The car is a 1998 Ford Expedition 4.6L RWD with 70K miles. I've never owned or worked on a RWD car so I know nothing about Rear Ends. I will be replacing my sisters Rear End fluid with Mobil1 Synthetic 75W-90. I'm not sure what weight it has right now. I was wondering if this is okay? As said above the car sees no towing...**** it usually only sees 2 people at a time. Any comments are appreciated.
75W-90 in a RWD SUV W/No Towing?
- Thread starter Sid
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Sid, I hate to make a blanket statement (often proven wrong), but I think most if not all late model Ford trucks call for 75W140 synthetic in the rear diff.
The wife drives a 2000 Explorer, and it specs a 75W-140 synthetic oil, whether towing or not.....
The wife drives a 2000 Explorer, and it specs a 75W-140 synthetic oil, whether towing or not.....
Well I called a trust Ford dealership and the parts guy said that they stock 75W-140 at the dealership because of it being a good all around fluid and because it's less parts for them to carry. But he said that 75W-90 should also be fine to go into the rear end. Only exception is that if the Rear End has Limited Slip it will need a Friction Modifier.
So I guess I could use the 75W-90 but what would be the difference?
So I guess I could use the 75W-90 but what would be the difference?
Sid,the 75W140 withstands 'shock loading' better than the 75W90. Shock loading happens when power is applied and removed suddenly from the diff gears. It's more extreme in towing situations; that's why 75W140 is recommended when towing. The thicker lube withstands the "squeezing out" effect better than the 75W90 when under pressure.
If it were mine, I'd use the 75W140, but that's just me.
If you do no towing go with the 75w90 as you will get better fuel economy over the 75w140
Hmmm. Well I think I'll stick with the 75W-90. The 90 weight is half the price of the 140 weight at $7.99 compared to $14.99. Plus she almost never stresses that thing. I wonder if the friction modifier does something to help that "squeezing out" effect?
I gotta apologize about sounding so anal. This is my sisters car and it is totally new to me.
That's something she needs. Big Bertha ain't getting any younger (Her SUV).
First, crawl underneath and look at the axle. You need to determine if you have limited slip rear. There will be a metal tag on one of the bolts that hold the pumpkin on the rear end. That tag will tell you what's in the rear now. If you have a LS rear, you are going to have to buy some friction modifier to go along with the M1. I believe Amsoil and Redline are the only ones that make a 75-90 or 140 that doesn't require a FM. If you don't plan on doing any towing, then a 75w90 will be what you want. There are thousands of those rear ends with that in them and have not had any problem. In fact, on F150 4x4 (which is pretty much the Expedetion with different clothes) manual will call for a 75w90 in the front regardless if towing or not.
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