Bardman

I didn't really have any intentions of modding this car, but the comments about long gears have got me thinking. What is actually involved in changing the ratios? I assume the work could be pretty localised (ie change some components in the gear box and no ecu or other changes required).

Is it a simple job or somewhat more involved? Bgb made some comments about changing ratios somewhere earlier, care to chime in?

Of course I will try the car myself before considering any change, but I am curious as to what's involved.

jphughan

First and second gear aren't feasible to change since they're on the very expensive mainshaft. The others might be, but GTGears said that it might not be cost-effective to offer them until these cars have been out for a while and owners get the mod itch. Even then, however, I seem to recall the expected cost being around $5K, not sure if that includes labor.

But as for ECU changes, you would probably break the automatic rev-match feature since the revs the ECU thinks are appropriate for your target gear won't be. Unless somebody manages to crack the ECU encryption, which from what I understand has gotten unbelievably strong in recent years across the industry, then you'd probably have to put up breaking that feature of the car.

I'd suggest contacting GTGears about this, since he's been the most active poster on this subject.

As for me, I'm predicting that the gears being long will depend entirely on what you're used to. For people coming from a GT3RS, sure they might be short. I'm coming from an E92 M3, and even though the top speeds of my gears are lower than the GT4's, my power to weight ratio isn't as good, so this car still may accelerate faster than I'm used to. I may well have to adapt my shifting strategy at certain tracks, but I think I'll live.

mgerber

Agreed with jphughan per the above in that checking with both BGB and Matt Monson at Guard (GTGears) are the things to do.

You have probably seen this thread, but in case not : https://rennlist.com/forums/gt4/8594...rbox-mods.html. There are relevant and interesting comments here about the economic viability of new 1st and 2nd gears, and a new mainshaft for this car. I won't comment on the "simplicity" of regearing a trans given the various skill sets of the folks on this forum, but I will say that the only folks I would let touch my trans are ones that are experts in this type of work and have been doing it for many years.

I do have a regeared trans in my 993 that has a new mainshaft, 5 new to me ratios (as we kept one stock ratio) and clubsport LSD from Guard. It was a pricey mod but for me worth it. Per Matt's comments in the thread I will see how the GT4 drives before concluding it needs a regear. Will be interesting to see what others think as we get more of them on the roads.

Matt G

supercup

You should figure $1,500 +/- for labor (althought might be more to drop the Cayman motor than the 911) and $900-$1,000 per gear (3,4,5 & 6). So $5,000 to $6,000 should be a reasanable range, but you probaby could change out 3,4 and 5 and use stock 5th for 6th. But it may not be worth the cost unless you are strictly going to track the car where you are trying to squeze every last second out of it.

I would get it, drive it and take it to the track, when you can't squeze any more time out of it stock, then mod the gears to gain the extra edge!

My guess is a PCA race class will evolve and it will require stock gearing and motor to keep a level playing field.

GrantG

deleted

GTgears

We've been making these gears for a year now. This gearbox is not new. We have 5 kits, three that change 3-6 and two for de guys that is 3-5. We've destined them for various top speeds. 5&6 are not interchangeable like a g50. You leave the stock 6th for hwy cruising. Gearbox comes out without removing engine. It is not an easy gearbox to work on. It is a pita and no service parts sold through Porsche. Gears are over $1k each.

Have a happy 4th.

Accel Junky

Seems to me that 2nd gear is going to be the most noticeable gear in need of changing. This whole gearing scenario reminds me of the early NSX U.S. gearing. Ridiculously tall 2nd gear.

Couldnt we just change the final drive at the expense of highway cruising efficiency?

jphughan

Yes, but that doesn't allow you to change the spacing between individual gears, so that's a much more heavy-handed approach. For example, if there's a 2500 RPM drop between one gear and the next one up, that won't change, whereas changing individual gears allows you to change the spacing between gears to preserve things like highway cruising, a usable 1st gear, and where you end up in the power after shifts. This was discussed in more detail in some other thread around here.

ShakeNBake

Anyone know what the GT4 gear ratios and final drive are?

mgerber

Specs attached.

supercup

Thanks for the info!

GTgears

Click the link and read the previous discussion. I answered the final drive question in detail.

ExMB

Ahem, you forgot the link I think in your post unless you are referring to the link provided by mgerber's post.

GTgears

Yes, the link already present in this thread.

Chris from Cali

I'm local to you guys (well sort of, Arvada) - I need to swing by when I pick up my car...