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Limits of the VW transaxle . . .

FM Former Member
Hi again,

Not really back, don't have a 356 anymore, but I do have a VW transaxle question if that's OK?

My little Fiat 600 project is honestly coming right along, I grafted the entire rear inner bulkhead of a Beetle into the open cavity of the Fiat shell, trimmed it to fit and managed to tack it to the inner panels and bolt it to the shortened Beetle pan in the stock position. Looks almost "factory" and is as ridged as can be. Gonna do the same thing up front, and even found a pair of VW rails/heater channels to do sides. I'm encouraged by the strength that this is going to impart to the car.

Anyway, a "friend of a friend" kinda deal has come along and I'll be trading my GM V6 with the VW adapter kit for a racing sand rail Rotary 13B with the VW adapter kit. The V6 was in the Ghia, but I've sort of had my way with Ghias and VW's and wanna try something different, a Rotary powered Fiat would fill the bill nicely.

Biggest question is concerning the RPM of the Rotary put through the VW transaxle. The transaxle is a pro-street TRANSFORM unit, four spiders, hardened keys and shafts, beam welded, side plates, the works, a nice mixture of 411 and bus gears for a true Free-Way Flyer (old skool, not just a '73 and up Super Beetle unit) with a good spread between them. It's the best that I could afford, but still has a limit. Not in strength, but maybe in sustained high RPMs. The VW wants to stay around three to four to (occasionally) five grand for the most part, the Rotary doesn't live until it's past five grand.

Anyone know what happens to the VW trans at sustained five to nine grand RPMs? Is that a no-big-deal thing? I could fashion a pump and cooler with a scavenge I suppose, I have a dry sump set-up and could pick up an electric pump from Summit if all that's necessary. Do any production cars use a trans cooler and pump for their manual transmissions? We have three locals yards that let you pic and poke through them, I could check there if I had a clue what to go after.

Looking for some help/info for sure ! ! !

As a wonderful side note (and I DO love an aside) the output figures for the TRANSFORM trans puts the speed/RPM at about 60 miles per hour at 2,500 RPM. Wonder what the terminal speed will be at 8,000 RPM?

Luckily the car has a wheelbase of about 48 inches so I won't have to worry about things getting squirrelly at 160 mph . . .

Any help? Greatly appreciated.

Thanks,

TC
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FM Former Member
Hi again,

Not really back, don't have a 356 anymore, but I do have a VW transaxle question if that's OK?

My little Fiat 600 project is honestly coming right along, I grafted the entire rear inner bulkhead of a Beetle into the open cavity of the Fiat shell, trimmed it to fit and managed to tack it to the inner panels and bolt it to the shortened Beetle pan in the stock position. Looks almost "factory" and is as ridged as can be. Gonna do the same thing up front, and even found a pair of VW rails/heater channels to do sides. I'm encouraged by the strength that this is going to impart to the car.

Anyway, a "friend of a friend" kinda deal has come along and I'll be trading my GM V6 with the VW adapter kit for a racing sand rail Rotary 13B with the VW adapter kit. The V6 was in the Ghia, but I've sort of had my way with Ghias and VW's and wanna try something different, a Rotary powered Fiat would fill the bill nicely.

Biggest question is concerning the RPM of the Rotary put through the VW transaxle. The transaxle is a pro-street TRANSFORM unit, four spiders, hardened keys and shafts, beam welded, side plates, the works, a nice mixture of 411 and bus gears for a true Free-Way Flyer (old skool, not just a '73 and up Super Beetle unit) with a good spread between them. It's the best that I could afford, but still has a limit. Not in strength, but maybe in sustained high RPMs. The VW wants to stay around three to four to (occasionally) five grand for the most part, the Rotary doesn't live until it's past five grand.

Anyone know what happens to the VW trans at sustained five to nine grand RPMs? Is that a no-big-deal thing? I could fashion a pump and cooler with a scavenge I suppose, I have a dry sump set-up and could pick up an electric pump from Summit if all that's necessary. Do any production cars use a trans cooler and pump for their manual transmissions? We have three locals yards that let you pic and poke through them, I could check there if I had a clue what to go after.

Looking for some help/info for sure ! ! !

As a wonderful side note (and I DO love an aside) the output figures for the TRANSFORM trans puts the speed/RPM at about 60 miles per hour at 2,500 RPM. Wonder what the terminal speed will be at 8,000 RPM?

Luckily the car has a wheelbase of about 48 inches so I won't have to worry about things getting squirrelly at 160 mph . . .

Any help? Greatly appreciated.

Thanks,

TC
FM Former Member
I'd thought to partially box in the trans and set some air ducts beneath the car to funnel air onto and around the trans, but wasn't sure if just being "out in the wind" where it sits is enough. I'm thinking that a thin gauge aluminum (OK . . . an old Stop sign, really.)heat shield with aluminum insulation sheets fitted between the engine and trans and running out and under to the sides of the compartment might not be a good idea as well. Isolate as much heat as possible in the back and fit intake ducts to help carry that hot air out the rear. I have some partially fabricated ducted plexi rear quarter windows almost finished up and have an old MOPAR shaker-style hood scoop that I've contoured to the rear of the roof. I thought that a wide thin clear plexi duct running from the roof, down the inside against the rear window and into the engine bay through the back (shelf/upper fire wall) would help somewhat as well.

I've often seen such things between carbs and intake/exhaust manifolds both aftermarket and stock on some British cars.

All of this is probably a good idea even if the Rotary doesn't work out as the VW engine for ir is very similar to Gordon's and the Fiat engine bay is traditionally cramped and very hot. Not that good for a VW mill at all.


Oh . . . made an error. The track is 50", the wheel base is around 76".
J justinh
You're right, very unlikely to break from torque with a rotary. The main issue is temp. The high RPMs and hooked to an engine that puts out a lot of heat like a rotary could cause problems. But even then, it could take an hour on the track before it's an issue. You could install an oil temp gauge first to see if it's really necessary or just install the cooler now. They're on some Porsche transaxles at least, or have added an aftermarket one if raced.

I doubt you'll find any in a regular junkyard though. A standard manual transmission in a road car doesn't need one.
tmpusfugittmpusfugit
On my Spyder I did the exhaust with ceramic coating, then ended up wrapping it with thermal tape too. but the transmission got quite hot still after extended runs at higher speeds...namely an hour or two at 90+/-. I built a transmission cooler for it using a 12 vdc gear drive pump, an external cooler, and took the oil out via the bottom transmission drain plug and pumped it back in via the fill plug. My transmission when hot would get hard to shift. After fitting the cooler, no more hard shifts. It nearly doubled the oil in play what with filling the pump the hoses and the cooler. I never put a temp sensor in the oil so I am not cerain how much it lowered the transmission temps, but before the cooler I could not leave my hand on the case, after fitting the cooler it was still quite warm but I could leave my hand on it. Not real scientific but.... and regards your gearing at 8000 rpm and terminal speed? Over 180mph...I don't think your areodynamics will allow that....

I had to buy the gear pump new, it flowed about 2gpm anything more than that would have been too much I think, as the transmission with cooler held about 1 gallon of oil
Gordon NicholsGordon NicholsMassachusetts 1993 CMC Supporting Member
Dude! Ice on the bay yet??

I had one dune buggy back in the days that we ran autocross and almost never got out of 2'nd gear. Running at that super-long course they used to have up in middle Cow-Hampshire the tranny would heat up to the point that it was REAL HARD to shift it leaving the course. We did a pump-cooler set up as mentioned above and that cured it. The cooler was pretty basic - like a 6-pass or something and the pump was something made for a farm insecticide system from Clem's out in Spencer. Worked great!

Headin home soon. Life has finally flowed around us.

Gn
FM Former Member
Sounds like the perfect solution !

Could you tell me where you bought the 12 vdc gear drive pump? I was thinking of going to Summit or even Speedway, but if you remember where you got yours, and you're as satisfied with the set-up as you seem, I'd just as soon try to duplicate what you've already field tested.

Thanks !

TC
tmpusfugittmpusfugit
TC, this is what I used http://www.enginegearonline.com/products.php?product=1-GPM-Gear-Pump-12%7B47%7D24-Volt

I still have the whole setup around here someplace. I took it off the car when I pulled the big engine...before I sold the car...finding it may be another story....I plan to use it on my current Speedster as soon as I get it on the road....

I did use a small coarse mesh inline filter before the pump to keep out gear debris....
FM Former Member
Once I get the front VW bulkhead in place, I'll shoot some pics. If things work out, if the trade goes as I expect, I ought to have the Rotary set-up here around the same time. I'll get some pics of that as well.

Hoping, but not too much. Don't wanna be disappointed, you know?

TC
FM Former Member
Thanks for the additional info.

My buddy (and partner in the race team) is a plumber, I'm covered on the fitting required. Despite the low pressure, I'll probably use the braided oil lines and AN fittings from the dry sump system, since I've already got 'em and they're top quality.

We pulled a 3.9 engine out of a Land Rover this afternoon and grabbed the hedge hog (trans cooler) out from behind the grill while we were there. It's a neat piece, so I use that for the transaxle cooler.
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