfriend, What do you think about using the Amsoil Synthetic universal ATF for the power steering fluid i replaced mine recently with the CASTROL synthetic power steering fluid and seems to work fine but i need to clean it out again???

 

[dogfriend]

It should be okay, I think. I believe that they specify regular Mercon ATF for the Power Steering, so AMSOil should be okay since it meets the Mercon and Mercon V spec.

 

[vbtruk]

i am going to remove the back cover plate on my rear diff to empty the old fluid out should i do the same on the front or does the front have a drain plug.
98 XLT 4X4 SOHC
thank's guy's.

 

[dogfriend]

does the front have a drain plug.

No, the front doesn't have a drain plug either. You can remove the cover or you can siphon the old stuff out through the fill hole. If you suck the old stuff out, you may leave a little of it behind but it won't cause any problems and you won't have to go through the trouble of resealing the cover.

 

[vbtruk]

OK i have done the tranny and transfer case with AMSOIL universal ATF and a full flush and it was quite good i didn't take the bath but my CAT converter did!
the only thing i had trouble with was removing the cat converter but she worked out great, the flush was easy and didn't spray at all i diconected the lines at the cooler and put them both in a bottle and started the car they both pumped out yucky red fluid and i just added the amount that came out so it's a lot eassier than taking it to the shop and cheaper.
The front diff i sucked out but i had a lot of problems geting the tube in to suck out the oil, is there a special tube to use or something anyway i didn't get it all out cos i only could add 1.5 quarts of the Amsoil 75-140 so will it be ok????

Rear diff next week with indiglows and i changed to Mobil1 5w-50.
Thanks for your help guys.
Just one more thing: how often should i change the fluid's now?

 

[vbtruk]

The front diff i sucked out but i had a lot of problems geting the tube in to suck out the oil, is there a special tube to use or something anyway i didn't get it all out cos i only could add 1.5 quarts of the Amsoil 75-140 so will it be ok????
Just one more thing: how often should i change the fluid's now?

 

[dogfriend]

Re: Capacity of Front Axle - My owner's manual says it holds 1.7 liters = 3.5 pints = about 1.8 quarts. So you actually got most of it out, and what you didn't get out will mix with the new stuff you put in. I wouldn't be worried about it.

Re: How long can I go before changing fluids again?

Engine oil - this is quite controversial, but you should be able to go longer intervals with syn oil. The best method is to have a used oil analysis done, this will tell you when the oil is no longer protecting the engine. I choose to just change it every 6k or so, this is very conservative with syn oil.

Front, Rear Axle - Gear lube and t-case lube doesn't get contaminated like engine oil does. With Syn gear lube, 100k is a reasonable interval. Again, the best way to tell is an oil analysis.

Trans - Ford recommends 60k for 'normal' service, 51k for 'severe' service for the 5R55E. In light of the problems that others have had with Exploder trannys, I'm going to use a 50k change interval with an external filter added to gather the extra bits floating around.

Transfer case - Ford recommends 60k for 'normal' service, 30k for 'severe' service. I will probably change at 50k when I do the tranny the next time.

 

[vbtruk]

Thanks Dogfriend, you have been a great help!!! I can definately say that now that i have finally switched to Mobil 1 5w-50 the motor runs much smoother as it get's quite hot here.