A reader asks: Can I use 75W-140 gear oil in my 2007 Harley-Davidson Road Glide transmission? Some say that the heavier oil quiets down the transmission. Is there any problem with this?
Our answer: It is perfectly acceptable to use 75W-140 gear oil in Harley-Davidson transmissions. But, do consider that 75W-140 is much thicker than oils typically used in Harley transmissions. For instance, AMSOIL V-Twin Synthetic Transmission Oil is an SAE 110 gear oil. Let’s discuss the pros and cons of going with 75W-140.
Pros
The reason that some Harley owners use 75W-140 is that the transmission tends to run quieter. The thicker fluid can dampen noises and rattles.
Cons
The downside to using a thicker oil is that it will hold more heat. Hotter transmission operating temperatures would be the result.
Other Considerations
Wear protection– Using a 75W-140 will not improve gear wear protection. AMSOIL V-Twin Synthetic Transmission Oil or AMSOIL V-Twin 20W-50 Synthetic Motorcycle Oil can provide maximum transmission life. Wear protection doesn’t necessarily improve by using a thicker oil.
Shifting performance– There is no shifting performance benefit to using a thicker fluid. A thicker transmission fluid may actually make gear selection slightly more difficult.
How Does 75W-140 Viscosity Compare To Other Transmission Oil Options?
Here are the viscosity numbers for AMSOIL V-Twin 20W-50, V-Twin Synthetic Transmission Fluid and Severe Gear Synthetic 75W-140. The oil viscosity is measured in centistokes (cST) at 100°C.
V-Twin 20W-50- 18.5 cST
V-Twin Transmission (SAE 110)- 20.7 cST
Severe Gear 75W-140- 27.2 cST
Note that different scales are used to measure the viscosity of motor oils and gear oils. That’s why the 20W-50 motorcycle oil’s viscosity is so close to that of the the SAE 110 transmission fluid.
Also note that the 75W-140 is a whopping 47% thicker than the commonly used 20W-50 and 31% thicker than the (SAE 110) V-Twin Transmission Fluid.
In conclusion, 75W-140 can certainly be used in Harley-Davidson transmissions. We’re not sure that the quieter operation is worth the hotter operating temps and (arguably) stiffer shifting.
If you have a Ram 1500 pick-up with the ZF-8HP 8-speed transmission and are thinking of taking your truck into your Dodge dealer for a transmission oil flush, here is an analysis of the costs of this procedure. We hope you are sitting down.
Photo credit: Wikipedia
A few months ago, we ran an article about the outlandish cost of an EcoDiesel engine oil change at Dodge dealerships. But we recently started hearing rumblings about the cost of an ATF flush for Ram 1500 trucks with ZF 8-speed automatic transmissions. So we called a few Dodge dealerships in Canada and the United States to verify. As we learned more about the cost of the ATF change, the price of the motor oil change seemed like a wonderful value!
Ram EcoDiesel Transmission Oil Change Cost
We called a few random Dodge dealers and asked for quotes on a complete ATF oil change for a 2015 Dodge Ram 1500 with the 3.0L EcoDiesel engine. The prices below are for a complete ATF change, replacement oil pan and labor. As you can see, there is a fairly wide range in prices, so the parts and procedure costs may vary at your Dodge dealership.
USA $824.00 to $1105.00 (before taxes)
Canada $1135.00 to $1490.00 (before taxes)
The German-made ZF-8HP75 8-speed transmission is found in several Ram models as well as some Dodge Charger, Challenger, Durango and Jeep Grand Cherokee models. This versatile transmission is even found in some Roll-Royce, Aston Martin, Range Rover and Maserati models.
What Makes This ATF Oil Change So Costly?
The main items billed for this ATF service are 9 (or so) quarts of the Mopar ZF 8&9 Speed ATF, a replacement oil pan (which has an integrated oil filter) and one or two hours of labor. The ATF and transmission pan are priced to the moon, so this is where the bill really skyrockets. The replacement cost of a complete ZF 8-speed transmission is $4000 USD which is relatively modest when one considers to the absurdity of a $1000-plus fluid change.
Note that as these ZF 8-speed transmissions are relatively new in Dodge applications, very few Dodge dealers have actually performed an oil change on them. More often than not, service advisors will offer their “$159.00 ATF Flush Special” when you request an ATF change for these trucks. Once you ask them to check on the cost of the ZF 8&9 Speed oil and the pan/filter, they quickly learn that this is no ordinary ATF flush.
Price of Mopar ZF 8&9 Speed ATF
USA- $43.25 to $48.87 per quart (946ml)
Canada- $58.40 to $70.00 per quart (946ml)
Your eyes aren’t deceiving you; Mopar ZF 8&9 Speed ATF costs almost $50 per quart in the US and upwards of $70 per quart in Canada. For a complete fluid change, 9 quarts will be required and possibly one or two extra for the flushing proposes. Why is this ATF so expensive? Who knows? There are top-flight full synthetic substitutes (we offer a suggestion below) that meet the ZF 8&9-Speed spec and are available for a fraction of what Dodge dealers charge for this oil.
Mopar ZF 8&9 Speed ATF is a full synthetic oil made by Shell and is also marketed as ZF Lifeguard 8. The industry spec for this oil is Shell “M-L12108”. Shell designed and manufactures this ATF for the OEM’s but does not market an M-L12108 compatible fluid under the Shell brand. This fluid has a low viscosity to minimize friction for maximum fuel economy. The factory-fill ZF fluid has a translucent, slightly green appearance with an additive that helps technicians detect leaks under UV light.
Price Of Mopar ZF Oil Pan (Part # 68225344AA)
USA- $335.00 To $378.55
Canada- $453.00 to $522.00
The Mopar 68225344AA oil pan for ZF transmissions is a plastic unit with a non-removable, non-serviceable oil filter molded into it. Therefore, the pan has to be replaced when a complete oil change service is performed. The filter itself has a synthetic media, while the pan also has strategically placed magnets to gather metal filings. Also included with this kit is a gasket, replacement pan bolts and a replacement oil fill plug. While this plastic oil pan is reasonably well-designed, its finest attribute is its ability to completely empty your wallet.
About The ZF-8HP75 8-Speed Transmission
The ZF 8HP transmission series was introduced in 2008 to great fanfare and has proven to be durable, efficient and a great performer in a very wide variety of applications. The reason that the industry is moving toward 8-speed transmissions (and more gears in some cases) is to improve fuel efficiency. With 8-speeds, the engine can always be in an optimum RPM range. ZF 8HP transmission gear shifts take place in milliseconds and can shift from 8th gear directly to 2nd when the situation warrants.
These transmissions do not have a dipstick or top fill port of any sort. Oil is added through a plug on the lower side of the transmission housing. There is much confusion at Dodge dealerships about the proper ATF change interval for these ZF transmissions. On one hand, they are actually marketed as “fill for life” implying that the oil never needs to be changed or checked unless there is a problem. On the other hand, there is a severe service fluid change interval set at 60,000 miles (100,000 kilometres).
Elite ZF 8&9 Speed ATF Replacements
We offer two synthetic automatic transmission fluids which cover the Shell M-L12108 specification for ZF 8&9 speed transmissions. The premium option is the AMSOIL Signature Series Fuel-Efficient Synthetic ATF. This elite ATF is designed for long drain intervals and protects during temperature extremes. We often refer to a tortuous field test AMSOIL conducted using AMSOIL Signature Series Multi-Vehicle Synthetic ATF (the sister product of Signature Series Fuel-Efficient Synthetic ATF) in Las Vegas taxi cabs over 100,000 miles. Signature Series Synthetic ATF is as tough as they make them.
The other AMSOIL product that covers the Shell M-L12108 spec is AMSOIL Signature Series OE Synthetic ATF. This is AMSOIL’s budget-priced synthetic ATF and is designed for OEM drain intervals. As transmission fluid changes are a relatively rare procedure, we would spring the few extra bucks for the ultra-premium Signature Series Fuel-Efficient Synthetic ATF.
AMSOIL has released two more synthetic oils for the motorcycle market. The new products are AMSOIL V-Twin Synthetic Transmission Oil and AMSOIL V-Twin Synthetic Primary Chaincase Oil. As the names imply, these products are specific to V-Twin motorcycles like Harley Davidson, Triumph and Indian motorcycles (produced before the 2013 model year).
Why Did AMSOIL Choose to Make Specific Primary Chaincase and Transmission Oils For V-Twin Motorcycles?
Apparently when it came to Triumph and Indian motorcycle models that have three separate sumps (one each for engine oil, primary chaincase fluid and transmission fluid), AMSOIL did not have suitable fluids for the primary and gearbox. These new transmission and chaincase fluids fill these small gaps in their product offerings.
There are also some motorcycle owners who prefer to use specialized primary chaincase and transmission oil in these components instead of motorcycle engine oil.
Should Harley-Davidson Owners Switch To These New Products?
For years, AMSOIL has been recommending their MCV Synthetic 20W-50 Motorcycle Oil in the engine, primaries and transmissions of modern day Harley-Davidson motorcycles. The effectiveness of their 20W-50 in all three holes has been proven over millions of miles by thousands of Harley owners. The feedback on MCV 20W-50 from our Harley customers has been nothing short of spectacular.
There is no advantage in terms of performance or wear protection in switching to these new products over MCV 20W-50 in the primary chaincase and transmission of your Harley. It is truly a sideways move. Apparently the new Transmission Oil may offer modestly quieter performance in some transmissions. It’s your call as to whether this trumps the luxury of using a single (very proven) product throughout your bike.
What Are The Benefits Of AMSOIL Synthetic Primary Chaincase Oil?
Provides cool, quiet operation
Improves clutch operation
Fights clutch slippage
Combats metal-to-metal wear
Can remain in service for 10,000 miles (16,000 km)
What Are The Benefits Of AMSOIL Synthetic V-Twin Transmission Oil?
Smooths out shifting
Eases gear selection
Dampens gearbox noises
Lowers friction for cooler operation
Maintains its viscosity for long-lasting wear protection
Delivers an ultra-long service life of 20,000 miles (32,000 km)
What Is The Viscosity Of The New Primary Chaincase and Transmissions Fluids?
The V-Twin Transmission Oil is an SAE 110 and Primary Chaincase Fluid falls into the SAE 90 range. These products cannot be substituted for one another. Each has a specific additive package designed exclusively for their intended purpose, so do not use the transmission fluid in the primary and do not use the primary fluid in the transmission.
Regarding MCV 20W-50 Motorcycle Engine Oil, keep in mind that engine oils and gear lubes are shown on a different scale (so you don’t accidentally pour gear oil into the engine). MCV 20W-50 and these new oils do share a similar viscosity and that’s one of the reasons why why MCV 20W-50 is quite suitable in primary and transmission use in Harley-Davidson motorcycles.
Kinematic Viscosity @ 100°C
AMSOIL MCV 20W-50- 20.4 cST
V-Twin Transmission Oil- 20.7 cST
V-Twin Primary Oil- 18.7 cST
Where Can I Buy New The New AMSOIL Synthetic V-Twin Primary Chaincase and Transmissions Fluids?
Here of course! We can rush these products out of our Canadian or US warehouses to your door in just a day or two. We also have a full suite of synthetic motorcycle engine oils and oil filters. Request a price list using the contact form on your upper right or call us at 1-800-748-5781.
A reader asks: “I’m looking to switch my Harley-Davidson Street Glide Special over to AMSOIL. Obviously the engine will take your synthetic 20W-50, but I’m curious about what to use in the primary and transmission. There are a lot of different combinations put out there on the internet. Some use gear lube in the transmission and chaincase. Some even use ATF in chaincase and claim they have great results. What is the best combination for my bike?”
Answer: For any Harley Twin-Cam engine, we highly recommend using AMSOIL Synthetic 20W-50 in “all three holes” (as they put it) for two essential reasons.
Update: AMSOIL now offers dedicated fluid for Harley Davidson primary chain-cases and transmissions. These are called AMSOIL V-Twin Primary Oil and AMSOIL V-Twin Transmission Oil. Should one use these dedicated fluids? Or is AMSOIL V-Twin 20W-50 acceptable for primary and transmission use? There truly is no wrong answer. AMSOIL V-Twin 20W-50 is designed for engine, primary and transmission use. It is certainly a highly competent and convenient choice for all three components. For those that prefer a specialized fluid, the V-Twin Primary and V-Twin Transmission Fluids will certainly provide outstanding performance and protection.
AMSOIL V-Twin 20W-50 Works (and works very well indeed)
AMSOIL 20W-50 Synthetic Motorcycle Oil is specifically designed to withstand the rigors of engine, transmission and primary chaincase use. Expect smooth, quiet shifting with maximum component life. It is contains additives to prevent wear and the 100% synthetic base oil will not shear down (thin out). Therefore, it will not leave transmission or primary components vulnerable to accelerated wear.
AMSOIL has secondary recommendations of AMSOIL Severe Gear 75W-110 for the transmission and Severe Gear 75W-140 for the primary, but the company themselves will tell you that there is absolutely no upside to using gear oil in these components rather than the 20W-50. Some may think that they are using a thicker oil by using a gear lube. But remember that engine oils and gear lubes use different viscosity scales to prevent confusion.
What About Gear Oil?
Let’s look at the actual viscosity numbers of AMSOIL 20W-50 Motorcycle Oil and AMSOIL Severe Gear 75W-90, 75W-110 and 75W-140. The industry standard for measuring viscosity is in “centistokes” at 100°C.
“MCV”AMSOIL 20W-50: 20.4
“SVG” Severe Gear 75W-90: 16.8
“SVT” Severe Gear 75W-110: 21.3
“SVO” Severe Gear 75W-140: 27.5
As you can see, the 20W-50 motorcycle oil is very close to the 75W-110 in terms of actual viscosity. So those opting for a gear lube thinking that they are using thicker oil, really are not. Those using an 80W or 75W-90 in their transmissions are actually using a much thinner oil. The 20W-50 motorcycle oil’s viscosity is right in the “sweet spot” for optimum operation in all three holes and the volumes of positive reviews we receive back this up.
Gear lubes do contain heavy doses of “extreme pressure” additives which many believe prevent transmission wear and provide quieter operation. Again, AMSOIL 20W-50 Motorcycle Oil is packed with additives specifically designed to prevent wear in clutches, gears, chains and sprockets. There is absolutely no downside to going the 20W-50 route.
Some tout the use of automatic transmission fluid (ATF) in Harley primary chaincases. We do not recommend this option. Again, let’s look at actual viscosity numbers to back this up. The viscosity of a typical ATF at 100°C is 7.5 centistokes. We submit that ATF viscosity is far too thin for this application and think that the risk of long term wear is far too great. AMSOIL 20W-50 has a viscosity of 20.4 centistokes.
Convenience: One Effective Product For Everything
The second main reason that we recommend using 20W-50 motorcycle oil in the engine, transmission and primary chaincase is that you can buy one product for everything. Therefore, you can keep one product on hand and bring one oil along on trips for top-ups. In conclusion, only does AMSOIL Synthetic 20W-50 work exceptionally well in all three holes, it keeps things simple.
AMSOIL has released two more synthetic oils for the motorcycle market. The new products are 
Should Harley-Davidson Owners Switch To These New Products?
