Hi everyone, i know this subject may have been beaten to death, but wanted to seek your opinions. I am awaiting arrival of my new bike (05 Deluxe), hopefully will see in next couple of weeks. My general understanding has been that 20W-50 should be used for engine and primary (or 10W-40 as alternative in primary), and 75W-90 Gear Oil in Tranny. As i am no mechanical genius by any stretch of the imagination, but what i have been told was gear oil is better for your tranny than oil, as gears will churn oil and cause foaming in a motor oil, whereas gear oil specifically addresses this issue and eliminates foaming and subsequent wear that may occur as a result. However, i contacted Amsoil yesterday and spoke with a tech there who told me this was no longer the case, and their 20W-50 should be used in all three holes. I advised him of above and he said was true in the past, but now they recommend 20W-50 be used in motor, primary, and tranny.. Any thoughts would be appreciated. thanks,mb.

 

HD recommends their 20w-50 in all three holes. Amsoil recommends their 20w-50 in all three holes. Mobil 1 recommends their V-Twin 20w-50 in all three holes. So you can use the stuff and be covered.

But some of us have heard anecdotal evidence from independent shops of seeing bikes that have used the HD stuff in all holes. The shops say they are seeing tranny failures, and they believe it is related to the use of the oil. But it is just anecdotal evidence, and so far I haven't seen any concrete, provable evidence that the oil caused the failures.

From what I've read and understood on a site dedicated to lubricants, gear oils and engine oils are measured differently. The 20w-50 engine oil and the 75w-90 gear oil are very close in viscosity, numbers notwithstanding. The synthetic engine oils are extremely shear resistant; at least as shear resistant as most gear oils. And that is why HD, Amsoil, & Mobil can recommend their motor oils for tranny use. Shear is what tears the oil molecules up and reduces the viscosity.

So the quick answer is you can use all three in the same hole. Whether you choose to do so is up to you. Personally, I'd stick with the 20w-50 of your choice in the motor, use nothing heavier than 10w-40 in the primary, and a synthetic gear oil (75w-90 or -140) in the tranny. One of the guys (TCSTD) on here recommends Redline Shockproof for trannies. It's good stuff, but sometimes hard to find. Mobil 1 has a good gear oil, and so does Castrol.

The HD Syn 3 and Castrol Syntec are Group 3 synthetics, meaning they are refined from dino oil until all its molecules are identical. Mobil 1 and Amsoil are Group 4 ("true") synthetics, meaning they are "built from scratch", and not refined from dino oil. If you choose to go with 10w-40 in the primary, use a motorcycle grade, as most auto oils in this weight might contain too much moly additive, and could cause some clutch slippage problems.

Here's what I normally run, based on oil analyses I had done on several oils, and also based on being a cheap, er, frugal ol' fart: Mobil 1 15w-50 car oil in the engine, automatic transmission fluid in the primary, and either Mobil 1 or Castrol 75w-90 synthetic gear oil in the tranny. My last bike was a '78 Shovel FLH and had over 200,000 miles (w/one top end job & 2 clutches) when I sold it. Present bike is an '87 Evo Sloptail and has over 100,000 miles (no rebuilds & now on 2nd clutch) on it. I change engine oil and primary fluid every 2500 - 3000 miles, and tranny oil every other engine oil change. I run synthetic because it withstands way more heat than dino oil, something important to me in Texas. Your '05 Twinkie motor runs hotter oil temps than earlier HD motors, so running a synthetic is good insurance, IMHO.

 

I agree with Skip about it being your choice, however one dealer tech i know has seen failures (3 to date) due to Syn 3 in the transmission and I feel we will see a lot more.The shift forks were blued( lack of proper lube) and the bearings were damaged. I believe in the redline shockproof heavy for this reason. When you use the 20/50 in the trans and you do a service, you will find metal"fuzz" on the drain plug magnet. This same "fuzz" also collects on the speed sensor in the trans which gives your ECM info on how fast you are going as measured off the 4 th gear cog which then translates this into timing , fuel delivery in FI bikes and a host of other things. Now if you use the 20/50 in the trans you can expect to not only get more wear but the "fuzz" will foul out the sensor causing replacement. You can clean it off , but it is usually temporary and will require replacement soon after. The FUZZ is your gears wearing because the shear factor in the 20/50 is not adequate for gears, need I say anymore.
When you use the redline in the trans, the lubricating properties are such that you get literally none of the "fuzz" or such a small amount the it does not cause a problem with the sensor. This indicates to me that your trans is being lubricated better with the redline.

I also use the HD primary oil in the primary as it is tried and true for ions and Mobil 1 V twin in the engine cause it doesn't get any better.

Redline is available here http://www.myoilshop.com/ where I buy it by the case delivered to my door in 3 days.

Just a bit more protection for me. AND YA KNOW WE NEED PROTECTION !