Adrian Burton - Here is an excel program that will calculate the rpm drop for any gear combination. Click here to download

901, 915, G50 normal and 993 normal gearboxes are not recommended as the crown wheel and pinion is too small and is not rated for the torque of a V8-PERIOD.

Standard (stock) gearing typically with the exception of 1st is quite usable for most applications. Here are some comparisons:

Chevrolet Corvette LS1 ’97-‘99
1st 2.66 overall 9.09
2nd 1.78 overall 6.09
3rd 1.30 overall 4.45
4th 1.00 overall 3.42
5th 0.74 overall 2.53
6th 0.50 overall 1.71
Final 3.42

Chevrolet Corvette ZR1 ’91-’93
1st 2.68 overall 9.25
2nd 1.80 overall 6.21
3rd 1.31 overall 4.52
4th 1.00 overall 3.45
5th 0.75 overall 2.59
6th 0.50 overall 1.73
Final 3.45

Ford Mustang Cobra ’93-‘96
1st 3.35 overall 10.32
2nd 1.99 overall 6.13
3rd 1.33 overall 4.10
4th 1.00 overall 3.08
5th 0.68 overall 2.09
Final 3.08

Ford Mustang Saleen S351R 1996
1st 3.27 overall 11.61
2nd 1.99 overall 7.06
3rd 1.34 overall 4.76
4th 1.00 overall 3.55
5th 0.68 overall 2.41
final 3.55

930 ’76-‘88
1st 2.25 overall 9.50
2nd 1.30 overall 5.51
3rd 0.89 overall 3.77
4th 0.63 overall 2.64
final 4.22

G50/50/52 ’89-‘94
1st 3.15 overall 10.84
2nd 1.79 overall 6.16
3rd 1.27 overall 4.37
4th 0.97 overall 3.34
5th 0.76 overall 2.61
final 3.44

G64/51 ’95-’98
1st 3.82 overall 13.14
2nd 2.15 overall 7.40
3rd 1.56 overall 5.37
4th 1.21 overall 4.16
5th 0.97 overall 3.34
6th 0.75 overall 2.58
final 3.44

G96/50 ’01-present
1st 3.82 overall 13.14
2nd 2.06 overall 7.09
3rd 1.41 overall 4.85
4th 1.12 overall 3.85
5th 0.92 overall 3.16
6th 0.75 overall 2.55
final 3.44

GT3 street car G96/90 ’99-present
1st 3.82 overall 13.14
2nd 2.15 overall 7.40
3rd 1.56 overall 5.37
4th 1.21 overall 4.16
5th 0.97 overall 3.34
6th 0.82 overall 2.82
final 3.44

*GT2/3/R/RS/CUP gearboxes came with a variety of ratios through the years. It’s more than likely a “used” gearbox will have “custom” ratios installed. If you don’t have a build history

Choosing the right gearbox:
Whether you are planning a budget or are already building a car, this is just as important of decision as choosing the right engine, suspension, tires, chassis and just about anything else you can think of. Some of the determining factors may include gearbox weight, dimension/clearance, HP/torque rating, shift linkage, personal preference (shift quality) and cost-all of which I will address.

930 4 speed:
The “early” version is approximately 120lbs dry and 1.1 inch shorter in the bell housing than the “late” version however the gear ratios were the same. Overall length is 26” for early and 27” for late. For mid-engine applications either the ring gear must be “flipped” or the gearbox must run “inverted” in which a lower center of gravity can be achieved however ground clearance may be an issue. Keep in mind the late version can be effectively shortened to early spec. The street version is rated for 300+HP while the “modified” race version is rated for 750+HP. Equipped with early type synchromesh engagement the 930 4 speed shifts much like the 901 and 915-only okay and not great. You can typically find a “builder” from $1000-$2500 but that’s just the beginning. With as old as these gearboxes are and based on our findings through the years, unless you have proof that it was recently serviced, have inspected it yourself or have had the opportunity to test drive it, by all means-rebuild the gearbox. The following list of what I call “minimum requirements” should be met:
1. Main 4 point thrust bearings
2. Synchros
3. Sliders and hubs
4. Synchro teeth (dog ring)
5. Hardware
To prepare for V8 mid-engine I recommend the following:
1. Flip ring gear or invert
2. PHII 80% LSD or PHII 3:1 torque bias differential
3. PHII heavy duty bearing retainer
4. PHII heavy duty side plate
5. PHII internal spray bar oiling system
6. PHII racing gears**
7. Tilton 12 VT electric transmission oil pump
8. PC203 flow thru cooler

**PHII racing gears are designed with low tooth counts (where permissible) to provide the thickest tooth base possible for strength while maintaining a nice quiet mesh. Heat treated and hardened to 59 to 61 RC and cut from EN36A billets our gears are upwards of 30% stronger than factory gears.

G50/50/52:
The predecessor to the 4 speed was the infamous G50/50 5 speed for 1989 only-which are getting hard to find. Now equipped with “Borg Warner” type cone synchromesh the shift quality greatly improved with this gearbox. The real bonus is that it uses the early type clutch, starter and tail housing therefore it’s shorter, the custom flywheel is cheaper and lighter, a heavy duty lightweight pressure plate and a HI Torque starter can be used-which is necessary with respect to torque required for a large displacement high compression engines.
The G50/52 produced from ’91-’94 as you would have guessed is more abundant. It used the same gear ratios as the 50/50 however the input shaft was a beefed up, the tail housing was longer and used a donut type mount, came with 20/100 LSD standard, and used a supported mount starter with a dual mass flywheel and clutch. The downside is that a heavy duty “street-able” lightweight single plate clutch and flywheel package is not available-therefore the bell housing and starter pocket must be modified to backdate the system. The tail section and shift shaft can also be backdated to keep length at a minimum.
I personally feel severe duty pressure plates require too much pedal effort and puts undue stress on both the shaft for the clutch release fork and the engine’s crankshaft. We are now offering a 7.25 inch twin disc lightweight clutch and flywheel package from Tilton Engineering to help alleviate this however it’s significantly less “street-able” as organic clutches are not yet available.
For mid-engine G50’s the ring gear cannot be moved to the opposite side so the gearbox must be inverted but that opens another can of worms. Once inverted the pinion gears are out of the oil! Without an oiling system you basically have to “overfill” the gearbox to get proper lubrication resulting in a loss of HP! Our internal oiling system will take care of this problem.
Both of these gearboxes were rated for 400+HP street cars-with the correct modifications 700+HP should not be a problem. One should be able to find a “builder” from $4500-$6500. New 50/52’s are currently available from Porsche to the tune of $13K.
Minimum requirements as follows:
1. synchros
2. main 4 point thrust bearings
3. hardware
4. gaskets
To prepare for V8 mid-engine I recommend the following:
1. steel synchros
2. PHII heavy duty shift forks
3. PHII heavy duty side plate
4. PHII motor sport LSD or 3:1 torque bias differential
5. PHII G50 internal spray bar oiling system
6. PHII racing gears**
7. inversion preparation
8. Tilton 12 VT electric transmission oil pump
9. PC203 flow thru cooler

I have checked out the Audi transaxles and I feel like I have a reasonable handle on what model years I need to look for (87+, right? because of the wider hardened 1st gear?), however there are a number of different gear and diff ratios available in the 016 case according to Brian Wolff (http://65.108.64.218/BriansCar/text1.htm). Where can I learn about gear ratio selection and stuff like that? It is something I have never really taken time to understand, but I would like to pick the best gear ratios for my torque curve. I also bought the Audi 5000 Bentley manuals with the intent of rebuilding the trans. Compared to rebuilding engines, how difficult should I expect a transmission to be? From the Bentley manual I get the impression that it shouldn't be TOO hard but I've never been inside of a tranny before.

Thanks in advance!

Portland, OR
downeygr@yahoo.com

mikeo - Posted: 04 Jul 2004 11:36 am

here's a really cool link I just found this morning...kind of like information overload though!!
http://pr0nsessd.dyndns.org/audi/Audi_01E_trans.html

tecsuo - Posted: 04 Jul 2004 03:47 pm

I have a v8 sbc and I am thinking about putting in a smaller crank and higher rating lifters. I know I will lose some torque, but I am want to push the torque curve towards the mid or higher end because I am using a 914.

Should I tune the engine to peek out each gear ratio ?
Would this give me a more extoic sound?

I am just trying to match the engine up with the tranny week points and strong areas

dB - Posted: 04 Jul 2004 05:04 pm

Hi:

So the Audi Trans Selecetion can be from the 016 series and the 01E group?

I am going need on of these in the next several weeks and I wanted to find out exactly what to order and any sources for such.

I was considering one of these:
016 Serial Number prefix 5N ..............Side Shifter
3.60 2.13 1.36 0.97 0.73 3.50 4.11 0.52

016 Serial Number prefix 3U ..............Side Shifter
3.60 1.88 1.19 0.84 0.64 3.50 3.89 0.52
1st 2nd 3rd 4th 5th rev diff speedo d

This was from Brian Wolf's documents but have not figured out what years they came from.

GaryHealy - Posted: 05 Jul 2004 07:14 am

The problem, that I see, with the Audi transaxle, is the poor selection of 1st gear ratio. A 3.5 first gear is useless in a V 8/ V 12 engine, unless you have a 2.77 ratio final drive. Now if you could come up with a 2.5 ratio first, with around a 3.9 final drive ratio, that would work. As for rebuilding a manual gearbox, sometimes you will need gear pullers and a press, to get things apart.

I will be using a Porsche 915 gearbox with : 2.4 first, 1.68 2nd, 1.26 3rd, 1.0 4th, .78 5th and 3.88 final. With this combo, shifting at 7000 RPM, the engine will drop to 5500 RPM between shifts. This is not the cheapest way to go, but there are lots of gear ratios avialable.

The 914 transaxle has around a 4.44 final drive ratio, combined with the first gear, is too low for a V 8. In the past, when we used to put small block motors into a Porsche 914, the first gear would not be used at all. We just had a 4 speed. The first gear in these trannys was the weak point also. As for engine size, I would use a 327 Chev or 302 Ford. Both are high reving engines, with the right camshaft. Keep the car weight to around 2600 pounds and hold on.

DiabloDealer - Posted: 05 Jul 2004 12:36 pm

Hi

I've been looking at transaxles as well, and as I'm in the UK I can get hold of Renault UN1 transaxles (which were used in the Lotus Espirit). There's a choice of 2 with the following gear ratios:-

UN1-13 5-speed
(3.36 1st),
(2.05 2nd),
(1.38 3rd),
(1.03 4th),
(0.82 5th),
(3.54 Reverse),
Final Drive Ratio 3.44

OR

UN1 6-speed
(2.57 1st),
(1.84 2nd),
(1.38 3rd),
(1.08 4th),
(0.92 5th),
(0.80 6th)
Final Drive Ratio 3.44

I'm planning to use a SBC with:
330bhp @ 5000RPM,
380ft.lbs Torque @ 3800RPM, and
Max.Rev.Limit @ 5500RPM.

Which of the 2 transaxles will work? I really need someone to help me and who knows their stuff on marrying up engines and transaxles and have graphs etc. to email.

I need to use brand new parts so as to get a brand new registration. If anyone knows of an Audi unit that I can just buy over the counter from an Audi dealer please tell me.

CrashRat - Posted: 05 Jul 2004 03:26 pm

Hey, thanks for all the info guys. Mike, that was another link I saw some time ago and forgot to bookmark. I'm specifically looking for something that makes all the numbers make sense though. I'd like to know why a 3.5 is too tall for a 1st gear, for example, and what the "ideal" final drive ratio should be and why. My engine has a dyno graph from when it was in the previous car that I would like to match up as best I can with the available gear ratios. Are there any decent resources out there that help explain that kind of stuff?

Gary, thanks for the insight into rebuilding the trans. It sounds like you have some experience. So long as I can use a gear puller and a shop press, and I have rebuilt a few engines, there shouldn't be much to worry about when tearing into a trans? Don't forget to give me a shout next time you're heading down here to see your family!

AdrianBurton - Posted: 06 Jul 2004 02:22 am

Crash,

I have an excel program that will calculate the rpm drop for any gear combination that you might use. I will send it to you

bpickell - Posted: 06 Jul 2004 06:15 am

[quote="CrashRat"] I'd like to know why a 3.5 is too tall for a 1st gear, for example, and what the "ideal" final drive ratio should be and why./quote]

Well, look at it like this... Have you ever ridden a 12 speed bike in first gear? Almost imposible to pedal right? Its the same way with an engine if the gear is too steap then it wil wrap up to fast and be just a waste of time in using it.. It would be like driving thirty and then droping down to first and wraping it up to shift to second..

Does that make any sense?

GaryHealy - Posted: 06 Jul 2004 05:55 pm

Crash, The gear ratio ratio for a first gear must include the first gear ratio and it must be multiplied by the final drive ratio (ring and pinion). A good ratio range for a V 8 car, should be around 8.5 :1 to 10 : 1. For dragstrip accerlation, you should be closer to 10 : 1 ratio. The Muncie 4-speed tranny, from a 1965 Corvette, has ratios of: 1st 2.20; 2nd 1.64; 3rd 1.28 and 4th of 1: 1. With a 3.70 ratio final drive this was a good street setup. With a 4.11 or 4.56 final drive, hello dragstrip. The Doug Nash/Richmond gear 5-speed, gear ratios were; 3.27; 2.13; 1.57; 1.23; and 5th 1 : 1. This tranny with a 3.07 final drive, had a 10.07 in first and the 3.07 final drive was a good crusing gear, in 5th. The Audi and Porsche transaxles both have around a 3.5 first gear with the Porsche final drive of 3.88 (915 tranny) and Audi probably close. This gives you a over ratio of 3.5 X 3.88 = 13.58. A nice ratio for a 4 wheel drive truck, which is used for pulling stumps. But not for our hi performance v 8s. Now you probably have more questions. We will get together, one of these weekends, and discuss this more.

CrashRat - Posted: 09 Jul 2004 06:01 am

Hey Adrian, thanks for the program. Sorry I've been a bit negligent in getting back to everyone. Work has just been beating me up the last couple of weeks. Gary, thanks for the informative post. I still have some holes in my understanding, but once work calms down I will spend a bit more time digging on the Internet and maybe grab a book or two. I just kind of want to get this process moving, because once I figure out exactly which trans I want it will probably take me a few weeks to actually find it and get it here.

Alright, I finally found time to cram some gear ratios into the spreadsheet that Adrian sent me. These #'s are if I use the Audi AAZ trans. They don't seem too out of proportion, unless I am missing something? 40.6mph in 1st seems about right. Please check the figures out and let me know if I'm still missing something.

http://www.gdowney.com/aaz_trans.htm

hiperf454 - Posted: 17 Jul 2004 02:26 pm

Hey Cash,
Just out of curiosity what motor are you running that turns 7500 rpm. The LT1 and LS1 max at about 5500. Which I think will drop all your gear speeds down alot. You have to have a pretty stout v8 to turn it up to 7500 and make any power.

CrashRat - Posted: 17 Jul 2004 09:28 pm

Hey Kelley, I typo'd. Should have been 6500. my engine's redline is 6700 but I wanted to be conservative. I have a BMW V12 with Autothority chips that was dyno'd 304rwhp while in the car. Autothority claims 342 crank hp. My engine was yanked from the donor 850 to make way for a tuned CSi transplant (386hp stock!).

at 6500rpm in first I would be running 36.3mph and 61.3 in 2nd using Audi's lowest available final drive of 3.89. I don't think that sounds too bad?

bpickell - Posted: 18 Jul 2004 05:06 am

Before Deciding on a trans I would figure out what speeds your shift points would be during normal driving... 36 MPH at 6500 that seems pretty steep. What would that be at 3000 RMP, 18 MPH? You would barely get moving and have to shift. Whats the Power band of your engine.? I don't know too many people that red line their engine when shifting...

CrashRat - Posted: 19 Jul 2004 10:23 am

Well, this weekend I drove both of our cars around the block paying careful attention to RPMs vs. speed. I also drove my friend's M3 to see what it looked like. All three cars have 5 speed manual or tiptronic transmissions. At 4,000 RPMS, all three cars were in the 18-22mph range in 1st. 2nd gear got me a low of 28 and a high of 34 at 4k. According to the gearing calculator, the Audi should get me 21.65mph in 1st at 4k and and 36.74 in 2nd. This is very close to what I'm used to driving so I don't really see a prob with the Audi ratios at all. Maybe the confusion is over the difference in rev ranges between an american V8 and other alternatives? The three cars I drove this weekend ran between 6000 and 6900RPM redline. The engine I'm putting in the Diablo replica will redline at 6700.

Based on all this, I think I am going to start scouring the planet for an AAZ Audi trans unless someone thinks I'm still barking up the wrong tree. Thanks for all the input!

Craig - Posted: 19 Jul 2004 12:24 pm

Go to the lounge at this address http://www.lambolounge.com/Chassis/Transmission/915/915.asp
part way down the page you will find "Download this Excel spreadsheet to do gear calculations - Gear Calculator" that should answer most of your questions. The numbers that are already in there are the stock 915 numbers and correct Diablo tire size.
BTW, gear #7 is the optional TL gear for fifth very hard to find but would be nice to have over stock.