Opinion on trans gearing

[herman maire]

I am looking at a supposedly motorsport trans, it has the 8/32 ring and pinion and all steel syncros.

1st- 13/41
2nd- 16/36
3rd- 20/34
4th- 21/28
5th- 25/29
6th- 33/44

Any help appreciated since I dont know how to make a gear chart. What is a trans like this worth? Is it much better than the 98 G50/20 unit I already have?

It seems 1st and 2nd will be VERY short.

[Bill Verburg]

double check 5 & 6, there is something hinkey about them, especially 6

yes, it seems very short

[herman maire]

Thanks Bill,

I will check 5&6 again.

whats your opinion on the rest of the gearing? Is it usable on the street ? what speeds would 1st and 2nd achieve

[herman maire]

I searched the archives and found some pretty good info

http://forums.pelicanparts.com/showthread.php?t=276073&highlight=transmission+gearing&page=2

[Bill Verburg]

Originally Posted by herman maire

Thanks Bill,

I will check 5&6 again.

whats your opinion on the rest of the gearing? Is it usable on the street ? what speeds would 1st and 2nd achieve

ignoring 5 & 6

this is JMO, the /20 is too short in 1 and too long in 6

w/ revs and tires the same for all
the box you are looking at 1>4 only is
39 62 82 100

my /30 is(I wouldn't go shorter than this)
46 72 95 119


a /32 is
46 72 95 116

a /20 is
38 71 103 129

[herman maire]

They are asking $7000 and I was thinking of selling off my trans to help pay for the other unit but it seems like I am better of finding a unit with better ratios.

The trans that I am looking at, the gearing does not seem to,to bad but I dont want to be revving at 3500@75mph in 6th either.

Thanks again for your help.

[Bill Verburg]

The worst thing about the /20s is that sometime in '95 and then up they started using 1 & 2 integral w/ the main shaft, to change them you need to replace the mainshaft

While steel syncros are nice, they are awfull expensive, $7k is getting to the range where you can get a factory rebuilt /31, the /32 is much more expensive.

A reasonable alternative is to redo the /20 3 > 6
maybe something like this, again same tires and revs as above for comparison
1 11:42 stock ~38mph
2 21:43 stock ~71mph
3 20:31 ~93mph
4 24:30 ~116mph
5 32:33 ~140mph
6 30:26 ~167mph

[Geary]

Herman,

It looks like the trans you are contemplating has:

1) a Motorsports (tall) 3.154 1st
2) familiar aftermarket close-ratio 2nd - 5th gears
3) an unfamiliar tall 6th for highway cruising (but with the numbers reversed)

[Bill Verburg]

What makes the trans unusually short is the 8:32 cwp
compared to a motorsports gearbox it is 16% - 17% shorter

[Geary]

True ... it's got quite close 2nd-5th gears. But all Motorsports boxes utilize the 8:32, and 1st still comes out to be a tad taller than the original 1st in the G50/20. What car (type & purpose) are you thinking of installing this into, Herman?

[Bill Verburg]

Originally Posted by Geary

True ... it's got quite close 2nd-5th gears. But all Motorsports boxes utilize the 8:32, and 1st still comes out to be a tad taller than the original 1st in the G50/20. What car (type & purpose) are you thinking of installing this into, Herman?

/30, /31, /32 all come w/ 9:31

[Geary]

Yes, I'm thinking of all the late model Motorsports boxes for early GT3R onward. The 3.154 was considered too tall with the 9:31 R&P and race tires.

The 3.154 x 4.000 equivalent with 3.444 R&P would be 3.66 (original is 3.81). 3.65 is considered by Rothsport to be the perfect replacement 1st gear ratio for street 993s using the G50/20 ... a ratio to be made later this year.

[Bill Verburg]

Just for comparison
My /30 which seems just about perfect for a lightly modded 3.8RS


The g50, Herman is interested in for his stockish 3.6


If his rev limit were 8k, it would make more sense

[Geary]

Definitely not a good choice for a street 993. The original owner probably had a street legal race car, and ruled his favorite short course.

[herman maire]

Thank you both for the info and opinions.

Bill, the graphs are great... I really, really appreciate it. Just a update, I spoke with the seller today and the trans comes from a 1999 Gt3 cup car/factory motorsport, the only year with the shifter rod before the cable shifter.

He says all the gear ratios are accurate but 5th and 6th still concerns me, seems like a strange gear sets.

The sellers final price is $5700. What do you guys think? Is it better to work with this trans ( all steel syncros) than my stock /20 . My REV limit is not 8000 but even at 6800 the gearing does not look to bad to me ( I have never driven a moded trans). It seems usable but I could be very wrong.

1st-39.4mph
2- 55.3
3-73.2
4-93.3
5-107.3
6-165.9

I also plan to turbo my car so I assume this Gt3 trans gearing would be even worse.

So for my street/ few track days a year 993 would you buy the cup car trans or just stick with the stock /20 unit for a while. I really want to start driving this thing in a few weeks.

How bad are the brass stock syncros? Do the steel syncros change the feel of the gear shift?

Sorry for all the questions.

Thanks again

[herman maire]

The seller just called me and all the ratios he gave me are wrong.
Bill, Can I bother you for another gear graph? I can paypal a fee if you like.

1-13/41
2-20/40
3-25/39
4-29/36
5-32/33
6-35/30

Now 4th and 5th seem strange no?

[Bill Verburg]

I think it's a pretty nice trans(very similar to my g50/30), for n/a 993 dual purpose car, as long as it's got a 9:31. W/ an 8:31 it's still going to be extremely short(~145 at the top of 6) for a dual purpose trans.



the turbo guys seem to like taller & fewer gears.

steel vs brass maybe a litlle crisper, hard to say comparing new to old.

$5700 outright is a great price if it's in good condition w/ all the motorsports parts and still has the motorsports 40/60 lsd also in good condition.

Just as an issue of interest to me what is the designation of the trans?

G96/92 used in '02 Cups have the same gearing also w/ an 8:32, i'm curious if it's the same trans.

here it is w/ the 8:32

[Tom W]

Just a second opinion to reinforce what Bill is telling you - it's very short. I have a G50/32 that I ran for the first time a week ago. It is much better than the G50/05 it replaced but I would never want shorter.

Bill: I think you had a typo above, the G50/3x final drive is 9:31 (3.444), not 9:32 (3.555) according to my shop manuals.

[Bill Verburg]

Originally Posted by Tom W

Bill: I think you had a typo above, the G50/3x final drive is 9:31 (3.444), not 9:32 (3.555) according to my shop manuals.

Thanks Tom, I just amended it

BTW did you sell the /32 lsd yet? If not I have a proposal for you

[Tom W]

Bill: No. Send me a PM with your email address. I had been hoping to sell the LSD with the old transmission, but neither has sold yet.