5 Speed - Berg 5 or Porsche 901/914?

I have always wanted to do a 901 trans conversion using a readily available 1970-73 914 901 based gear box. 

The 70-73 914 used a rear shifter (really off to side but not as much as the '75-76 ones) rear mounted 5 speed transaxle that is easily available for around $250.  Why?  914's were very prone to rusting in half and the unitized body is costly to repair.  The transaxle was geared perfectly for an aircooled 1.7/1.8/2.0L engine yet can handle 300 HP V8 engine power.  Regretfuly it is designed for a mid engine applications so the R&P has to be flipped and a breather vent moved.  Then a 901 nose cone and hockey puck or machined ones are need.  Early 914 owners frequently swap out the tail shifter for the later more direct shifting side shifting transmission so they often  excess the early tail shifters adding to numbers and lowering value.  The 914 employs heavier CVC joints and axle shafts so that advantage too. The 914 5 speed shifter can be used too as well as the 914 (or a VW semiauto self supporting) starter.  (there is no bearing in trans for the normal T1 starter).  It does need a trans mount and requires case plus engine horn clearancing.  It takes a car with IRS or conversion to IRS. Suspect cost would be $2500?

Porsche 912/911 901 from 1965-1970 are very costly (the Porsche stigma!) and are often well used so often require a costly rebuild.  I'd think the 911 gear ratios an not right for a 4 cylinder T1.  Just used trans could be $4k?

I don't now much about the Gene Berg conversion except that he shoves another gear set into a T1 case (with case mods).  I've always thought the T1 transaxle was the weak spot in Speedsters so avoided looking at this choice.  The gear selection seems to just place gears closer together where the 914 had a nice top gear comfortable over drive.  T1 would also have the weaker CVC/axles.  Believe cost is $5-6k (?) but not sure if that's with good core trans or outright. Believe they are available for swing and IRS.

Mike - there is an entire red Speedster in Calif for like $8900 with a Porsche 901 5 Spd already installed - was posted on SAMBA and here.  I mean if Madness is to strike - go whole hog!  https://www.thesamba.com/vw/cl...etail.php?id=2095170

Good info on 901 gear ratios:

http://www.blueskymotorsports....p;id=17&Itemid=6

WOLFGANG posted:

The gear selection seems to just place gears closer together where the 914 had a nice top gear comfortable over drive.

 

My thinking is exactly the opposite of this. There are about a billion possible gear combinations in VW gearing, and almost all are readily available. Yes, a Berg 5 is long money, but still much, much shorter than the current 901 prices.

Getting the right ratios is not at all hard with the VW transaxle. I'm not arguing it's better, I'm saying the choice should not be made because of a perceived lack of available gears.

@WOLFGANG if you haven't already, take a look here:

https://www.bugat5speed.de/en/...transmission-901-914

WOLFGANG posted:

I have always wanted to do a 901 trans conversion using a readily available 1970-73 914 901 based gear box... 

I don't now much about the Gene Berg conversion except that he shoves another gear set into a T1 case (with case mods).  I've always thought the T1 transaxle was the weak spot in Speedsters so avoided looking at this choice.  The gear selection seems to just place gears closer together where the 914 had a nice top gear comfortable over drive.  T1 would also have the weaker CVC/axles.  Believe cost is $5-6k (?) but not sure if that's with good core trans or outright. Believe they are available for swing and IRS.

Good info on 901 gear ratios:

http://www.blueskymotorsports....p;id=17&Itemid=6

 

You are right, Greg, the ideal transaxle would be much stronger to start with. The type 1 can be beefed up considerably (I know you already know this, but bear with me), but being originally designed for an economy car with much less horsepower than most guys typically run, it has design limitations that we are forced to live with. That said, it does quite well in front of all but the most extreme engines, as long as it's treated with some respect. The beauty of a type 1 transaxle over early 911/914, however, is 2fold- the shift pattern and the nicer shifting synchros.

And yes, essentially the Berg kit "shoves another gearset into a T1 case", but there's more to it than that. Your comment "the gear selection seems to just place gears closer together where the 914 had a nice top gear comfortable over drive" is a little misleading, as the T1 gears work perfectly well for their intended purpose in a stock (or near stock) engine in a much more un-aerodynamic car at legal speeds, and 4th is already an overdrive (less than 1:1). I think for a smaller type 1 engine, you'd find 914 gearing all wrong- 1st is too tall, the inbetweens are alright but 5th is probably too tall as well (and causing overheating).For our purposes custom gearing is required, but most people look at that as an opportunity. While the statement "T1 would also have the weaker CV's/axles" is also true, in all but the most powerful cars it has proven to be pretty much a non-issue.

You are right, a Berg 5 will cost 5-$6,000 when finished (and that's with you providing a good core), and while it seems an awful lot to spend on gears, you've gotta drive it to appreciate it. I'm not saying it's the only (or the best) way, but for some guys...Al

I've been driving a Berg 5 for about a year now, and can offer some perspective.

I'm not familiar enough with the technical differences between the Berg and the 901 to advise, but my mechanic considered this the only sensible option for me, probably for most of the reasons Greg mentioned.

I have a 2024 cc mild stroker and 'just placing gears closer together' was the whole point of the five-speed. For me, the problem with the four-speed transaxle is the wide gaps between 2-3 and 3-4. I frequently found myself on the verge of lugging fourth, but reluctant to downshift because of how high the revs would be in third. With a close ratio five-speed, you have the right gear at any speed, on any grade. The car becomes quieter and more drivable around town and much more aggressive on the steep, twisty foothill roads all around here.

With a 3.88 r&p and modest power, the stock VW .89 top gear is already enough of an overdrive. Even with the five-speed, I like to hold top gear up as many hills as possible, so anything higher than .89 would be too much. Also, with modest low-end torque (below 2000 rpm), I like the low stock VW first and second for inching up steep grades when stuck in traffic.

So, the usual five-speed drill with an engine like mine is to keep stock first, second, and top gears, lower third a little to close the 2-3 gap, and drop in a fourth gear that pretty evenly splits the difference between third and fifth.

You just can't believe how it transforms the car. The biggest surprise is how much quicker it is off the line. I never realized how much of a hole I was falling into between second and third when trying to stay with traffic. Those 1200 rpm drops when shifting are now 700 or 800.

Vive la difference!

One more thing to add- the 901 trans (5 speed, limited slip diff, aluminum case) will be as much as 47 lbs. heavier than a VW trans (stock single side cover 4 speed- 72 lbs.). You have to fabricate the front mount, clearance the frame horns and figure out the shifter too. It's not terribly difficult if you can weld, but it's certainly not a drop in.

@Sacto Mitch- Great testimonial Mitch! My apologies for asking (I know you've told me before), what gears are you running?

If you're truly happy with the 4 speed you have, great, but close gears and a 5th just makes these cars all that much more fun (and that is what this is about, right?). People will spend anywhere from 4 or 5 to $10,000 (or more!) on an engine, but balk at any more than 1,000 or $1500 on trans upgrades. It doesn't matter which way you go, but if you do add a gear you'll wonder how you ever did without it...Al

I have to admit that I recently gained a new appreciation of the benefits of a close ratio 5-speed on the recent Tour de Smo.  On the twisty roads I frequently found myself in situations where I was a little too slow for one gear and a little too fast for the one below.  More ratios to choose from, with smaller gaps between them, would have eliminated that problem.

Berg-5, hands down. Talk to @Anthony, he has a couple of 'em lying around...

@Terry Nuckels can you elaborate on why hands down? Did you use the Berg-5 shifter or modify some other? If modify, what is involved?

Thanks.

Early 901 trans were aluminium but later ones were are magnesium (per Pelican).  I had a '72 914 1.7L and it was the dull magnesium color so thinking all 914 were magnesium.  If you grind the high casting marks off and the sparks are bright white - it's magnesium (was actually quite scary!). They weigh 119# so not light.

Here's chart that shows 914 info.  The tail shifter trans was used to early '73 and has the HAO prefix (HA is the side shifter which is more work/expense to convert). Looking at the tail shift it will look to be to the side - but the real side shifter is even further forward.  One on left is the later side shift - on the right is the tail shift.

http://www.bigporsche.com/history914w.htm

Here's another view of side shift -

I've had my Berg-5 for over 6 years and 20,000 miles. I looked into the 901 and didn't want to get into a lot of modifications and fabricating. @Anthony Tony worked with me on the gearing - many choices! Installation required a little grinding down on the torsion tube, a little widening of the transaxle tunnel, a new Berg mid-mount. In all, it took Tony and I around 2-3 hours for the installation. 

I drive aggressively through the winding roads of the Sierra foothills. The close ratio of the 5-speed keeps the revs up and the fun-factor meter pegged at 11. I installed a VintageSpeed shifter because I didn't like the looks of the Berg-5 shifter.

If you have a 901 laying around (with the shifter) that doesn't need gears reworked and you have good fabricating skills - go for it. But if that 901 needs a rebuild, especially if you're having to buy one, I think you'll find the Berg-5 to be the more economical move.

@Terry Nuckels what did you have to do to your VintageSpeed shifter to make it work with the Berg-5? I would like to keep my CSP shifter.

Is there a front mount in addition to the mid mount?

You'll have to contact CSP to find out if they make a 5-speed shift plate for your shifter. I bought a VintageSpeed 5-speed shifter. And yes, there is a front mount as well.

I have just about decided to go with Berg if I do a 5 speed. A trans. builder suggested replacing the rubber bits on the front mount with aluminum. Have you Berg 5 owners done this? It seems like if this was done the rubber bits on the mid-mount wouldn't be needed. With a 4 speed the mid mount prevents the front mount moving up. With the aluminum on the front mount with the Berg 5 it wouldn't be able to move up even without the rubber at the mid-mount.

I would stay with the rubber pieces, Michael; you don't need to be solidly mounted and it will be  quieter. Any idea what ratios you're going to do for the gearstack?

The rubber breaks down. Tony recently replaced mine with the aluminum ones. Regarding noise, the Berg-5 is definitely a "louder" transaxle, especially on deceleration. BIG nose cone. However, it isn't any louder with the aluminum mount.

I recently switched from a failed rubber mount to a CB Rhino mount which transmits quite a bit of tranny noise, although it's not objectionable.  Scared me a little at first until Stan told me what it was.

I experienced more noise as well, particularly in 4th gear. Sort of worried me as I had also changed fluid at the same time I had replaced the mounts. I thought I had messed something up.

Have you tried Archoil ?  Check it on Jay Leno...

Having followed Sacto Mitch around the twisting roads on the recent Tour d Hoe' I can personally attest to the difference in his shift pattern. I was always winding 2nd or lugging 3rd when he was pulling away from me. 

Just when I thought it was safe to come back...

TRP posted:

Just when I thought it was safe to come back...

Oh, how I like that comment.

Welcome back.

Terry Nuckels posted:

... Regarding noise, the Berg-5 is definitely a "louder" transaxle, especially on deceleration...

Although you can do a fair bit to strengthen the trans (weld synchro cones, harder keys, shimming gears for a little less movement, etc) to make up for it originally being designed for a much lower powered economy car, there is no way to stop things from moving on deceleration with a more powerful engine. Bigger engines subject the trans to more "thrust" (I'm not sure if that's the right word) on deceleration and I've been told it would take a major re-design to eliminate the noise. And it's not the addition of the extra gear; all VW type 1 4 speeds have this issue, so it's something we have to live with. Al

I had a really well rebuilt Type I one of the quietest boxes and it was still noisy on downshifting Al is right it just is plain older technology  

The five-speed is definitely louder than the four-speed was, and as Terry says, there's noise on trailing throttle that wasn't there with the four-speed.

This is probably amped up by the new aluminum front mount which Tony thought was necessary. Besides the gearbox sounds, it transmits more engine vibration directly to the frame and body. Which is a good thing - it reminds you to keep the engine synched and tuned real purty.

Making the new cogs (3rd and 4th) Weddle gears probably didn't quiet things down any, either.

If this were a Boxster, I'd probably be in a huff about the new sounds - you know, harder to hear your iPhone tunes streaming to the Bose.

But in the Speedster, it's now much easier to imagine that it's 1960 and I'm Hans Herrmann at the Targa Florio.

Is it possible, Mitch, that the new front mount is transmitting more noise into the cabin?

PS- Do you know what the new ratios in the 5 speed are?

ALB posted:

Is it possible, Mitch, that the new front mount is transmitting more noise into the cabin?

PS- Do you know what the new ratios in the 5 speed are?

Yeah, exactly Al - the new mount transmits all drivetrain sounds - engine and transaxle - into the cabin more. The engine you're only slightly more aware of, but on trailing throttle, the gearbox sounds a little like a race car. Oh, damn.

I've kinda gotten used to it and - in a funny way - these seem like the kind of sounds a Speedster ought to be making.

BTW, here are the five ratios (with a 3.88 r&p)

1st     3.78

2nd    2.06

3rd     1.48

4th     1.14

5th     .89

FWIW, this is a "pick your poison" affair. I've got a humble 4-speed, and have run it with a late VW front mount (the giant one), and with a Bug-Pack adapter and an early Prothane mount. The same transaxle sounded "old-timey" with the VW mount, and "like-a-bad bearing" with the much more solid mount.

It's one of the weak points on an old design, but as I have a car with old technology (on purpose), it's just part of the deal.

Michael - does your car have an IRS box or a swing? If it's a swing then the Berg is the leas expensive and more common route between the two.

Unless you can find a berg already built in the specs you like, plan on spending about a year from start to finish. 

ted

I was hoping it would be more like 6 months. I only got to drive my Speedster two times this year and had no trip to Carlisle. I would hate to miss the next driving season. The builder wants to use my current transmission. Since it was built more than 30 years ago he thinks it would have better quality parts than what is available now.

My car is IRS.

Michael- if you're going to do it, START NOW!  The 3rd/4th ratios that Mitch posted above are exactly what you want with a stock mainshaft and .89 4th. You can always find another trans to throw in for the spring/summer to keep you mobile 'till it's built.

The car is only down for a few days. It's the building that takes forever. Even if you are using your existing trans you could time it so the teardown and build up could happen in the off season.

Being in Michigan the off season is about here. But, a year would extend past the off season. And, the car would be down for the year if my current transmission is used for the build.

@ALB, I assume you meant .89 fifth in the 5 speed. What do you think about using .82 with a 3.88 R&P?

That's why I suggested finding a used trans to throw in the car for next season. Or look for a good late model core (look for a single side cover cased trans) to build from. That way you don't miss the driving season. And yes, I meant .89 in 5th (thanks for catching that). What do you think of the highway speeds your car can do? Does your trans have a 3.88/.89 combo in it now?

It has a 3.88/.89 combo now although when driving, the revs per mph seem higher than that combination would yield. Maybe my speedometer is off. I did ask Palo Alto Speedometer to calibrate it for my tire size. My current trans has a single side cover case with an earlier nose cone. My pan is a '72. I have been talking to Anthony about building it. As I said, my trans was built over 30 years ago and only has about 5000 miles on it. Anthony thought things like the 3.88 R&P could be better quality than what is commonly available now.

I understand that there is some concern about a .82 lowering revs at highway cruising and thereby reducing fan speed and cooling. I recently replaced my 6.75 crank pulley with a 7 inch. That would compensate somewhat.

With a well designed set of gears the rpm drop to the next gear gets shorter as you shift up. In a stock trans, at 3500 rpm the shift from 1st to 2nd lands at about 1900 rpm, to 3rd it drops to 2200 rpm and into 4th at about 2400. With 1.48 and 1.12 in 3rd and 4th, the shift from 2nd to 3rd lands at about 2500 rpm (300 rpm shorter than stock), the shift from 3rd gives 2600 in 4th and into .89 in 5th hits 2650 rpm.

The 1.12-.89 would make the 4-5 spacing really good for canyon/mountain (and general rippin' around!) driving and still give acceptable highway speeds. Going to .82 will give higher highway speeds  (6?mph faster at 3500 rpm), but will lengthen the 4-5 split slightly. Still better than stock 3-4, but now the rpm drops to about 2530 or so rpm, so it is slightly wider than the 1.48/1.12 split, which is not ideal. As I said, still better (130-140 rpm) than the stock 3-4 shift, and perfectly doable, but it won't accelerate quite as nicely in 5th as it would with the .89.

Your 2110 should carry either top gear easily. It all depends on what you want, and once it's built you'll never look back! _{(think big, big BIG SEG here!)}   Al

I appreciate all the thoughtful replies.

This thread is like seeing your ex-girlfriend walk by.  So many bad memories.

Please elaborate. I seem to remember an old thread.