Changing rear differential fluid on F250

[pacem]

It is that big fully floating differential.

I got 3 cans of Mobil 1 75w-90 and 8 oz of posi additive and also RTV from dealership. They say not to use a gasket. Must also make sure the surface is clean.

BTW this is 89 F250 - I presume the fluid is original. It is not very high mileage however.

[ January 16, 2004, 01:21 AM: Message edited by: pacem ]

 

[Jeffrey Behr]

I'd think 75-140 would be better for a heavy-duty diff. What does Ford recommend?

 

[wulimaster]

Before draining, make sure you can remove the fill plug.

You might need another quart. Check with your owners manual.

 

[ChrisW]

Also, a tip I've heard is to warm up the fluid to make it flow better. About 15 minutes of driving should do this, provided you're not in 20 below weather.

 

[pacem]

You are right, the capacity is 3.9 Liters. So I will need another quart. I hear I need to add 2 LSD bottles, each one holding 8 oz. This is Dana 80, fully floating axle differential.

As for 75w-90 versus 75w-140 - I don't know. The owner's manual doesn't say. I hear that OEM was 75w-140, but the 75w-90 I got is Mobil 1 synthetic which is supposed to take heat much better. What putting it in be a big mistake? I hear others have done it. But then I don't know if they tow a 9,000 lbs weight.

Really, what I want is 75w-140 synthetic, but I couldn't find it anywhere, even Mobil1 75w-90 was pretty hard to find. I know I can get dino 75w-140, could I get 1qt and mix it with the other 3? Or should I insist on finding 75w-140?

 

[Rebel Rouser]

Based on past threads I've read here, the synthetic 75w-90 should be fine in your application. You may see an increase in MPG with it. Those in the trucking industry say that's what the big trucks use that put millions of towing miles on.

RTV works good sealing the cover. I use the higher temp orange stuff. Leave it set an hour, fill and drive. It's recommended to drive several tight figure of 8 patterns in a parking lot to get the FM worked into the clutch packs after the change.

 

[heyjay]

I think Dana axles of that vintage work fine with a good 75W-90. The 75W-140 will give better protection in very heavy use, but you might sacrifice MPG. Though it won't be a huge difference.

I run Mobil MobilLube SHC 75W-90 in my Eaton Dana HP-40 heavy truck axles. This product exceeds Eaton's extended warranty and drain rating.

The regular Mobil 1 Gear Oil 75W-90 will most certainly NOT meet the Eaton requirements and you will void your Eaton Dana extended warranty if you use it.

Anyway, purchased by the pail, the SHC is $4.25 a quart and Mobil 1 Gear Oil is $5.25 a quart at the local Mobil distributer.

You can find info on Mobil 1 75W-140 "Light Truck and SUV Formula" at:

http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil1_75W-140_SyntheticGearLubricant.asp

If you don't have a Limited Slip, a commercial synthetic gear lube like SHC 75W-90 will be more efficient, and offer much better high temp protection.

When you wrestle that sheet metal cover off, don't be surprised to find a bunch of sludge and gunk. Take your time to properly clean it out. An aftermarket cover like a Mag Hytec makes future servicing MUCH easier.

 

[White 03]

I think the Moble will work fine. I found Amsoil has 75w 140 and that is what I used in a 99 with the Ford differential.

If your limited slip is as poor at limiting slip as mine is you might want to try the Moble first before adding the extra additive. I used the Amsoil and nothing else and have no clutch grabbing or any other problems. It might be doing better in the traction department which was what I was looking for.

 

[Schmoe]

On 4x4, at least 01 F150 and up, it is 75W-140 in the rear and 75W-90 in the front. But, this has the tow package. From what I've gathered on the other Ford sites, the heavier stuff is factory IF your going to be towing or hauling a lot. There is some sacrifice on MPG. I think from 01 and up, the factory fluids are lifetime, so I've heard. If you have LS, need to add friction modifyier, but you don't if you use Redline. But in retrospect, this is what I just came across from a fellow member over at fordf150.net:
I called the dealership and talked to a service tech. and he said that the friction modifier is most likely to blame. It prevents the limited slip from engaging quite as early especially if the fluid is cold. He said if you wanted beter "posi track" in the rear end to change the fluid out again and not add the modifier or at least not the entire bottle like I did. Hope this helps anyone who's thinking about changing their rear diff fluid.

[ January 16, 2004, 01:26 PM: Message edited by: Schmoe ]

 

[heyjay]

I have a 2000 GMC Sierra with the optional G80 "GovLok." At 1000km / 600mi I did the initial axle service and made a boo-boo.

I have pails of commercial gear oil in my shop. I put Exxon SGO 75W-90 in my rear axle. I didn't notice anything until 2 months later when we had an early snow.

The rear end was slipping and chattering like crazy. I knew I made a boo-boo so called up Exxon: they told me to drain that stuff out ASAP or I would ruin my GovLok clutch plates.

I checked out the Eaton site as Eaton makes the GovLok. They have very contradictory advice, especially when compared to folks who claim to NOT use the LS additive:

http://www.traction.eaton.com

http://www.traction.eaton.com/prod6.htm

I drained the SGO out, added 3 tubes of CRC Trans-X PosiTrak additive, and put in the cheapest NAPA 80W-90 I could find (Claims suitable for Limited Slip). Drove around for 2 weeks.

The G80 gradually came back to life, so I then drained the 80W-90 and refilled with 1 tube of Trans-X and Mobil 1 Gear Oil 75W-90 (Claims suitable for LS). Has been fine since.

 

[pacem]

I decided to get 75W-140 instead, synthetic -- when I find it.
If I had a F150, a lower weight would be okay, but I am looking at towing some pretty significant weights (9000 lbs) so I don't want to take any chances. It is a 2WD so it has no front differential.

I also thought about mixing Mobil 1: 2 qt of 75w-90 and 2 qt or 75w-140, but I think I will go with full -140.

[ January 16, 2004, 04:02 PM: Message edited by: pacem ]

 

[heyjay]

Any Mobil commercial distributer should have it in stock. Call the Mobil help line at 1-800-662-4525 and wait for the prompt that tells you how to find a retailer in your area.

Do you have a Limited Slip? If not, I'd go with a commercial product like Mobil MobilLube SHC 75W-90.

My Eaton Dana HP-40 axles in the trucks pull some heavy weight too, and Eaton recommends a 75W-90 ONLY on the newer HP-40 axles.

 

[pacem]

Yes, it does have LSD (Posi)

I hear there are places online where you can order Royale purple, and I suppose Mobile 1. I even tried ebay, but not much oil there.

 

[Robbie Alexander]

GL-5 in both standard and limited slip
All temps for GM MEDium duty Synthetic 75w-90
In a limited slip depends on TEMPS. above 40F I think its 140 and between 10-100F a 90 is fine.

I guess it depends what Medium duty is?

 

[wulimaster]

I drained out the synthetic 75w140 factory fill over a year ago and replaced it with 75w90 Amsoil Series 2000 on my 2000 Excursion diesel. Picked up 8% city, 11% better highway mileage. Also drained out the dino 75w90 in the front diff and filled with the same synthetic as the rear at the same time. I don't tow anything big so that wasn't a concern for me. I believe I have the dana 70 series.

Wasn't the factory fill 80w90 dino back in 1989? If so, then you should be ok with the 75w90 synthetic.

Don't add the additive until you notice that you need it.

Don't forget the figure 8's.

 

[pacem]

It would certainly be interesting to determine what factory used in 1989 - I cannot possibly go wrong with that. Can anyone provide a definitive answer to that?

 

[Rebel Rouser]

The Mobil1 75w-90 you already have will work fine.

 

[oilcan]

I used 75-90 Neo Synthetic gear oil on my 86 F250 4x4. I did this two years ago an have pulled in temps of 118 degrees ambiet & low of 20 degrees, and in high heat there was a very noticeable difference alot cooler and this rearend has 160,000 miles on it.

 

[Chris B.]

Go with the M1 75w90. I know for a fact that scores of semi trucks use M1 75w90 in the rear ends and it does not get anymore heavy duty then that!

 

[heyjay]

quote:

---

Originally posted by Chris B.:
Go with the M1 75w90. I know for a fact that scores of semi trucks use M1 75w90 in the rear ends and it does not get anymore heavy duty then that!

---

I run commercial equipment with Eaton Dana HP-40 tandems. Mobil 1 Gear Oil is NOT approved for use in Eaton Dana axles for the 750,000 mile extended warranty with 500,000 mile oil drains.

You must meet the appropriate "E500" Eaton Dana specification, such as PS109, PS 163, and PS 037. If you run a Mack axle, it must be certified to GO-J Plus for extended drains and warranty. If you run an Arvin Meritor axle, it must be certified to 0-76N.

The commercial product Mobil MobilLube SHC 75W-90 exceeds the above requirements. Although Mobil 1 Gear Oil may be based on SHC, the additive package designed for Limited Slip service disqualifies it for commercial HD approvals in Eaton Dana and other HD axles.

As you would imagine, you can NOT use the commercial Mobil MobilLube SHC 75W-90 in limited slip or GM GovLok (Order code G80) applications. The clutch plates will slip and chatter.

Jerry