Yea or Nea - redline friction modifiers in the gearbox?

Capacity is 3.5 Litres give or take - you'll need 4 bottles regardless.

I'd recommend no modifier for at least a fortnight or 500 miles whichever takes longer. It can take at least that length of time for any diff chatter to disappear.

I don't think modifier is the correct treatment for a sticky 2nd gear. I presume your're talking about a cold box? If so and if it's fine once it warms up I'd say just accept it as character. If it happens all the time you probably need to accept it or have the box stripped and repaired.

The modifier is designed to introduce a certain amount of slip of the diff clutches and in doing so it will probably make selection of gears slightly less slick not more.

I think Brian Crall used to say that most (like 80%+) of the cars he used this oil in did not need the modifier.

 

Do not do this. Trust me. Been there, done that. If you add friction modifier in with straight Redline oil, the chatter will go away, but the car will be difficult to shift and the bushing will eventually fail again.

Use Redline lightweight shockproof gear oil. It has friction modifier in it, but it comes that way from Redline. This stuff is phenomenal. My chatter went away completely and the car has never shifted better!

 

Absolutely not, that stuff is "snake oil." If it was any good, the major manufacturers:
Shell, Chevron, Exxon/Mobil would be doing it.

 

It sounds like you may have a cracked shifter bushing - it's a relatively common problem and can cause the symptoms you describe, particularly the lock-out at high rpm. If replacing the bushing doesn't sort it I'd move on to check/reset the linkage as you mention.

Your research as regards the modifier seems pretty comprehensive and on the money. Well done.

 

A month or so ago I preemptively ordered the Hill bushing to install in my car. Sure enough the factory bushing was cracked in two when I got it apart to install. The shifter immediately felt more precise and 'rifle bolt' like. Night and day difference.

A week or so later I changed my gearbox oil with the Redline 75W/90NS. A relatively simple procedure and should take around 2 hours if you're handy. I purchased 4 quarts but was only able to re-fill with 2.7 or so before the level was near the max line. So I currently have a spare bottle in the garage and if I were to do it again I'd only order 3 bottles knowing that's about all you're going to get out of the gearbox. 3.5 liters is the factory 'dry' fill. The fluid worked great though although I must say I can't discern a noticeable difference from the two year old fluid that was in there. I've never (before or after) had any chatter or oddities however.

Just my recent experience on my 25k mile F430.