Rear differential fluid change
Thread Starter
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Mountain Pass
Joined: Jul 2008
Posts: 197
Likes: 38
From: SC coast Myrtle Beach
Rear differential fluid change
So, I decided to change out my rear axle differential fluid yesterday afternoon. There has been about 90,000 miles since I did it years ago when I installed a new aluminum cast diff shell on the housing which has its own drain plug. I had put two NEODYMIUM rare earth magnets onto the internal side of that drain plug using jb weld. Wow what a good thing. When I pulled that plug out, it looked like a glob of dark mud! It captured a huge amount of metal wear! I suggest doing that if you plan a diff fluid change.
https://tinyurl.com/54tfh6wf
Also, it seems I only got about two quarts of fluid out yet it took the full 3.3L as published. No drips from under the truck ever so could it be a worn pinion seal? I guess after another 20,000 I will crawl under there and top up the fill.
https://tinyurl.com/54tfh6wf
Also, it seems I only got about two quarts of fluid out yet it took the full 3.3L as published. No drips from under the truck ever so could it be a worn pinion seal? I guess after another 20,000 I will crawl under there and top up the fill.
Cargo Master
Joined: Oct 2005
Posts: 2,084
Likes: 94
From: Stanton, Michigan, USA
TretpFlyr,
You said, "No drips from under the truck ever..." which would tell me your pinion seal is still good.
apache84,
Who said , "If the pinion seal was leaking .....it would be wet under the diff and all around the yoke."
So TretpFlyr,
Where did the 1.3L of missing gear lube go? Has it been running all this time with only 60% of the gear lube that it should have had in it? If it was running without the proper amount of gear lube, that would explain why you found the "...glob of dark mud! It captured a huge amount of metal wear!" on the plug magnet...
I have seen where a tech will put in gear lube - not measuring the amount added, then not turn the wheels any, but when the lube is dribbling out at the fill hole, he called it good enough. Whereas if he would have put in the plug, started & ran the wheels a bit while still on the stands - then shut it down, re-check the gear lube level, he likely could have / should have added the remainder of necessary gear lube...because running the gears some had pulled some gear lube away from the plug hole allowing it to accept the proper amount of lube......This is why we measure the re-fill amount........
Just my 2 cents,
BarnieTrk
You said, "No drips from under the truck ever..." which would tell me your pinion seal is still good.
apache84,
Who said , "If the pinion seal was leaking .....it would be wet under the diff and all around the yoke."
So TretpFlyr,
Where did the 1.3L of missing gear lube go? Has it been running all this time with only 60% of the gear lube that it should have had in it? If it was running without the proper amount of gear lube, that would explain why you found the "...glob of dark mud! It captured a huge amount of metal wear!" on the plug magnet...
I have seen where a tech will put in gear lube - not measuring the amount added, then not turn the wheels any, but when the lube is dribbling out at the fill hole, he called it good enough. Whereas if he would have put in the plug, started & ran the wheels a bit while still on the stands - then shut it down, re-check the gear lube level, he likely could have / should have added the remainder of necessary gear lube...because running the gears some had pulled some gear lube away from the plug hole allowing it to accept the proper amount of lube......This is why we measure the re-fill amount........
Just my 2 cents,
BarnieTrk
Laughing Gas
Joined: Feb 2014
Posts: 815
Likes: 296
From: KY
Couldn't tell you where it went, but a leak should be obvious. Things dry at the outer axle tube ends and brake areas? Is your truck parked on 100% level ground so lube didnt run down one of the tubes? Vent line clean? RE, fill to dribble out and the spin the diff and refill again is a no go.. You'll end up overfilled for one and typically every mfg'er Ive seen typically says anywhere from 1/2 to 5/8 below the fill plug hole to dribbling out the fill hole is OK. I always do the later. I will add in the world of NP 241 and others Id guess, Transfer cases its a normal occurrence to have all the ATF disappear. They say it evaporates. I have many jeeps and it dies happen. Dry as a bone underneath, but easy to have a quart of ATF disappear over lesser than 90K miles. Go figure.
Thread Starter
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Mountain Pass
Joined: Jul 2008
Posts: 197
Likes: 38
From: SC coast Myrtle Beach
It is a wet looking dampness but no drips when parked. I have always wondered how the differential case is ventilated, if not the case must pressurize under heat and hard use like towing.
Thread Starter
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Mountain Pass
Joined: Jul 2008
Posts: 197
Likes: 38
From: SC coast Myrtle Beach
I remember putting in a FULL 4 quarts when I did the case change on the differential. That was because it had a slightly higher capacity. In my years of operating farm equipment like tractors and tillers, I always would "top up" the gear oil annually and there were never any visible leaks or drips in the barn (dirt floor with plywood under the motors). I guess the "grease fairy" just takes her share. An old master mechanic told me that "son, man can not make any motor seal that is 100% perfect". I think whats happening is that the case might be pressurizing a bit and pushing some fluid out but only during use.
On this fill, I got in about 3.5 quarts before grease was constantly coming out the top hole. I used a pump in the bottle and if pumping aggressively, grease would indeed back out the hole so must go slow and take time. That grease is thick. I will check it all again in a few months.
On this fill, I got in about 3.5 quarts before grease was constantly coming out the top hole. I used a pump in the bottle and if pumping aggressively, grease would indeed back out the hole so must go slow and take time. That grease is thick. I will check it all again in a few months.
Thread Starter
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Mountain Pass
Joined: Jul 2008
Posts: 197
Likes: 38
From: SC coast Myrtle Beach
Yep . . just like aging good whiskey in oak, you must top up the barrel. The whiskey fairy gets its share. In our case, its the fluid fairy. Lol.
I am going to check and top up the fill hole in a few thousand miles. I have do do a radiator flush refill also.
For a 24 yo truck, it is expected that the seals on about everything are worn. Solution is to paint the driveway black or park in the barn.
I am going to check and top up the fill hole in a few thousand miles. I have do do a radiator flush refill also.
For a 24 yo truck, it is expected that the seals on about everything are worn. Solution is to paint the driveway black or park in the barn.
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Moderator
Joined: May 2004
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From: Home Base Nebraska
The proper fluid level is 1/4 below the fill plug cold, after it warms up it will show full. If you fill it to where it comes out of the hole it will be over filled.
Denny
Denny
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Laughing Gas
Joined: Feb 2014
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From: KY
I have a 99 SD 250 4x4 with a aftermarket bigger cover as well, and it sure seems like a gallon was more than I put in my diff when I serviced it I cant recall for sure. But...it you were on flat ground what you added seems the norm. You really should make sure the diff vent line is there and not plugged up. Yes, it will heat up and potentially push lube past the seals. You should have a rubber line coming off one of the axle tubes heading up under the frame somewhere. It should also have a little plastic gizmo on the end that acts like a breather and prevents water intrusion.
Thread Starter
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Mountain Pass
Joined: Jul 2008
Posts: 197
Likes: 38
From: SC coast Myrtle Beach
Okay, thanks. I am going to crawl back under there tomorrow and take a look. Not familiar with a vent tube. This is the first I have heard of it and the manual does not mention it.
More Turbo
Joined: Jun 2009
Posts: 661
Likes: 186
From: Lakeland, MN
Vent is in the bolt going thru the brake flex hose to hardline body, its to the left of the pumpkin looking at it from the back. A slight overfill is not a bad thing. It insures the outer hub bearings are always flooded with oil. I have made many 3/16 plate diff covers for axles and always raise the fill hole 1/4 to 3/8" above the stock pumpkin fill plug hole. I also drill and tap a 1/2" NPT hole into the bottom of the diff so a flush plug with a magnet can be used and the diff fluid can easily be dumped completely.
Thread Starter
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Mountain Pass
Joined: Jul 2008
Posts: 197
Likes: 38
From: SC coast Myrtle Beach
Thats a good thing. Every tractor I have ever run has that. Seems that Ford would have designed this for all trucks. When the drive system goes out on a tractor or boat, there is no economical way to replace.
FTE Legend
Joined: Mar 2017
Posts: 31,891
Likes: 9,176
From: Western NY
So, I decided to change out my rear axle differential fluid yesterday afternoon. There has been about 90,000 miles since I did it years ago when I installed a new aluminum cast diff shell on the housing which has its own drain plug. I had put two NEODYMIUM rare earth magnets onto the internal side of that drain plug using jb weld. Wow what a good thing. When I pulled that plug out, it looked like a glob of dark mud! It captured a huge amount of metal wear! I suggest doing that if you plan a diff fluid change.
https://tinyurl.com/54tfh6wf
Also, it seems I only got about two quarts of fluid out yet it took the full 3.3L as published. No drips from under the truck ever so could it be a worn pinion seal? I guess after another 20,000 I will crawl under there and top up the fill.
https://tinyurl.com/54tfh6wf
Also, it seems I only got about two quarts of fluid out yet it took the full 3.3L as published. No drips from under the truck ever so could it be a worn pinion seal? I guess after another 20,000 I will crawl under there and top up the fill.
https://www.ford-trucks.com/forums/1...-10-5-a-2.html
Here's the post where I link to where I bought mine and the ones I used. I'm overdue for a rear diff lube change so probably next spring for sure...
https://www.ford-trucks.com/forums/1...l#post18849554
Last edited by Overkill2; Oct 26, 2024 at 09:50 PM. Reason: Add to post