Transaxle options?

Advice needed: I have a VS with a 4.12 R&P in a swingaxle, but I want to upgrade to a at least a "freeway flyer" or better yet a pro street comp with a 3.89 R&P.

I've been looking around for a donor VW car and found a running super beetle that has an IRS tranaxle: the trans & eng are good and it's a driver...whole car for way cheap as it's been sidelined due to lots-o-rust.
So here's the questions:

1. how much work is it to convert my swing axle Speedster to an IRS?

2. Is it worth the effort? What would I gain by doing this? How much of the Super Beetle IRS set-up ( mounts, suspension, axles, etc. etc. ) would have to be used to replace my existing swingaxle setp in my VS?

3. am I better off just sticking to the swingaxle setup where I already have a camber compensator?

4. If I stick with the swingaxle setup, when I order the new transaxle (using the IRS as the core), Am I correct in assuming that a transaxle purchase from KCR, Rancho, etc. doesn't matter if the "core" is either version?

Tips? Advice from the experts? Anyone done this?
Thxs
Doug

The conversion that you asked about can be done. It's "common" enough that there are alignment jigs available to set the position of the diagonals and brackets. You can purchase the brackets and hardware from to do the job, although I only know of one person who has actually done it.

You really ought to post your question here . . .

http://www.shoptalkforums.com/viewforum.php?f=50&sid=e7b720c3cd4cee84911273c2a7f5275b

. . . to get a complete answer or even a link to a step-by-step. I'm SURE that one of the magazines has covered this in the past.


To really make a success of it, you would need to remove the body from the pan. This would help make the welding easier and let you repaint the area without messing around. Remember that this is a crucial alignment point. You can keep the original spring plates and torsion bar set-up, most if not all of the rest will be from the IRS donor car.

There is a very big improvement in the IRS over the swing axle, but you won't see this unless you drive to the limit. Day to day driving, at everyday speeds in nice weather won't be any different for the most part. The faster and more aggressively you drive, the harder you push the old-style suspension, the more you'll notice a difference in the IRS.

When you order the new transaxle, ask the manufacturer if they accept an IRS in trade as a core. You can sometimes negotiate, depending. They probably require a one for one trade, but everything can be negotiated these days.

Depending upon your situation, you might even consider a pan swap or IRS rear clip. Since the pans are cut-'n-shut anyway it might be an option. If you don't have disks up front, an IRS pan swap would almost be a necessity to really enjoy the car.

Regardless, it's gonna be work, just decide on how much you want to do.

Luck,


Forum Prick

I know that Rancho will convert the IRS to swing axle side covers, etc. at no difference in price......You would use your original axles, tubes, etc.....Call Mike at Rancho and discuss what you want in the way of performance, and have your tire diameter, engine size, and vehicle weight handy.....You can have your core rebuilt or probably do an exchange.....

I run a Street-Pro freeway flyer, with 3.88R&P and a .84 fourth gear...70mph is at about 3200 rpm.....The car is 1300lbs and has 24.75 in. dia tires in the rear. (Spyder) Acceleration takes a dive, but with available torque, it pulls strongly, even in 4th....Engine is 1915cc C.B. Perf.

I have almost exactly the same setup in my Speedster that Leon has in his Spyder. It's a good overall combination.

As for the trouble of converting from swing-axle to IRS, I'm just not sure it's worth it. I have swing-axles in my car, along with a camber compensator and front discs (rear coming soon, I hope), and I am quite pleased with the handling. Unless you're planning to autocross it, I'm not sure you'll get enough benefit to justify the effort.

A question for you freeway flier owners:
Do you find that you need to let the rpm's drop quite a bit in 4th before down shifting into 3rd?
My thinking is that will a tall 4th gear and an early down shift 4th to 3rd, would run the rpm's up and possibly over rev the motor. ~Alan

1st gear 2.58
2nd gear 1.86
3rd gear 1.26
4th gear 0.93

Ring and Pinion Ratio 3.44
Resultant final drive 3.20

RPM @ 65 MPH 2815

So, to your question, no, downshifts from 4th to 3rd work fine with this gearing. On the next transmission for the next car I think I will stick with 3.88 R&P however. The 3.44 is perhaps overkill, but the car is light (Spyder) and the engine is big and high on torque...

I haven't had any issues going 4th to 3rd. I put in a VW "Factory Flier" last year and really like it much better than the 4.12. I ride in 3rd a lot around town and go into 4th to "quiet" things down when needed. With the 50 series tires, the ratio falls from 3.88 to somewhere around 3.68.

~WB

Jim, I agree with you. I have a stock-geared freeway flier with the 3.44 final. It is a bit overkill. 1st is too short, second gets me up to 60, third is good to 95, and fourth I haven't touched the top end. I am sure I would be airborne in short order, never taken it over 110. Anywhere between 45 and up is good for fourth, downshifting is no problem, revlimiter set at 6500. Mine came with my Spyder via Trans-West. Most guys would agree that the 3.88 is the way to go. Also, 3.88 is the max size for a Quaife differential, it won't fit with the 3.44 R & P.

Rear tires 195/60 15, fronts 185/65.

Danny, I also agree that a stock first is way too short for most of our lighter weight higher HP cars. My first Speedster was stock geared freeway flyer with about a 160 hp Bergmann engine. Didn't take very long for me to buy something more like I am running in my Spyder today, just with a 3.88 dif.

Stock VW first is usually 3:80 so moving 1st to 2.65 is a big change
1st 3.80 (stock)
2nd 2.06 (stock)

The way I geared mine moves everything closer together, and solves the 1st gear problem.

The bad news with my selection is 2 fold, it costs a bunch, the new 1st and second gear set runs something like $900 just for the gears, and the second issue is the car has a top end that can't be used (at least by me) as the aerodynamics are very wrong starting at about 115-120mph....I have been well over 125 once, (tach said 6000 which would equal 139 mph) not going back there again, I discovered I had little or no steering...not a very good feeling.

I know that CB has run their Spyder through the quarter at 140mph (10.49 seconds). Pat Downs is a braver man than me.....

But, the good news is 1st gear is good for up to 60 mph, and 65 mph cruising is under 3K in 4th..... and 3rd gear for moving around in traffic is a lot of fun....

I am running 205x50x15" tires in the rear

Thxs for the advice from everyone: I'll call KCR & Rancho to talk to them about switching the "core" IRS over to swingaxles, and talk to them about gearing options,too. I'll definitely go to the 3.88 ratio versus the 4.12 R&P to get the cruising RPM's down to around 3,000RPM. If they can re-do the IRS core, I can keep the current swingaxle in the speedster and not have any down time until late Fall when the car goes up for storage and I get to do projects on it... I put a BN-2 gas heater in this Winter so I can go to J-tubes and A-1 exhaust this coming Fall and have good heat when I do the Trans & engine swap is what's scheduled for this Fall. I'm gearing up now for parts and related things (external Derale/fan cooler, SS braided lines, exhaust, etc )so that everything else is ready then.

I agree on not doing the switch to IRS: looks like way too much work unless I were to really push the car handling wise / autocross it..which I don't, so I'll stick with the swing / camber compensator I have and use the IRS as a core.

Thxs, Team Evil, for the air cooled shoptalk link: that's a great resource! And also to Jim for his gearing suggestions. I also got an email from the shoptalk forum posting who was suggesting the Berg 5 speed, but it's pricey..$4k+, so that's out.

Doug

Several of you on this thread have mentioned, "cruising at 65 MPH at 3XXX RPM...". I guess that is a good metric, but out here in La La Land, nobody, and I mean nobody drives at 65 MPH. It's virtually impossible to get anywhere (well, anywhere worth driving to) without getting on a freeway. And once on a freeway, the average speed sure isn't 65 MPH. Semis are doing 70, Grandma in her Hyundai is doing 75 MPH, and both left lanes are doing 80 MPH. I drive I-5 over 2000 miles north and south every year (in my pickup) and the cruise controls is set at 78 MPH to keep up with the right lane!

I too have a 3.89 freeway flyer, 25 inch tires and a stock .89 4th gear. I am pretty happy with the power of my 2367 engine, but I sure do wish I had a 5 or 6 speed when going any distance on a feeway. Next time . . . .

So I'm drivin' at 55 and shitting in a dark bathroom to save fuel for the environment and Mother America and you fools are storming along at 85 with the air conditioner running and a latte in the cup holder?

I think that we need a national (enforced) speed limit WAY before electric cars. Of course, THEN we'll have to figure out a way of keeping the cops in line. You folks in California really don't seem to be able to keep the bitches on the leash.

Actually; tranny rebuilders charge more for the IRS due to their more limited availability as compard to swingaxles. I'm pretty sure there won't be a problem in accepting your IRS as core.

Doug, the Gene Berg 5 speed won't give you an over/over drive in 5th, In just about every situation, 2nd, 3rd and 4th are closely spaced and 5th gear is the same as 4th in a standard 4 speed transaxle.

There comes a point in a VW engine where the power needed to propel the car vs the amount of air generated by the cooling fan come together, sometimes in a disastrous way. If the engine is forced to move the car at a given speed and, the fan isn't producing enough air (RPM's create the air via the fan) then the engine will overheat.

In other words, if you slow down the engine via gearing but make the engine work harder by increased speed, the fan won't blow enough air to cool the engine

I've had the 4:12 with a .82 4th and also the 3:88 with the .82 4th. I actually preferred the 4:12 but that also is dependant on the power band of your engine. It all has to work together. Tall gearing is fine if you have gobs of power but for the smaller displacements, you are better off not overdoing it. You also have to think about the fan rpms so you do not over heat (like in the middle of summer here in Las Vegas) or overcool in some cases. You have to take in consideration, all variables so all is one fine tuned machine. Porsche picked out the ultimate gearing to match their engine power/torque curves for all of their 1600 cc and lesser displacement powerplants. When I drive my 356 SC or 912, I can really appreciate what they can do with 105 SAE HP and these cars are heavier! I just put in a 4:12 with .82 4th in my Speedster and will be driving pretty soon. Anyway, just my 2 cents...put a little more thought into it. Research your engine (cam, heads, exhaust, compression ratio, vehicle weight, etc....) and try to match the transaxle to these variables. Good luck.

Guys this has been one of the best FF threads I have ever read. And I have checked out a few on Samba, STF, here, etc.

Very informative please keep it up. And keep posting your ratio's and opinions.

Tony, are you going to add Air Conditioning to you Speedster in LV?

How does Air Conditioning factor in with a mild 1776, with stock 165-15R tires and a 4:11? If I go to a mild FF (.82 4th gear) maybe I can keep from getting run over by grandma in her Kia.

I could also just stay stock and cruise at 4000 rpm and turn up the radio.

Dave

For all you'se guys contemplating a "Freeway Flyer" to "keep your revs down on the highway", remember this:

YOU'RE NOT DRIVING A WATER COOLED CAR!!

SLOW ENGINE REVS MEANS REDUCED COOLING CAPABILITY!

DRIVING FAST MEANS YOUR ENGINE NEEDS MORE COOLING!

LESS COOLING MEANS SHORTER ENGINE LIFE!

Now that I'm done shouting, keep those engine revs ABOVE 3500 on the highway and your engine will last much longer.

I NEVER drop revs below 2,500 and usually keep them above 3,000. Sure, you look a little weird running 2'nd and 3'rd around town, but so what? People who know these engines keep them rev'ed because THAT keeps them cool.

Oh, and one last shout: TAKE THAT "POWER PULLEY" OFF AND THROW IT IN THE TRASH CAN - FOR GOOD!

gn

BTW: When I cruise with the New England TYP 356 club (mostly original, steel 356's), we all run 3,750 - 4,000 rpm when cruising on the Interstates - yes, somewhere far North of 75 mph (usually North of 80) and my oil temp sits around 200F. I wouldn't worry about running that rev range for days at a time....these engines will take it.

Hey Gordon,

My power pulley is sitting near the trash can, want it? Maybe I can flog it on the Samba for $10 bucks.

My comfortable cruising RPM is around 3250 - 3750 with bursts of up to 4200. And it is not fast enough. This is what we have to do in Southern Califronia freeways. Unless you want to be KILLED BY A KIA! That's why I'm interested in higher gearing. I'm feeling the need for top speed.

At 4000+ RPM it feels like a jet on lift off. Just have to get used to it I guess.
In my old 58 bus I was far enough away from the engine I could never hear it above the 8-track. Blew it up once to "Born on the Bayou" on the way home from my future wife's house. I had it on real loud. The bus was a camper and came equipped with at least one surfboard and took many trips to 3M's, Raul's, K-42.

Dave

There is some sage advice from experienced engine builders and drivers in this thread. The most important advice is to keep in mind that all things on an ACVW must work together for the motor to remain cool. I recently had my transaxle changed from close ratio 3rd and 4th to a stock 3rd and 0.82 bus 4th. The final drive is 3.88, so I now drive 70MPG at 3,000 RPM.

When I built the 2180cc motor, my goal was reliability and cool running. I threw away the power pulley, installed the factory thermostat and air baffles on my doghouse shroud, painted the tin dark grey, and installed full flow oiling with the filter in the air flow, thinline sump, 1 5/8 Sidewinder exhaust to get the hot gasses out, and an Engle 110 cam to keep the torque low and strong. After warming up, the oil temp is rock steady at 175 degrees. It does not overheat because the motor was purposely built to run at 3,000 RPM in an efficient manner for this light car. I do not have or need an auxilliary oil cooler.

Probably the biggest mistake is to put in a camshaft that builds torque too high in the RPM band, and then attempt to cruise at RPMs below 3,000. That motor will be running in an inefficient manner, will build excessive heat, and will get poor fuel mileage. At cruise, you need to remain well into the torque curve of your motor configuration.

Just my experience and 2 cents.

If anyone is pitching their power pulleys, feel free to send them along to me. We use them on the engines for the drag cars.

They're perfect for the high RPM engines. Most have a pretty accurate degree ring on them, turn the fan enough to keep the engines cool while waiting in the lanes, but don't turn the fan so fast under racing conditions that it will come apart on us.

Perfect ! !

I forgot to add that along with 3.88 and 50 series tires I run a 356 alt. pulley for a bit extra cooling.

~WB

I converted a swing axle chassis to IRS using brackets and pins from CIP. Welding to the rear forks was a bit tricky but not too bad for a first time. Next one will be easy.
You will need an alignment jig for placement of the arms, and I bought one on Samba

Used a Porker 915 LSD 5 speed box and conversion kit from Bug@5speed.
Make sure you get 100mm flanges on the box so that you can use Type 2/944 CV joints

My trailing arms are 944T (narrow pre 86) and drive shafts from the same 944

I'd recommend doing a complete custom pro-street transaxle from Rancho or somebody similar. The Rancho catalog is a good place to start to see what ratios are available- you can do almost anything you want. Plug the combinations into a gear ratio calculator (like this one on CBs site: http://www.et-studios.com/motorsports/gears/gears.html).

Keep in mind that a 3.88 R/P is stronger than a 4.11, and therefore more desirable. I'd recommend ending up with a .89 4th gear (stock) or a .85- I've got a .82, which is great for my 2332 (200 lb ft of torque at 2500 RPM), but a bit "long" for anything less. I'd go with a longer first, and then space the ratios to have 5500 rpm shifts that drop down to 3000 rpm or so, but keep 3rd a bit closer to 4th than then rest of them.

Lastly, do a search for specific gear ratios- I posed at length in late 2004, early 2005 about my "perfect" gear ratios. I love them. Do your homework, talk to a reputable transaxle guy, and you'll love what you get as well.

As for IRS v swing- I think you're gonna need to run what you brung, or your going to end up with a whole lot of work for very little return.