| Author | Message | ||
| Jim Schrecengost (Schrec)
Registered Member Username: Schrec Post Number: 76 Registered: 2-2007 Posted From: 24.2.127.94 Rating: N/A |
Just finished the conversion and went and got it inspected which it passed!!!! Up shifting no problem......Down shifting well I need some advice. Anybody have any?? I have read thru the archives and tried and tried to do it right but it just didn't want to do it. Only a couple of times did I do it right. I realize practice makes perfect but ........... Thanks Jim | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1399 Registered: 12-2000 Posted From: 67.181.166.160  Rating: N/A |
Jim - Have you read this: http://www.busnut.com/bbs/messages/12262/16204.html?1167073154 After doing so, send me a private message or call (between 0700 - 2100 CA time) - info's in profile, click on my name to the left. FWIW & HTH. . .  | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 189 Registered: 10-2003 Posted From: 74.244.14.221  Rating: N/A |
I am also very new to this and I realise every bus is different but what works on my FLX with 6-71 and 5 speed spicer is the following. As I am slowing down when my RPM's reach about 1500 I depress the clutch put it in neutral let the clutch out and stab the throttle so it revs up around 2300 push the clutch in and the next lowest gear will slip in | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 288 Registered: 2-2001 Posted From: 71.236.40.26 Rating: |
Jim, it took me about 5,000 miles to get pretty decent at downshifting. I kept trying to drive it like a modern car or light truck. You have to get the engine speed matched to the wheel speed (in whichever gear you want). Download RJ's great directions, learn them & you will quickly master it. I also find that each bus has a different rythm or speed to shift at. If you try to rush the old girl, she won't go. Also, in addition to throttle & accelerator linkage being lubed & not sloppy (worn parts), correct idle speed is really important to easy shifting, both at a stop and underway. If she idles high, it will be hard to shift. | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 2071 Registered: 1-2001 Posted From: 75.108.85.14 Rating: |
A tachometer is the most valuable addition you can add to help solve this problem. Richard | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 504 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Everything above is right on! RJ's advice is the way to downshift silently. I have to respectfully differ with him on dead throttle starts in bigger buses, I'd burn off a clutch, or break something sitting there slipping trying to get going in mine on flat ground. On a grade would be out of the question. BUT, it doesn't matter that his trans is sideways, and mine isn't, its the same trans, and definitely the way to shift it! George | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 290 Registered: 2-2001 Posted From: 69.139.115.193 Rating: N/A |
George, we have all seen semi tractors pulled from a dead start by one strong man. I have towed our bus with a little 4 cyl car. Hows come a 300hp diesel can't get it moving on a flat parking lot? One thing I DO know is that if your Detroit's governor & rack are adjusted wrong, the engine will not respond to load changes & you then have to give it throttle like a gas engine. Mine (170HP 6-71) has all kinds of power at idle & will easily move the bus. When I let out the clutch & slow the engine, the governor responds & the engine goes RRRuump! & gets the bus moving, even backing up. That said, this does not work well on a grade & often throttle IS required then. | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 704 Registered: 11-2005 Posted From: 208.54.200.228 Rating: N/A |
Jim, If you're downshifting just to slow down I don't recommend that-it is totally unnecessary except for long downhill mt grades. Air brakes are much better for this. If you're downshifting to climb grades the best method is hold the throttle down, VERY quickly double shift and you will be rewarded by a silky smooth shift. This is RJ's method as I remember. George, I assume by dead throttle you mean at idle for starts on level ground. I've never seen a diesel vehicle of any kind that wouldn't do that easily due to the tremendous torque at idle compared to gas engines. I've never driven a big bus(>35') but assume it has a larger engine and is geared accordingly, so the result should be the same. I agree with JimBob, your gov is not taking up the slack when you release the clutch. Mine does that easily and you can feel it surge as the clutch comes out. I don't slowly ease it out, I let it right out but don't pop it. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 505 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Gus, Unfortunately, the result isn't the same. The bus weighed 33,000 with no seats, and has 13.5 X 24.5 tires. It will go 21 mph in 1st gear, 34 in 2nd, 53 in 3rd, and I know it will go more than 85 in 4th, that's just as fast as I dared go on a public hiway with old tires. The power steering pump is noisy, and I can judge the engine speed by the whine from the steering wheel. At 85 mph, the whine is not at "against the gov" pitch! I know the speedo is correct at 60, as it takes exactly a minute per mile. The V12 would start it with no throttle, and a lot of patience, but why? If you note the difference in speeds between mine and those RJ uses, the reason is obvious. I fully understand that the more throttle applied while slipping the clutch, the more wear will occur, but am also at a loss as to why so many people think a "dead throttle start" is nirvana? Like it or not, if making an engine start a bus at idle isn't lugging it, I don't know what is! No matter how good it makes you feel, you are making the engine produce a lot of power at idle (400) rpm. Then, no matter how slowly you depress the throttle, you are again asking the engine to accelerate the bus from idle. I call that lugging an engine. The point is moot, because my next start will be with an 8V92 and a 740! Gus, unfortunately you are trying to apply what happens with a bus that has half the weight, and about 20 mph less top speed, to my bus, and it just doesn't work. I went to Ohm's funeral too! George | ||
| Kyle Brandt (Kyle4501)
Registered Member Username: Kyle4501 Post Number: 437 Registered: 9-2004 Posted From: 65.23.106.193 Rating: N/A |
One of mine won't do a dead throttle start & everything is properly adjusted. BUT the clutch in it was designed for a big truck & not bus. Prev. owner thought it a great idea to put the heavy duty truck unit in it - big mistake as far as I'm concerned. My other buses handle the D.T. starts just fine & I don't feel it is lugging the engine because there is plenty of power to accelerate faster if more throttle is applied. My guess is the MC6 weighed so much, a 12V71 was chosen for the engine. This engine had sufficient power to move the bus at higher speeds. This increased weight, power & speed was too much for a "normal bus clutch" to handle with a decent service life & the heavier duty was required. The heavy duty clutches obviously perform differently. | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 705 Registered: 11-2005 Posted From: 208.54.200.253 Rating: N/A |
George, Welcome to the old guys club! You do love a good argument! It is obvious to me that your bus is way over (Under?)geared in that your overall ratio is way too low. My 4104 won't even go 21mph in first gear wide open and it could use a lower first gear. As I said before, your bus is much heavier but so is the power much greater. These standard trans buses suffer more for lack of high ratio first gear than anything. It is no wonder that yours won't idle from dead stop with larger wheels. I still maintain that yours had the correct overall ratio it would idle from stop in first with no problem. Every large diesel vehicle I ever drove, including 18 wheelers, was designed to do just that. I was always cautioned in all diesel vehicles not to add fuel before the clutch was released. I totally disagree that the engine is lugging at an idle start on level ground. In the first place the engine is at a minimum load and power output is very small, the gov immediately takes up the rpm slack. Serious lugging is at highway speed under high load and high rpm (Climbing hills) and high BMEP, this is the engine killer, not idle starts. To reverse your "The V12 would start it with no throttle, and a lot of patience, but why?" comment, why not? Idle starts are dead simple, require no coordinating of any type and are very easy for beginners. The defense rests!! | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 506 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Gus, I liked your humor in the electrical post, just too bad somebody else didn't get it. If this thing of mine was only geared for 15 mph in first, it would probably start on flat ground just fine. Now I have another 4104 owner telling me my rack is out of adjustment, and/or I have a bad governor? Nope, I have a 33,000+ pound bus that is geared for a top speed of at least 20 mph more than his, is 5 feet longer, has two more wheels, and is 6 inches wider, for starters. Didn't some 4104s come with 20 inch wheels? A whole lot of people are applying how to drive a truck with a ten speed etc to one of these buses with a four speed, and in the larger ones, it just won't work. My bus is much heavier, and the power is much greater, which makes the work the clutch must do MUCH GREATER, then we add a high final ratio, and there is just no reasonable way this bus will start in a reasonable amount of time without some throttle. Since it is my clutch, my trans, my universals, and my driveshaft, I choose to put on a little throttle, and ease off the clutch, and it starts smoothly. We can argue lugging all day, but high rpm is never lugging. You would never allow your engine to slow to 400 rpm at 20 mph in 4th, with some throttle on, but the governor is going to move the fuel rack to the same amount of fuel being injected to keep the engine running while you are letting off the clutch with no throttle. At least we disagree honorably! Regards, George | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 2073 Registered: 1-2001 Posted From: 75.108.85.14 Rating: |
I always started my 4104, even on a slight upgrade using no throttle till after the clutch was fully engaged.I never felt it was lugging the engine and I never had any clutch problems. Richard | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 706 Registered: 11-2005 Posted From: 208.54.200.161 Rating: N/A |
George, All 4104s came with 20" wheels and most still have them as far as I know. Don't know any real reason to change unless there happens to be a complete power train change. I assumed yours came originally with 20" also. Is this incorrect? I think you are slowly burning up your clutch with your method. I hope I'm wrong on that. I agree with the truck philosophy and also think that yours originally was meant to be started the same way. High rpm is lugging if the engine is overloaded, this is true at any rpm but worse at high rpm and high fuel flow. At idle it is not overloaded, it is just barely loaded. Note again the earlier post about moving his bus with a small pickup-or the teeth of a strongman!! (Message edited by gusc on July 24, 2008) | ||
| Douglas Wotring (Tekebird)
Registered Member Username: Tekebird Post Number: 377 Registered: 10-2004 Posted From: 71.59.75.212 Rating: N/A |
most 04's now have 22.5's.....usually were changed while still in revenue service. l. Lugging? pretty much anytime you apply throtle and the bus does not accelerate is lugging. That is bus si slowing down on a grade and you just apply more juice and no increase in speed is a result. you can alos lug at low speeds I for one was trained to downshift instead of braking. it reduces break wear and the need for adjustments and if you are driving properly and thinking well ahead of where you are....you will find yourself driving much smoother and in the right gear say when coming to a stoplight.......if you brake without downshifting good chance you will find yourself in a downshift or lug scenerio if the ight changes to green. generally, you should never downshift while going down grade as you are risking getting stuck in neutral.....and then overheating or loosing your brakes when your bus starts to sucumb to the forces of gravity as for starting. you can push start a 4104 for example on flat ground with a 100# woman pushing the bus, | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1401 Registered: 12-2000 Posted From: 67.181.166.160 Rating: |
Gus & George - This is entertaining! For the newbies following this thread, let me explain a "dead throttle start". It is not simply dumping the clutch from a dead start. Lots of 18-wheeler drivers do something similar to this with their gazillion-speed transmissions down in double-bottom super-compound low when they've got 80,000 lbs on board. But that's what those powertrains are designed to withstand. However, with a coach driveline, dumping the clutch is a good way to tear it up - big time! With a common coach manual gearbox, it means feathering the clutch gently through the take-up point without adding any throttle until the clutch is fully engaged. Think "finesse". . . Practice with a stick-shift car in a parking lot to get the hang of it. Stop, put into first, feather out the clutch till the car's rolling, put the clutch back in and try it again until you can do it smoothly every time. Keep your right foot off the throttle, just use the clutch. End of lesson for the newbies. . . Now for some more fun & games: Done on level ground, and with practice, virtually every stick-shift coach I've ever driven can get rolling using this technique - including this one, which I drove in the early '80's. A Canadian car originally, it still had the 12V71 and four-speed in it. And boy, was it an absolute ball to drive - almost as much fun as the sportscar 4106! (Allstate had one of those, too, painted in a similar livery.)  Now, before I have to get out the fire extinguisher, let me just add that, altho you could get that MC-6 rolling with the massive torque of that 12V71 and careful clutch action, the unit was a little happier if you feathered the throttle slightly as you feathered the clutch thru the take-up point. Again, finesse is the word here - think of the white dress & red wine! Of course, this discussion is totally inapplicable to those who "stab & steer" - we're talking about "drivers" here. LOL!! FWIW & HTH. . . (Message edited by rjlong on July 25, 2008) | ||
| Jack Hart (Jackhartjr)
Registered Member Username: Jackhartjr Post Number: 31 Registered: 8-2007 Posted From: 205.188.117.73 Rating: |
Jim, after years of teaching truck drivers how to shift I can say that most problems are because they tried to 'rush' the shift. Slow it down a little...it will soon be second nature! JAck | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 707 Registered: 11-2005 Posted From: 208.54.200.110 Rating: N/A |
Doug, As I understand it there is no difference in 20s and 22.5s except the latter is tubeless. My theory on downshifting is that brakes are a lot cheaper than clutches and trans! The exception to this, of course, is long down grades. I'm talking about down shifting on level ground, a complete waste of human and mechanical effort. There is no way a 4104 lugs when starting from idle on level ground, the gov automatically increases both engine and bus speed, at least mine does. If you lug a 671 very much at idle it will quit. If a 100 lb woman can push start it and she doesn't lug then I won't worry about a 215 HP diesel engine lugging! Adding fuel while under way with no acceleration is entirely another matter. RJ, I don't think anyone so far has recommended dumping the clutch. I certainly never meant to imply that. In an 80,000 lb 18 wheeler that is a good way to snap a "U" joint or driveshaft. This is fun! (Message edited by gusc on July 25, 2008) (Message edited by gusc on July 25, 2008) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 507 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
Gus, I wouldn't even call this a heated discussion, let alone an argument. Amicable, and an agreement to disagree also come to mind. There was nothing wrong with the clutch, or the governor, the problem was too high a low gear, period. I'm not picking on 4104 owners, but the difference between a 4104, and an MC6 is 5 feet in length, 6 inches in width, (The MAK board is really wrong here) over a hundred cubic feet of bay space, tag axles, and about 12,000 pounds. Then there is the little matter of 13.5 X 24.5 tires, and what they do to drive ratios. That is not a typo, and I haven't left out an 80 (as in percent of tire size) either! The bottom line in difference in top speed between the two, with the same transmission, is at least 20 mph, which drastically changes the way you have to start it. I agree that a truck with a decent trans can be started easily with no throttle, but you can't compare a Roadranger to an 8844 either. How much oil pressure do you have on your main bearings when you are making the engine start the bus and accelerate it from idle? Not a very nice question, considering the civility of this thread, but something to think about! If I were the only person who would ever drive this bus, I would have kept the buzzin dozen, and put in a 1063C. The same overall length, a nice low low, which would certainly allow a no throttle start, and a low reverse, which is real nice in tight spaces. Then FIVE more synchronized gears, which allow quick shifts, and no loss of momentum waiting for the engine to slow down in the double clutch. And, once again, there was nothing wrong with either the governor, or the throttle linkage, as suggested by another 4104 owner. Regards, George | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 508 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
Good Morning! RJ says it right again, and thanks for the GREAT picture! I'll post another interesting picture when I get home, and scan it. Its not as good as RJ's, but is interesting to compare sizes. My bus started happily with a little finesse on both the throttle and the clutch, and that's the simple answer. Looking at revs per mile, 20 inch tube type wheels, with I think 12.00 tires, and 22.5 tubeless are essentially the same, just don't quote me on the 12.00 without a book in front of me. NOW, look closely at the left rear fenders over the drive and tag axles in RJ's picture. There is nothing deceptive in that picture, and the tag is not sitting in a hole! The drive tires are 13.5 X 24.5, while the tags are 12.5 X 22.5. NOTE THE HUGE DIFFERENCE!!! The other thing to be noted here, is that Greyhound changed 82 of the hundred to an 8V71T and a 740 in 1973, due to driveline problems. The remaining 18 were left with the V12 for service in the Canadian Rockies. The prosecution rests. (The second post above was done last night, but the wireless network was down where I was last night, so nothing to do but save it till morning.) George (Message edited by George Mc6 on July 25, 2008) | ||
| Mel La Plante (Mel_4104)
Registered Member Username: Mel_4104 Post Number: 54 Registered: 7-2006 Posted From: 154.5.114.172 Rating: N/A |
just remember that the trannies in GM buses were not syncromesh trannies and are very tricky to shift. all the long time drivers of these buses laugh about ticking a gear now and then and anyone that tells you they do not and never do are telling fibs. the 20 in. tires were mounted on split rims and were tube type tires. the split rims are very dangerous to work with very few people today will work on one. s lot of people were killed or hurt when the rims came apart. switching to the 22.5 and the tubless tire preverted people from mounting a tude type tire on the newer tubeless rims. the out side dia. of both tires is the same this is why you can change to tubless by going from 22 in. to 22.5 and not having to change the speedo. | ||
| Mel La Plante (Mel_4104)
Registered Member Username: Mel_4104 Post Number: 55 Registered: 7-2006 Posted From: 154.5.114.172 Rating: N/A |
sorry about the type error it should read 20 in. to 22.5 | ||
| Frank Allen (Frank66)
Registered Member Username: Frank66 Post Number: 87 Registered: 10-2005 Posted From: 205.188.117.73 Rating: |
Better listen to RJ long on the dead throttle start up, if not your gonna find your clutch laying on the highway, beleive it!! Frank allen 4106 | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 509 Registered: 8-2006 Posted From: 76.91.197.153 Rating: |
Well, I've owned it for 22 years. Driven it thru Oregon, Washington, Idaho, Nevada, Utah, Arizona, and British Columbia, (I live in California) over 30,000 miles ON THE SAME USED CLUTCH THAT WAS IN IT WHEN I BOUGHT IT FROM THE CHARTER COMPANY! What you really don't want to hear, is that I have never had to adjust it either, so I must be doing something right. Where I used to live, residential trash pickup was very expensive, and the cans had to be taken to the street. With a local license, the county dump fee was two dollars a load. So, me and two of the neighbors bought plastic cans with locking lids, and every two weeks we filled the bays with plastic cans and drove to the dump. Very easy, as we didn't have to lift the full cans a foot. (The bay doors are bi-fold, the bottom third swings down.) Although I don't drive a truck for a living, my class A commercial license, with doubles and tank type vehicle endorsements is still current, along with the medical cert. I just love a good argument! George | ||
| Jim Rink (Fakeguy)
Registered Member Username: Fakeguy Post Number: 108 Registered: 1-2005 Posted From: 70.61.17.52  Rating: N/A |
RJ. great article and very relieving for me...nice to know that I am not the only former truck driver who, being used to 10-13 speed trannys, have to learn to SLOW IT DOWN. Good info. Thank you | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 709 Registered: 11-2005 Posted From: 206.40.238.45 Rating: N/A |
George, I keep saying this, there is very little load on a DD when starting on level ground at idle if the gearing is anywhere near reasonable, regardless of the size of the bus. So, oil pressure to the bearings is a non issue, we're talking about split seconds here!! We 4104 owners are immune to any negative remarks anyway, we are happy campers with our little Aluminum buses!! This has been kind of a fun string. (Message edited by gusc on July 30, 2008) | ||
| David Lower (Dave_l)
Registered Member Username: Dave_l Post Number: 30 Registered: 11-2007 Posted From: 76.10.155.5  Rating: N/A |
Hi all I know this is off topic but I thought George may see it. At rvmotorized.com there is a MC6 for sale in florida, nice looking one. Dave L | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 511 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Thanks Dave, I wouldn't have seen it otherwise. George | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 190 Registered: 10-2003 Posted From: 66.165.176.60 Rating: N/A |
Just another place to look if you haven't George. This is where I got my coach www.thebusman.com |
