4:12 or 3:88 Tranny for a VS?

Fellas,
What are the pros and cons with each transmission? I understand the 3:88 is simply better for highway driving but not much else?

Thanks in advance for posting comments.

I'm running a final drive of 4.125 and a top gear of 0.82. I guess you could call this a 'freeway flyer' Works out to 3170 rpm at 70 mile per hour on 195x65x or 3120 rpm (at 70 mph) on 205x65. By comparison, a top hear of 0.88 would give you (again a 70 mph) 3440 rpm with the 195s and 3386 rpm with the 205s. Since I do a lot of highway driving it works out well for me.
Ron

I'd go with the longer legs. If you have a .89 4th gear, get the 3.88 unless you really like to hear the engine sing... all the time.

Scott, I opted for the low gears, 412 because I drive mostly on two lane roads with curves. Also remember the lower gears will give faster acceleration if you don't have a King Kong engine. I don't have a problem listening to a great sounding engine at 3700 rpm down the freeway. Eddie

Hey fellas,
Gear ratios are not only a function of the drivetrain, but also of the engines ability to supply sufficient torque at a given engine speed. A 4.12 axle ratio with a large diameter tire can be made to give exactly the same highway RPM as a 3.88 axle ratio and a smaller diameter tire. The main differences are: 1) You can get really wide tires with a larger diameter tire(flaired cars) and 2) you need a larger displacement engine with a mild cam to deliver torque at lower RPM. In other words, you have to consider the speed of the whole drivetrain.

If anyone is interested, I have a great Excel spread sheet with built in formulas, that alows you to input any tire size, tranny gear and rear axle ratio. It wil calcualte tire diameter, tire width, road speed for any engine RPM, total overall torque multiplication (tires, tranny and rear axle combined) and other stuff. You can even run it through all five gears if you want. You computer will need to have Xcell to work. I don't see any way to make attachments to this email, so send me a separate mail at deklipfe@bechtel.com.

I have a VS. I do most of my driving on secondary roads in Massachusetts and Connecticut. The 3.88 is OK for hauling ass on the highway, but...

I wish I had the standard gearbox for it's closer ratios between second and third. I don't think more HP would help. The gears are still very tall between 2nd and 3rd.

I'm more autocross than F1.

(Message Edited 4/28/2003 4:07:40 PM)

It's a little more complicated than just selecting a ring and pinion ratio; car weight, and power and torque curves, and tire diameters enter into the equation, too (of course the replicas are lightweights).

If you multiply your top gear ratio times the ring/pinion ratio that gives overall ratio. For instance, an overall ratio of about 3.5 to 1 with 25" diameter tires (loaded radius of 12.5" at speed) will give you a decent 70 mph cruise (around 3,100 RPM).

But you need to have a correlated 1st, 2nd, and 3rd gear in your 4-speed. I don't have my old Speedster "Drivers Guide" here with me but approximating the B-B-A-B transmission ratios of the original Speedsters should work well (would require a custom built transaxle).

The 912 4-speed ratios are 1st=11:34 (3.091), 2nd=19:32 (1.684), 3rd=24:27 (1.125), 4th=28:24 (0.857), ring/pinion=7:31 (4.429) With tires around 25" (165 /hr 15).

(Message Edited 4/28/2003 4:25:58 PM)

Really, the only way to have your cake and eat it too is to go with a Porsche 5 speed or a Gene Berg 5 speed. For those of us who can not afford the 5 speeds...well, we will have to give up some power for a decent highway cruising rpm. I wouldn't want my tranny combo with a stock 1776, but with a 140/150 hp 2110 I should be okay.
Ron (p.s. I guess we could just slow down....nah dumb idea)

Just for more confusion, I used a 3:44 R&P with the normal gear splits from a newer (71+) single side cover IRS for years. The early swing axle tranny had much broader gear changes, 1st is too short, 2-3 too long and 4 to short for todays highway speeds.

For my street use, regular driver speedster, I'd reccomend the newer IRS gear splits and 3:88's for comfortable street driving over the early trannys ratios. The 3:44's just stretch everything out a bit more. This all is with stock tire diameters and pretty stock VW torque curves on the lighter speedster. It would stink on tall tires or any high strung power house or if you were interested in getting down a drag strip in a hurry.

I have a small 1640 with dual 34 webers and I love it for my type of driving. Effective ratios are improved for occasional autocross events with a change of all 4 tires, smaller, stickier, lower profile tires to increase the acceleration and lower the car.

The 3:44 came from Transform and many Vintage cars came with the same R&P.

It all really comes down to your driving style. I run a 3:88 with a high forth. It works fine around town, but comes into it's forte in third and forth. Great cruiser, nice gear set up for faster two lanes, highways. And althoung the 3:88 cuts down on off the line runs... well, I still hold my own in town. I also love crusiing at 75 without the exhaust tone sounding like a wound out top.

Jim OKC

I'm like you, Jim. I do a lot of highway cruising where 70-75 mph is the norm. I just don't like seeing my tach at 3700 to 4000 rpm for extended period of time. (okay, sometimes its 75 to 80 mph)
Ron
P.S. (Okay sometimes it 80 to 85 mph, but that's only when I leave my wife at home)

Ron,
Under that proper and sensible exterior beats the heart of a bad boy. Go for it, dude!
John H.