ehall

You know that one of these days I'm coming out to Vegas to take you up on that. I just still have too many projects going.

odurandina

i recently sourced a spare 968 transmission with very low miles which will be getting rebuilt as explained below....


i've been researching for some time how to set 968 transmissions up for more top end without breaking the bank.... at one time i was under the assumption that any and all Audi 01e 5th and 6th gearsets were interchangable with the 968. apparently, not so...

as it turns out, the 968 guys are stuck with either having maybe, like a .810 gearset made, or running the stock 5th .912 gear (which is too low), or running a .729 5th gear available from the (Audi A4 01e box, FPN FRL) which drops the rpm down lower than would be ideal after coming out of the low, stock 4th gear, but it is what i will be running.


the .729 5th grear will make about 160 mph @ 6,000 rpm (running a 25.6 inch tire).... the .600 6th gear will make 195 mph @ 6,000 rpm, or about 188 mph running a 25 inch tire... and the gearsets will bolt right into a 968 box.... a .680 is also available making a perfect top gear for turbo and supercharged 968s.


anyway... Scott, at Advanced Automotion, Corpus Christi, TX has a vast knowledge all the Audi 01e, and 968 boxes, rebuild kits, etc....

http://www.advancedautomotion.com/



other very knowledgable sources:


Roger at California Motorsports, Lake Havasu, AZ

http://www.californiamotorsports.net/


rebuild kits; JH Motorsports, California....

http://www.jhmotorsports.com/shop/catalog/home.php


Jerry Janzing, All Pro Cars (the GT40 people like the Audi A4 diesel, 944, and 968 transmission);

http://www.allprocars.com/web/



Scott Dewitt from Advanced Automotion posts on this forum...

http://www.gt40s.com/forum/gt40-tech...e-6-speed.html



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Chris White

V8 swap into a 968 and modifying the transmission for better top end…..without breaking the bank…..

I think you will be following the current administrations economic theory when it comes to breaking the bank…..

Chris White

I was in the mood to run numbers so I cooked up a quick spreadsheet – looks like your numbers are off a bit.

968ls1

I went down this 6 speed road several years ago with the LS1 combo and explored all the ratio option mentioned in this thread. I even tried to get Albins in Australia build a custom 3:22 R&P but they had tooling breakage issues and the cost of the gear set was 3K with a 6pc minimum. I then build a 6 speed with a .60 6th and a GT LSD it was expensive and frankly a big waste of $$. Regardless of the two overdrive ratios 1st through 4th are too damn close to to make proper use of the LS torque curve. On the street found myself skipping gears rather than making useless shifts. On the track I would need to often shift in mid corner cause I was out of RPM due to the tight ratios. A 951 trans axle with a .729 5th is the best combo for this conversion and won't break the bank **** I could of built 2 951 boxes for the cost of the 968 trans. The 951 ratios are well suited for the V8 torque curve and the cruise RPM (.729 5th) at 75mph is 2418rpm and at 180mph is 5804rpm so it works. I compared the ratios of the 951 to the aftermarket Tremec 5 speeds that are used primarily behind V8's and the ratios are damn near identical to the 951. If you just want a 6 speed so you can say you have a 6 speed do it but it is a disadvantage in performance, drive ablity and cost when it comes to these conversions. I have been doing this now for 15 years and have yet to damage/blow up a 951 trans but I don't abuse them and have always made sure they in good working order. Bottom line the 6 speed is NOT the way to go if you want the best value and performance.

odurandina

Chris,

please keep in mind that i prefer to run a slightly larger tire, about 25.65" on my 275-35-18s... (a 295-30-18 is about 24.8")... running the larger tires seems to improves the ride significantly, and gives exactly 25 mph per 1000 rpm in the stock 6th gear.... so the speed/rpm numbers i've provided would be correct for the slightly larger tires i'm running....



got me something to barter.... the entire insides of this transmission for pennies on the dollar,

http://www.worldimpex.com/parts/genu...edu_79973.html


and then i have 2 968 transmissions. the current box i'm running in my car, seems to be very good. this box might get the retrofitted gears. or maybe i'll install them in the other box i have with just 48 k miles. that should help soften the blow.


btw, crunching some numbers last night, i discovered that as it turns out i think i will enjoy the ultra-tall 5th gear, after all, considering that it will become my most-commonly used gear for cruising the secondary roads. the engine would be seeing onliy 2,100 rpm at 55 mph.... surely, no good for the track but, it will save a lot on the wear and tear of the engine. then 6th gear, will see even about 70 mph at just over 2,100 rpm....


from all ranges of driving, from putting around like an old lady on the secondary roads, to spirited driving, to flat-out, "f_ck-you-you-sorry-piece of ****" driving, the rpm numbers would look like this:


changing from 3rd gear to 4th at 2,583 rpm @ 35.0 mph will yield 2,000 rpm in 4th gear....

change from 4th gear at 2,800 rpm to 5th @ 49.0 mph will yield 1,838 rpm in 5th gear....

change from 4th/3,400 rpm to 5th @ 59.5 mph gives 2,232 rpm in 5th gear....

change from 4th/4,000 rpm to 5th @ 70.3 mph = 2,626 rpm in 5th gear....

change from 4th/4,500 rpm to 5th @ 78.8 mph = 2,954 rpm in 5th gear....

change from 4th/4,800 rpm to 5th @ 84.0 mph = 3,151 rpm in 5th gear....

flat out, changing from 4th/6,000 rpm to 5th @ 105.0 mph = 3,939 rpm in 5th gear with plenty of room to run from 4,000 rpm to 160 mph at 6,000 rpm before changing to 6th gear.


as Tom mentions, the 1st through 4th gears are really bloody hell once the stock Variocam is abandoned, and more hp comes on board.... but, after taking a closer, i think i won't find too much fault with running such a tall 5th gear, and it will still be a vast improvement over the stock 968 5th, especially, considering that i will be driving this car all over the country, and i don't wish to beat the crap out of the engine. it is a bit taller than i would prefer,

but, considering that the LS2 can make about 400 + ft/lbs of torque in the low 3,000s,
switching from 4th to 5th still looks to be ok.

odurandina

you must have been reading my mind, as i've been to hell and back crunching the numbers for a long time and came to the same conclusion. talked to Tony G. on the phone a couple of times about this this as well, and the conclusion was unanimous — that the tall ratio 944 boxes are the only way to go.

running the bigger tires helps a little, but still not enough... i've determined that in real world driving, i'll be starting softly in 1st gear without dumping the clutch, and skipping second gear altogether.

that's the significant downside of staying with the 968 box.... but the biggest reason i chose to stay with it is that i reallllyy love the idea of being able to do ALL my long-haul driving between 5th and 6th and being able to keep the engine between 2,000 to 3,000 rpm all the way towards 100 mph....

if i ever make it out to my favorite lonely highway in south dakota again, i'm hoping to videotape a 190 mph pass from the roadside, and that threshold would be eclipsed at just under 5,900 rpm...

A.Wayne

I heard Corvette's come with a v8 and a 6 spd .. Hmmmmm ...

Cole

So do Audi S4, Audi RS4, Cayenne GTS, BMW M5, BMW 540i sport,..etc etc etc etc etc the list could go on forever. So what!!?!?? This thread is about specific Porsches

odurandina

Bruce Wayne's just messin'. we/ve been to hell and back on the OT forums talking about the coming economic collapse, the sad state of politics/the modern political crisis, fema, Bush family secrets, the JFK assassination ad nauseam, and now the hot topic up there is the subject of supertroll "Arthur...." we agree on more stuff than Mr. Wayne would probably care to admit.... anyway,


1. i like Corvettes. the modern Corvette "theory" retains quite a bit of 924, 944, 968, 928 DNA in it's modern transaxle platform.

2. i really like the 944 but, i happen to like the 968 design even more.

3. the 944/968/948 is part of the long line of classic, front engine "egg cabin, extended front," sports cars, that evolved from the the Cobra, old Jaguars, Ferrari Daytonas, Datsun/Nissan 240, 260, 280, 300, 350, 370 Zeta cars, and i can still see quite similar lines in the Infinity G37...

4. the 948/968 V8 is almost becoming a car brand in and of itself, much like the Cobra and GT 40 kit cars.

5. i want a car with good road manners that can go REALLY fast.

6. one modern car i really like is the Ferrari California. it's a touring supercar more than a sports car...

but, since can't afford one, i'll have to settle on the 968.




at the very least, i'll need be able to make a little more power than a stock LS2 can make between 4,000 and say, about 6,300 rpm.

your suggestion of streching out the power beyond 6,000 rpm also sounds good.

A.Wayne

Well Cole.... he's not putting one of those V8's in his 944 now is he..


OD...

The last time i looked a 928 came with a v8, has the same headlights as a 968 and it's about as egg looking as a car get's..


Pretty close to your requirements huh.....

odurandina

4 monster combos/comparo....


as a novice to the LSx, i've been trying to learn what i can here and there... recently i decided to seek advice from a few vaunted engine builders including a revered shop in Illinois; Automotive Engine Specialties (AES), the good folks at Total Engine Airflow in Ohio and Comp Cams in Tennessee about some different combinations that would work with the stock LS3 intake/heads and be able to stay under the 944/968's hood without any issues.... interestingly, they were all virtually unanimous about a couple of points... 1; that the LS7 block is by far, the best option for long service life when going past 400 c.i... 2; in the case of the LS3 there's very little to be gained from running a FAST, and for a street application the LS3 intake and heads will still make decent power running a mild cam or adding displacement (of course, LS7 heads are ideal for the LS7 short block, but there are some cost advantages to staying with LS3 heads).


i came across a very nice find this past week... and you can configure a potent Z06 (LS7) engine for thousands of dollars less than an off the shelf LS7 longblock and still retain near-maximum service life..... to show just how much a bargain this combo looks like compared to a bone stock LS7 GM crate, i did a cost comparo for 4 complete engines..... look at the result; nearly a 5 thousand dollar savings in a something that looks pretty reliable;


i chose an extremely mild cam that falls about halfway between stock and a GM hotcam to retain full streetability w/ good fuel economy.... total estimate would be before adding serpentine, bellhousing, clutch, starter, wiring harness and computer....



Option #1. LS3 376 c.i. crate - (Crate Engine Depot); $6,204

http://www.crateenginedepot.com/LS3-...70-P10590.aspx

TPC ceramic coat long-tubes $1,100

total before adding serpentine, bellhousing, w harness/comp, clutch, starter; about $7,300

result; about 445~450 hp at the crank and w/ very friendly street manners.



Option #2. LS3 376 c.i. crate w/ mild cam - (Crate Engine Depot); $6,204...

http://www.crateenginedepot.com/LS3-...70-P10590.aspx

*comp cams mild cam (54-535-11) $399
beehive valvespring set (26918) $337
chrome-moly pushrods (795516) $146
TPC ceramic coat long-tubes $1,100

total before adding serpentine, bellhousing, w harness/comp, clutch, starter; about $8,200

result; about 470~480 hp at the crank and w/ friendly street manners (slight lope).



Option #3. LS7 427 c.i. w/ LS3 heads/intake

virgin short block - Scoggin Dickey; $5,999
features real LS7 block, siamese-bore cylinders, forged crank, rods ect...

http://sdparts.com/details/scoggin-d...er/sdls7sb427d

from parts bin, add fully assembled GM LS3 rect port heads, H20 pump, and all other parts to finish crate; (source LS3 intake, fuel rail, and manual throttle body from ebay)... total; about $2,200....
add 30 hp comp cams mild cam (54-535-11) $399.00
beehive valvespring set (26918) $337.00
chrome-moly pushrods (795516) $146.43
TPC ceramic coat long-tubes $1,100.00

total before adding serpentine, bellhousing, w harness/comp, clutch, starter; $10,200

result; about 505~510 hp (at least) at the crank w/ slight lope at idle.



Option #4. Z06 LS7 (GM's highest output n/a engine); about $14,000...
engine is basically a fully-race prepped hand built motor from the factory.
add Eric's TPC ceramic coat long-tubes $1,100.00

result; about 525~530 hp at the crank w/ big block thump at idle @ $15,100.

600 hp (crank) setups are fairly routine after going to bigger cams.



more;

http://www.gmhightechperformance.com...y/viewall.html

LS3;

Introduced on the 2008 Corvette, the LS3 brought LS base performance to an unprecedented level: 430 horsepower from 6.2L (376 cu in) - making it the most powerful base Corvette engine in history. The LS3 block has larger bores than the LS2, and a strengthened casting to support the high-output LS9 supercharged engine of the Corvette ZR1. The LS3 was offered in the Pontiac G8 GXP and is also the standard V-8 engine in the new, 2010 Camaro SS.


LS7;

The LS7 is the standard engine in the Corvette Z06 and its 7.0L displacement (427 cubic inches) makes it the largest LS engine offered in a production car. Unlike all other LSx engines, the LS7 uses a Siamese-bore cylinder block design - required for its big, 4.125-inch bores. Competition-proven heads and lightweight components, such as titanium rods and intake valves, make the LS7 a street-tuned racing engine, with 505 horsepower. LS7 engines are built by hand at the GM Performance Build Center in Wixom, Mich.



.

acorad

fwiw, the stock 951 trans has a 0.83 5th gear, however the NA 0.73 5th is easily swapped in. Another option is to swap in the 0.68 5th from the early 80's Audi 5000 Diesel, it'll drop your rpm's around 200 lower than the NA 0.73 5th.

odurandina

yep, some of us would love that gear. but Tom's using his car for the track.

DFASTEST951

I tried to find the audi diesel fifth gearset. hard to source. So I have the na fifth in my five speed. I already hit 194mph with my stock gearbox. We'll see what this one allows me.