FL5 Transmission Fluid recommendation

[Spart]

My understanding is that GL5 will damage bronze parts

"Using GL5 gear oil, which is typically intended for differentials, could harm the transmission, especially if it has parts sensitive to the additives in GL5, such as synchronizers or other internal components."

Yes, don't consider a GL-5 in any weight for this or nearly any other manual transmission. They usually contain sulfur-phosphorus extreme pressure (EP) additive, which is great for a hypoid gear in a ring/pinion differential. Our cars on the other hand, being FWD only, do not have hypoid gears in the diff and thus have no need for the EP additive. Additionally (and most concerningly) that additive is corrosive to the yellow metals in your synchros, and possibly also shift forks, bushings, and thrust bearings depending on the particular trans.

GL-5 is what I put in the front and rear diffs of my Tacoma. The gearbox gets a separate GL-4 fluid, even though it's similar in viscosity to the diff fluid and I could save a few bucks by consolidating consumables.

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[Another Motorist]

Anyone run redline fluid in fl5?

 

[AspecR]

Anyone run redline fluid in fl5?

Yes, I run Redline MT-90 GL4 in my car. If your car is stock then use the MT-80. I only use the 90 because my car has full bolt-ons including a bigger turbo so it helps in absorbing some of the extra stress the drivetrain would experience.

It helped reduce some of that 1-2 notchiness, felt more slick going through each gear as well. The improvement could be felt immediately.

 

[Spart]

If your car is stock then use the MT-80.

Did you mean Redline MTL? (75W80)

MT-80 isn't a thing. MT-85 is.

Redline MT-LV or Redline MTL would be in the correct/adjacent viscosity range to the OEM Honda MTL, MT-85 is higher viscosity than OEM by a good amount. See my post on page 3.

 

[AspecR]

Did you mean Redline MTL? (75W80)

MT-80 isn't a thing. MT-85 is.

Redline MT-LV or Redline MTL would be in the correct/adjacent viscosity range to the OEM Honda MTL, MT-85 is higher viscosity than OEM by a good amount. See my post on page 3.

My bad, MTL is correct. I'm so used to MT90 I forgot MT80 isn't a thing and MTL is OE equivalent

 

[Ktrw]

I'm running Redline MTL as well, and it's doing great. Maybe a bit smoother getting into 2nd gear compared to the factory fluid, but not a huge difference. I just really wanted to get fresh fluid in the trans after everything had broken in.

I will say when the car was brand new everything felt a bit more notchy and I had a few 2nd gear grinding issues that were completely random. After a few thousand miles everything felt much better, so it wasn't really going to fix a problem since I wasn't having any.

 

[Spart]

I'm running Redline MTL as well, and it's doing great. Maybe a bit smoother getting into 2nd gear compared to the factory fluid, but not a huge difference. I just really wanted to get fresh fluid in the trans after everything had broken in.

I will say when the car was brand new everything felt a bit more notchy and I had a few 2nd gear grinding issues that were completely random. After a few thousand miles everything felt much better, so it wasn't really going to fix a problem since I wasn't having any.

I'm considering doing an A/B test with Redline MTL and AC Delco 10-4014.

My main gripe with the OE fluid is that the synchros don't feel smooth. It feels like they're working harder than they should, making the shift effort higher than it should be. I do not have any grind issues.

 

[zumbooruk]

Amazon dropped price to $16.19/qt with subscribe and save $17.99 without

ACDelco GM Original Equipment 10-4014 Friction Modified Synchromesh Transmission Fluid, 1 qt

https://www.amazon.com/ACDelco-10-4014-Friction-Synchromesh-Transmission/dp/B0026JK8FK/

 

[zumbooruk]

yet another Amazon sale $15.29/qt with subscribe and save, $16.99 without

https://www.amazon.com/ACDelco-10-4014-Friction-Synchromesh-Transmission/dp/B0026JK8FK/

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