Redline D4 ATF

[Scaroline]

Has anyone used redline D4 ATF for the manual transmission in the blackwings? I'm considering this for using the car in a cold climate to eliminate the notchy shifting. I don't plan on taking it to the track at all.

 

[BKC1]

First and foremost, notchy shifting is not caused by transmission fluid. It's caused by two things:

1. Failure to get the clutch pedal all the way down, especially on the 1-2 shift.
2. Air in the hydraulic system.

The 1-2 shift technique is hard to perfect, partially because the 1-2 shift is the first "real" shift you do with the car in motion. When you're accelerating hard, the 1-2 shift is the hardest to perform properly, because you're being thrown backwards and forwards by the G-forces while concentrating on driving.

The GM hydraulic system specs provide very little margin between the amount of fluid volume that a 3/4" diameter master cylinder can provide at full travel, and the amount of fluid that the slave cylinder requires to fully disengage the clutch. That's why all my V's get 13/16" masters, which move more volume at the cost of higher pedal effort. Not only can I be sloppier in my clutch pedal, I can go longer periods of time between bleeding.

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Secondly, better transmission fluid can improve the effectiveness of the synchros, allowing you to shift faster. But if you fail to get the pedal down, even with better fluid, you're still going to feel the crunch, because the crunch is caused by slamming the sleeve into the blocker ring / engagement teeth (see figure below) while one side is still being driven.

In the linked video, I skipped to the point where the sleeve engages with the blocker, which exerts force on the synchro. If the amount of force is excessive, you perceive the shift as "notchy." If you forcefully ram the gears together despite this resistance, it's called "crunchy" because you just forced the tips of the teeth together.

Another thing that you're probably not thinking about is the effect that the inertia of the clutch has on the synchro effort. The LF4 clutch has a MMOI of 41.02 lb-ft^2. That's a huge number. When changing gears, the synchro has to fight that inertia (assuming that the clutch is fully disengaged)--if not, the synchro is fighting some or all of the engine's inertia too.

By contrast, the Tilton ST-246 w/steel flywheel and a LS7 clutch w/Fidanza aluminum flywheel (which are considered medium weight clutches) have a MMOI of 24.80 and 24.60 respectively (60% of OEM). You will not believe how much faster the engine revs with these clutches, or how easy it is to put the car into gear. I'm working to fabricate custom LF4 flywheels for the Tilton ST-246, so if anyone's interested, let me know.

 

[Scaroline]

First and foremost, notchy shifting is NOT caused by transmission fluid. It's caused by two things:

1. Failure to get the clutch pedal all the way down, especially on the 1-2 shift where you're getting thrown back and forwards in your seat.
2. Air in the hydraulic system.

If you look at the GM hydraulic system specs, there is barely any margin in the amount of volume that a 3/4" diameter master cylinder has to generate the travel in the slave cylinder necessary to fully disengage the clutch. That's why all my V's eventually get 13/16" masters, which move more volume at the cost of higher pedal effort. Not only can I be sloppier in my clutch pedal actuation, I can go longer periods between bleeds.

Not sure if "notchy" is the right word (english is not my first language). I meant that the transmission doesn't go into 2nd very easily. The issue is more apparent when its colder however its never really "buttery" smooth even when warm unless I upshift above 3500 rpm or downshift so the revs in second are above 3000 rpm. I do make sure to push the clutch all the way down and have never developed the habit of pressing it partially and changing gears.

 

[BKC1]

Not sure if "notchy" is the right word (english is not my first language). I meant that the transmission doesn't go into 2nd very easily. The issue is more apparent when its colder however its never really "buttery" smooth even when warm unless I upshift above 3500 rpm or downshift so the revs in second are above 3000 rpm. I do make sure to push the clutch all the way down and have never developed the habit of pressing it partially and changing gears.

The two most common terms are "notchy" and "crunchy." On the internet, many people are imprecise with their word choice, but it's also common for both things to happen at the same time, because they're rooted in the same cause.

Let's get a couple of things out of the way:

• If you're having problems shifting 1-2, it's probably your technique.
• If you're having problems shifting into first or reverse, your clutch probably needs to be bled.

I never jump to the conclusion that the owner is blameless. Most people think they're above-average drivers and won't consider the possibility that they need to work on fundamentals. But, if you've bled your clutch and you're sure your foot is getting all the way to the floor when you shift, then it's time to start looking for mechanical causes.

Let's briefly talk about when it's normal to look for mechanical problems. If you have a new car (less than 30k miles), barring a once-in-a-million screwup on the dealer end, you should NOT be having any mechanical problems. If there are problems that soon, you should look at yourself first and foremost, then if you can't find a problem with yourself, have the dealer look at the car. Most people get to 60-80k miles before they change fluids.

I recommend changing the transmission fluid in the first 10k miles (to get rid of the break-in debris), and thereafter every 5 years or every 30-50k miles depending on how hard you drive. When the fluid gets old or worn out, there's a number of things that happen to it including the anti-foaming additives no longer working. When those additives break down your oil is done and your transmission won't be far behind. This goes for the differential as well.

If you want to improve the capability of the synchros use 3 qts D4 ATF + 1 qt 75W80 MTL. Start with the ATF and add the MTL second--you will only get about 0.5 qt of MTL in before the fluid reaches the fill hole. Drive the car for several days. If that isn't responsive enough, increase the ratio to 1 quart MTL.

You can use the remainder of the 1 qt bottle to do achieve a 0.8 qt ratio if you carefully measure what you have left in the MTL bottle and drain that amount out of the transmission before adding the remainder of the MTL. Do not use straight ATF of any brand (Mobil 1 ATF, Royal Purple, Redline, AMSOIL, despite all claiming Dextron III compatibility they all shift worse than OEM fluid and make the transmission sound like a rock grinder).

Overall, do your research and don't trust the advice of strangers, including me. In support of myself, I have almost 15 years daily-driving (including in sub-zero temps) and racing T-56 and TR-6060s with various oils, including OEM Dextron III, Mobil 1 ATF, Royal Purple Synchromax, and D4 ATF + MTL. I am a challenging person to work with, I question everything, and I'm anal about maintenance. I invested a lot of time and money to learn these lessons, and I'm hoping that someone else can benefit from them.

 

[Scaroline]

The two most common terms are "notchy" and "crunchy." On the internet, people are imprecise with their word choice, but it's also common for both things to happen at the same time, because they're rooted in the same cause.

• If the clutch is partially disengaged when you shift, the synchros have to work harder than normal, resulting in notchy shifting and possibly a crunch if you're manhandling the shifter.

Let's get a couple of things out of the way:

• If you're having problems shifting 1-2, it's probably your technique.
• If you're having problems shifting into first or reverse, your clutch probably needs to be bled.

Most people think they're above average drivers and won't consider the possibility that they need to work on their fundamentals. If you've bled your clutch and you're sure your foot is getting all the way to the floor when you shift, then it's time to start looking at mechanical root causes.

Even if you say you've bled the clutch, it's still #1 on my list of suspects, because most people don't know how to properly bleed, and I've fielded tons of phone calls over the years from people that were bleeding incorrectly. Once I corrected their technique the problem went away.

That being said, if you want to improve the capability of the synchros use 3 qts D4 ATF + 1 qt 75W80 MTL (start with ATF, and add MTL second--you will only get about 0.5 qt of MTL in before the fluid reaches the fill hole). Do not use straight ATF of any brand (Mobil 1 ATF, Valvoline, Redline, and AMSOIL, despite all claiming Dextron III compatibility they all shift much worse than OEM fluid and make the transmission sound like a rock grinder).

My recommendation: use OEM for daily-driven, D4 ATF + MTL for daily/street/track, and HP-MTF if you're circuit racing.

I only have a problem going into 2nd (upshift and downshift). Sometimes it only goes into 1st halfway but I nudged it a little harder than usual and it seems fine. All others seem relatively fine, albeit I have not shifting extremely fast. I have not bled the clutch since I was under the impression that it only needed to be done later on after driving many miles. The car has currently has about 1250 miles.

 

[BKC1]

I only have a problem going into 2nd (upshift and downshift). Sometimes it only goes into 1st halfway but I nudged it a little harder than usual and it seems fine. All others seem relatively fine, albeit I have not shifting extremely fast. I have not bled the clutch since I was under the impression that it only needed to be done later on after driving many miles. The car has currently has about 1250 miles.

Is this your first car, or first car with a T-56 or TR-6060? If so, it's probably your shifting technique and/or the normal amount of effort required to shift into 2nd.

If you want to make it easier, better oil and a lighter clutch will both help. The clutch will change it a lot more than the oil will.

 

[Scaroline]

Is this your first car, or first car with a T-56 or TR-6060? If so, it's probably your shifting technique and/or the normal amount of effort required to shift into 2nd.

If you want to make it easier, better oil and a lighter clutch will both help. The clutch will change it a lot more than the oil will.

This is my first tr6060. I have driven other manuals that were easier to engage gears in albeit they were not track oriented cars like the blackwings. Maybe I just need to be a bit more aggressive into 2nd.

 

[Super Saloon]

A “notchy” or more difficult 1-2 shift is common feedback on this platform, and something I have experienced as well.

For me personally, my issue got better after my car got broken in and it’s much better when the car is warmed up. It’s also improved as the weather has gotten warmer.

While I appreciate that BKC1 has far more technical knowledge than I do about the trans, I don’t know that this is “user error” given the collective feedback and experiences of others with this same issue.

I can’t answer the OPs original question, but wanted to call out that this is common feedback. I have been driving manual for 17 years and the 1-2 shift has been more noticeable on this platform than any other manual vehicle I have owned. All other gears shift extremely mechanical and smooth, and again the issue goes away once the trans is warmed up.

 

[rubberduck]

I have had zero issues with my 6060 in 1.5+ years with my 5BW. No 1-2 lack of smoothness and never popped out of any gear. I attribute this to living in a warm climate and driving my Jeep that has a horrible 6-spd; very long throw, vague gates, so one needs to be very deliberate about shifting. Also I’m convinced that there is a lot of variation in the 6060 likely due to assembly and/or slight tolerance issues on the internals.

Want to learn how to get very good with an MT, drive an old IH pickup.

 

[jddrake]

A “notchy” or more difficult 1-2 shift is common feedback on this platform, and something I have experienced as well.

For me personally, my issue got better after my car got broken in and it’s much better when the car is warmed up. It’s also improved as the weather has gotten warmer.

While I appreciate that BKC1 has far more technical knowledge than I do about the trans, I don’t know that this is “user error” given the collective feedback and experiences of others with this same issue.

I can’t answer the OPs original question, but wanted to call out that this is common feedback. I have been driving manual for 17 years and the 1-2 shift has been more noticeable on this platform than any other manual vehicle I have owned. All other gears shift extremely mechanical and smooth, and again the issue goes away once the trans is warmed up.

I have just over 8k miles on my 4 BW (purchased April 2023 and live in NJ) and have experienced the 1st -2nd shift symptoms discussed here since the beginning. It is most pronounced with the 1st shift out of the driveway and improves from there. In sub 30's weather, the 1st shift can sometimes be an outright struggle to get into 2nd. In warmer weather it is minimal to unnoticeable. I have asked the dealership to assess twice but both times they said no issues noticed. Though I don't believe they've driven it from a true cold conditions scenario.

 

[minn19]

I used Redline fluid for the same reason on my previous ZL1 1LE and I thought it made it better, especially in the cold. It didn’t completely get rid of the problem, but it was better.

 

[Champale]

OP - changing to a different transmission fluid will most likely improve your 1-2 shifts. Tremecs are notorious for exhibiting the symptoms you describe. It is not user error.

BTW I am not an 'Amsoil guy' so to speak but it has been great in my GT350R's Tremec TR3160. The stock fluid in my 5BW hasn't caused any issues for me.

 

[Rob CT4-V]

T-56's are notorious for cold shifting problems and a switch to better fluid will certainly help. I'm sure the TR-6060 is the same way, although no experience with them.