Can I use 80w 90 instead of 75w 140???

[97splorer]

I am in the process of changing my rear diffy fluid and the guy told me that I could use 80w 90 gear oil. As i was about to remove the cover the tag says 140 oil only. Any thoughts??

 

[97splorer]

anyone???

 

[Robb]

My service manual directly calls for 80W90.

 

[Eneurb]

You need to use synthetic 75w140.

 

[97splorer]

Do I use friction modifier with the synthetic 75w 140?

 

[aldive]

I use Amsoil 80 w 90 with no addded friction modifier in my LS 3.73, Never had a single problem.

http://www.amsoil.com/products/agl.htm

 

[97splorer]

So which is right to use? 75w 140 or 80w 90?

 

[alexefron]

You need friction modifyer if you have a limited slip, as for the oil i dont know.

 

[Con Seann3ry]

I think either one will probably work fine

 

[Ford_Racing_Guy]

with most synthetic gear lubes you usually don't need to add the friction modifier because the synthetic lube already has the components in it

 

[Fred Garvin]

Ford calls for the synthetic 75W140 WITH 4 oz of the friction modifier in the rear diffy.

"with most synthetic gear lubes you usually don't need to add the friction modifier because the synthetic lube already has the components in it"

So why does Ford call for the SYNTHETIC 75W140 WITH the friction modifier?

 

[Eneurb]

I always use synthetic with modifer in lsd diffs...

 

[Robb]

Ford calls for the synthetic 75W140 WITH 4 oz of the friction modifier in the rear diffy.

Where are you getting this info? My '95 Ford service manual calls for no such thing. Is there a difference between the '95 and '97 rear 8.8s?

 

[aldive]

In my '99 Ford calls for the following:

Rear Axle, Conventional SAE 80W-90
Rear Axle, Traction-Lok 75W-140 Synthetic

 

[smiley1]

Rear Axle, Conventional SAE 80W-90
Rear Axle, Traction-Lok 75W-140 Synthetic

This is what my 98 calls for as well as I have the LSD.

I emailed Amsoil with the same question. This is the response I got:

To: Rob

From: AMSOIL Technical Services

Thank you for contacting AMSOIL with your concerns.

In response to your inquiry, the corporate recommendations for gear lube mirror the OEM spec’s closely because in some cases using the wrong viscosity can cause foaming issues. We would follow Fords’ lead on this and suggest AMSOIL Synthetic Severe Gear 75W90 Gear Lube (SVG) for the front and AMSOIL Synthetic Severe Gear 75W140 Gear Lube (SVO) for the rear.

Thank you again for the opportunity to respond to your concerns. As always, please feel free to contact us again if we can be of further assistance.

Sincerely,

Jim Van

AMSOIL Technical Services

They say 75-90 for the front and not 80-90 as I stated that Ford recommended 75-90. Oops. Correct weight for the front is 80-90.

I hope this helps you folks.

 

[97splorer]

thanks, I just finished and I used 75w 140 synthetic with 4 oz of friction modifier.