| Author | Message | ||
| quantum merlin (Quantum500)
Registered Member Username: Quantum500 Post Number: 11 Registered: 8-2007 Posted From: 71.33.238.169 Rating: N/A |
Is there a way to put together a either a 2-speed transmission coupled with the auto, or a 2 speed rear end in a mc8? Seems like a top speed of 68 could get a little bit boring plus hard on fuel. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 625 Registered: 12-2000 Posted From: 76.1.180.218 Rating: N/A |
What rear end do you have in our MC8? We have a 3.73 in ours and can easily run 74-75 (Although w prefer to use non interstates and try to run 60-65) . A friend has a 102A3 with a 3.33 rear end. Jack | ||
| Douglas Wotring (Tekebird)
Registered Member Username: Tekebird Post Number: 243 Registered: 10-2004 Posted From: 71.59.75.212 Rating: N/A |
I'll have to check and see what my rear end is but I can easily do 80. I think more often that not lake of speed is caused by a tired engine not the gearing. before the new engine my 04 did not like grades. Since....most east coast grades require no downshift. | ||
| quantum merlin (Quantum500)
Registered Member Username: Quantum500 Post Number: 12 Registered: 8-2007 Posted From: 71.33.238.182 Rating: N/A |
Its actually a bus I'm looking at purchasing. I just wanted to know my options. If its geared for 80 in high what is first gear like? | ||
| Douglas Wotring (Tekebird)
Registered Member Username: Tekebird Post Number: 244 Registered: 10-2004 Posted From: 71.59.75.212 Rating: N/A |
they are all slow, if your concerned about it you don't want a bus | ||
| Mark R. Obtinario (Cowlitzcoach)
Registered Member Username: Cowlitzcoach Post Number: 158 Registered: 4-2001 Posted From: 204.245.250.149 Rating: N/A |
Most MCI's of that vintage tached out about 75 MPH. My -7 would do 73 on the flat. It just didn't particularly like the hills. First gear was adequate with the Allison. What are you trying to accomplish with an auxillary transmission or 2-speed rear end? Most 2-speed rear ends would give a deeper low end but rarely a higher top end. An overdrive auxillary would give a much higher top end but would rarely help on most hills. If the bus is truly geared to a top speed of 68 it should climb almost any hill without slowing appreciably. Crusing at 65 MPH is really not that bad. In OR, the top speed is supposedly only 65 MPH anyway. In WA, 70 MPH. Are you in that big of a rush to get somewhere? Mark O. | ||
| quantum merlin (Quantum500)
Registered Member Username: Quantum500 Post Number: 13 Registered: 8-2007 Posted From: 67.41.221.134 Rating: N/A |
Sometimes yes  Other times no. I'm just asking questions. "they are all slow, if your concerned about it you don't want a bus" Doug So why do owners go to all the expense to put a 8v92 in or a 500hp series 60 if they aren't concerned about going fast or at least kind of fast? I live in the west where pretty much anything that has four lanes is 65 + all interestate travel is 75 and there are a few places where 80 is the limit.....at least during the day. 65 is just fine in my book as long as the limit is 60 | ||
| norcal kyle (Kylexisxrad)
Registered Member Username: Kylexisxrad Post Number: 177 Registered: 12-2005 Posted From: 76.105.27.223 Rating: |
my eagle can do 80 but i like to hang around 65, sometimes 70-ish. the trip is half the fun, right? i actually really enjoy the act of driving my bus, so keeping it a bit slower gives me a bit more time to drive. my bus doesnt have to worry about staying on schedule or getting to the destination quickly anymore, so i don't feel the need to have a 525hp motor in the back. some guys like to climb a 10 mile 8% grade at 65, but 2nd gear @ 25-27mph works out nicely for me. just plan accordingly. its all preference. kyle in norcal 1980 Eagle 10 #30223 | ||
| Jim Wilke (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 180 Registered: 2-2001 Posted From: 69.77.151.201 Rating: N/A |
Merlin, you will need to find out what top RPM the governor is set to. Many of the bus companies would limit RPM to control max bus speed and fuel consumption. (If the bus would do 80, the driver likely would run 80.) Sometimes the gov is set as low as 1650. The Detroit can run at 2150 indefinitely & fire trucks & pumps are redlined around 2400. Marine DDs are set at 2300 max but normally would only use full RPMs for 1 hour out of 12, running about 2100 the rest of the time. If you can determine the axle ratio, there is a speed calculator that will let you figure top speed with different tire & gear combos once you know top RPMs. I was watching a clip from a tractor pull where the DD was governed at 6,000 RPM but lifespans are measured in a few hours at most that way. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 626 Registered: 12-2000 Posted From: 76.1.180.218 Rating: N/A |
I look at driving our bus the way my brother looks at riding his Harley. "When I am behind the wheel, I am already where I want to be". Another thing to remember is "the faster you are going, the longer it will take you to stop". Stopping distance from 75 is much greater than 65. My concern with any vehicle that weighs 30,000+ is not how fast I can go it is how fast can I stop! More horsepower is great for maintaining speed on uphill grades, but I am not setting up for Bonnevile. Jack | ||
| Douglas Wotring (Tekebird)
Registered Member Username: Tekebird Post Number: 245 Registered: 10-2004 Posted From: 71.59.75.212 Rating: N/A |
Quantum, people repower mainly because it is what they want to do.....but use the power as a reason. although there are good success stories on repowers, there are just as many if not more failures.....Most of these being engineering issues in the cooling systems. Although a bit more HP will get you up a hill faster in the long run it does not add up to much other than ones ego not being bruised by being passed on hills. on a Coast to coast trip in my 4104 (6-71) It took a wopping 2 hours or so longer than doing the same trip in my pickup. Did I mention I was towing said Pickup with the bus both times I made that trip. That is a prime example of what spending all the time and money will get you if all goes as planned on a repower. Most oftewn the issue is that MOST buses that hit the used market are in need of a rebuild. a tired engine will produce drastically less power than a fresh one. now the disclaimer: People do do repowers and all sorts of things that are not as designed. Many do a good job and have little to no problems., many do it and never publish the problems they have. the % of peopkle who can pull it off from a skill perspective are few and far between. But they are out there. Again...if your worried about a few miles per hour or 1 MPG a bus is likely not the best Mode for you. you can make anything perform better but often at the expense of reliability | ||
| quantum merlin (Quantum500)
Registered Member Username: Quantum500 Post Number: 14 Registered: 8-2007 Posted From: 70.57.21.17 Rating: N/A |
Thanks for the different prespectives. I know that going fast is not the answer and really doesn't speed the trip up if arriving at a certian time is more important than the trip its self. I really don't like following RV's that are going 10 to 15 mph under the posted speed limit though. If anything that is more dangerous than going over in my opinion. For a couple of reasons. Some dummy is gonna pass no matter what the risk. Some dummy isn't going to be paying attention and come up on you hot and heavy. Sometimes I am that dummy. Ideally I would like to run about 1750 rpm at 70mph in high and have a top speed of under 10mph in low. About the only thing I would do in the repower category is upgrade to turbo's for high elevation. Some of those 10000' + passes around colorado have to be unfriendly to a DDN. More air with the same amount of fuel will not create more heat and has a good possiblity of making things cooler. I may be interested in better performance, but not to the extremes that I would be compromising reliability. I would think more gears to choose from would actually make things last longer considering that you would be less likely to lug the engine. | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1127 Registered: 5-2001 Posted From: 65.74.67.130 Rating: N/A |
Quantum, the spread in the gears on our coach is about 4:1. Top speed in low is 20 and top speed in high is 80. Short of going to an automatic, that's what we get with a vee drive. To do what you are talking about will require a tee drive coach, and many of them will not take a long transmission because the driveline is too short. That narrows your choices considerably. I understand that a number of people have put Road Rangers in Eagles. Good luck. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1067 Registered: 12-2000 Posted From: 74.12.87.79 Rating: N/A |
With an 8V71, you will want to be attentive to the horsepower and torque numbers around your wished for RPM target. The luxury of lowering RPM's through gearing, maintaining the same top speed, to achieve a better fuel consumption, will only be a happy experience if the motor in question has the excess power to maintain a modest gradeability. That usually means a power to weight ratio of the more modern 4 strokes or the 2 stroke furnace called 8V92. Over-gear any motor, and a headwind will slow you down, never mind a rise in the road. For some indication on the current power plant, see what choices the truckers were making for different conditions with final gearing ratios in the mid 70's with an 8V71. They had to be smart with gearing in those days. As one who usually roars the Great Lakes to Florida highways with a time clock running, you 'll be finding me staying stock MC8 with 270 HP/HT740 and 3.7 rears. happy coaching! buswarrior | ||
| Mel La Plante (Mel_4104)
Registered Member Username: Mel_4104 Post Number: 47 Registered: 7-2006 Posted From: 207.81.78.121 Rating: N/A |
well it looks to me that you should get a sticks and glue,as they are faster than most old buses out there and every couple years you can get a new one with more power and faster. however i will keep my 4104, it is not fast and sure is not over powered but that is ok with the wife and me.one time we met a couple that were headed for Tucson like us however they had a nice new motorhome and sure enough within 2 blocks from the dock in Port Angles they passed us blowing the horn, well we go at 55-60 and keep out of other people way and let faster traffic go by. well when we got to Tucson they had not arrived yet and did not for another 2 days. asked where they were and was told of all the stress driving down there and asked what they seen and they said they never seen any thing except the center line, and i could agree with them at 65-80 they better only be watching that center line, on there way home they slowed down a great deal and were amazed at what there is to see. but just rember, do it your way, it is your life to live and enjoy the road you take. | ||
| Jim Wilke (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 181 Registered: 2-2001 Posted From: 69.77.151.201 Rating: N/A |
Merlin don't let 'em get you down. While a bus is NOT the fastest way to get somewhere, it is the best in my opinion. They are as safe as anything can be, they ride more comfortably than any sticks & staples I've seen (ESPECIALLY in a gusty crosswind!) and we calculate if we eat most meals aboard & travel more than 2 days, it's equal to or less expensive than taking the car. Most of these buses should be capable of 70-75 as they were built. There are some of the older ones or transits that were never meant to go that fast. Sixty five was zipping right along when the 4104 was designed for two-lanes after WWII before Interstate highways were built in the 50s & 60s. However, today the average Interstate speed is 75 or 80 (Actual, not posted, lest I stir up disagreement.) Our stock 4104 with the "tall gears" does 74 all day long with a two valve 6-71 putting out about 170HP. It can go faster down hill or drafting a semi but out in the open on flat ground the air resistance keeps her at that speed. Your coach should be able to do about that fast or better if everything is set up right. That's why I mentioned checking top RPM & gear ratio. But I think you have it a little wrong. Keeping the bus down at 68 will reduce the fuel consumption. That & safety is why the bus companies limited top end. | ||
| quantum merlin (Quantum500)
Registered Member Username: Quantum500 Post Number: 16 Registered: 8-2007 Posted From: 71.33.238.169 Rating: N/A |
So I don't have any first hand experience with the coach but it seems to me the hot setup would be 3.33 gears with a 2 speed rear end that would effectively geared it down double. I think that would give me exactly what I was talking about above. The question is; Is that really worth it or would the coach be just fine the way it is? FYI its a 740 Allison behind a 8v71 with 4:10 gears in a MC8. So my new question will a 2-speed rear end fit into a MC8? What do the MCI coaches of that era have for differentials? As in brand and model. | ||
| Jim Shepherd (Rv_safetyman)
Registered Member Username: Rv_safetyman Post Number: 260 Registered: 1-2004 Posted From: 72.171.0.145 Rating: N/A |
Merlin, typical two speed rear ends have a 30% gear change. That allows them to "split" the transmission gear changes. I have not heard of any "deep" ratio in a two speed rear end. This subject has come up before and, as I recall, no one found a two speed rear end that was compatible with the bus housings that we have in MCIs, Prevosts and Eagles. For those of us that have drop boxes, I am sure that there is no two speed option. If the bus is a "T" drive, it might be possible to install a complete truck rear end that can accommodate a two speed differential, but that is a big job Jim Shepherd Evergreen, CO ’85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission Somewhere between a tin tent and a finished product Bus Project details: http://www.rvsafetysystems.com/busproject.htm (Message edited by rv_safetyman on September 12, 2007) (Message edited by rv_safetyman on September 12, 2007) | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 157 Registered: 8-2004 Posted From: 12.77.116.8 Rating: N/A |
Merlin, another thing to think about here is that you're looking for a two-speed axle that would give you a 20% overdrive (actually, probably less would be better ... high gear with stock rear end is probably close to what the bus/engine/gearing will pull). Most of what's available for trucks is a two-speed *underdrive* - they give a lower gear for low-speed pulling, acceleration, etc. There are some "overdrive" gearings out there but, as has been pointed out, they're not made for/don't fit/not suitable for buses. If you *really* need to change your overall, high speed top gear ratio, you can do that by changing the rear axle, but -- as has also been noted -- you gotta be careful at that. These gearings were chosen carefully to match the bus and engine (weight, performance, engine power, torque curve, etc.) and even small changes to the numbers can take you to places you don't want to be. | ||
| quantum merlin (Quantum500)
Registered Member Username: Quantum500 Post Number: 17 Registered: 8-2007 Posted From: 67.41.221.134 Rating: N/A |
Looks as if its one of those things thats better left alone. Thanks for all the responses. It was good learning material! | ||
| Jim Wilke (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 183 Registered: 2-2001 Posted From: 69.77.151.201 Rating: N/A |
Well, you might resolve your delemma by the time you determine what the engine is turning. By the way, get an assistant to help you determine if the throttle is being opened all the way. (My 4104 was not!) If it's an air throttle, build up full air, shut the engine off & pull the pin connecting the throttle cylinder to the gov. throttle arm. Get your helper to give it full throttle at the front. When they do, you move the lever on the governor & see if full throttle on the engine lever matches the foot throttle. Cable throttle same but no air needed. Often due to wear, misadjustment or previous owner intent, the foot isn't giving full RPMs. (This is also a good time to get out your photo tachometer & verify full engine RPM in neutral.) Your on the road RPMs will be about 50 less than what it will do unloaded. Do not trust an installed dash tachometer for this number as they are often inaccurate on either idle or top RPMs. | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1294 Registered: 12-2000 Posted From: 67.181.189.94 Rating: N/A |
Merlin - Are you sure the rear axle ratio in this MC-8 you're talking about is a 4:10? That's the common ratio for V-drive GMC 35-foot coaches, the OEM stock ratio for an MC-8 with the powertrain you mentioned is a 3.70:1. FWIW & HTH. . . | ||
| Justin Griffith (Justin25taylor)
Registered Member Username: Justin25taylor Post Number: 47 Registered: 4-2007 Posted From: 71.155.170.64 Rating: N/A |
I have had my Eagle 10 over 80mph many times at about 1900-2000 rpm. I will find out and post the gear ratio. It has a 6-92/Auto. It was ordered as a shell and converted by Birmingham coach for an entertainer when it was new so I know the ratio was a option. (Speed is money to the ignorant big shots in the music biz.) It really does not like to climb hills. The slightest grade requires a down shift. Most of the other Eagle 10's I have driven top out at 70-75ish. The 05's with 8v71/4 speed that I have driven all go 72 (even off a cliff ). | ||
| quantum merlin (Quantum500)
Registered Member Username: Quantum500 Post Number: 20 Registered: 8-2007 Posted From: 67.41.221.134 Rating: N/A |
"Merlin - Are you sure the rear axle ratio in this MC-8 you're talking about is a 4:10? That's the common ratio for V-drive GMC 35-foot coaches, the OEM stock ratio for an MC-8 with the powertrain you mentioned is a 3.70:1. FWIW & HTH. . . :-)" RJ Long No I'm not sure. I'm not sure of any of the history of the coach at this time either. Did any of the MCI coaches of that era have 4:10 gears? | ||
| Jim Wilke (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 184 Registered: 2-2001 Posted From: 69.77.151.201 Rating: N/A |
The easiest way to be CERTAIN of the ratio is to remove the bolts that hold the driveshaft flange to the differential flange. Normally, the ratio is stamped into the end of the pinion shaft. If it is not there, you can put a mark on a rear tire and 4 or more on the driveshaft, have someone start the bus & creep very slowly straight ahead one revolution of the tire while counting the turns of the driveshaft. Might take some fiddling with a creeper & or a mirror on a stick and a tire mark observer. Prudence would dictate being behind the tires if the bus is creeping forward & making sure the driver is not angry with you! | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1070 Registered: 12-2000 Posted From: 74.12.73.114 Rating: N/A |
You can see the driveshaft, sort of, down through the holes in the floor down the back on an MCI. Saves you crawling underneath... And you may try the opposite, mark the tire, and the driveshaft, and drive forward a certain number of driveshaft turns and go clock the mark on the tire. Easier for a "committee" to assign a clock position to a tire and move a distinct number of driveshaft turns than the opposite? Your choice! happy coaching! buswarrior | ||
| Jim Wilke (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 185 Registered: 2-2001 Posted From: 74.128.150.52 Rating: N/A |
Buswarrior, I thought it would be easier to figure the ratio if the tire rotation was "1", therefore if the drive shaft turned 3 1/3 times, etc. it would be a snap. Hey waddya want from me, I ALWAYS do things the hard way. I was born feet first. That's why I decided it would be relaxing & fun to have a bus! (Not sure what excuse the rest of you have!) |
