It's been a while since I last posted anything on the forum, but anyways - I have an F-Type V6 manual that I use primarily (only) as a track car. It has some light mods; KW Variant 3 coilovers, Quicksilver sports exhaust, ProTrack wheels (18x9.5" in the front and 18x10" in the rear) with Nankang AR-1 tires, a swapped LSD from a V6 S, carbon fibre roof, better rotors and brake pads and an as track focused wheel setting as the F-Type chassis allows with 2 degrees camber in the front and some toe out.

Main weaknesses are the brakes (still run the 355 mm front/ 325 mm rear dimensions) and the gearbox. The brakes I will upgrade this year, but the gearbox I don't really know what to do about. When it gets hot after ~10 minutes of intensive track driving, it feels "soggy" and inprecise, and it is sometimes really difficult to get in 2nd gear when I want to accelerate out of a steep corner. As soon as it cools down, it feels "notchy" and tight again.

So; do you guys know what I can do to remedy that? I have very little knowledge of the mechanics of a manual gearbox. Is it a problem that would get addressed if I install a short shifter (like if it's related to the plastic shaft), or is it something related to the synchro rings that somehow can't take the heat and change shape ever so slightly?

Thankful for some advice.

 

If the gearbox starts feeling different when it gets hot, I'd look to the oil in it. Try changing to a high quality synthetic and see how that changes things. The short-throw shifter will reduce the distance the lever needs to move for a shift, at the expense of slightly more effort. Mostly, the extra effort is not noticeable. Again, if the feel changes with heat, look at the oil first.

 

Thanks, appreciate the advice. I've been looking around on the web without finding much information on what performance gearbox oil I can try with. In ZFs documentation for the S6-45 the only aftermarket oil they recommend is FUCHS Titan FFL-3. How do I know what will work? I need something that can handle a bit of heat.

Again, grateful for some guidance.

 

I got some Red Line DCTF but haven't put it in yet. I got that because I have had good experience with Red Line and they supported the racing I used to do. They claim that's compatible with BMW MTF-LT-5. From ZF:I expect Red Line is not readily available where you are, but look for the BMW MTF-LT-5 spec.

 

Ah, thanks, got it. Will do precisely that! 👍

 

Just to confirm, when you are in a tight turn and the g's are loaded up, you find it hard to get into some gears?

The reason I ask this is that it could be the transmission tunnel flexing a bit under corner loads. In my S2000 race car, it has a similar challenge where on racing slicks, the g's in corner twist the transmission so getting into gear sometimes can be difficult without the transmission being "in place". You can look at transmission braces. Likely there isn't one specifically for the F-Type but it's basically a piece of stiff metal that attaches to the transmission and the chassis.

 

Hmm OK this is really good input. Thanks, appreciate it. Will see what I can do about that - maybe I can go to one of the race workshops we have in Stockholm and get them to custom build something.

 

I hadn't thought of the chassis winding up enough to cause shifting trouble but mostly because you talked of heat, and tired oil was the first thing that came to mind. The first symptom I'd expect as your gearbox oil is at the end of its service life is difficulty shifting. It's worth changing anyway just so you know that fresh, quality oil is in there. If it solves the problem on its own, great.

 

When I drove manual trans cars (every car I have ever owned other than the last three, all Jags!) it was a well known "cheat fix" for poor shifting to replace the manual trans fluid with auto trans fluid. Might work on the F-Type manual 'box, might not.
Another thing which worked well for me was the gearbox additive Nulon G70, see here: https://www.ebay.com/sch/i.html?_fro...70&_sacat=6000
A good ol' Aussie product!

 

In the UK, sawdust was the additive of choice by dodgy car dealers!

 

You might need to take a good look at your transmission mounts? They may be weak and allowing the transmission to lean over while accelerating and cornering hard, making it hard to shift? I'm not sure if anyone makes stiffer trans mounts for the F Type or maybe you just need new ones.
I have a BMW M Roadster and the OEM Trans mounts on those are way to soft and make shifting almost impossible while accelerating and cornering hard. Putting in reinforce trans mounts cured the problem.
This is along the same line as jlsthlm is talking, but simply stiffening up the trans mounts instead up putting in a hard brace. I think a hard brace could lead to other problems and a lot of vibrations unless this strictly a race car?

 

In general, all of the driveline mounts are going to allow flex. For street cars, they are typically soft mounts all through the driveline (including engine) to reduce vibrations into the chassis. Yes, you can change all of the mounts to be solid (my race car has solid mounts throughout), but it does introduce vibrations and a lot of vibrations into the chassis. If the car is purely a track car, probably not an issue but not going to be an option for a dual purpose car.

 

Thanks all for the good input. I will both change oil and look at how I can stiffen up the transmission mounting or installing bracers. I'll let you know if anything changes... this year's season is over now though, so I'll feedback in spring of 2024!