Rear end gear oil consensus request
11-07-2010, 09:33 PM
#1
Member
Thread Starter
Join Date: Nov 2010
Posts: 33
Likes: 0
Received 0 Likes
on
0 Posts
Rear end gear oil consensus request
Been reading up and searching and just can't seem to get a strong consensus on what gear oil to use in my 2000 3.55 LS 2wd rear end?
It's been about 50/50 in my reading.....whether to use 75w140 or 75w90.
Here's what I know (think):
1. Gotta use Synthetic Gear Oil
2. Gotta add Friction Modifier
3. Manual calls for 75w140
4. 75w90 is better if not towing and will give slightly better mileage
5. 50/50 on whether to use a gasket vs RTV
Looking for any and all $.02...especially on #4.
Thx
It's been about 50/50 in my reading.....whether to use 75w140 or 75w90.
Here's what I know (think):
1. Gotta use Synthetic Gear Oil
2. Gotta add Friction Modifier
3. Manual calls for 75w140
4. 75w90 is better if not towing and will give slightly better mileage
5. 50/50 on whether to use a gasket vs RTV
Looking for any and all $.02...especially on #4.
Thx
11-07-2010, 10:57 PM
#2
1. Yes
2. Yes
3. What Ford recommends
4. I doubt that mileage will improve even slightly noticeably making this change. Even if you're not towing, you're always hauling around 2.5 tons of truck itself so there is still a decent amount of heat created. I've seen the argument about 75w140 synthetic not being able to adsorb water and instead use the 75w90 because it can, but I never have witnessed any proof of those claims.
5. I changed mine a few months ago and just used RTV, no gasket. If you feel better using one go ahead, but they come from the factory with no gasket so I felt pretty safe just to use RTV.
I used Castrol severe gear 75w140 when I did mine because it was the only synthetic the local auto store had. I've had no leaks and no problems since doing it. My 2 cents.
2. Yes
3. What Ford recommends
4. I doubt that mileage will improve even slightly noticeably making this change. Even if you're not towing, you're always hauling around 2.5 tons of truck itself so there is still a decent amount of heat created. I've seen the argument about 75w140 synthetic not being able to adsorb water and instead use the 75w90 because it can, but I never have witnessed any proof of those claims.
5. I changed mine a few months ago and just used RTV, no gasket. If you feel better using one go ahead, but they come from the factory with no gasket so I felt pretty safe just to use RTV.
I used Castrol severe gear 75w140 when I did mine because it was the only synthetic the local auto store had. I've had no leaks and no problems since doing it. My 2 cents.
11-08-2010, 02:14 AM
#3
Just changed mine a few weeks ago, I used the Motorcraft 75-140 synthetic. Just make sure if you have a Limited Slip that you use the friction modifier. Went to the local Ford dealer and for 3 quarts and the friction modifier ran about $68. And be careful not to get the friction modifier on anything you want to keep because the smell will never come out.