4104 gearing

[Jay52999]

I'm a newbie busnut but I'm in love with my 4104 only issue is the high gearing I tow a pretty heavy trailer and rig what can I do for a lower gear is there a spliter box or anything I can do about needing  a low gear ?? I'd hate to be on a grade and have to stop. There must be something out there?? What did they do back in the day ??

[richard5933]

Welcome to the forum.

Aside from your question on gearing, I hope you read through the various threads on towing to be sure you are not pulling that weight bumper or engine cradle alone. A hitch on a GM bus needs to secure to something forward of the engine. There are ways to set up a hitch safely on an old GM bus, you just have to know how.

Back in the day? They didn't tow, and they had the routes carefully set to avoid taking the bus in places they couldn't go.

I have a 4108 with an 8V71 and a 4-speed. I also have a problem with first gear being way too tall for getting a good start on a hill. How I've dealt with it is by being very proactive in route planning and being really careful where I park. A guy can get into a really tight spot trying to start off on a steep hill. This summer we were at a campground where the road leaving was about an 8% grade, and we walked it first to be sure there was a flat spot at the end of the road - didn't want to have to wait for traffic on that hill as we'd have trouble getting moving again.

Reverse is also quite tall, so be careful where you park and don't leave yourself nose down on a steep hill, especially if you won't be able to pull forward to get out.

Never heard of a two-speed rear axle being installed on a V-drive, but some of the guys with more experience will surely chime in with a more definitive answer.

There are steps you can take to up the power of your engine, particularly if it's a tired engine which hasn't been touched in years. That might give you some help getting moving.

Best advice I can give is to do what I've been doing - be careful where you go and especially where you stop. Slipping the clutch to get moving is not a great idea, so proper planning is essential.

[chessie4905]

If your top speed is around 68 to 70 mph your axle ratio is 4:11.Your choice is to find a differential carrier assembly from a city bus of same vintage. 4:56 ratio. Only down side is 10mph reduction in top speed. Will start out and backup up beautifully.. Another choice would be to change tire size to 11:00 r22.5. That will help some and reduce top speed 3 to 4 mph.

[Nova Eona]

Not much that can be easily done to help this issue mechanically, but there's another thread around here which details a good emergency procedure in case you manage to get yourself stuck.  In short, modify your fast idle (or add one if you don't have it) so that you can give the engine a little bump in power starting off without introducing human lag into the equation - we fleshbags can't adjust the throttle quick enough to apply power without risking damage to the drivetrain while starting off.  Not for everyday starting, but handy in a pinch.

Mine came to me sans fast idle, so I'm in the process of building an arduino-controlled cruise control / fast idle system that'll let me select my RPM at will when needed, should be cool when done.

[dtcerrato]

What is your top speed on flat highway? If you can get it into the mid to high 70s you may have a 356 differential. Our 4104 with a stock engine and a 411 differential has towed plenty a heavy trailer & toads. It is a turtle but has always done what's asked of it sometimes with the help of the four down toad...!

[Coach_and_Crown_Guy]

I'm new to signing in here but have lurked for years. I own several Crowns but no Coach yet, due to the money involved in acquiring and owning one, and a deep respect for the costs of keeping it in good shape. I intend on getting one for sure and have my preferences when the day comes to shop around with enough money to do it right. I've been on the skoolie site for several years but only get involved when a Crown thread pops up.

I've been driving commercially, first school, and then charter buses and semi-trucks since 1969 and learned on Crowns and then 4104's. I still drive Charter with Coaches and Crowns, so what's wrong with me?? 

I owned my own Charter company for several years and got out after a few years, got that out of my system, best business I ever got out of.

Same with the Truck thing, I tried a Tractor for a few years, same thing, too much regulation and impossible to make or keep any money after expenses and repairs. I'd rather drive for someone else and let him pay the bills since all I really want is to drive and have the fun of driving and the people I meet and the cool places I get to go and see.

The Towing thing is getting lost here. You Really need to check out how that's secured to the bumper/engine cradle assembly. It's important it's done correctly or you can rip it out of the bus entirely and set it on the ground. The entire Engine/Trans cradle WILL fall out. There are only FOUR attachment points and they aren't designed for pulling any loads with any kind of trailer hitch.

I don't know if anyone knows about this, but there was an optional two-speed clutch available for those 4104's or anything else using that 6-71 engine/trans package in Transit/Suburbans coaches at the time which was the very most common setup GM was making on all the various models being built. They pretty much were all using the same drive train and engine/trans cradle design which was very smart and eliminated many problems for cross vehicle parts commonality, Very, Very, well conceived and executed. They called it the Hydra-shift, I think. That's what I remember anyway.

I started out with a Charter Company in the early 70's that had a mixed fleet with 4104's, 4903's and Crowns. Five of the 4104's had the two-speed clutch "splitter" optional setup installed. They bought these used from a San Francisco company who ordered them new from GM. It was an extremely little known option, but I've since seen it also in a 4103 that a friend of mine owned and it was still working at the time. I conclude from this that GM had it around and available for years but most customers didn't order it if they intended the buses to stay on mostly flat terrain.

I drove these a lot and we did things with them that were unheard of for a standard 4104 at the time. We'd pass the new Greyhound MC7's with the 8V-71's on hills all the time, and we'd do other special things like coming up next to another bus and then we'd split either up or down and walk away from them. It was a blast.

The only problem with these was that the parts became harder and harder to find and as they encountered repair issues and the parts weren't available they were being forced to disable the two speed clutch function, which turned them into a completely normal standard 4-spd 4104 with no special magical powers. Very sad.

The two speed clutch was a very cool design where there was a special two position clutch installed in the flywheel housing between the engine and transmission. Remember GM engineered this so it worked like it was meant to be there. It worked this way. There was a single double-sided clutch plate with friction material on both sides, set between two steel rotating plates. One plate was connected directly to the output shaft to the transmission 1:1 ratio. The other plate had a planetary gear in it's hub that caused a slight lowering of the speed of the output shaft 1:.85 or whatever, I never knew the real ratio. This caused the output to the transmission to be slightly lower and with a little more torque input to the transmission. This means that the splitter was actually not an overdrive but an UNDERdrive outputting a slightly slower engine speed to the transmission. This gave much better hill and start on grade performance with no hit on high speed freeway driving. When they were disabled due to lack of parts they were just another 4104 with all the same issues of not getting yourself in a position where you couldn't pull the bus out of wherever it happened to be sitting. It was a fact of life and what we all were very aware of and protected ourselves from.

If anyone is interested I can explain the best way to drive these with the Hydra-Shift since they introduced some complications and contradictory gear ratios in the normal shifting of the bus. Not troublesome but definitely to be handled by the driver to get the most out of it. That's all back in the day when the Driver Really had to know how to Drive his vehicle, which today is mostly a lost art. That's sad too.

Another good Gotcha, and never to be forgotten, is to NEVER ever let yourself get to where you have to rely on the reverse (solenoid) to get you out of wherever you are now, because that's when the damn thing will fail. NEVER put the bus in a position that you can't drive out of by going forward, or you will experience Senior Murphy in his full and complete splendor. By the way, even if this happens, how many here know about the trick to kick the reverse lever on the transmission with your foot??

GM left about a 3" extension on the reverse lever that the solenoid pulls on, this is so it can manually be pulled and held in while the transmission is pulled back into second gear. It's a two man job, which I've had to do a few times but it works perfectly, which shows just how great the GM coaches were conceived and constructed. GM's were and are to this day some of the best engineered and built coaches ever. A nearly 70+ year old 4104 in good condition will still look and drive better than lots of the newer coaches with no rattles, bad handling, bad ride, or other problems, and they stand up to all the wear and tear through the years because everything is made of aluminum and steel and not fiberglass and composites.

I say this also about Crowns and for the very same reasons. I love GM's and Crowns for the fact they were built to be driven HARD and also to be simple to maintain and kept on the road. This isn't done much in our throw away world. But I'm not biased or anything. Anyone who knows me knows I love good engineering and despise marketing expediency, and the just barely good enough ways of doing things today with life times of only about 10-15 years, instead of the decades the older buses were, and are, still capable of, and showing us all every day they can still do.

By the way, the 6-71's didn't have a fast idle from the factory since the A/C was driven by a separate engine on the left side behind the front wheel. Not enough power left over for an engine driven A/C anyway. But when the 8V-71's were finally developed and available they did start driving the A/C from the engine and removed the separate engine setup recovering some space and allowing for larger luggage bays, hence the 4106 was born.

The fast idle was needed primarily to keep the alternator output up so the batteries weren't depleted by the massive internal air circulating fans, but also to keep the A/C compressor running efficiently and also to keep the main engine oil pressure up so the engine wasn't being lugged with the A/C load at the usual 5psi idle oil pressure, not a good idea. A real Three-fer for sure. So fast idle became the norm with a new governor design and various controls to set it and make it work to protect the engine and batteries.

[chessie4905]

We had the hydrashift in our 4104 for a couple of years. It provided overdrive in each gear. Top speed in 4th over was high 80's with our governor set to 2450. Unfortunately parts and info was scarce on it. (before internet). We removed it when clutches failed on way back from Texas. Fortunately direct still worked ok, so made it home OK.
I don't  know for sure, but suspect most parts from this were taken from the vs series transmissions from that time. If we could compare the parts, the planetary may be the same, including clutches. Probably never know now. I did buy a hydrashift operators manual on Ebay a few years ago. It stated to shift it without depressing clutch, which we didn't  know back then. It did have a wet clutch like 4905's

[Coach_and_Crown_Guy]

I was tempted to say that the Hydra-shifts had a taller rear-end since I seem to remember they were real dogs on starting when it was disabled/removed, like with a taller rear end, but I didn't want to go out on a limb if I was wrong. I'm real sure that the Hydra-shift was actually an under-drive since that's what the planetary gear arrangement always does. The apparent overdrive and 80mph speed is due to a higher rear-end ratio and the direct 1:1 output to the transmission.

But I must say the standard run of the mill rear-end (4:11?) 4-spd 4104 did a fine job of cruising at about 73 when the road allowed for it. I have no idea what the rpm was since they didn't have tachometers. I'd guess around 2250 since I know that company and they took real good care of their buses but set them up to run Really good and fast. So you probably could get 80 at 2400 out of it. I really don't know what the rear-ends ratios were since it was a long time ago and I wasn't all that involved in the maintenance and little ins and outs of the options available.

My experience was that GM built their buses with the same features and driveability which made them such outstanding fleet buses where any driver could jump from one to another and find exactly the same controls and performance and just drive it away with total confidence. I did that all the time sometimes using 3 or more buses a day for different jobs and destinations.

Check out the manual again and let me know if I'm wrong on this point. I think I've only seen one of those manuals in all my years and I wasn't in a position to acquire it and the guy wouldn't part with it anyway. Oh Well. Hydra-shift parts, usually the wearing parts like the special two faced clutch member, are totally Unobtanium today which is too bad since it was a very nice and well executed design and why you don't usually see them in operating condition today if ever found in the wild.

I also remember that the operators manual instructed the driver to pull the button without using the clutch, BUT the owners didn't want us to wear out the clutch plate so they had us use the clutch to try and extend the life since they were getting hard to find even then in the 1970's. They were such a blast to drive and we really had the confidence to take the bus into situations we would not normally try with a standard 4-spd 4104. Like you said I/We would always get out and walk the area to make sure we could get the thing out again.

I always say that I must walk with most any Coach, even today with the large size usually, to verify I can get in and out. But with a Crown the usual drill is that if I can drive it in I can usually expect to drive it back out again. There are exceptions of course and I have shied away from some situations but they are few and far between with a Crown. I've taken Crowns into some of the most horrendous camps with the nastiest roads imaginable where most regular passenger cars would fear to tread. I consider them like 35ft Jeeps.....almost.

[chessie4905]

we had 4:11 rear. planetary gear setups can provide underdrive, direct, or overdrive depending on which of the components is held stationary. check how auto transmissions work on google. Ill see if I can post info off the GM booklet concerning ratio.

[windtrader]

First welcome CoachCrownGuy and great you decided to join. Obviously, you have great depth of knowledge to add in an ever decreasing and shrinking busnut world.


I won't take this thread OT so quickly so look for my question in a new thread.

[TomC]

Take that 4 speed out and install a Allison V730-all problems solved.

[chessie4905]

Fuel mileage and power will both be down though.

[buswarrior]

Hydrashift was a rare as hen's teeth piece of equipment 20 years ago, amongst active busnuts...

Go looking in long abandonned coaches, the ones that have been stationary cabins.

Few have heard of them, fewer ever saw one.

Reported to break in less than caring hands, but it would be fun to have one in a camper!

Happy coaching!
Buswarrior

[chessie4905]

put one in a 4104 and you  lose the #1 item 4104's are famous for. Reliability. If it breaks down on the road, keep money aside for towing. NOBODY is going to know how to repair it and parts specific to it are non existent.

[RJ]

Take that 4 speed out and install a Allison V730-all problems solved.

Tom -

A V-730 bolted to the 6-71 will hang out the passenger side of a 4104, plus the driveline angle will be all cattywampus, thus chewing up U-joints.

Those that have installed a V-730 have also repowered to either a 6V92 or an 8V71, and replaced the rear axle for one out of a 4106 or later V-8-powered GM coach.

Problem solved.