3:88 transmission

Hi all,

I am in the process of buying a speedster that does not have a 3:88 transmission. I am just curious as to the difference it makes compared to the 4:12. Is it a big difference? Do the rpm's with the 4:12 go really high at highway speeds? And lastly, would it be a huge project and cost a lot of $$ to swap transmissions? Thanks!

I think the 3:88 is great for highway driving. That said, for around town stop light fun the 4:12 may be better.

This thread interests me, as I am shopping for a car. I drove a nice IM yesterday with 2110 engine and 3.88 transmission, and really liked how it drove. Good acceleration and power, plus nice gaps between the gears.

Are there general guidelines for mixing engine size and transmissions?

David, I have a 4:12, and have never had any concern with the ratio for street or highway. I personally don't think it makes a whole heck of a lot of difference, just my 2 cents

Hey thanks Gary, that sets my mind at ease. In other words, when your traveling 60-65 mph, you don't find the rpms unusually high?

David, I am having a new IM being built right now and Henry is installing a 4:12 with a taller fourth gear .82 for me. This way I get the low end torque around town and on the freeway the rpms will be lower do to the taller fourth gear. This may be an option you may want to check out.

Oz

What size motor and how much torque do you have? With a smaller motor the 4.12 maybe more fun. Depends on your tire size to.

David,
I have to disagree with Gary this time, I've had both and the
3:88 is 10 times better for highway driving....and the low end
isn't that noticeably different, whatever sacrafice you make on the low end is well worth the switch....
We all like the curvy roads but you usually have to take a freeway to get to them...At least in L.A.

Yeah, I am planning on driving the highways quite a bit. The car I'm picking up has a 1600cc, which is fine for me because I like to cruise. Is the 4:12 really bad on the highway as far as rpms go? Would it be possible to modify or swap the 4:12 to make it more highway compatible, or would that involve a lot of $$$?

David heres my facts
......Running 195-65's on the rear, these have a 25" diameter ..........with my 4:12 tranny at 3200 rpm, I'm traveling at 66 MPH. With a stroker 1885 engine I feel comfortable pulling strong up 5000-5500 rpm, so at 66 mph I am in my rpm midrange and have lots of poop left...

If I choose to rip ...in 4 th gear at 5000 RPM, I'm running at 101 mph. Not really something you want to do for long in a 1500 lb car, that is light in the front.

That's the facts, Jack

Gclarke "The Vacaville Guy"

The 4:12 with a taller fourth gear i.e. the .82 is a Freeway Flyer set up.
When shifting at highway speeds from fourth to third , there is a larger ratio gap than in a standard four speed trans.
Hence, you have to get accustomed to allowing the car to slow down somewhat in fourth prior to down shifting into third.
A quick fourth to third downshift will run the engine rpm's up rather high but not as severe as it would be downshifting from fourth to second in standard ratio trans.

David, alot depends on the engine, I have a very srtong 1776 that makes it's power and torque up in the rev range. I have a 412 R&P and love it for this engine. I can accelerate with a 2110 to 60 mph, and cruise all day at 65 to 80 mph at 3500 to 4000. Remember, contrary to what some people say VW's will live longest and stay coolest between 3K and 4K.

Eddie

The cheap guys rear end switch is a taller set of tires. Drive the 4.12 with your chosen tires. Then change to taller (larger diameter) tires. A little math should get you the equivalent ratio of a 3.88.
Did this once on an old Corvair. The taller tires gave a big improvement in cornering (probably because they were a bit wider and rubbed the body in corners) but the LOOK was awesome! Only trouble was I was driving at near full throttle just trying to stay up with traffic on some of the hills on a local freeway! Not a good result.

My advice would be, buy the car and see how you find it.

Swapping out the gearbox is a straightforward and cheap job, which you may or may not need to do.

Get the car, and see how it suits your driving style, in the knowledge you can easily remedy things if it doesn't

On thing I did not see mentioned was building a custom gearbox with a gear pack that suits your particular needs.
Prior to melting down my 1776 pulled nicely through teh 4k s and then just went flat. But if I shifted the wide ratio gear box engaged the next gear at about 2500 and the car bogs. SO the solution would seem to me is to put a gear set in that is close ratio first thru third and then and real tall forth. ANyone have any experince? I for one like to zip around and while I do not expect wheel smoking kick butt performance, smooth acceleration thru the gears to about 45-50 would be nice and then a tall fourth allowing cruising at 3k at 60mph.
ANyone have any experience.\

Ralph, Stan Galat has some interesting info on gearing. You might check with him.

J

I agree with Vince's post. Like Vince, I have a 3:88 in my VS (which will be in a new home soon.). While it may not pull as strong out of the hole, it is great in the midrange and also long haul cruising. And I have not had a problem keeping it above 2000 rpms around town.

It may be old news, but I drove my 1776 (good build) with an oil-cooler and a 3:88 to LA and back to OKC without one single heating problem. And I flogged the car all the way. Long Uphill climbs through the AZ/CA desert were a breeze, and I blew into LA doing 4300-4500 rpms (so I wouldn't get ran over)after doing 1600 miles in two days. My point is: the 3:88 made the long runs at 75-80 mph easy to do... and, the car was really feeling strong in that 70-80 mph range.

Now, I think you could pull the same trip off with a 4:12 with the tall 4th gear.. and that may be a nice way to go if you really like the low end guts feel. So I am not knockin' that set up at all. It sounds good to me.

I can tell you from my semi-rookie perspective the 3:88 may be something to consider if you plan to take some road trips. It pulls reasonably strong in 1st.. but it is not the best set-up for a little stoplight to stoplight action.

And... another $$ choice would be to go with a 901 5spd with the taller 5th installed. I received a note from an IM owner that had her 1776 hooked up to the 5spd. She is thrilled with it after three season's use. John Leader also has one mated to his 2332 and tells me it is a great set up. I think the 5th is about the same as a tall 4th on a VW.. but you have so much more room to work 3rd and 4th for RPM runs. And it pulls strong out of the hole too. That's what I've heard anyway. Sounds like the best of all driving worlds to me.

Jim

Jim,

You've got the right idea. My 2110 with a 901 5spd is a very good combination 1st through 4th is great in the city, 5th around 3000 on the highway.

Karl

No doubt if you don't mind the extra expense the 901 5 speed is the way to go.....but the tall 4th gear works you just have to get used to revving the engine to about 4000 rpm before shifting to 4th or you will bog the engine and you need to wait for about 2500 rpm in 4th gear slowing down before you downshift to 3rd or you will have more then desired rpms when you put it in third. You get used to it and don't even notice it after awhile.

Jim:

Any more details/thoughts on your new car?

Yes, I'll post a little something soon. Its been FUN so far, and Henry is definitely a great man to work with.

My IM Speedster has a 901 5-speed with selected ratios; this is probably the best way to go on a new car but can add significantly to the cost. For instance, a 904 input shaft that allows total customization of 2nd gear costs $700. The GT torque-biased limited slip differential is about another $1,400.

If you're going with a Porsche gearbox, then why would you put in a 901 instead of a 915? I had a 901 box in my 911 pickup, and I hated the tranny/shifter. A G50 would be a perfect choice, but it's a big tranny and the motor would probably sit too far back.
Ron

Ralph, I have a 4.12 final and an aftermarket .77 4th gear backing my 2110. The RPM drop takes some getting used to but the revs at 75-80 are real easy and my mileage (US gal) is about 27/gal so I like the combination and it's less costly than replacing the R&P.
Rick

Ive been recently giving a lot of thought about a tranny upgrade, this trend is very interesting... Would you have a 4.12r&p with a tall 4th .82 or a 3.88 r&p with regular .89 4th? (1776 here, not 2110 yet). Engine gurus predict death due to overheating problems...
What about those 5th gear kits? Your opinions are greatly appreciated! - JJ

Hola JJ:

I grew up hearing that you always want to keep these engines rev'd at 3,000 or higher. The biggest reason was to keep the fan spinning fast enough to provide adequate cooling. That was the reason that Porsche went to the smaller diameter 356 fan pulley - to get the fan speed up when running the taller final drive ratio, and, hence, lower engine speed.

There's nothing wrong with having the engine spinning at 3,200 or so at 70 mph - that's even what the Berg 5-speed tranny's did, since they didn't have a big overdrive 4th. In fact, the Berg 5-speed had the same 4'th gear ratio as a stock VW - what they DID is provide close ratio gearing on 1 - 4 and then the usual .87 or so fourth.

OK, then...to answer your question, crank up your calculator and do the math on those fourth gear ratios and whatever you want as a rear-end gear-set, and see what the engine will be turning for RPM's at 70mph, given the size of the rear tire circumference and the differential gear ratio in fourth. If it's anywhere North of 3,000 RPM that's probably OK, but not over 3500. If you decide to run a 356 fan pulley regardless of the ratio set you choose, that's probably a good decision, too. I used to have something in Excel that did this sort of thing, but have just migrated over to a Mac (yay!) and can't find my old spreadsheet - it wasn't hard to construct, anyway...

I, personally, wouldn't run a so-called "Freeway flyer" with a higher geared rear end ratio with anything less than a 2,110, and, even then, I would have a 356 fan pulley and STILL would worry about keeping it cool. You might get 4 - 5 more miles per gallon, but can easily eat that savings up buying an external oil cooler to keep the oil cool(er), but the REAL benefit of the 356 pulley is increased air flow across the heads - where cooling is much more important.

Besides, I'm one of those guys who rarely get higher than third gear around town...

Gordon

One huge mistake I see made all the time is guy trying to "Slow down" the engine on the freeway...


Guys, this isn't a watercooled cra. If your engine isn't turning at leat 32-3400 RPM at 70 MPH the engine isn't cooling well.

High gears put more load on the engine as the car is still the same wight with the same frontal area causing drag. This increassed load creates heat and then due to the gearing being too tall to allow for enough engine RPM the cooling fan doesn't turn and the heat thats being created is harded to shed. This is especially true with TI based engines because they have less finnage on their heads and need all the air flow and pressure they can get to expel that heat...

Its not as bad with a Type IV, we can run higher gears and the engine lives fine because it cools drastically better...

The moral of the story is don't over drive your car to make it quieter or more modern sounding. RPM is your friend for cooling those heads!

I'll debate this one ! The speedsterI am assembling has a Freeway flyer mated to a 1905 stroker motor runing stock 165x 15 tires . This set up works out to an acceptable ratio that will get the MPG's, have decent pull in fourth and still turn enough RPM's to cool the motor due to the 165 tires. Just my 1.5 cents!

OK, I

Damn good post,Stan

Thoughtful as ever......I seldom have the time (or patience) to crank through the numbers like that, instead, going with my "gut" and living with the results and then slowly, over time, making it right. Thinking it out and making it right from the get-go is a much better (and probably cheaper) way to go.

I have an old Floyd Clymer Porsche 356A Owners manual kicking around somewhere, in which the author has made a trip to the Porsche factory and is shocked to see the factory mechanics driving around the factroy in lower gears with the engines cranking 4 grand all the time. He was told "That's the way to drive these cars - they cool much better that way and they are designed for consistent higher revs".

Looks like you are designing the rest of you car around that idea, and you should end up with a great, driveable combination.

gn

...Continued from previous

My approach with my new engine and transaxle is this: shift-points should occur at the h/p peak, and drop me into the heart of the torque peak- in every gear. This is most easily accomplished by changing the ratios of the individual gears (as opposed to the r/p). Sliding the speed at any given RPM up or down is then a function of the r/p. I

Gord thanks for your reply on the smaller pulley for higher cooling, this is one thing I will be upgrading soon before any tranny/engine upgrade, I just wonder about is why this smaller generator/alternator pulley improvement, is not widely recognized in tech articles and then parts be offered in magazine ads? Manufacturers could be selling them by the thousands! and welded & balanced fans too... Another thing is how to ask for one (diameter)? I have seen some online catalogs selling the smaller 356 pulley, but there

The first time I saw the smaller pulley idea was when reading a very good book titled, "How to Hot Rod Your V.W. Engine" by Bill Fisher. The book is available on Amazon.com for less than $15.00. There's also a book called "How To Rebuild Your V.W. Engine" by Tom Wilson, which is an interesting walk through for stockers (not "Stalkers").

I'm not sure if the information in the book has been up-dated to take into consideration some of the improvements that have been made to strengthening and full-flowing Type 1 cases as production moved to Mexico and Brazil. But I think for many of us on this forum reading this book would expose issues that should be considered when trying to wring more horsepower out of these little engines.

Would anyone know if the stock 1968 VW swingaxle has a 4.12 r&p or 3:88 r&p? My bigger motor is just about done, the ratio rockers come tomorrow, and depending on my current r&p I'm wondering if I want to swap out the trans for a more highway friendly trans plus go with a short axle transplant to get the wheels and tires sitting better in the fenders.

Thanks,

TC

'68 Beetle- 4:12 r/p

Thanks!

That means that it's kind of better for around town, but would cause the engine to rev higher for highway use. Right?

TC

Yep!; still though, I have a 3.88 in my car and while in the highway it's still in the safe zone (for air cooled VW's) which is over the 3,000 RPM mark.

Yeah, but with a 4:12 R/P and the engine You're building, it'll be a KILLER between close-spaced stop lights under 200 yards!!

Might be a helluvan autocross machine, too!

FWIW - I believe you will find the final ratio (4th x R/P) was very similar over the years with the bug. The 3:88 came as the hp grew over but, what I like more than ever in the later trannies are the more even gear splits, 1st is a little longer and 2-3 are closer than early years.

A stock 3:88 is slower out of the hole, but a very enjoyable driver. Of course talking with any one of the VW tranny shops can mix & match anything you might dream up.

I've used a 3:44 R/P for 6 summers, 1650cc and 30k+ mi. It ain't no drag car, but gets me to the ice cream shop just fine. Overheating has never been problem with any R/P I've used. Getting good air has been an issue with thses tubs and that causes problems. I'm not selling the 3:44 idea at all, but life is full of compromises and this is one. Drag fast or highway cruising, exactly what type driving you will do should be the first consideration in this choice.

Not that I'm a big Berg follower, but what Gene did was use the stock 4th gear in his 5-speed conversions, thus no reduction in engine RPM or fan speed at highway speed.

Later

Boston Bob