I work at a shop in SLO CA and the other day I went to a shop that rebuilds rear ends and diffs to pick up some parts. I noticed that they only seemed to have conventional Valvoline gear oil and no synthetics. I asked a tech what they use in their rebuilt diff units and he told me just regular gear oil and not synthetics because they have had problems with running synthetics. I found this hard to believe. My boss told me he runs conventional gear oil in his Jeep differentials also because he has seen problems with running synthetics. Does anyone know what kind of problems a synthetic gear oil could cause? I didn't have enough time to ask the tech at the Diff and tranny shop what kind of "problems" they've seen and when I asked my boss he just told me that's what the Diff and tranny shop recommends so that's what he runs, which is a conventional Chevron 80w-90 GL-5. He uses his Jeep for some heavy Off Roading so I don't know if that application has something to do with using a conventional over a synthetic gear oil.
Why A Conventional Over a Synthetic Gear Oil?
- Thread starter John With Beastly 302
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I have been using synthetic in differentials in the vehicles I have owned and have never had a problem.
A "problem with running 'synthetics'" is a rather blanket statement.
First of all, what type of problem were they having? Was it a financial, "expense", problem?? Businesses are in the business of making profit and nothing comes before this one objective.
If the problem was related to actual transmission function, then which "synthetics" did they use? Did they try multiple synthetics? Did they try Royal Purple or Lucas, which both seem to be inferior to Red Line and Amsoil?
Amsoil's MTG gear lube seems like it might be a little too thin for transmissions, honestly.... or at least older transmissions with 150k or 200k+ miles. For a new transmission, Amsoil MTG could be the very best choice... and is more than likely what I would choose if I were going to buy a new car.
But Red Line looks to have a very extensive lineup of gear oils of various weights and thicknesses.
I would theorize that THIS is the reason that they don't want to fool with them is that they want a "one-size fits all" approach for the cheapest $$ they can handle. And who can really blame them??
First of all, what type of problem were they having? Was it a financial, "expense", problem?? Businesses are in the business of making profit and nothing comes before this one objective.
If the problem was related to actual transmission function, then which "synthetics" did they use? Did they try multiple synthetics? Did they try Royal Purple or Lucas, which both seem to be inferior to Red Line and Amsoil?
Amsoil's MTG gear lube seems like it might be a little too thin for transmissions, honestly.... or at least older transmissions with 150k or 200k+ miles. For a new transmission, Amsoil MTG could be the very best choice... and is more than likely what I would choose if I were going to buy a new car.
But Red Line looks to have a very extensive lineup of gear oils of various weights and thicknesses.
I would theorize that THIS is the reason that they don't want to fool with them is that they want a "one-size fits all" approach for the cheapest $$ they can handle. And who can really blame them??
Interesting.
Never heard this before.
I'm running a Semi-synthetic in my wife's Xterra.
I have Amsoil in my F-150.
Neither have issues. But then again I really don't haul anything heavy with either of them.
Now that I think about it. In a rebuilt differential or gear box it would make sense for the first fill to be conventional. Only because you would want to change it out after a few thousand miles to get all the junk out of there.
I can't see how Synthetics could be bad except for their bottom line or for a shortened change interval.
Never heard this before.
I'm running a Semi-synthetic in my wife's Xterra.
I have Amsoil in my F-150.
Neither have issues. But then again I really don't haul anything heavy with either of them.
Now that I think about it. In a rebuilt differential or gear box it would make sense for the first fill to be conventional. Only because you would want to change it out after a few thousand miles to get all the junk out of there.
I can't see how Synthetics could be bad except for their bottom line or for a shortened change interval.
I've never heard of anyone having problems with synthetic gear oil in a differential. My 2010 Silverado came from the factory with synthetic lube in the differential and so did our Peterbilt. I use it in my old Studebakers and haven't had any problems with them either. Maybe someone at the rebuild shop had a problem with synthetic lube in a limited slip differential, but most of the lubes have additive in them or it can be added if necessary. I'll bet it has to do with the price of the synthetic lube over the conventional lube.
I use dino oil in everything. Except my BMWs that have a limited slip. Mobil 1 75 90 stopped the clutches from chattering. My Ranger gets by on dino gear lube and the trans takes Mercon With LSD, you need a friction modifier. If you read the label, it will say that it is OK as a LSD FILL. If it says OK for top off only. not fill. then dont use it That is all I know about gear lube.
There's a lot of cars and trucks that came from the factory with synthetic gear oil. Not sure why there is a belief that it will somehow harm the rear axle. I would think the additive package would be a fault in that case. not the group type of the oil.
I have used Amsoil and Redline full synthetic gear lubes, both without issues in diffs and in gearboxes. For the last 6 years I have been using a synthetic blend from Schaeffers called "Synthetic Plus" 75W-90. I believe it is the best of both worlds if there is such a thing.
I don't know of what kind of "problems" they were talking about either and I'm going to talk to the guys at the gear shop and find out Monday because it doesn't make sense.
We just recently talked about it and answered why: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2861519&page=1
Been down this road and here are a few answers,
First, with regards to traction aids, some of the limited slip and locker manufacturers are building units designed before the general availability of syns. These devices are "calibrated" to the friction characteristics of mineral oils. In the case of two limited slips, I was able to talk to engineers at those companies and get the reasons why.
The engineers at Auburn Gear say the cone clutches on their HP or PRo Series LSD (designed by Borg Warner in the '50s) will immediately loose effectiveness (loss of bias ratio) with synthetics and over time, the cone clutch surfaces will become polished and the bias ratio (just google the term if you don't know it) effectively goes away.
The Eaton Truetrac (designed by Tractech and introduced in 1988) is a gear type limited slip that was designed for use with mineral gear oils. Since the unit relies on a certain amount of friction between the gears, a reduction of that tends to reduce the bias ratio. Some syns have been known to cause an odd squeaking noise in the Truetrac when it's biasing. This is why the instruction say "mineral oil only."
Synthetic oils, in general, do not resist moisture as well as a good mineral oil, so axles or gearboxes that face moisture may be better of with a mineral (a 4x4 for example). Hydrolysis (chemistry changes) and corrosion can be more a problem with synthetic gear oils when water is present. It's not universal and some oils are better or worse.
I interviewed the owner and one tech at a well known axle builder on the west coast as to why they recommend mineral oil vs synthetic. I'm not going to name them but it was clear to me they weren't all that knowledgable about oils. They relied more on cause and effect in their narrow slice of the market to dictate their policy. The explanation they gave me, and I'm just repeating what they told me, not endorsing it, is that synthetics left the gear faces of the ring and pinion gears "polished" and down the road, it was about impossible to read a pattern on them. Since they dealt with race and HP cars that were frequently torn down for various reasons (more so than an ordinary car), a polished gear would make it hard for them to set back up correctly.
I've done a fair bit of axle work and gear setup and I haven't seen many "polished" gear faces. I talked to a few other axle builders and their penchant for mineral gear oils seemed even less coherent. On one hand, you have to figure these professionals must know what they are doing. On the other hand, what I know about oils leads me in another direction. I reserve judgement until I get a clearer explanation.
Would I disregard advice to use a mineral? Maybe. I would heed it when the mfr. makes it a part of a warranty, which some of the aftermarket axle builders do. I would heed it in the case of a traction aid because if I install a LSD, I want to get the full benefit from it. Otherwise, I would use a syn for the obvious benefits.
First, with regards to traction aids, some of the limited slip and locker manufacturers are building units designed before the general availability of syns. These devices are "calibrated" to the friction characteristics of mineral oils. In the case of two limited slips, I was able to talk to engineers at those companies and get the reasons why.
The engineers at Auburn Gear say the cone clutches on their HP or PRo Series LSD (designed by Borg Warner in the '50s) will immediately loose effectiveness (loss of bias ratio) with synthetics and over time, the cone clutch surfaces will become polished and the bias ratio (just google the term if you don't know it) effectively goes away.
The Eaton Truetrac (designed by Tractech and introduced in 1988) is a gear type limited slip that was designed for use with mineral gear oils. Since the unit relies on a certain amount of friction between the gears, a reduction of that tends to reduce the bias ratio. Some syns have been known to cause an odd squeaking noise in the Truetrac when it's biasing. This is why the instruction say "mineral oil only."
Synthetic oils, in general, do not resist moisture as well as a good mineral oil, so axles or gearboxes that face moisture may be better of with a mineral (a 4x4 for example). Hydrolysis (chemistry changes) and corrosion can be more a problem with synthetic gear oils when water is present. It's not universal and some oils are better or worse.
I interviewed the owner and one tech at a well known axle builder on the west coast as to why they recommend mineral oil vs synthetic. I'm not going to name them but it was clear to me they weren't all that knowledgable about oils. They relied more on cause and effect in their narrow slice of the market to dictate their policy. The explanation they gave me, and I'm just repeating what they told me, not endorsing it, is that synthetics left the gear faces of the ring and pinion gears "polished" and down the road, it was about impossible to read a pattern on them. Since they dealt with race and HP cars that were frequently torn down for various reasons (more so than an ordinary car), a polished gear would make it hard for them to set back up correctly.
I've done a fair bit of axle work and gear setup and I haven't seen many "polished" gear faces. I talked to a few other axle builders and their penchant for mineral gear oils seemed even less coherent. On one hand, you have to figure these professionals must know what they are doing. On the other hand, what I know about oils leads me in another direction. I reserve judgement until I get a clearer explanation.
Would I disregard advice to use a mineral? Maybe. I would heed it when the mfr. makes it a part of a warranty, which some of the aftermarket axle builders do. I would heed it in the case of a traction aid because if I install a LSD, I want to get the full benefit from it. Otherwise, I would use a syn for the obvious benefits.
Originally Posted By: Jim Allen
Been down this road and here are a few answers,
First, with regards to traction aids, some of the limited slip and locker manufacturers are building units designed before the general availability of syns. These devices are "calibrated" to the friction characteristics of mineral oils. In the case of two limited slips, I was able to talk to engineers at those companies and get the reasons why.
The engineers at Auburn Gear say the cone clutches on their HP or PRo Series LSD (designed by Borg Warner in the '50s) will immediately loose effectiveness (loss of bias ratio) with synthetics and over time, the cone clutch surfaces will become polished and the bias ratio (just google the term if you don't know it) effectively goes away.
The Eaton Truetrac (designed by Tractech and introduced in 1988) is a gear type limited slip that was designed for use with mineral gear oils. Since the unit relies on a certain amount of friction between the gears, a reduction of that tends to reduce the bias ratio. Some syns have been known to cause an odd squeaking noise in the Truetrac when it's biasing. This is why the instruction say "mineral oil only."
Synthetic oils, in general, do not resist moisture as well as a good mineral oil, so axles or gearboxes that face moisture may be better of with a mineral (a 4x4 for example). Hydrolysis (chemistry changes) and corrosion can be more a problem with synthetic gear oils when water is present. It's not universal and some oils are better or worse.
I interviewed the owner and one tech at a well known axle builder on the west coast as to why they recommend mineral oil vs synthetic. I'm not going to name them but it was clear to me they weren't all that knowledgable about oils. They relied more on cause and effect in their narrow slice of the market to dictate their policy. The explanation they gave me, and I'm just repeating what they told me, not endorsing it, is that synthetics left the gear faces of the ring and pinion gears "polished" and down the road, it was about impossible to read a pattern on them. Since they dealt with race and HP cars that were frequently torn down for various reasons (more so than an ordinary car), a polished gear would make it hard for them to set back up correctly.
I've done a fair bit of axle work and gear setup and I haven't seen many "polished" gear faces. I talked to a few other axle builders and their penchant for mineral gear oils seemed even less coherent. On one hand, you have to figure these professionals must know what they are doing. On the other hand, what I know about oils leads me in another direction. I reserve judgement until I get a clearer explanation.
Would I disregard advice to use a mineral? Maybe. I would heed it when the mfr. makes it a part of a warranty, which some of the aftermarket axle builders do. I would heed it in the case of a traction aid because if I install a LSD, I want to get the full benefit from it. Otherwise, I would use a syn for the obvious benefits.
Interesting.
Been down this road and here are a few answers,
First, with regards to traction aids, some of the limited slip and locker manufacturers are building units designed before the general availability of syns. These devices are "calibrated" to the friction characteristics of mineral oils. In the case of two limited slips, I was able to talk to engineers at those companies and get the reasons why.
The engineers at Auburn Gear say the cone clutches on their HP or PRo Series LSD (designed by Borg Warner in the '50s) will immediately loose effectiveness (loss of bias ratio) with synthetics and over time, the cone clutch surfaces will become polished and the bias ratio (just google the term if you don't know it) effectively goes away.
The Eaton Truetrac (designed by Tractech and introduced in 1988) is a gear type limited slip that was designed for use with mineral gear oils. Since the unit relies on a certain amount of friction between the gears, a reduction of that tends to reduce the bias ratio. Some syns have been known to cause an odd squeaking noise in the Truetrac when it's biasing. This is why the instruction say "mineral oil only."
Synthetic oils, in general, do not resist moisture as well as a good mineral oil, so axles or gearboxes that face moisture may be better of with a mineral (a 4x4 for example). Hydrolysis (chemistry changes) and corrosion can be more a problem with synthetic gear oils when water is present. It's not universal and some oils are better or worse.
I interviewed the owner and one tech at a well known axle builder on the west coast as to why they recommend mineral oil vs synthetic. I'm not going to name them but it was clear to me they weren't all that knowledgable about oils. They relied more on cause and effect in their narrow slice of the market to dictate their policy. The explanation they gave me, and I'm just repeating what they told me, not endorsing it, is that synthetics left the gear faces of the ring and pinion gears "polished" and down the road, it was about impossible to read a pattern on them. Since they dealt with race and HP cars that were frequently torn down for various reasons (more so than an ordinary car), a polished gear would make it hard for them to set back up correctly.
I've done a fair bit of axle work and gear setup and I haven't seen many "polished" gear faces. I talked to a few other axle builders and their penchant for mineral gear oils seemed even less coherent. On one hand, you have to figure these professionals must know what they are doing. On the other hand, what I know about oils leads me in another direction. I reserve judgement until I get a clearer explanation.
Would I disregard advice to use a mineral? Maybe. I would heed it when the mfr. makes it a part of a warranty, which some of the aftermarket axle builders do. I would heed it in the case of a traction aid because if I install a LSD, I want to get the full benefit from it. Otherwise, I would use a syn for the obvious benefits.
Interesting.
The differential on my RX is quieter on Conventional lube.
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