5w-40 in a Twin Cam 88?

[Litzner]

I have been using M1 15w50 in my old Dyna Wide Glide since I have owned it. When it come to the trans and primary I used Red Line's products for sometime and they just have not been impressing me. My shifts are hard, finding neutral is a pain. I also find that the Red Line seems to sludge up in the bottom. I also killed a rear end in a truck using Red Line Lightweight Shockproof gear oil, which according to my mechanic the fluid just didn't seem to be getting to where it needed to be.

I have since been moving all of my gear oil needs over to Mystik JT7 that I can get easy and cheap at a local store. The Harley seems to like it in the gear box, but I hear those like anything. I swapped the primary over to some 5w40 T6 I had that was wet clutch compatible from the Red Line Primary lube I was running and it has made a huge difference so far. Shifts are way softer especially when cold and finding neutral has been easier.

This has made me think about looking at the other lubes I have been using. I use Valvoline Blue 5w40 in my old 7.3 and it seems to like it. I then decided to try the 5w40 in my side by side and the initial cold start valve tick on that Polaris 900 motor has been better since then. Then I was thinking, if I just cut my lawn mower and Harley over to this Valvoline Blue 5w40 I only need to buy 1 jug of oil for all of my engines. Is a 40 weight too light for the air cooled TC88? I can't imagine it sees much more extreme pressures then the old 7.3 right?

 

[NOTEVIL81]

I have been using M1 15w50 in my old Dyna Wide Glide since I have owned it. When it come to the trans and primary I used Red Line's products for sometime and they just have not been impressing me. My shifts are hard, finding neutral is a pain. I also find that the Red Line seems to sludge up in the bottom. I also killed a rear end in a truck using Red Line Lightweight Shockproof gear oil, which according to my mechanic the fluid just didn't seem to be getting to where it needed to be.

I have since been moving all of my gear oil needs over to Mystik JT7 that I can get easy and cheap at a local store. The Harley seems to like it in the gear box, but I hear those like anything. I swapped the primary over to some 5w40 T6 I had that was wet clutch compatible from the Red Line Primary lube I was running and it has made a huge difference so far. Shifts are way softer especially when cold and finding neutral has been easier.

This has made me think about looking at the other lubes I have been using. I use Valvoline Blue 5w40 in my old 7.3 and it seems to like it. I then decided to try the 5w40 in my side by side and the initial cold start valve tick on that Polaris 900 motor has been better since then. Then I was thinking, if I just cut my lawn mower and Harley over to this Valvoline Blue 5w40 I only need to buy 1 jug of oil for all of my engines. Is a 40 weight too light for the air cooled TC88? I can't imagine it sees much more extreme pressures then the old 7.3 right?

There's really no reason for anything exotic in the transmission. Harley originally asked for twenty fifty engine oil In the six speed. As you know , it's a gearbox , so it gets oil. Really see no failures in the transmissions Due to the oil. Failures in the transmission is generally the Sliders. As you can see in the picture Slider is worn on Left side. Ninety percent of the time that's because the shift fork is bent. Not Centered in the slider. The causes hard neutral and Missed gear Engagement.
All primaries We use rotella 15/40 Diesel no matter what clutch basket is in it. Compensators seem to last very long with that oil and clutch packs Don't Glaze.
Engine.
Oil is your choice Generally valvoline 4 STROKE 20/50.. These bikes are ridden like they're hated. Hope I gave you a little insight.

 

[NOTEVIL81]

Oh trans any gear oil . I.
Don't care for royal purple products. But their gear oil does seem to make shifts very smooth. Compared to mobile or valvoline.

 

[EvoMan]

Only your 5th post in 12 years…..you need to get out more often

After many years and much research, I’m a firm believer in motorcycle specific oil and particularly in using V-Twin oils in a Harley. As Lake Speed Jr likes to say, application dictates chemistry.

In my ‘89 Electra Glide with an 80 cubic inch Evo motor, I’m using Castrol Power 1 V-Twin 20W-50. In my 2018 Tri Glide with an 107 M8 motor, I’m running Mobil 1 V-Twin 20W-50.

With the heat that is generated, especially the rear cylinder of a Harley, a V-Twin oil that is formulated with the proper additive package and that is resistant to HTHS, is essential in wear prevention and also preventing viscosity break down.

After researching dedicated manual transmission fluids, I found that the additive package is more similar to a motor oil than it is of a gear oil. I eventually will be using the same oil in my primary and transmission that I use in the engine on both bikes.

Valvoline Blue 5W-40 is a diesel oil. It’s not a good idea to use diesel oil in a gas engine. Check out the video below on why not to use it in your Harley.

 

[Litzner]

Only your 5th post in 12 years…..you need to get out more often

After many years and much research, I’m a firm believer in motorcycle specific oil and particularly in using V-Twin oils in a Harley. As Lake Speed Jr likes to say, application dictates chemistry.

In my ‘89 Electra Glide with an 80 cubic inch Evo motor, I’m using Castrol Power 1 V-Twin 20W-50. In my 2018 Tri Glide with an 107 M8 motor, I’m running Mobil 1 V-Twin 20W-50.

With the heat that is generated, especially the rear cylinder of a Harley, a V-Twin oil that is formulated with the proper additive package and that is resistant to HTHS, is essential in wear prevention and also preventing viscosity break down.

After researching dedicated manual transmission fluids, I found that the additive package is more similar to a motor oil than it is of a gear oil. I eventually will be using the same oil in my primary and transmission that I use in the engine on both bikes.

Valvoline Blue 5W-40 is a diesel oil. It’s not a good idea to use diesel oil in a gas engine. Check out the video below on why not to use it in your Harley.

I have seen that video, but it’s an apple vs. oranges comparison. He was comparing a non-gasoline rated oil (not spark SN/SP/etc) to a gasoline rated oil. Many diesel oils are also gasoline rated, like T6 5w40 and Valvoline Blue 5w40. Also this diesel only rated oil was specifically very bad for modern DI engines, not EFI or carburetor mostly due to the heavy detergent content.Specifically the Valvoline isn’t heavily loaded with detergents like many diesel rated oils, so the additive pack even appears to look more like a gasoline rated oil.

 

[NOTEVIL81]

I have seen that video, but it’s an apple vs. oranges comparison. He was comparing a non-gasoline rated oil (not spark SN/SP/etc) to a gasoline rated oil. Many diesel oils are also gasoline rated, like T6 5w40 and Valvoline Blue 5w40. Also this diesel only rated oil was specifically very bad for modern DI engines, not EFI or carburetor mostly due to the heavy detergent content.Specifically the Valvoline isn’t heavily loaded with detergents like many diesel rated oils, so the additive pack even appears to look more like a gasoline rated oil.

Of course you can use any oil you want. I don't know what your expertise is in building Harley-Davidson engines. But apples to oranges are Harley engine uses roller bearings. And an automotive engine uses Babbitt bearings. Every engine builder in the Harley world uses 20/50 in shovel engines, Evo engines, twin cam engines, and M8. The Only Exception would be an EVO or a shovel motor crossing the hot desert would run straight 60.

 

[NOTEVIL81]

If you're 88 in motor is a 99 to 02 I'm sure you know that's a timkin bearing crankshaft. So I would definitely recommend the 20/50

 

[BigCahuna]

I bought my current bike 2 years ago. it's a '06 Harley Road King ex NYC Police bike. The oil looked like new when I bought it, so I didn't see any reason to change it at that time. Come first time to change it, I went with what I've been running for years. Engine Castrol 20/50 mc oil synthetic. Primary got a qt of 15/40 diesel oil,. and the trans got 20 oz's of Fram store brand 80/90 wt gear oil. I also do a cable clutch adjustment at that time. My manual says to use 10/40 wt engine oil when the bike is being used under 40 degrees f. But I don't have issues with it starting with the 20/50 so I leave it in all year. I haven't found using high priced oils to be of any benefit in Harley's. They run the same and last as long.,,,

 

[repairman54]

In my '01 FLHR its been V twin 20-50w since new. I went to Red Line heavy shockproof in the trans, it lessens the clunk some. Red Line in the primary also.

 

[alarmguy]

103 H/O 2014 Road King
I could never put a 5/40 in a 20/50 engine. Oils temps can get up to 270 degrees in heavy traffic on hot day.
I used Harley oil when first new for a short period, then went to 15w50 Semi Synthetic diesel oil. Since my manual says if HD oil not available you can use diesel oil until you can get HD oil again. No mention API of gasoline oil.

So I have used Mystic 15/50 Diesel oil for a decade now. Recently for fun I have been using 15/50 Mobil 1 for no other reason than just because.

 

[Nuclear_42]

I just run Amsoil dedicated V-twin primary and transmission fluids. Very easy to find neutral and shifts smooth. Their V twin oil change kits are awesome. Very pleased with results in my 05 twin cam 88.

 

[Silverado12]

When I had my 2007 96" Twin Cam (all stock) I used Valvoline VR1 20W-50 in the motor, Rotella T4 15W-40 in the primary and Harley branded "Formula+" oil in the transmission.

 

[NOTEVIL81]

Good choices Silverado 12 love the 07 6-speed ,straight cut 5th gear instead of helical. I just don't care for formula plus one Citgo manufactured outside the United States and it is GL1.

 

[SOUNDMAN5000]

My Harley (s) Trans, oil and primary 28 year fluid story...

With my then new 1997 Heritage Softail with an added EV-27 cam early on that I purchased new about 28 years ago, I always used REVTECH Brand Mineral 20w 50 at times the REVTECH Pure 25w-60 for my beach trips in the hot summer, gave a bit better oil pressure in stopped traffic in the Summer heat but that was years ago. I would also use the Harley brand mineral oil and primary fluid in the primary and trans fluid in the trans.

When my EVO was perhaps a year old I changed the oil to once to Mobil 1 Synthetic V-Twin 20w-50, but that first ride with the M1 at every red light I got a tic,tic,tic, so I did less than 20 miles, dumped that oil, refilled with mineral and to this day 28 years later I have never heard a tic, I have seen others say evo's like mineral but that was my 20 mile Synthetic experience.

So I ran the REVTECH mostly in the early first 8-10 years then on the advice of a local Harley tech that said many of his customers were using Synergyn Syngear II in the trans loved it.
The Synergyn was a 80W-140 Synthetic gear oil and tinted red.

So I changing to that Synergyn made perhaps more difference than anything I have ever done to the bike. After those first 10 years of 1st gear "CLUNK" and neutral was always impossible to find, after that Synergyn change I was like WoW what an improvement! Shifts like butter. Less to no clunk, neutral easer to find, everything was just better!

So I used that Synergynof trans fluid about 10 years and then one day when time to do a fluid change... I could no longer find it!
Synergyn was once well regarded on the race circuit but I think the owner may have passed as to the best of my knowledge and research now no longer produced!

So I started researching options, reading reviews, Harley threads and I remember the Redline Shockproof Gear oil was very highly suggested.

Harley about this time recently introduced The then New Harley Heavy Gear Oil. A 80w-140 Synthetic blend that had good reviews, Was EZ to find at my dealer so I tried that stuff.I HATED IT! My Heart just sank as the bad shifting, the 1st gear clunk , the I can't find neutral, bad feel shifting returned that has been gone 10 years with the Synergyn! Took me back 10 years!

So I had to try and find a Trans fluid that would once again FIX thos trans issues so many Harley trans experience.
After reading lots of reviews, I almost purchased the Redline Shockproof ( based on positive reviews) but I decided to try Bel-Ray V-Twin 85w-140 Trans fluid and thought its time for all the fluids so I also purchased Bel-Ray Mineral 20w 50 oil and the Bel-Ray V-Twin Primary fluid.
So this was about 5 years ago with my now old EVO! I was blown away with the Bel-Ray, My Trans performance went back to how she acted with the Synergyn! No to little clunk! Shifts like butter just perfect but what I didn't expect was what changing from the normal REVTECH then Harley 360 oil was with the Bel-Ray in the engine it was like i had a blanket or something on the top end.
The valve train what I thought was just normal valve train noise ( no tic but noise ) was reduced with the Bel) ray oil.

So Bel-Ray became my new fluid of choice in my now older EVO, all in all runs best with Bel-Ray.

So in 2023 I buy a new M8 Harley Street Glide, I had the Stage 2 cam installed day one with 16 miles on the bike.
At exactly 100 miles (I had seen on a Harley forum it was suggested Bel-Ray was a good break-in oil). so I changed to the Bel-Ray V-Twin mineral 20w-50 at exactly 100, Once again I noticed on my new bike less top end noise than with the factory fill oil!
at the first 1k service I took my own fluid to the dealer, yes Bel-Ray V-Twin Trans, Primary and I did decide to try the Bel-Ray Semi-Synthetic 20w-50.

I'm not a huge synthetic fan ( I know most folks now are ) but even in my new Feuling vented dipstick instructions Feuling suggest using Mineral oil and not Synthetic to provide less piston blow-by. Im not trying to change anyones mind as I know Synthetic has its place and many fans but I will only go semi synthetic in my m8 Harley and never full and may should have stayed 100% Mineral as that Bel-Ray mineral is very special stuff.

I do not do extended fluid changes, I at a minimum have always done and always will do 2x oil changes per year Spring and Fall and 1x a year Primary and Trans but if I ever did lots of miles I would do more fluid changes so any extended mile benefits synthetic may offer would not help me and my situation as I prefer low mile fluid changes a less noise top end V-Twin.

So this is my Harley fluid 1st hand experiences, I have done around at least 75 oil changes on a few bikes myself in the last almost 30 years!

 

[Overfill]

Bel-Ray has had many UOA/VOA come back with significant amounts of antimony. I would bet it is a Vanlube product.

 

[Bailey28]

I bought a 2007 RK 96ci with the 6 speed transmission and 15,000 miles on it. I use it for doing small circles in between orange cones. Got Lucas primary chaincase fluid in it, that gives me a consistent clutch feel.

The transmission has Redline MT90 GL4 in it. Still has the neutral to 1st gear clunk in it, cold or hot.

Like the OP, the engine oil was clean when I bought it and I have not changed it yet. The engine runs pretty quiet compared to other Harley's I have ridden. I want to try the Mystic semi synthetic 15w-50 in the engine the next oil change. 2 gallon jug at Rural King is $40.

***I replaced the front motor mount and did notice that the new mount made a noticeable difference in how smooth the bike shifts while moving, especially going into 4th gear***

 

[loneryder]

I have been using M1 15w50 in my old Dyna Wide Glide since I have owned it. When it come to the trans and primary I used Red Line's products for sometime and they just have not been impressing me. My shifts are hard, finding neutral is a pain. I also find that the Red Line seems to sludge up in the bottom. I also killed a rear end in a truck using Red Line Lightweight Shockproof gear oil, which according to my mechanic the fluid just didn't seem to be getting to where it needed to be.

I have since been moving all of my gear oil needs over to Mystik JT7 that I can get easy and cheap at a local store. The Harley seems to like it in the gear box, but I hear those like anything. I swapped the primary over to some 5w40 T6 I had that was wet clutch compatible from the Red Line Primary lube I was running and it has made a huge difference so far. Shifts are way softer especially when cold and finding neutral has been easier.

This has made me think about looking at the other lubes I have been using. I use Valvoline Blue 5w40 in my old 7.3 and it seems to like it. I then decided to try the 5w40 in my side by side and the initial cold start valve tick on that Polaris 900 motor has been better since then. Then I was thinking, if I just cut my lawn mower and Harley over to this Valvoline Blue 5w40 I only need to buy 1 jug of oil for all of my engines. Is a 40 weight too light for the air cooled TC88? I can't imagine it sees much more extreme pressures then the old 7.3 right?

That's odd. I got the smoothest shifting with the Red Line Shockproof in the tranny. In more than one Harley.

 

[repairman54]

I'm using the Heavy shockproof not the lighter MT90. Zero issues hot or cold.