Bus 4 spd trans, Anybody done this Options

[jwalters]

QUOTE (andys @ Jan 22 2005, 12:58 AM)

What are each of the "net" ratios (1 thru 4 x final drive ratio)? I seem to recall that you can't get a tall enough 4th/R&P combo, as most applications are either for very tall tires and/or drag race applications. Can you point me to info on available ratio's that would perhaps suit higher HP motors? You will need about a 3.00:1 "net" ratio or better. The 901 is 3.14:1, a 915 is 2.94:1, and a 944T (016R) is 2.80:1..........Thanks, Andy

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) The true net ratio of any trans is 1:1-however, none are made to this standard, therre would be no torque mulitplication-I believe you are referring to the first gear ratio in the tranny minus the final drive, if not, clarify. Also- the manufacturer net is subjective--it depends on the entire setup from the factory to include final drive ratio and factory specified tire diameter..again--TIRE DIAMETER as soon as you take off those 165-15's, the net is no longer as advertised by the factory. It changes to correspond with the new diameter.

The overall net ratio is highly dependant on engine produced TORQUE--not HP --torque wins this equation, because that is what the factory finalizes the ratio of torque multiplication. The factories with all the hard math still will try 100's of tire and cog combinations to match the INTENDED purpose of the vehicle-i.e. how much tq to make it do this....-as we all know the purpose of the 914 was not top speed, nor was it 0-60, it was just give it enough gear to get out of its own way--take a 85 hp 1.8l and bump it up to 150 with the commensurate rise in tq and those stock cogs are going to piss you off--that is if you had the knowledge to know better--and most people do not--I did not either till just about ten years ago until I picked up a book called "auto math" while in a bookstore getting some coffee and perusing the porsche pubs.

Truely enlightening read--all must go right now to the nearest barnes-and noble and buy one, it will astound you.

Top speed is more highly dependant on top rpm and the engines ability to redline in top gear--basically, if it does--then it needs more final drive or a cog change, or both. When you are able to attain top speed with the engine giving out at about 250 rpm below redline-you have a good final drive--the cogs are what get you to this level--it is a very involved process, one of which why top race teams will test for a week before race--it is to finalize final drive among other things.

[SpecialK]

I hear ya talkin', but all I see is your avatar (IMG:http://www.914world.com/bbs2/html/emoticons/drooley.gif)

You've done a little research on this subject, haven't you.

I'll stick with my 901, but this is an interesting read for sure.

[redshift]

You are never going to be happy with a gear that leaves you with revs on the table at speeds you need to be at on roads you have to drive on.

1500rpm would destroy your motor, and suck if you had to get out of the way.


M

[carambola]

i don't know about ratio's and stuff like that ... but i run 195's in the rear and 80mph indicated leaves me running about 4000rpm maybe a smidge under in my TI ghia

[scotty b]

Bus tranny will bolt right up to a type 4 engine, after all they were made that way!! Bus is stronger but won't have the top end without gear changes. Four rib trannies are the best, I think they were 72-75? I have a bus with a 2.0 type 4 in my baja and it is great, but again I'm not looking to run 7000 rpm in that car (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[TC/914]

I just had RANCHO build a type I swing axle trans for my 356 coupe for all of the same reasons quoted here. Cost and performance being most important. The trans has all of the go-fast goodies installed plus a combination of type I and II gears for an overdrive fourth WAY beyond their freeway-flyer version. I thought that the shape of the 356 could handle and deserved the higher top speed that a VW trans would offer.

I have an IRS VW (TransForm) freeway-flyer trans in the cellar, now it's definately going into the 914.

THANKS for the push . . . !!

TC

[jwalters]

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) Hi guys! Man did burn the midnight oil last night--I cant believe my rant went on -and on--ohh boy--sure did not mean to put all that out-

Oh and by the way I need to correct myself--I fudged the numbers for the 901 5th speed set--it is actually .71:1 and not 1.4:1--big difference, but alas, a .84 and 3.88:1 R&P is still taller than our 901 with a .71 fifth and 4.429:1 R&P setup--which means better highway revs and economy.

Redshift-I am not going to go the ultimate freeeway flyer special--a guy asked what was the lowest gear set available for the T1 slushbox--And yes a stock T4 cooling system will not cool at 1500 rpms on the interstate--but--a 6 conversion would--the fourth gear set is like our fifth--would you just pounce on it at 70 mph and expect anything spectacular to happen?? No, it would not--unless that motor is hotted wayyyy up--but then again, my motor will be turbo--so my torque out put will be fat across the board- so even if 4th is long--2-3 is short and short coupled--just a single gear change and BAM! Gone from sight..

Carambola, are they 50 series?? What you did, and many people do, is go to a small sidewall, tire diameter reduction--they are more intersted in handling ( as if stock was not good enough in this little pocket rocket corner carver )--which does this:( rough example) With stock tires 165-15, and a 4.4 R&P-you drop down to 50 series and minus 3 inches of diameter--even tho you have not touched the R&P--it now "thinks" it is a 5.12:1--which means shorter--if you do allot of stop and go this is good, because it has a higher torque multiplication--hence, you accelerate like you have an extra 25 hp under the deck, but then at say 70 mph cruising speed, your rpm will suffer and your fuel economy will suffer and you will not be able to blast ( on a non-public road ) to the same top speed as if they were stock 165-15... (IMG:http://www.914world.com/bbs2/html/emoticons/aktion035.gif)

[scotty b]

TC what did you have to do to mount the vw trans in the 356 and how has it performed?

[jwalters]

QUOTE (TC/914 @ Jan 22 2005, 09:57 AM)

I just had RANCHO build a type I swing axle trans for my 356 coupe for all of the same reasons quoted here. Cost and performance being most important. The trans has all of the go-fast goodies installed plus a combination of type I and II gears for an overdrive fourth WAY beyond their freeway-flyer version. I thought that the shape of the 356 could handle and deserved the higher top speed that a VW trans would offer. I have an IRS VW (TransForm) freeway-flyer trans in the cellar, now it's definately going into the 914. THANKS for the push . . . !! TC

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) very welcome man!!---so how does the 356 perform??? still got original engine or did you upgrade to T1 or T4? Congrats!

Oh and also--if ---when you do upgrade the teener--upgrade the cooling system as well- or it will overheat at low revs on the freeway--I myself am stacking 3 oil cooler fans to my deck lid grill ( underside) and running a microswitch to the cooling flap arm--when the flaps are all the way open it will energize a relay and turn on the fans to augment to stocker very important for me to seal the bay extra good so all that extra 2500 cfm of air goes thru the engine... (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[carambola]

i appologize must have been thinking of something else. not 195 but 165r15 and 185/55 15 up front for a total of 10% speedo error on the high side

[TC/914]

Hey Guys,

I just got the shipping confirmation from RANCHO so the trans will get here this coming week, The original engine and trans is out for now/for ever probably. The new engine is built around an aluminum race case with a drop in stroked Demelo crank and 94 pistons/barrels. It's got all of the usual stuff done to it, but the carbs are Kadrons rather than the old Webs. I thought that I'd give AJ's stuff a try and see what the fuss was all about.

Even though it's a 914 board, I'll try to (covertly) keep you posted on the progress. When the trans gets here we'll start fabricating the mount, probably base it around the 411 bracket with adjustable diagonals to the shock mount area for a bit of pre-load? Maybe even duplicate a cleaner version of the '68 Type II engine hanger as well. I've got all the VW bits and pieces along with most of the suspension parts from the old sand buggy so it SHOULD be pretty simple to fabricate something slick. I'd LIKE to have it be a bolt-in as well in order to save the originality of the tub (it's a Pre-A Continental Coupe), but I'm not married to the idea.

The 914 is NOW going to get the treatment as well, unfortunately . . . I've got the trans already hanging around and the old sand buggy will provide the shifter box and cable linkage. I also have the old Oberg oil filter and cooler so THAT part's also taken care of as well. Too easy to begin, and always too difficult to finish . . . now I'll have TWO Porsches up on jack stands.

If robin complains, I'll just tell her that it's "JWALTERS" fault. HE STARTED IT! !

[jwalters]

(IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/beer.gif)

[Tom Perso]

I had a Rancho IRS trans in my Bug with a 2270cc T4 motor. It had a 3.88 R/P and a bus 4th gear and it cruised on the highway at 75 running 3500rpm (195/65's on the back). It also had the SB mainshafts, yada yada yada. It was build for Shad Law's 2615cc (80mm x 102) Nikkies equipped motor in his T4 before he went with a 915 from a 912.

To bolt a T4 to an IRS trans you need a 210 or 215 mm bus flywheel with the center opened up to hold a T1 input shaft bearing. I had my flywheel EDM'd out to press in the bearing.

(IMG:http://www.qtm.net/~persoj/graphics/vw/flywheel_bushing.jpg)

Then I ran the corresponding bus clutch and a KEP Gold 200mm T1 disc. Held the 2270 no problem.

It was no more expensive than doing a decent clutch job on a bug... No expensive conversion flywheels needed.

Later,
Tom

[andys]

QUOTE (jwalters @ Jan 22 2005, 12:40 AM)

[/QUOTE] (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) The true net ratio of any trans is 1:1-however, none are made to this standard, therre would be no torque mulitplication-I believe you are referring to the first gear ratio in the tranny minus the final drive, if not, clarify.

Jwalters,

I guess I didn't make myself clear, so let me give it another shot. What I refer to as net, is the transmission gear ratio (any gear) multiplied by the R&P ratio. When you do this, it is much easier to compare the transmission ratios of one trans to another. If you don't, then you are always doing math. All the gear ratio charts that I have, have had this conversion done just for that reason. Tire size is of course yet another ingredient; BTDT. In dry lake racing, small gear ratio or tire roll-out changes can have a very significant impact on attaining top speed.

Back to my original comment, You will need something better than 3.00:1 (top gear, be it a 4, 5, or 6 speed, multiplied by the R&P ratio) to gain any significan advantage in lowering freeway/cruise RPM.

"but alas, a .84 and 3.88:1 R&P is still taller than our 901 with a .71 fifth and 4.429:1 R&P setup--which means better highway revs and economy."

Better try that math again....0.84 x 3.88 = 3.259.
0.71 x 4.429 = 3.145. The 901 has the taller (lower numerical) final (net) ratio yeilding a lower highway RPM.

Back to the Rancho/sand buggy racer transaxles. I only saw 3.86 as the tallest (lowest numerical) R&P ratio available. Are any 4th gears available that can take us to something better than the 901 final ratio? Sure would be nice......I just love those prices!!!

Andy

[reverie]

Tom Perso, that was excellent info... thank you!

The tallest VW gears I've heard of are 0.82 4th (some years of Bus?), and for
ring/pinion there's the 3.888 (Superbeetle?) and the 3.555 (aftermarket).

But what kind of 3rd gear to go with that.. (IMG:http://www.914world.com/bbs2/html/emoticons/huh.gif)

[jwalters]

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) Andys---I do admit I have not done this kind of math in a long time, and I do not have my cheat book auto math in front of me--but to kinda look at this from the other side of the coin:

Lets say that high gear is 1:1 + a 4.429:1 R&P , net ratio = 4.429

A .71 and .84 high gear is less than one--we are taking away--hence, subtraction, I do remember that much from the pre algebra course I took ( I am not a mathematician, and do not claim to be, I use cheat sheets all the time)

So this is not a multiplication problem----A 4.429 R&P is being turned slightly more than per engine rotation, or, .29 times more or put into a % --29% more if the input shaft = 1, and it does. Due to the overdriven .71 gearset

With high gear we have taken away tq multiplication--we are now subtracting tq from a 1:1 constant

So now plug this into the equation--

1 - .84 = .16
1 - .71 = .29 These are the difference of our 1:1 constant

We then take these away from our R&P : Because it is being overdriven by this much with our constant of 1 :

3.88 - .16 = 3.72 Final drive The engine is turning 3.72 times per full revolution of the wheel.

4.429 - .29 = 4.139 final drive The engine is turning 4.139 times per full revolution of the wheel.

This is a difference of .419 between the two, not much on paper, but a tremendous amount in practice.

Remember, the high gear is overdriving the input shaft to the R&P, 1:1 is our base constant--if the high gear set was in fact 1:1, but because of the overdriven high gear we must take this difference away from the R&P.
only when the cogs are of a greater value than 1 do they become a Division equation of underdrive, hence, a 12 tooth input meshed with a 27 tooth output you get a ratio, or division of 2.25:1, hence the 12 tooth one will turn 2.25 times for one turn of the 27 toothed one. We are discussing less than one, .71 & .84 This is a division equation of overdrive to be subtracted from the R&P. All underdrive equations are added to the R&P.

The gear sets themselve only multiply torque, this is a theoretical value-they do not multiply themslves, they divide speed for speed.

I hope this makes sense, the term torque multiplication is just that--theoretical tq--the gears are meshed in a multiplicative manner--whatever gear is driving the other it has a constant of 1, no matter how many teeth it has, it is still 1-but by mulitplying 1 you only get the same constant--- therefore-they always divide speed for speed. A division of a ratio of 12:27 is 2.25:1, this does in fact mean that the work output is multiplied by that same constant, 1 x 2.25 = 2.25, or 100 ftlb of tq x 2.25 = 225 ftlb of tq. But work is not tangible, you cannot hold horspower in your hands ( the numerical value) so this stays in theory only.

But I also do admit that I could be wrong--as I stated I am no mathematician, and even I am staring at my avatar a little too much (IMG:http://www.914world.com/bbs2/html/emoticons/wub.gif)

[Cap'n Krusty]

QUOTE (TC/914 @ Jan 21 2005, 05:07 PM)

I'll tell you what I think if you PM me as to where that great avatar came from! Swapping a type one trans would be pretty easy and has been already thought out by the mid engine sand buggy boys. A quick visit to http://shoptalkforums.com/ or http://www.thesamba.com/vw/forum/ will answer all of your parts matching questions regarding brackets, shifter, etc. along with which starter will fit the type one trans and which flywheel will need to be used on your engine. I would suspect a 70 flywheel with a semi-automatic VW Bug starter will do the trick. Otherwise, just talk with the folks at RANCHO and describe what you want. Everything else is pretty much a bolt it. Good luck with a cool idea! TC

Starter from a "semi automatic"? Same starter as the 914, so why bother changing it? European Racing (or Red Lion), sells the converted pressure plates. Other than that, it's a bolt in. For use in a 914, you have to figure out the linkage and some way to mount the trans at the rear. I've used T4 motors in Buggies and Bugs before, and it's no big deal. As for the lister who can flop the diff in 30 minutes, good luck! Without resetting the R&P locations, you're likely to eat them up in minutes. At a time when bug and buggie owners are looking for Porsche trannies, I fail to understand why anyone would be looking for their castoffs ...................... The Cap'n

[jwalters]

Yea well the buggie guys are more interested in trannies other than the 901-----

And to take off my side plates and swap the diff is a non-event--no pinion to pull--and just keep the same shims on the respective side--a quick check with prussian blue would show it will be more than ok for running---

but you do have to change the input shaft bearing--the T1 tranny snout is a larger diameter than the 901??

I know a 200 mm disc will run fine in the 215 flywheel and plate...and the linkage is still a pull, like the 901, and a quick check will show the pulley and mount will bolt up to the side case like the 901.

Mounting the trans to the 914 chassis is super easy--a pair of mild steel elephant ears bolted to the shift cap perimeter with extended studs , and with a section bent to the proper angle to mate to the rubber mounts is a brake press and plate bender away...too easy to do---and my cv output shafts bolt right up to the T1, so no changing components there-

I just want to do away with a red herring---I have 3 901's that all need work--and again, for the price of a set of synchros----------------------------

BTW- has anybody ever noticed that the 901 says VW on it???

[andys]

QUOTE (jwalters @ Jan 23 2005, 05:55 AM)

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) Andys---I do admit I have not done this kind of math in a long time, and I do not have my cheat book auto math in front of me--but to kinda look at this from the other side of the coin: Lets say that high gear is 1:1 + a 4.429:1 R&P , net ratio = 4.429 A .71 and .84 high gear is less than one--we are taking away--hence, subtraction, I do remember that much from the pre algebra course I took ( I am not a mathematician, and do not claim to be, I use cheat sheets all the time) [Edited] (IMG:http://www.914world.com/bbs2/html/emoticons/wub.gif)

jwalters,

I have never seen gear ratio's calculated as you have, and I beleive them to be in error. I have attached a link to an easy to use gear ratio speed chart that will hopefully demonstrate the proper outcome. Just plug in the numbers. I think this would be easier than to debate on this forum. I hope you find this helpful, and leads to an accurate outcome. Also, I hope this VW Bus transaxle thing has some potential. It is an interesting and simple alternative. Good Luck.

http://www.geocities.com/z_design_studio/t...on_boxster.html

Andy

[Mueller]

Andy,

thanks for the link...that is pretty slick (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)