who's running a 3.88 R/P

Ok so I shelved my big SUBARU conversion project. Too much work and summer is coming up fast. so...I'm staying air cooled. Motor will be a 2017 rated at 125 hp and 138 lbs.

I plan to spend alot of time on the freeway with my IM that I just bought. I basically have no choice living off of i80 in a rural area. To go anywhere I HAVE to use the freeway. Taller gears are needed if I want to use the fast lane and not die from rev' poisoning.

Builder wants to use a 4.12 with an ..82 4th. I personally want a 3.88 with a .89 4th. What I don't want is a big gap between 3 and 4 and that's what I'll get if I go his route.

I know these motors need a certain amount of RPM's to cool properly and that's basically the basis of his arguement. I say put a slightly larger pulley on to keep the fan spinning at the proper rate so I can run a taller ratio. Plus I'll have taller 1/2/3 gears with not so much gap. Ideal in my mind. Maybe I'll toss in an external oil cooler. I know that alone doesn't directly cool the heads but it can't hurt.

I've had high gearing with other 4 speeds before and it's no fun on the freeway. Nobody likes to mosey in the slow lane with the mini vans and 12 wheelers ie boredom, rock chips etc.. And def' not in California where even my 80 year old mum' drives like a nut. I've gotta' have a good crusing speed.

Any feedback/personal experience will be appreciated

i'm running a 3.88 and i can easily go 90mph (T4 motor). There was more room left on the power/rpm but i didnt realize how fast i was going (so i slowed down).

cruising at 60mph (100kph) is ~2800-3000 rpm IIRC

I run a 2110CC motor with a 3:88 final drive. stock 1-2-3- ratios with a .82 4th gear. This motor pulls that gear just fine, no cooling problems. There is a pretty big gap between 3rd and 4th. The motor pulls it with no problem, but if I lived in the mountains I'd go with the .89 4th and 3:88 final drive.

Yep I'll probably go with the 3.88 and higher 4th...and just to be safe I'll get a head temp gauge. Now I have to tell the builder...haha.

This guy is a real pro. There's gonna' be some tension..but I won't take no. I hate to piss off the builder. He's one of the top guys in the biz. SAMBA loves this guy...Raby loves this guy. And for good reason. Chico is the best.

I had a Rancho tranny with 3.88 R/P and extra tall 4th in my 1915cc Spyder..... I loved the car, but the tall 4th made for a more down shifting than I liked in the hills around here....

The added acceleration of a standard 4th with 3.88 R/P would have been about perfect for my app... My .02.

If Chico is recommending going with a 4.12 instead of a 3.88 there may in his thinking be a good reason...the differences between a 3.88 and a 4.12 is not significant.....with a .82 4th gear a 4.12 will run 2954rpm at 65 miles per hour, while a 3.88 will turn 2782rpm. Less than a 200 rpm difference.

I have had these cars with 4.12, 3.88, and 3.44. The 3.44 was a bit too much or too far IMO and the differences between the 3.88 and 4.12 are not worth the price difference IMO.

My current car has a 3.88....where we really need to spend $$$ is in the first and 2nd gears of the cars....3.80 is far too low for most of our cars...the more proper 1st/2nd gear set is over $1000 these days however.

Barne!
I have what you need.
I'm in a similar environment as you, down the hill in Grass Valley.
I went with a 3.88 r/p on a Berg 5-speed.
3.80, 2.06, 1.48, 1.17, .089
Fifth gear used to be my fourth as I found it comfortable for freeway speeds but the closer ratios afforded by an extra gear makes it a lot of fun for racing through the twisties.

Terry's Berg five-speed sounds fun, but I have the .89 r&p and 3:88 fourth you asked about. I live in fourth on the highway, and every time I tap the gas I go a little faster. The actual gear was sourced from a microbus' gearbox from back in the day, not a shop or recent production run somewhere.

I don't know what that gear is rated for, but I have pushed it so far (only once) that the whole car came off the ground. I've also outrun Russ Crosby's 911 on the highway pretty handily.

It'll probably do you okay for moseying around out West.

I am told mine is a 3.88. It has a 1776 with CB heads, balanced crank, and I have no idea of the horsepower but would probably guess 85-90 or so. I really like the gearing as-is. Freeway cruising is fine, and I came over a pretty decent pass back from Fresno with no problems at all. With your motor my gut says go taller on the gearing out of the two choices.

thanks for all the replies guys. I got ahold of the Chico today and we hashed it out. I'll be going 3.88 with the higher .89 4th. I promised him I'd keep an eagle on the motor temps, oil and keep the valve train in order.

I've sourced some Stork gauges...nice used cond. Oil temp/CHT...and a clock If I want it. I'd love to have an origianl Porsche clock but Not sure if the dash is big enough.The other 2 of those are def' goin in.

I'll need the external oil filter/cooler

plus quality synthetic ie not Mobil 1..most likely some fanchy shmancy' exotic euro oil..possibly Castrol Euro blend..not sure. If anybody has a favorite oil with oil test facts to back it I'd love to hear about it.

And of course if I want more cruising speed I can always bump up the tire size...he didn't recommend it but says that's one easy way to get a taller gear..doh. One of my favorite tricks.

I really want to keep care of the motor. For me...and Chico who seems like the most sincere builder you'd ever talk to. ALWAYS answers the phone. ALWAYS HELPFUL. Nice down to earth guy

About the Gene Berg box. That's one close as* ratio transaxle. I'd probably have to drop 2500 to get it right? I figure luckily...possibly...semi cheaply find a 5 speed Porsche box if anything..and if that fails then teh 'Berg will be on the menu.

I had a 4.12 with a .82 4th and didn't like it. The gap between 3rd and 4th was annoying.
I now have a 3.88 with a .89 4th. the gear spread between 1st and 3rd is better, but I wish I'd gone with the 3.44.

I was dreaming of 3.44. Reading Samba and other sites posts about it convinced me it wasn't a good idea for my altitude. Sounds good on paper..a nice tall gear...awesome cruising. But then it's the same 'cooling' issue that dominates the general consensus.

Anybody running an oversize pulley for better fan speed? That also sounds good on paper. Then I listen to Jake Raby and he makes sure everyone understands that takes more power...and in turn more heat. Still maybe a 'slightly oversized' pulley couldn't hurt?

I hear people say they 'cruise' at 60..65. Not here. You do that and forget about it'. 75 is crusing. 65 is the middle lane...and 60 is the Mosey' lane.

barne-

A minor point, but there is no "oversized" pulley.

There are only two pulley sizes for the generator/alternator available-- VW and 356 Porsche. The 356 pulley is smaller, and therefore spins the fan and alternator faster.

On the crank side of things, there are more options-- but they go the wrong way for additional cooling. A stock-VW sized crank pulley is about as big as you'll ever find. There are many, many smaller sizes available (from "power-pulley" to "drag pulley"). These spin the fan and alternator slower.

A stock sized crank and alternator pulley should cool adequately in a hot climate depending on the type of tin you are using, and your engines cam and compression ratio.

Contrary to what a lot of guys are posting on the Samba and elsewhere, I've never observed my engine running hot on the freeway from the fan spinning too slowly-- but then again, I've had bigger engines running "low-stress" on the highway for many years. Counter-intuitively, I've found that a larger engine under light load runs cooler than a smaller engine that is highly stressed. From my observations, the sweet-spot for the fan (from an efficiency standpoint) seems to somewhere between 3000 and 4000 RPM, which makes sense if you think about where a stock Beetle engine ran at highway speeds in the early '50s.

makes total sense Stan.

barne

Sam at Rancho took 1st gear to 3.10 from 3.80. 2nd gear 1.93 from 2.06. left 3rd at 1.26 and 4th at .89. Most of my driving is in foothills above Clovis. With 24.5 inch rear wheels that increased 1st gear speed at 4000 rpms to 26mph from the "stump puller" 17mph at 4000rpms. Have mild 2110. 3.88 final. I am somewhat familiar with your area and I believe the change in the first two gears is much more important than 4th. Other than front end, that is the best money I've spent. I'm not a wrench at all, just my 2 cents. Good Luck.

Bob

On my last car with a 3.44 and a .94 4th gear, I had a theoretical top speed of 171mph. Now, even if the engine had the HP to go there, and it mostly likely did have, the aerodynamics would not allow that with a stock body...my point is nearly 1/2 of the top end performance was outside where most of us would ever venture. The gearing I had in that car/transmission ended up costing me over $2800 8 years ago. Today I am guessing it would run over $3500. LSD? Add $1100 more. And the net result was I had a car that had a nice cruising RPM, a diff / RP that precluded use of an LSD, and a top end that was of no use at all. Even though the engine could crank 7500rpm it's torque maxes at about 5500rpm.

Jake insists, rightly so, of matching the engine, the tramnsmission gearing, and the driving requirements to build an engine or to build a transmission. What is ideal for my engine and driving expectations may be a dismal failure for yours.

If I were to order a transmission today, I would order a rhino case, forged aluminum or billet side plates, welded 3rd and 4th gears, 3.88 with LSD, 2.58 first gear, 1.86 2nd, 1.26 3rd, .94 4th. But that is specifically for a high torque 200+ hp engine...and a lighter than normal car.

And I have been running "power pullies" on the last 2 engines, with sand seals, temp guauges on the heads, and on the oil system. No overheating in the Texas sun at any speed, and I have driven a bunch on days where the ambient temps were 100 degrees +/- a bit. I use a DTM fan setup with external cooling. I am running Nickies so that does tend to change the heat transfer equation however....

Transaxle #2 built last year is geared a bit differently than Jim's recommendation, but is built identically: white rhino case, welded 3 and 4, ZF LSD (rare as hen's teeth, and grossly expensive).

I'm running a .89 4th with a 3.88 with my (actual) 200 hp 2332. I had a .82/3.88, but my present gearing is just better for all the reasons Jim said-- I've got the H/P to push the car down the road at a theoretical 150 mph, but the car itself would be airborne by 120. 110 is about all I feel comfortable with before the front end gets too light.

I wouldn't run a .89/3.44 or a .82/3.88 unless I had a 5 speed, and built 4th to be a legitimate 100 mph gear at redline. Everything is a compromise, but I think .89/3.88 is about as good as it's gonna' get with a speedster running an air-cooled mill.

thanks stan..and jim. great points

I will have welded 3/4's.Modifying the lower gears would cost$ too much. Not in the budget for sure

ZF Limited Slip. Impessive

To fine tune I'll def' play with tire size. My latest thought was stay with lower profiles for TAHOE (elevatation 6200)..and occasional trips to the coast I'll have a second set of taller tires. Real world testing I should be able to come to some tire decisions

Another update> I've also decided on JAKES' DTM shroud for the Chico p'plant.

Stan, I like my 3.88/89 set-up, except for the high rpm at highway speeds. To date, I've not been able to figure out what's going on. With my transmission, and 185/65-15 tires (24.5")I should be turning 3316 rpm at 70 mph. I'm not. My tach reads closer to 3800 rpm.
I thought it was my tach, so I had it sent back to the place that redid my gauges for recalibration (the place Henry sends all his gauges to). Now, at 70 mph the tach sits at around 3650 rpm, which is almost 350 rpm higher than it should be (using a GPS for speed reading).
Could it still be the tach?
Once I get the IM back on the road I plan on going for a drive with my laptop hooked up to the fuel injection ECU. This should give me an accurate rpm reading, which I can compare to my dash tach.
I'm betting (hoping) that the dash tach is still reading high.

I run 195/65R15s, Ron, and my RPMs match up perfectly with what the gear ratio calculator says it should be. I had my gauges redone at North Hollywood Speedometer (the place Henry uses) as well, and I really doubt yours is off that much.

I ran your info through a gear calculator, and um... are you 100% sure you have a 3.88 R/P? The numbers your are seeing are a lot closer to a .89/4.11. Perhaps the builder messed up?

It happens...

Stan I'm also looking to go 195/65/15's. Got any favorite summer tires I should be considering? Did a little TIRE RACK research and 2 tires that got my attention were the Bridgestone Ecopios and the Goodrich TA's. Both seem to be a good value and decent performers

I'm 99% sure it now has a 3.88. When I mentioned to Henry (months after I had the 3.88 installed) about the high rpm at highway speeds, he said he usually installs 3.44 R/Ps on his big motored cars. I wish I had asked his advice first. :(

If I could, I'd go with a slightly wider, higher tire, but with my current wheels (6 inches wide, offset unknown)and 185/65-15 tires I have less than 4mm clearance on the passenger side.

Also, by my calculations, installing 205/65-15 tires would only drop my rpm (at 70 mph) from 3316 to 3186; a decrease of only 130 rpm. That doesn't seem like much, for a one inch increase in diameter (24.5 to 25.5). Are my numbers out?

Two tires I'd recommend in your tire size:

1. Potenza RE960AS Pole Position (I have them on my car)

2. Michelin Pilot Exalto AS.

Henry has me wearing Yokohama AVS ES100 Summer. 195/60/15.

I had the Potenza 960AS Pole Positions on my Acura, and they were great. I believe the new owner has not yet replaced them. I also believe that Bridgestone has replaced them with another model called (I think) the 970AS Pole Position. I would certainly look at them.

+1 on the 960 Bridgestones. MUCH stickier than previous tires, especially under braking.

bridgestone. nice, typically I'm all over those pole position. However this time around I'm trying to stay away from Z rated tires. Crummy snow/ice beaten roads make for a noisy ride.

Aiming for H or V rated...maybe R.

The drivetrain is costing me a meeelin' bux so the budget is gettin tighter. I just found out I have to file an amended tax return by Monday...doh..

Umm, the 960 Bridgestones are H-rated, at least they are in the 60 and 65 series tires that we would use.

In front, I have had good luck with 195 60R 15 Kumhos with the 88H rating. The rears are 205 60R 15s, also Kumho 88H. They go for about $80 a copy now for just the tires.

They've lasted 65-ish thousand miles.

65k! Holy rotation batman...

I dont' mind H rated. Roads here are beaten by snow and ice. They suck. Any kind of cush' is welcome. SR is outta' the question of course. Those are for sissies