mikeb7

It looks to me that all of these Porsche boxes shown above are what the world calls "close ratio".

Generally, anything with a 1:1 5th gear (or 4th if a 4spd) is referred to as a close ratio box, differentiating it from an overdrive box where 5th is 0.85:1 or the like (and the ratios accordingly more widely spaced).

Without an available overdrive box, the point of calling it "close ratio" gets a little lost, other than for the purpose of sounding good in sales brochures.

Landseer

Here are the 85/6 and later ratios.

Again, a difference with the Euro car transmissions compared to USA.

(now at least we have some data archived in this thread)

svp928

Back in the old days, overdrives were just that- overdrive....I had a close-ratio 4spd in Chevelle with a 2:20 first gear, the std 4spd was about a 3:0, so that made it "close ratio".
Notice the diff in the layshaft ratio- this makes a noticeable difference..

mikeb7

True, with the old Muncie's there was the M20 wide ratio and the M21/22 close ratio. Thought the wide ratio first gear was only about 2.5:1, verses 2.2:1 on the close ratio, though.

But back to Getrags....it does look from the various charts above that there was a tendency for the ROW cars to have slightly closer ratios, although in some cases on earlier cars the ROW boxes were also available here in other years. I didn't see the ratios for the earliest (28.03) boxes.

mark kibort

Steve, they dont matter at all after they are multiplied by the other gears. The end ratio is ALL that matters. THAT determines the closeness of the ratios.

For anyone playing around, the best way to look at ratios is just to look at redline MPH in each gear. I posted what I feel is also important, the closeness of the gears via percentage RPM drop, and the actual resultant ratios.

Almost ALL 928s have the same closeness in their gear ratios. the biggest difference is really only in the respective 5th gears (which we as racers could careless about, because most tracks never allow us to use them)

mark kibort

actually, the chevy corvette has near the same "closesness" as our 928s. I did the comparison a long time ago. But, in the end, it has a 1:1 in 4th and 5th and 5th are overdrive. anyway, close ratio gear box means, closer ratios than are normally found. the only close ratio cars I know of are the GT3 and GT3 cup cars, where those ration drop the RPM by 80 to 85% vs our and the world near standard of 70 to 75% as in our cars as well.

mk

mark kibort

Didnt I not only give the raw data as the manuals provide, but multiplied them all out for you to show the REAL difference for comparison??

Landseer

Yes, I knew you were going to fire back with that. You did !!!!

But we didn't have the model years and the transmissions straight --- for instance the -07 being a USA....

And this is a very different feeling box, by the way.

mark kibort

And why wouldnt I fire back with that???

They are all the same gear spacing as shown by the DATA below.
They are not going to "Feel" any difference, especially when comparing a -07 to a -05. what are you really feeling in reality?????? you can feel a 4-5% differnce in 1st and 2nd gear? 45 to 47mph redine differences??? com'mon, who are we kidding here. I guarantee, I could make a MUCH bigger change that NOONE would be able to notice on my car. (i.e. 6% change in tire size for example)

EVERYONE, since we are getting in th weeds with perception and values, why dont we do all of ourselves a favor. when comparing gear boxes, just quote the redline MPH in each gear. The, anyone can join in and make comments about the reality of the comparisons.
(e.g. S4 2.2 = 55mph, 80mph, 118mph, 155mph, and 226mph for 1st through 5th)

>>>>>>>>

The 05 (euro 2.72) , the 07 (US 2.72) and the 08 (US 2.2) all have near IDENTICAL gear rations and near identical gear spacing. The ONLY difference is a very slight difference between the 05s shift from 2nd to 3rd, but all other shifts are identical as far as spacing (excluding 5th)
(i.e. for the euro (-05) box:
66% drop for 1st to 2nd
75% drop for 2nd to 3rd,
74% drop for 3rd-4th

The US 2.72 (-07)
66%
71% the only reason it is not as close, is due to the shorter gearing of 1st/2nd
75%. so, actualy closer ratio her than euro

the US 2.26 (-08)
66%
71%
75% also closer ratio here vs euro

More noteworthy are all the 3 above gear boxes have near the same ratios as well.

-05 (2.72 euro)
9.7
6.5
4.9
3.64

-07 (2.72 US)
10.2 (actually shorter than euro)
6.8 slightly shorter to euro.
4.86 near identical to euro
3.67 near identical to euro

-08 (2.26 US)
9.65
6.41
4.58
3.45)

S4 2.2 (and the US 85s) has a slightly taller 1st, same over all spacing, and a 4.2 3rd, and 3.2 4th, which are very close to US 2.26 by only 4% difference which is much less than when I put 305 tires vs stock diameters, so the difference is VERY slight)

8.9 1st
5.9 2nd 66%
4.2 3rd 71%
3.2 4th 76%

mikeb7

I think we're on the same page, Mark.

I guess my over arching point was that, "close ratio" being a rather vague term, it's therefore only useful as a relative one. If there is no wide ratio, overdrive, or other box to differentiate from, calling it "close ratio" doesn't mean much. Or as you said, "close ratio gear box means, closer ratios than are normally found." And since the gear ratios in all the boxes available don't differ by much...

It seemed like people were chasing their tails trying to figure out which boxes were the close ratio boxes, and the answer is either that they all are or that none of them are, depending on how you want to look at it.

Landseer

Nobody is chasing tails here.

We have an original poster that needs a gearbox and TT.

So this entire discussion will provide him, and others later, the comparison framework.

That includes the discussion about the acceleration feel of the boxes, which is rounded out nicely by Mark's descriptions --- basically saying no difference should be seen, even taking into account the layshafts. Whether everybody agrees or not, at least the points are on the table.

I think then, the differences I feel may be a result of the very different engine poweriing this -07 box, not the gearboxes per se. Will you give me that one, Mark? USA 84 @ 220HP ish vs Euro 84 (with mods)

mark kibort

Of course Ill give you that one! you are talking two differnent power plants!

Like I said, the 2.75 vs 2.26 or 2.2 is not that big of deal. its different not better. Having raced them on the same track with the same power (scots vs my old 5 liter part euro one with 2.75 and one with 2.2) I can say the word is out which one is better. There is a different feel because the shift points were different, but those were very different gear boxes. (2.2 vs 2.75) The real differences are found in the acutal ratios.

The interesting thing about the gear ratios, is that the desired ratios will change based on the use and power you have and then eventually come back as you go up in power. Its a moving target with no one correct answer for all instances.

RPetty

This is fun.

Hard to understand at times, but fun.

I'm learning a lot!

Thanks

mark kibort

I think you will be fine, no matter what direction you go. The only gocha might be with rebuilding as the costs can jump pretty high depending on what they find in there.
all I can say, is it became a different car when I got my 85 gear box in my older 928.

mk

RPetty

Thank you Mark,

I value all that is posted to me.

I'll keep you posted.