| Author | Message | ||
| HuskyPups (63.178.213.11)
Rating: N/A |
Howdy Folks: Thanks for the wonderful bbs and the informative answers to my previous post. Now that I know what I want (late model 4905) and what I want to do with it (maybe, subject to approval by the "Boss"), I think I know just enough to be dangerous. I've read through the archives here and over on the yahoo gmc club until my eyes crossed, uncrossed, and recrossed again but I can't seem to find (other than tantalizing hints) the answers to these questions: (1). What transmissions will fit (are "Stock") in a 4905? (2). Same for rearend gearing. (3). Is there a tranny that has over drive (better mpg) that will fit (without 'major' modification), and if so are they worth it? (4). Which is better (less maint, better mpg), Auto or Manual (hhmm, opened the BIG can-o-worms didn't I)? (5). What kind of fuel mileage can I expect? I would like to be able to cruise at ~70 mph (I hate getting blown off the road by Mr. Mo Ron going 85-90 when I'm going 60) and still get 8-10 mpg (30-40 mpg would be bunches better :^). Is this possible, the 8-10mpg, or am I really certifiable like the Wife says? (6). How does tire size factor into all of this? (7). How should this monster be powered? 8V71 or 6V92TA? Or should I forget about the eng/trans and just hitch up the ole' sled team and cruise with Husky Power? (8). Should I just go ahead and call the "Guys in white suits with nets"? After re-reading these questions I realized just how little I do know!! Any of you care to edumacate this po' dumb boy from the hills of TN? Any advise to help keep me from sounding really stupid when I go bus shopping would be greatly welcome. Thanks in advance and Happy buss'n Dave p.s. Look out for future "silly questions"  | ||
| RJ Long (24.127.8.58)
Rating: N/A |
Ok, Dave, you asked: (1). What transmissions will fit (are "Stock") in a 4905? ~ The OEM "stock" transmission in the GM parlor coaches, starting with the 4106, is the Spicer 7145 four-speed manual. This includes your dream 4905. ~ Depending on the year, the "optional" transmission was either the VS2-8 or V-730 Allison three-speed automatic. (V-730 in late production, about '77 or so on.) (2). Same for rearend gearing. ~ The stock rear axle ratio for the 4905 is 4.375:1. With the OEM 12Rx22.5 tires, this gives you 65.5 mph at 1900 rpm. ~ The stock rear axle ratio for the 35-foot 4108, produced during the same time frame, is 4.125:1. With the same size tires mentioned above, this equals 65.5 mph at 1800 rpm. ~ The "taller" 4.125 ring/pinion can be installed into the 4905, however, as with any taller ratio, it will increase your top speed but reduce your hill-climbing ability. ~ Those are your two choices for rear axles. The others that are available are primarily transit gearing - quick to 30 mph, out of steam at 55. (3). Is there a tranny that has over drive (better mpg) that will fit (without 'major' modification), and if so are they worth it? ~ No to both questions. (4). Which is better (less maint, better mpg), Auto or Manual (hhmm, opened the BIG can-o-worms didn't I)? ~ In the GMCs, the manual gearboxes give better fuel mileage. Which one is more reliable depends on YOUR driving style. ~ Many GMs have ATs installed not for the fuel mileage, but so Mama can drive, too. Better check with her, 'cause if Mama ain't happy, ain't NOBODY happy! (5). What kind of fuel mileage can I expect? I would like to be able to cruise at ~70 mph (I hate getting blown off the road by Mr. Mo Ron going 85-90 when I'm going 60) and still get 8-10 mpg (30-40 mpg would be bunches better :^). Is this possible, the 8-10mpg, or am I really certifiable like the Wife says? ~ Like the Mercedes salesman told the prospective customer: "If you're worried about the fuel mileage, you cannot afford the car!" ~ Realistically, a stock 4905 will give you 5.5 - 7.5 mpg, depending on whether you run 65 or 75, how much weight you stuff into it, and if you're running a diesel genset off the main tank. ~ Your "toad", however, will easily surpass 40 mpg as it rolls along in the draft of the 4905. . . lol (6). How does tire size factor into all of this? ~ OEM tires are 12Rx22.5. Only 11Rx24.5 are taller, again, like the axle ratios, giving you more top speed and poorer hill-climbing. ~ Do not go smaller than OEM, however, do shop for sizes. If you look at Michelin or Bridgestone's web sites, you'll see that different 12Rx22.5s have different diameters, and therefore different revolutions per mile. (7). How should this monster be powered? 8V71 or 6V92TA? Or should I forget about the eng/trans and just hitch up the ole' sled team and cruise with Husky Power? ~ Huskies should do nicely, about 60 of them. . . ~ How FAST do you want to go uphill? That's only where the real difference is, performance-wise. And/or if you live in the Western US where most passes over our little mountain ranges are at the 4000 - 7000' foot level. The turbo six will not lose as much performace at higher elevations vs the naturally aspirated version. ~ The 8V71 came stock in the 4905, usually tuned for 275 hp @ 2100 rpm with N60 injectors. Changing the cam timing and bumping the injectors to N65s gives about 305 hp, or what the trucker's commonly referred to as a "318". ~ The 6V92TA also produced the same HP, but can easily be bumped to 350 hp by changing the injectors and turbocharger. Camshaft timing remains the same. ~ There are some LH-rotation 8V71TA tank engines out there that produce 370 hp, but they're harder to find than a 6V92TA. ~ Remember - GMC coach engines turn the opposite of most truck and T-drive bus motors. If you put a 6V92TA out of a truck directly into a GM without changing the rotaion, you'll end up with three/four speeds in reverse! (8). Should I just go ahead and call the "Guys in white suits with nets"? ~ Nah, just go listen 100 times to the the Statler Brothers sing "Flowers on the Wall". . . And order the book "Beginner's Guide to Converted Coaches", by Larry Plachno. Either from Amazon.com or busmag.com. NOW!!! Before Mama puts you away. . . 8^) RJ PD4106-2784 "The Giant Greenbrier" Fresno CA | ||
| DrivingMissLazy (65.207.109.140)
Rating: N/A |
RJ, I would like to compliment you on the excellent job you do of explaining things. I look forward to your well put posts. Richard | ||
| RJ Long (24.127.8.58)
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Thanks, Richard. I appreciate those kind words. RJ | ||
| Jim Stacy (32.101.44.84)
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RJ, Good info, well said. Jim Stacy | ||
| RJ Long (24.127.8.58)
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Thanks, Jim. As I said to Richard, I appreciate your kind words. RJ | ||
| HuskyPups (198.211.213.105)
Rating: N/A |
RJ: All I can say is, WOWZERS! When you answer a post you really answer a post! Since you are being so kind, if I may impose some more? Does the bevel grear (is this the proper term/spelling?) change the final grear ratio? (Am I correct in thinking that this gear is what makes a 'v' drive work?) Which is more common, a 'wet' or 'dry' clutch? Pros/Cons on clutch type? Thank for the previous info (now if I can keep it from leaking outta my head). Dave | ||
| Scott Whitney (24.205.239.26) Rating: N/A |
Hi RJ, All of your answers are excellent info. and always read your posts with interest. But can I pose a request for clarification of answer #3? You stated that no overdrive is available [for the VS2-8 or V730]. But according to my bus manual (Flxible transit), my VS2-8 has three states: (I won't call them 'speeds' because technically it is only a two speed) 1) hydraulic drive 2) direct drive 3) overdrive I know this has been discussed at length in the past and maybe it is just a matter of semantics, but it might be worthy of a recap. Any thoughts? Scott | ||
| RJ Long (24.127.8.58)
Rating: N/A |
For Dave: The bevel gearset does affect the final drive ratio. The 4905 stock 4-spd manual gearbox has a bevel ratio of 0.808:1, and when you do the math, it gives an overall final drive ratio of 3.53:1 in fourth gear. With the V-730 automatic, the basic bevel gearset ratio is 0.870:1, overall equals 3.80:1 The bevel gearset is located between the clutch and transmission, where it is better able to handle the higher torque output of the 8V71 engine. The earlier GMs (4104 & back) had the bevels after the transmission, where it could easily handle the 6-71's lower torque output. And yes, it is this gearset that makes the v-drive "work", plus the angled pinion in the rear axle. Dry clutches were used in all GMC manual gearbox coaches until the introduction of the "Buffalos" in 1966. GM then switched to "wet" clutches, and subsequently drove drivers nuts. Wet clutches are a bear when cold, but quite nice when hot. But trying to put them into gear after sitting in neutral can be an embarrassing task, because you either "grind them until they fit" or have to shut the engine off, put it in first, then restart the engine. Your passengers wonder what's going on. . . Naturally, the 4905 has a wet clutch. . . For Scott: Oops, forgot about the "overdrive" in the VS2 series automatics. . . was only thinkin' about the manual gearboxes. I've forgotten how the circuitry works to provide the OD in that transmission, but I seem to remember that several converters have incorporated electrical switches to control the shift solenoids, in order to provide enhanced performance. IIRC, I think George Lowry said his VS2-equipped 4106 would do over 80 mph in OD on the flats, but just chug up the hills at 20 mph in unlocked hydraulic drive. . . Most of the V-730 equipped coaches will climb at about 30 mph in second gear. . . HTH, RJ PD4106-2784 Fresno CA | ||
| Scott Whitney (24.205.239.26) Rating: N/A |
Hi RJ, I think the VS2-8 shifts based on fluid pressure. It gets to a certain psi then goes into Direct and then OD. Being low on fluid is easily noticed by having trouble getting into OD. Some people have rigged up ways of keeping it in the gear they desire. I'd like to do that at some point as well. Don KS/TX has his rigged that way and tells me he goes 70MPH and THEN goes into OD. . . I have learned how to watch the speed and keep it where I want based on speed. Keeping in direct drive down hills works pretty well as long as I keep speed under about 44mph. (my speedo reads 39 due to calibration, but that is another story) At 45 it will shift into OD, so I have to keep under 44 down hills. (unless it is wide open and straight, of course - got no Jake) Steep up hills keep me in hydraulic drive at about 20-25mph. Must keep it in hydraulic drive by watching speed otherwise it shifts to direct and then lugs and I have to drop down to about 19mph to get it to downshift it again. My top speed is about 65MPH in OD with my transit gears. Nothing to write home about, but works for me. Here are my approx. shift pts. Don't know why it doesn't up and down shift at the same speed. Would have been easier to memorize in the beginning. . . Hydraulic --} Direct: 25MPH Hydraulic {-- Direct: 20MPH Direct --} Overdrive: 45MPH Direct {-- Overdrive: 40MPH For simplicity I think of Hydraulic as '1st' Direct at '2nd' Overdrive as '3rd' although, technically speaking, this is not the case. The VS2 is only a two speed, although I have seen it referred to as a three speed in one of my manuals. : ^ ) Scott | ||
| Don KS/TX (63.157.176.251)
Rating: N/A |
Good job Scott. The VS2 shifts up and down at different points intentionally, is set by rpm actually, not really speed. My research on 4905's has never let me find a V730 powered one, in fact you must chop away a lot of stuff to get one to fit thru the bulkhead, and I have never found anything in the maint, operators, or parts manual suggesting this option. (Not saying that they do not exist, just never found one or the evidence yet) There are variations to the bevel drive ratio in a VS2, but most of us have the definitely overdriven one. Mine cruises at 1500 rpm at 70 mph, getting close to 9 mph doing that. It will of course run over 100 if you had a long down hill and a tail wind and wanted to do it. Since it is automatic, shifting down is not a big deal. I just love it! | ||
| HuskyPups (198.211.213.105)
Rating: N/A |
HHmmm, more food for thought. Thanks all for the informative answers to questions I'm sure you have all heard (and answered) before. Momma won't (not can't, but WON'T, even if you paid her) even consider driving a bus (She says our conversion van is to big, go figure). That is the principle reason for asking the mpg questions (if I gotta do all the driving I may as well get the most performance possible). Not to mention the fact that I prefer a 'stick shift'. Husky Power is cost prohibitive as well. I can't afford to hire a front loader to follow us around (Super-Dooper-pooper-scooper), so I guess engine selection will be low on the list of 'I wants'. Guess I need to do more reading and thinking and figure out what I need vs. what I want. Thanks again for 'splain it.... Dave ps watch out for more questions later (alittle knowledge is a dangerous thing:^) | ||
| RJ Long (24.127.8.58)
Rating: N/A |
Dave - Not being a gamblin' man, I'd betcha a Pepsi that if you got a 4905 with an A/T and took Mama to a BIG empty parking lot , or an industrial park on the weekend, you might not be able to get her out from behind the wheel! The 4905 is one of the "sweetest" coaches to drive that's ever been built. . . RJ | ||
| Ol Jim, hisself (163.205.54.75) Rating: N/A |
Hey, Don, I almost bought a 1980 H8H649 (updated version of the 4905). This bus had a V730 from the factory. I also have (somewhere at home) a copy of a manual for the conversion from 4-speed to auto. It lists all the parts required, gives a template for the bulkhead cuts, and a step-bystep procedure for the exchange. Now, all I need is a 730, some time, and LOTS of money :>) | ||
| Don KS/TX (63.157.177.215)
Rating: N/A |
Did you see the build sheet, or where did you get the feeling it was a factory V730? Don't want to make it sound like I am doubting you, I am sure there were some. Every bus that someone told me was a factory V730, had obvious indications that it was an aftermarket add on (including one H8H of a friend of mine) Do you recall what it used for differential gearing and shift method? The giveaway to me is the clutch pedal still laying there on the floor, shifter and clutch rods still in the tunnel, shifter arms on the firewall, etc. If anyone ever finds one, I would love to see the build sheets. That goes for the VS2 models also. Very scarce to say the least. I would LOVE to get a copy of your conversion instructions, hint, hint. | ||
| HuskyPups (63.178.213.57)
Rating: N/A |
Just a side note: I still feel like a kid sneaking out to play with the 'big' boys. You guys and gals have all 'been there, done that', and prob got the tee-shirt to boot. Gesh, one of the days maybe I'll have own 'toy' (bus) to take out and play:^) Happy Bussn' Dave | ||
| Stephen Fessenden (Sffess) (63.27.89.93)
Rating: N/A |
Don, the serial number on the coach Ol' Jim is referring to is H8H649 A220. Maybe someone can look it up. I am sure it was a factory V730. No indication that there was ever a clutch or manual shifter. Bulkhead looked unmodified to me. Made for that transmission. | ||
| RJ Long (24.127.8.58)
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H8H649-A220: New York Bus Tours (New York Bus Service), Bronx, NY, July 1980, Fleet number 1437. Did a quick search, couldn't find this company listed anymore, possibly absorbed by someone else. Luke at US Coach may be familiar with the company and perhaps even the bus itself. . . RJ | ||
| Mike Eades (Mike14905) (206.62.203.70)
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My Da Book shows the 730 as an option. Mike | ||
| Stephen Fessenden (Sffess) (63.27.88.92)
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H8H649-A220 ended its commercial service days with Grayline, running Miami, Ft Lauderdale, Tri-rail Station, Disney and the Space center. It had a 2 piece transit type door. | ||
| RJ Long (24.127.8.58)
Rating: N/A |
A two-piece door? That IS unusual on a GMC parlor coach!! Any pics available? Steve - email me off the board, please. RJ |