No need to flush. Just change it with a good synthetic 75w90 and ubare good for the next 100k as long as the fluid level is good.
Neglected rear diff
- Thread starter dlundblad
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Originally Posted By: jk_636
All additives run out eventually. Isn't that why we pay the extra couple bucks to Blackstone to get a TBN? Arguably, diff. oil needs to be changed every 30-100k miles depending on the severity of service.
Wrong test, wrong idea...
Acids are formed in engines by the products of combustion and moisture, and are neutralised by the alkali reserves in the oil....more acid forming fuel (like sulfur rich bunker oil), more TBN in the oil...typically those marine engines would have a separate lubricant compartment for the bearings, and one for the pistons/blowby high TBN oil (and the crosshead).
Unless you have a real problem, you don't have combustion residue in your differential, and wouldn't be requesting a TBN (the additives are acidic also).
Diff oil, depending on VII may thin down some, but unless loaded with dust/water, or goes too thin...it doesn't need to be changed that often.
All additives run out eventually. Isn't that why we pay the extra couple bucks to Blackstone to get a TBN? Arguably, diff. oil needs to be changed every 30-100k miles depending on the severity of service.
Wrong test, wrong idea...
Acids are formed in engines by the products of combustion and moisture, and are neutralised by the alkali reserves in the oil....more acid forming fuel (like sulfur rich bunker oil), more TBN in the oil...typically those marine engines would have a separate lubricant compartment for the bearings, and one for the pistons/blowby high TBN oil (and the crosshead).
Unless you have a real problem, you don't have combustion residue in your differential, and wouldn't be requesting a TBN (the additives are acidic also).
Diff oil, depending on VII may thin down some, but unless loaded with dust/water, or goes too thin...it doesn't need to be changed that often.
Originally Posted By: expat
So the Diff has 75k on it and the oil may have been changed at least once.
How is this neglected?
Heck, I have put many times this mileage in a Diff or Gearbox, on Factory fill, and not changed the oil.
The diff was ran without a magnet for who knows how long. That is why I'm worried.
So the Diff has 75k on it and the oil may have been changed at least once.
How is this neglected?
Heck, I have put many times this mileage in a Diff or Gearbox, on Factory fill, and not changed the oil.
The diff was ran without a magnet for who knows how long. That is why I'm worried.
This is a neglected diff. Obvious water contamination. It got a full rebuild.
Originally Posted By: 19jacobob93
Just changed the 15 years and 205k old factory diff oil on the Falcon last week! Was very black (must be all that blow by!
) and filled it up with some dino Nulon 80w90. It was fine and silent before and still is now, and isn't leaking or anything so I wouldn't worry about it
I had to google what a falcon was.. I assume Ford right? Looks like a cross between our Taurus and the newer ones look like the Fusion. Not bad looking at all.. I assume they can be bought with diesels too?
Off topic:
Apparently this is what Mel Gibson drove in the Mad Max movies too? Lol. The new one comes out May 15th. I cant wait! They are odd movies, but I am hoping Tom Hardy will be able to entice the lady to watch it with me. She always says she'd trade me in in a heart beat.
Just changed the 15 years and 205k old factory diff oil on the Falcon last week! Was very black (must be all that blow by!
) and filled it up with some dino Nulon 80w90. It was fine and silent before and still is now, and isn't leaking or anything so I wouldn't worry about itI had to google what a falcon was.. I assume Ford right? Looks like a cross between our Taurus and the newer ones look like the Fusion. Not bad looking at all.. I assume they can be bought with diesels too?
Off topic:
Apparently this is what Mel Gibson drove in the Mad Max movies too? Lol. The new one comes out May 15th. I cant wait! They are odd movies, but I am hoping Tom Hardy will be able to entice the lady to watch it with me. She always says she'd trade me in in a heart beat.
dlundblad, in my humble opinion you are way overthinking this. Just drain the axle oil and replace with fresh GL-5 rated oil and forget it, unless you think it's been contaminated with water or something. 75k miles and 17 years on gear oil is not neglect.
Originally Posted By: Shannow
Originally Posted By: jk_636
All additives run out eventually. Isn't that why we pay the extra couple bucks to Blackstone to get a TBN? Arguably, diff. oil needs to be changed every 30-100k miles depending on the severity of service.
Wrong test, wrong idea...
Acids are formed in engines by the products of combustion and moisture, and are neutralised by the alkali reserves in the oil....more acid forming fuel (like sulfur rich bunker oil), more TBN in the oil...typically those marine engines would have a separate lubricant compartment for the bearings, and one for the pistons/blowby high TBN oil (and the crosshead).
Unless you have a real problem, you don't have combustion residue in your differential, and wouldn't be requesting a TBN (the additives are acidic also).
Diff oil, depending on VII may thin down some, but unless loaded with dust/water, or goes too thin...it doesn't need to be changed that often.
Wrong again. The idea was that after enough heat and friction, additives and oils begin to break down and degrade. Both condition are found in rear differentials, especially those that tow consistently heavy loads.
Originally Posted By: jk_636
All additives run out eventually. Isn't that why we pay the extra couple bucks to Blackstone to get a TBN? Arguably, diff. oil needs to be changed every 30-100k miles depending on the severity of service.
Wrong test, wrong idea...
Acids are formed in engines by the products of combustion and moisture, and are neutralised by the alkali reserves in the oil....more acid forming fuel (like sulfur rich bunker oil), more TBN in the oil...typically those marine engines would have a separate lubricant compartment for the bearings, and one for the pistons/blowby high TBN oil (and the crosshead).
Unless you have a real problem, you don't have combustion residue in your differential, and wouldn't be requesting a TBN (the additives are acidic also).
Diff oil, depending on VII may thin down some, but unless loaded with dust/water, or goes too thin...it doesn't need to be changed that often.
Wrong again. The idea was that after enough heat and friction, additives and oils begin to break down and degrade. Both condition are found in rear differentials, especially those that tow consistently heavy loads.
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Originally Posted By: jk_636
Originally Posted By: Shannow
Originally Posted By: jk_636
All additives run out eventually. Isn't that why we pay the extra couple bucks to Blackstone to get a TBN? Arguably, diff. oil needs to be changed every 30-100k miles depending on the severity of service.
Wrong test, wrong idea...
Acids are formed in engines by the products of combustion and moisture, and are neutralised by the alkali reserves in the oil....more acid forming fuel (like sulfur rich bunker oil), more TBN in the oil...typically those marine engines would have a separate lubricant compartment for the bearings, and one for the pistons/blowby high TBN oil (and the crosshead).
Unless you have a real problem, you don't have combustion residue in your differential, and wouldn't be requesting a TBN (the additives are acidic also).
Diff oil, depending on VII may thin down some, but unless loaded with dust/water, or goes too thin...it doesn't need to be changed that often.
Wrong again. The idea was that after enough heat and friction, additives and oils begin to break down and degrade. Both condition are found in rear differentials, especially those that tow consistently heavy loads.
No, he's quite right. TBN testing is useless for a diff because it doesn't see combustion byproducts. Also, as per Doug Hillary's post, it sounds like additive break-down is not as big an issue as we think it is.
Originally Posted By: Shannow
Originally Posted By: jk_636
All additives run out eventually. Isn't that why we pay the extra couple bucks to Blackstone to get a TBN? Arguably, diff. oil needs to be changed every 30-100k miles depending on the severity of service.
Wrong test, wrong idea...
Acids are formed in engines by the products of combustion and moisture, and are neutralised by the alkali reserves in the oil....more acid forming fuel (like sulfur rich bunker oil), more TBN in the oil...typically those marine engines would have a separate lubricant compartment for the bearings, and one for the pistons/blowby high TBN oil (and the crosshead).
Unless you have a real problem, you don't have combustion residue in your differential, and wouldn't be requesting a TBN (the additives are acidic also).
Diff oil, depending on VII may thin down some, but unless loaded with dust/water, or goes too thin...it doesn't need to be changed that often.
Wrong again. The idea was that after enough heat and friction, additives and oils begin to break down and degrade. Both condition are found in rear differentials, especially those that tow consistently heavy loads.
No, he's quite right. TBN testing is useless for a diff because it doesn't see combustion byproducts. Also, as per Doug Hillary's post, it sounds like additive break-down is not as big an issue as we think it is.
Good overall advice in this thread, as 901Memphis, Doug Hillary, barkingspider, and others have said: Keep things simple and use a 75W-90 lube (like Walmart's SuperTech), which is superior to the gear lube used 18 years ago when your Blazer was built.
IF your application was a late-model vehicle, then Amsoil Severe Gear 75W-90/140 would be worth using.
After your differentials are serviced, I'd be more concerned with the gaskets and seals of major driveline components and focus on other things for improved reliability.
In the long-run, prevention is always much better than redemption.
IF your application was a late-model vehicle, then Amsoil Severe Gear 75W-90/140 would be worth using.
After your differentials are serviced, I'd be more concerned with the gaskets and seals of major driveline components and focus on other things for improved reliability.
In the long-run, prevention is always much better than redemption.
Originally Posted By: mjoekingz28
Originally Posted By: dlundblad
Originally Posted By: artificialist
Is this the kind of differential that has a removable pan? When I deal with that kind of differential, I like to blast it with brake cleaner until I no longer see any gray slime. Afterwards, I fill with premium fluid.
I use the method you mentioned on differentials that don't have a removable pan. That is what I have done to my own car. I used Valvoline conventional because I found no less expensive oil that contained LS additives.
Do you know if this truck has limited slip or not? That would be a factor in which gear oil you choose.
When you say removable pan, do you mean a differential cover? This has a removable pan. I shot a good dose of brake cleaner into it and a lot of chunky oil clumps dripped out.
I still have it dripping now which is best I suppose. I might hit it again tomorrow with some more brake cleaner.
*I dont think it has LSD. We supported the rear end while one wheel went forward and the other went in the opposite direction.
IS there a way to check for posi-trac, aka 2 tires turning, without lighting them up? You see, my rears are almost bald and I'm in no shape for new ones just yet.
With the vehicle on a lift, or jacked up on stands, turn one of the rear wheels. If the opposite wheel turns in the other direction, you do NOT have a limited slip differential.
Yes, differential fluid degrades over time. Under certain heavy load conditions, such as towing up hill, the use of full synthetics can be of benefit. The main benefit is lowering the differential a few degrees in temperature.
For maximum protection, I recommend using an aftermarket differential cover with cooling fins, drain plug, and magnetic dip stick. I have a Mag-Hytec cover installed on one of my vehicles and have had good results. The ease of checking the differential oil and draining when needed is a breeze.
Originally Posted By: dlundblad
Originally Posted By: artificialist
Is this the kind of differential that has a removable pan? When I deal with that kind of differential, I like to blast it with brake cleaner until I no longer see any gray slime. Afterwards, I fill with premium fluid.
I use the method you mentioned on differentials that don't have a removable pan. That is what I have done to my own car. I used Valvoline conventional because I found no less expensive oil that contained LS additives.
Do you know if this truck has limited slip or not? That would be a factor in which gear oil you choose.
When you say removable pan, do you mean a differential cover? This has a removable pan. I shot a good dose of brake cleaner into it and a lot of chunky oil clumps dripped out.
I still have it dripping now which is best I suppose. I might hit it again tomorrow with some more brake cleaner.
*I dont think it has LSD. We supported the rear end while one wheel went forward and the other went in the opposite direction.
IS there a way to check for posi-trac, aka 2 tires turning, without lighting them up? You see, my rears are almost bald and I'm in no shape for new ones just yet.
With the vehicle on a lift, or jacked up on stands, turn one of the rear wheels. If the opposite wheel turns in the other direction, you do NOT have a limited slip differential.
Yes, differential fluid degrades over time. Under certain heavy load conditions, such as towing up hill, the use of full synthetics can be of benefit. The main benefit is lowering the differential a few degrees in temperature.
For maximum protection, I recommend using an aftermarket differential cover with cooling fins, drain plug, and magnetic dip stick. I have a Mag-Hytec cover installed on one of my vehicles and have had good results. The ease of checking the differential oil and draining when needed is a breeze.
To the OP, many differentials are not equipped with a magnetic plug. The location on the Blazers plug is prone to rounding out due to it's location and was most likely replaced when the last service was performed. I wouldn't consider that too much of a problem personally.
Towing kills rear ends with heat build up. Just drain it, refill and forget about it. If you don't tow, and don't ford rivers don't worry about it.
Every 100k is a good service interval for differentials, or never.
Every 100k is a good service interval for differentials, or never.
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