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Tue Nov 27, 2007 3:10 pm

Hi Everyone,
In the process of getting a drive train built for my 65 bus. Most likely I'll be going with a 1776 dual port (for reliability.)

I want to keep the stock tranny but go to a higher r/p. 3.88 or maybe even a 3.44?

I'm located in Santa Clara, CA and was curious if anyone local has a 3.88 or 3.44 r/p in their bus that I could possibly come check out?

Thanks,
cale
(408)828-6421

Tue Nov 27, 2007 3:41 pm

Are you going to be keeping the reduction boxes?

Both of those R&P's are kinda tall for engines with a 69mm crank. The 3:88 will work but it's very tall meaning it's going to bog down when you hit a hill, a headwind, or have a load (ie more than one person in the bus)

It all depends if you have the engine to push it. A 4:12 R&P with a .84 4th gear and 24-25" tall tires (185-r-14) will get you a 65-70mph cruising speed with no problems. Any faster in a stock height bus with stock brakes is fairly unsafe.

Tue Nov 27, 2007 4:13 pm

Mike,

Yes, keeping the RGB's. Aiming for a "close to stock" restoration.

So you're saying that a 1776 isn't enough power for the even the 3.88?

I kind of wanted to avoid doing a tall 4th gear because I'm afraid of the lag from 3rd to 4th gear. Where I live there are a lot of 50 mph expressways and I'm thinking that the motor would be over revving in 3rd but lugging in 4th. Know what I mean?

That's why I liked the idea of keeping the stock gears in the tranny and just changing out the r/p...hmmm...

Are you talking about bogging down in 4th? I don't care if I have to get into 3rd gear to climb hills, it's the long stretches of highway I'm concerned about. 65mph (not faster) is what I'm trying to achieve.

But if you're saying the 1776 will bog down even with just 2 people then I might be thinking of other options...

Thanks for the input. It's appreciated!

Cale

Tue Nov 27, 2007 5:43 pm

If 65mph is all you want to do, just stick with the stock 4.12 r&p. With around stock sized tires (24-25" diameter), it's good for up to about 70ish mph at 4k RPM, which is perfectly fine for cruising.

Tue Nov 27, 2007 6:34 pm

Bus transaxles use an .82 fourth gear stock. You should be fine with a 3.88 and reduction boxes. Maybe a 3.44 with a bigger motor but the 3.44 is WAY more expensive than a 3.88.

Tue Nov 27, 2007 7:49 pm

Cale,
I've got a 3.88 Rand P and a dual carbed 1776. Come and take her for a spin. I'm in Santa Cruz. It will be back on the road in 2 weeks. I'm doing a little work on her. You're welcome to take her up 17, that's the test for any bus!

Tue Nov 27, 2007 8:37 pm

Hey Cale,

Sorry I'm not up your way but I have a 1776 with dual Kadrons and a 3.88 r/p with reduction boxes and stock tranny and I think it's great. I don't do much over 65 on the freeway and find the gearing is real suitable for the soft grades we have down here. There are times I have to drop to 3rd on a grade, but when hasn't a bus had to take the right lane and enjoy the scenery (I know there are a lot of straight axeled, big motored, slammed fire breathing buses out there that won't stand for moving over to the right lane).

I think it's a good combo...

Scott

Tue Nov 27, 2007 8:37 pm

I had the 3.88 x .82 with big nut RGB's before I converted to IRS. I thought that was a great trans even though I had only a 1600 SP engine. Hills were always a problem with the 1600. You will like the trans even more than did since you will be throwing a 1776 at it.

Tue Nov 27, 2007 8:40 pm

Scott's '63 23 wrote: (I know there are a lot of straight axeled, big motored, slammed fire breathing buses out there that won't stand for moving over to the right lane).
Hey, I resemble that statement (all except the straight axle and slammed). :wink:

Tue Nov 27, 2007 8:42 pm

Okay. I just did a freaking ton of calculations regarding final drive ratios, ring and pinon combinations, and 4th gear combinations.

Most VW engines redline around 4k ish RPM. Each engine is different, as is its powerband. If your engine is operating outside its powerband it will:
a. Not have as much power as it should
b. Not be able to climb hills as easily
c. Not be running efficently
d. Run hot
e. Get bad mileage
f. Wear out prematurely

That being said you need to figure out where your powerband is, and where you want to be doing most of your RPM's when on the highway. Once you decide where your particular engine is suited, then it's time to talk gears. Check out the following image:

That graph is from the '66-69 bently, and covers the 1500sp engines. Obviously, you're going to have more torque and HP, but the curves should be roughly similar. You can see from the graph that you'd want all your acceleration and hill pulling power in 4th gear between 3500-4000 rpm. That being said, check this out:

Your bus stock should have* a 4.37:1 ring and pinion with 1.26:1 Reduction boxes, and a .82 4th gear. Assuming you're running stock tires (185-70-14's) you should be going 15.74mph per every 1000rpm in 4th gear. Meaning:
3000 rpm = 47.22mph
4000 rpm = 62.96mph
5000 rmp = 78.77mph

65mph would equal 4,129.6rpm

A 4.12 ring and pinion with your same 1.26 reduction boxes with a .82 4th will yield the following results:

3000 rpm = 50.13 mph
4000 rpm = 66.84 mph
5000 rpm = 83.55 mph

A 3.88 ring and pinion with your 1.26 Reduction boxes and a .82 4th gear would yield the following results:

3000 rpm = 53.13
4000 rpm = 70.84
5000 rpm = 88.53

A 3.44 Ring and Pinion with 1.26 Reduction Boxes and a .84 4th gear would yield the following results:

3000 rpm = 60mph
4000 rpm = 80mph
5000 rpm = 100 mph

That being said, there's certain things like drive train efficancy, wind resistance, drag coefficents, rolling resistance, momentum, and gravity to consider. If you have the motor to push it and you're only worried about cruising speed at any given RPM and not acceleration speed between gears and live in a flat, windless place by all means run the highest Ring and Pinion combination you can. In the real world situation with a motor producing around 60hp in a 3000lb bus with buckets of wind resistance the 4.12 R&P with the .82 4th gear sounds like it's better suited to what you want to do.

Tue Nov 27, 2007 8:43 pm

RockNbus wrote: Scott's '63 23 wrote: (I know there are a lot of straight axeled, big motored, slammed fire breathing buses out there that won't stand for moving over to the right lane).
Hey, I resemble that statement (all except the straight axle and slammed). :wink:

No slam intended. I actually hate moving over to the right lane in my bus unless my wife's with me and then I do it because she feels safer...

Tue Nov 27, 2007 8:52 pm

Scott's '63 23 wrote: unless my wife's with me and then I do it because she feels safer...

Ya, my wife has the safety jitters too. She especially hates when I come up kind of close to the car in front of me as I am stopping for a signal. She never quite feels safe, just different levels of 'unsafe'

Tue Nov 27, 2007 9:32 pm

Good post.... I was thinking 3.44 might work with a type IV conversion.

Tue Nov 27, 2007 10:00 pm

Fan speed is directly associated with engine RPM, so don't forget that if you're pushing an unaerodynamic bus with tall gears up a large hill with a full load and the fan speed is slowed down, the engine is going to run really REALLY hot.

Das Dragon (fellow samba member) told me a story about a mutual friend that has a mid-60's split with a 1776cc engine. He rebuilt the trans with a 3.44 R&P because a certain parts vendor with no first hand experiance with said R&P told him it'd be the best thing since sliced bread. It always runs hot, and off the line speed suffered horribly. More time is spent in each gear and acceleration is slower. It takes much longer to actually get it up to speed, and is harder to hold his speed because of the power to weight / overall gear ratio conversation. Don't forget that VW spent a TON of money and had a small army of engineers picking out the optimum gear ratios for what the bus was designed to do. A 4:12 with the 0.82 4th gear will cruise cross country just fine at 65mph all day long...

Here's the scans of my calculations and the formulas used to create them:

References here:
http://www.type2.com/library/misc/calcspd.htm
http://www.i405.com/vw/tech/Trans/

Oh, and God help you if you wanted to run taller tires with that R&P...

Tue Nov 27, 2007 10:46 pm

big bus mike wrote: Fan speed is directly associated with engine RPM, so don't forget that if you're pushing an unaerodynamic bus with tall gears up a large hill with a full load and the fan speed is slowed down, the engine is going to run really REALLY hot.

Das Dragon (fellow samba member) told me a story about a mutual friend that has a mid-60's split with a 1776cc engine. He rebuilt the trans with a 3.44 R&P because a certain parts vendor with no first hand experiance with said R&P told him it'd be the best thing since sliced bread. It always runs hot, and off the line speed suffered horribly. More time is spent in each gear and acceleration is slower. It takes much longer to actually get it up to speed, and is harder to hold his speed because of the power to weight / overall gear ratio conversation. Don't forget that VW spent a TON of money and had a small army of engineers picking out the optimum gear ratios for what the bus was designed to do. A 4:12 with the 0.82 4th gear will cruise cross country just fine at 65mph all day long...

Here's the scans of my calculations and the formulas used to create them:

References here:
http://www.type2.com/library/misc/calcspd.htm
http://www.i405.com/vw/tech/Trans/

Oh, and God help you if you wanted to run taller tires with that R&P...

The author of 1405.com vw tech used his calculations to decide on using a 3.44 r/p trans. The first person I personally knew to use one back in 1999 or was it 98. I do not remember what his 3rd and 4th gears were (they were both shorter gears) but he drove his Westy with that trans from Havasu to Washington and back on a regular basis with a NEW Mexi 1600 with duel Kadrons and 1.25 ratio rockers. According to an older dyno test in Hot VW's this engine combo made 72 HP at 4500 or maybe 5000 rpm, but I don't remember were the torque band was.He stated it was the best thing since canned milk. He went from a stock geared 4.12/82 4th geared trans.

I just remembered that Clara was at my shop and installed that trans in the bus.

Mikes numbers give you a real insite to trans gearing, speed, engine rpm, etc. It's always a hard choice. I have tried at least 10 or more gear ratio's in many of my buses and my favorite is still the 4.12/82 4th. They just WORK.

I have run 3.44, 3.88, 4.12 and 4.37 r/p's and up to a .77 4th gear.
Not any of my buses have the same geared transmissions in them. Always playing with trans and engine combinations.

Wed Nov 28, 2007 5:45 am

my trans that was just rebuilt for my 65= 4.12 r/p 3.80 1st 2.06 2nd 1.26 3rd and .82 4th. 1.26RGB's. my original trans is popping out of 4th once in awhile.

Wed Nov 28, 2007 8:36 am

If running hot is an issue because of the engine turning slower, the 356 generator pulley is the fix. The downside is it will take some power away that you are adding with the 1776. However, I did use it with my 1600 SP and 3.88 x .82 big nut. Both CHT and oil temps showed a substantial drop with that pulley.

Wed Nov 28, 2007 11:24 am

Wow! Thanks everyone for the wealth of information!

The number stamped on the side of my trans is H734 622. I was told that I have a 4.37 r/p. Is my stock 4th gear already .82?

If I go with the 4.12 r/p and a .82 4th, will the trans perform like it does stock (shifting from 3rd to 4th) or will there be a big jump to 4th gear?

The reason I ask, is because there are a lot of 45-50mph expressways in my area and I don't want to be between gears (over revving in 3rd, lugging in 4th).

It seems like many agree that the 4.12 .82 setup is the way to go. I was also told that by Mark @ Stictly Foreign. The only thing I'm concerned about is my question above (shifting from 3rd to 4th.)

That's why I was thinking about doing just the 3.88...so the gear ratios in the tranny would remain stock. Opinions???

-Mike, thank you for your calculations. Those give me a good knowledge of the gearing/rpm's.

Again, thanks to everyone for their input!
Cale

Wed Nov 28, 2007 11:27 am

by the way, my 1776 will have a rejetted stock 34 PICT carb and a stock oil bath air cleaner w/ a header and exhaust system...

Wed Nov 28, 2007 5:41 pm

IF your trans hasn't ever been changed or messed with, it should have a 4.37 ring and pinion and a .82 4th gear. The 3-4 jump is going to be the same (as far as the difference between the gears go) as it would be with the 4.12. The taller ring and pinion is going to allow you to make that jump at a higher overall speed. It moves all your shift points up as well, so you're going to have more time spent in each gear, and the accleration is going to be slower.

The 3rd to 4th jump is what it is. The .82 bus 4th gear is tall and there are plenty of situations pulling hills where its just too fast for 3rd but too slow for 4th. If you don't have the power to pull it, than back off the throttle and ride it out in 3rd gear.

With the stock carb and the stock oil bath, you're limiting yourself as far as how much power your engine has. I built a similar 1776 with 8:1 compression and a 34 pict 3 but it had single port heads (more torque) with adapter end castings (old DDS units). That bus was a '65 with a 3.88 r&p with a .82 4th gear. It cruised ok, but it took a long time to get it up to cruising speed. The next bus I built was a '67 westy with a 1776cc dual port with dual Kadrons. It had a 4.12 R&P with a .82 4th. That bus is more fun to drive, if you can put a tangable value on that. It cruises nicer, acclerates faster, and has more hill pulling power. The only difference is that it reaches its rpm limit at a lower speed. Both buses cruise comfortably at 65mph.