85W-140 in place of 80W-90 temporarily

[Y_K]

Hi,

In a pinch: I didn't have a 90 gear oil. Had to replace the whole rear axle assembly on a 2001 P71 panther. Do I need to replace it ASAP?
The 40C viscosity is on a high side. It is Chevron Delo ESI 85W-140

Chevron Delo ESI Gear Oil Spec Sheet

it drives and 'feels' well though. The car sees minimum 40 miles of highway daily, odometer broke at 780k miles a few years ago.
Keeping it for unknown to me reasons, never had any major work before, and this time around it was cheap actually.

Thank you for your input in advance

 

[Falcon_LS]

Export models got 75W-140 right at the factory. With that kind of highway driving, I would leave it in there and not worry about it at all.

 

[zeng]

Yeah, KV@40*C of 341 cSt is too high against 140 cSt ..... and you might find the drive lethargic and underpowered.
But it's not a con here since..
Quote:
it drives and 'feels' well though.
...... especially while you're on 40 miles of highway driving... spirited one if you wish.

In my work machines , I replaced 80W90 and UTTO 5W30 all with SAE 140 gear oils..... and you know what? It runs cooler!
80W90: 85ish *C drops to 68-70*C, and
5W30 : 75ish *C drops to 48-52*C.

If I were you, I would run this 85W140 as it is, with longer OCI than xW90's ..... possibly additional 50% longer OCI.

Edit: Oops, miss Falcon's post.

 

[aquariuscsm]

Originally Posted By: Y_K
odometer broke at 780k


This car has 780,000 original miles??

 

[zeng]

Originally Posted By: Y_K
Had to replace the whole rear axle assembly on a 2001 P71 panther.

Btw, what were the damages on the previous unit ? ..... at 780k , did you use 75W90 or thinner gear oils previously ?

 

[Linctex]

Originally Posted By: aquariuscsm
Originally Posted By: Y_K
odometer broke at 780k


This car has 780,000 original miles??


Wow, I've never seen any Ford 8.8" rear last that long!!

 

[Ethan1]

How many people keep a car going for 780k to find out how long the axle will last? Most cars go to the junkyard with their original axles and likely the original gear oil

 

[Y_K]

Originally Posted By: Linctex
Wow, I've never seen any Ford 8.8" rear last that long!!


The passenger side one was replaced at around 480k. I used to own a small towncar company and had an interest in a cab co. Drove myself both to learn the ropes too, helped to understand the market better. Owned 28 panthers at one point. This particular one has been surprisingly dependable. Dinged, scratched, etc. totally unattractive and theft-proof. Transmission sends warning signs though. It is now a go to school car for a family member.

We used to mix both Delo ESI oils 1:1 to get something akin to a stout ISO 220 gear oil for pennies, worked very well. Those were few quarts left over from the old stash. I have Mobil Delvac 75W-90 and LE 1605 on its way for my other vehicle in case I decide to overthink this one.

In terms of mileage reduction: we see no differenc ein this application. My main concern is the potential thermal effect on the seals...

Add: Damages on the previous unit. When we pulled the axles, there was too much damage and a galaxy of shavings and fragments everywhere - impossible to flush and clean.
I have done that once before, and the new axle was shot in about 14k miles.

Thank you all.

 

[L_Sludger]

Very impressive overall mileage. Once you get that many miles on a car you just want to keep driving it as a matter of principle.
(I own cars with 300k miles)

 

[BrianF]

Rune the 140 weight and forget about it.