| Author | Message | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 316 Registered: 10-2003 Posted From: 66.165.176.62  Rating: N/A |
I'm sure this has been encountered before by you fine folks. My Flx has a 6-71 Nat and a spicer 6000 series 5-speed. I have noticed that the gear ratios seem to be pretty tall in the trans and getting her going from a stop on an incline can be a bit of a struggle for the 6-71. Off the top of my head the options I see are switching to a manual with more gears, going automatic or some sort of 2 speed reduction unit in front of the diff though I don't think I have the room for that. Maybe change the final drive ratio but I'm not sure I want to impact fuel economy that much. Would like to hear all opinions and what has worked for you | ||||||||||||||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 179 Registered: 1-2005 Posted From: 208.66.38.115 Rating: N/A |
How about a little more horsepower out of the old 6/71, mileage would be controlled by your right foot.>>>Dan | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 317 Registered: 10-2003 Posted From: 66.165.176.62 Rating: N/A |
Dan, How does one accomplish that? It already has an updated 4 valve head. My understanding is that turbo requires a major rework with new blower, pistons etc. If it weren't so fresh (40,000) on an inframe rebuild I might consider finding a good running 8-71 but I hate to go that direction when it runs so well. | ||||||||||||||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 765 Registered: 10-2006 Posted From: 76.250.203.186 Rating: N/A |
Low gear is usually enough to get started on most highway hills , 6-7% not the side of Rocky Top. If she goes up the hill and accelerates in 1st , the gears are fine. The top tranny gear was HIGH as an attempt to get the best fuel mileage, Good Idea!! Shift in a timly manner and you will climb far better than with a slushpump. Row Row Row the Boat is for buses too. FF (Message edited by FAST FRED on May 08, 2009) | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 318 Registered: 10-2003 Posted From: 66.165.176.62 Rating: N/A |
Fred, You are right it does get moving it just takes a while to build RPMs. I suppose it could be driving experience too. I don't add much RPM while letting the clutch out fearing I will toast the clutch. It always moves just seems to take a while to build RPM's from 600-1000 when starting on an incline. Once above 1200 it pulls real well | ||||||||||||||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1449 Registered: 10-2003 Posted From: 71.58.110.9  Rating: N/A |
See if you have enough room to change to a Roadranger with nice creeping low to an overdrive top gear. An RTO 9509 would be perfect if there is enough room. Hopping up the 6-71 won't help start out torque, but will make a major improvement in mid range and top governed speed. The 4104's have this problem of starting out on a grade. 411 gears instead of the 355's help, but hurt top speed and there isn't anything to be added for more gears. I've heard that the gears out of a ACF Brill IC-41 trans will give a lower 1st gear at the expense of a large gap between 3rd and 4th. I know about this gap, had a Brill. Detroit Diesel made a MAJOR Mistake in not producing an inline 6-92. | ||||||||||||||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 39 Registered: 2-2009 Posted From: 64.163.110.102  Rating: |
okay you guys..why do a 9 spd when you could have a 10? Same physical size basically and one more gear. Also, there are more ratios available in 10s than 9s. Generally speaking, the 10 can be had with 2 or 3 different low gear ratios, and other than direct in high gear, there are at least two or three overdrive ratios too. I agree wih john that if you could fit a Fuller Roadranger in there...DO IT! If you need transmission lengths for Fuller, PM me. (Message edited by DaveG on May 08, 2009) | ||||||||||||||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1580 Registered: 12-2000 Posted From: 76.66.19.195  Rating: N/A |
If that coach will allow you to fully engage the clutch without using the throttle on the hills in question, I wouldn't worry about it too much. In choosing a new transmission, hold out for as even gear spacing as you can find. Even percentage increases between gears is much nicer than every gear being a different rpm to shift. Super 10 transmission might be a nice option for a bus conversion. 5 shifts, each is split, range shift is automatic. Choose to split or not each gear, so drive it like a 5 speed, or something in between. 17% for each of the 10 gear shifts, IIRC? happy coaching! buswarrior | ||||||||||||||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 83 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
If you already have a Spicer trans, I would switch to a Spicer (now made by Meritor) 7 spd transmission. Available in either direct or overdrive final drive. Then you'll have plenty of starting power. I had that transmission in a GMC Astro with a 6V-92TA. It was the direct drive model, and always had plenty of power to start the 80,000lb loads. It could be pulled into first without the clutch-pretty amazing transmission. Also, the 7spd does not have any air shifters, so switching from the 5 to the 7 would be relatively easy. Good Luck, TomC | ||||||||||||||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 768 Registered: 10-2006 Posted From: 76.194.80.204 Rating: N/A |
It always moves just seems to take a while to build RPM's from 600-1000 when starting on an incline. There is no supprise , there isn't much HP or torque at under 1100, so live with it. Yes the faster you get the clutch fully engaged , the longer it will last. TO me it wouldn't be worth much hassle (engine or tranny swop) just to speed up the few seconds rarely spent starting in 1st on a steep hill. A few Grand and 20-100 hours for 5 seconds of inconvienance , once in a while? FF | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 320 Registered: 10-2003 Posted From: 74.244.14.221 Rating: N/A |
So let me ask then am I worrying too much about slipping the clutch a little to get it moving? In a car I wouldn't think twice about slipping it longer to get it moving but somehow I was assuming with the increased weight of the coach the forces involved might not allow that | ||||||||||||||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1542 Registered: 12-2000 Posted From: 98.192.173.82  Rating: N/A |
Tim - Are you properly using a Dead Throttle Start to get your coach moving on the flat? Do you know how to use the air brake release delay to assist you getting going on a slight grade? Sometimes it's just a matter of some education, not cash. FWIW & HTH  | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 321 Registered: 10-2003 Posted From: 66.156.75.86 Rating: N/A |
RJ yes she will do a DTS on the flat but not an incline. As for the airbrake release yes I apply full brake while bringing the clutch part way up then slip my foot from brake to accelerator but I have been leary of bringing the RPMs up to where the detroit makes torque for fear of burning the clutch. If that isn't an issue than starting on an incline would be easy. On the flip side starting on an incline now without bringing the RPMs up results in black smoke and not a lot of forward movement which I'm sure isn't good for her either. So am I going to cause clutch damage by bringing the detroit up to 1000RPM while starting on an incline? If not I won't sweat any of this | ||||||||||||||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1457 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
Fred apparently hasn't dealt with this problem in his 06 since it has a lower 1st gear. How much does your coach weigh? What is the rear axle ratio? 7,8,9,10 speeds; whatever, the point is that you have several options instead of "live with it" and it isn't worth spending that money. There is going to be a place that will risk burning up the clutch that you will get into sooner or later. Even Fred knows this, altough I think he mentioned that his 06 now has a 4.375 rear, which would greatly help starting out, although at a penalty to top speed, which may not be a problem for him. Usually, we look out and try to avoid getting into that situation, but it happens once in a while. Some clutch plates are available that have metallic facing that will tolerate slipping more than organic lining, although at a cost: faster flywheel and pressure plate surface scoring and wear. It's nice to have a low and reverse that will allow an idle speed ease off the clutch starting out without the sweating. I'm sure most of the coach owners with manual transmissions would like a much lower 1st and reverse. I'm mostly referring to the early ones with 4 speed models. | ||||||||||||||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 819 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Tim, If length is an issue, a Spicer 1063C is the answer. It is the same length as an 8844, (Short) 6 forward speeds, top 5 synchro, and a nice low low and reverse. A dead throttle start on a hill with one of these is a snap, as is moving around a campground. Your clutch will love it, and they're so old they're real cheap. Drawbacks? Single rod shift, they're wide, and a funny shift pattern. Yours may be single rod already... HTH, George | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 322 Registered: 10-2003 Posted From: 66.156.75.86 Rating: N/A |
George, Yes I am already single rod shift so that might be easier. FWIW I just looked at the build plate my rear end ratio is a 3.58. | ||||||||||||||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1461 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
That's good since you have a direct top gear, and also explains why starting out on a hill is difficult. If you have the room, Roadrangers are all over the place in about any model, number of speeds, and ratios. AND the RT9509, RT910's are plentiful and since many were behind Detroits, shouldn't be any problem to get the correct items needed cheap at a truck salvage yard. Try not to get any overdrive ratio higher numerically than about .80, as anything more will lug the engine when cruising.If it is a Roadranger, it would be referred to as an RTO model. BTW, how long is your current driveshaft, u-joint to u-joint? While you are at it, how long is the current transmission from where Clutch housing attaches to engine to u-joint on output flange or yoke? | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 323 Registered: 10-2003 Posted From: 74.244.14.221 Rating: N/A |
Chessie, I'll be back over at the bus tomorrw so I'll get those measurements. From what I recall from the last time I was underneath changing the diff fluid the shaft is pretty short. By the way my wife suprised me with a dvd of "the big bus" yesterday Stay tuned | ||||||||||||||
| David Evans (Dmd)
Registered Member Username: Dmd Post Number: 316 Registered: 10-2004 Posted From: 173.77.212.104  Rating: N/A |
With the former high prices for scrap last summer and fall, how many truck yards scrapped alot of old iron ? I know the bus yard in Durham is gone, altho there wasent much left anyway. | ||||||||||||||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1587 Registered: 12-2000 Posted From: 76.69.142.22 Rating: N/A |
Depends on how you want to spend your resources? In my mind, black smoke as you make the revolutions from a start is preferable to clutch slipping. From what you write, it sounds like you are suitably respectful to your clutch, and I applaud you for that. Don't stop working hard at keeping the revs as low as possible during a quick take up of the clutch. If you are going to swap, I'd be inclined to go for as many gears as you can find, dollar for dollar. A multi-geared roadranger allows you the flexibility to skip or use the different gear ratios as you desire. More gears means more overlap, which is a good thing. A four speed pretty much has no overlap, you are rigidly in whatever gear for whatever road speed and that's it. Hit a hill that 3rd doesn't quite let the engine pull, and all the way down to 2nd you go. More gears, more chances to put the engine into max power. With that 3.58 differential, I'd be leaning heavily to a direct transmission, an overdrive will be hard for your engine to pull, unless there's a steroid boost for that in your future too! These upgrades just don't stop at one piece, dontcha know? happy coaching! buswarrior (Message edited by buswarrior on May 10, 2009) | ||||||||||||||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 462 Registered: 3-2007 Posted From: 71.55.197.237  Rating: N/A |
Hey COME ON DOWN TO Ocala,FL. The salvage yard her is still full of trucks. Gomer | ||||||||||||||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 895 Registered: 11-2005 Posted From: 208.54.200.33  Rating: N/A |
First gear in a 9 sp is plenty low but between 8th and 9th is too much of a gap. As David said, the 10sp is much better because the ratios are closer. First gear in almost any truck trans is plenty low for a bus, most of them are so low they aren't even used except with a load. | ||||||||||||||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1464 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
Even so, the gap is less than the four speeds. I think the newer versions of the ten speeds were redesigned to provide a better spread of ratios compared to the early ones. The 9 speed I was going to use in the Brill was changed to an overdrive and I added an overdrive splitter section; RT009509. Actually even a 7 speed model would probably do the job nicely, but the 9's and 10's are probably going to be the most plentiful. | ||||||||||||||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1544 Registered: 12-2000 Posted From: 98.192.173.82 Rating: N/A |
A long time ago, in a college town 250 miles north of here, this busnut used to pilot a 40-foot, three-axle yellow Twinkie powered by a mid-ship pancake 6-71 bolted to a 10-spd RoadRanger. (It's how I paid for my college education - great p/t job!!) Here, was the shift pattern:
There is also a button on the side of the gearshift with two positions: down for low range, up for high. As you can see from the table, low range is 1 - 5, then pulling the button gives you the 6 -10 high range, with the pattern being identical in both ranges - at least for this model RoadRanger. We also had a pusher three-axle Gillig on the property w/ an 8V71 mated to the same 10-spd RoadRanger. As a joke, we'd always assign a new driver that coach his first day "solo", just to see how he/she'd handle themselves - they never got behind the wheel of this bus during training. On their first day solo, the experienced drivers would listen to the radio in the dispatch office, waiting for the newbie to call in asking for help. Why? Look at the shift pattern below:
All levity aside, when driving the 10-spds, 99% of the time, it was 3, 5, pull the button, 7, 9, 10 when empty, and 2, 4, pull the button, 6, 8, 10 when loaded - especially w/ HS students. Rarely were any of the other gears used for the local runs. Field trips, however, were another story, depending on where the group was going. If it was the HS Marching Band (favorite group, by far!) with all their gear, and we were off some place where we'd have to climb one of the many 6% grades to get out of this valley, then the narrow splits of the 10-spd were used and welcomed. But I think I only used 1st once in the entire time I drove skoolies w/ RoadRangers. Of course, I never did try to try and launch a boat with Twinkie, nor climb the side of the TransAmerica Pyramid! FWIW & HTH. . . PS: I also had the elementary kids convinced that the clutch was only for starting and stopping the bus - easy to do w/ a RoadRanger!! | ||||||||||||||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 696 Registered: 7-2006 Posted From: 70.210.224.227 Rating: N/A |
Neat post RJ... ! RCB | ||||||||||||||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 898 Registered: 11-2005 Posted From: 208.54.200.61 Rating: N/A |
John, Almost anything is better than the four speed, mostly because of the tall first gear. A five or six speed with a granny low would be perfect. Anything above 7 is overkill for a bus but my guess is that 9 speeds are the most commonly available in salvage yards. I drove an 18 wheeler with a 9 sp for years and it was awful. 9th was too high for a lot of hills and 8th was too slow, otherwise it wasn't bad. | ||||||||||||||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 49 Registered: 2-2009 Posted From: 71.139.244.152 Rating: |
I think I've said it before, but different versions of 10 speeds can have different ratios, usually on the bottom end and up top. That's what the letter after the numbers mean RTX-14609A (direct), RTX-14609B, etc. There are C ratios too. | ||||||||||||||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1596 Registered: 12-2000 Posted From: 76.66.16.242 Rating: N/A |
Yes, A, B, C, ratios for the Roadrangers. My preference is percentage changes as close to equal as available. You want to rev to the same RPM in each gear and shift. Different percentages yields different shift points for each gear. The 7 speed Spicer in some later model MCI are a pain, different RPM for every gear... happy coaching! buswarrior | ||||||||||||||
| Larry Baird (Airhog)
Registered Member Username: Airhog Post Number: 157 Registered: 1-2001 Posted From: 71.102.2.43  Rating: N/A |
In my 10 speed RTO the 9th and 10th are reversed, 10th is direct and 9th is 20% over. The splits are 300 rpm, much better then the 600 rpm the 4 speed had. | ||||||||||||||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 84 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
If you want equal ratio spaces, the 10spds fit that mold. B model has enough ratio-the wide C model that is used on big trucks is just not needed in a bus (it has the same ratio span as a 13 spd). Good Luck, TomC | ||||||||||||||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 55 Registered: 2-2009 Posted From: 71.139.244.152 Rating: |
Larry, the RTX is an overdrive (like the RTO) with a standard shift pattern. | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 324 Registered: 10-2003 Posted From: 74.244.14.221 Rating: N/A |
OK sorry for the delay in getting measurements we decided to go camping on Lake Lanier for a few days. For those not familiar with the driveline layout on a Flx the engine runs fore and aft and is offset toward the passenger side. The driveshaft passes over the top of the axle tube into a drop box. Now for some measurements to see what the possibilities are. U-joint to u-joint is 20". Front of the bellhousing to the first u-joint is 32". Back of the trans case to the diff is 10". One question about the road rangers do they use syncros like the spicer? | ||||||||||||||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1285 Registered: 5-2001 Posted From: 65.74.69.200 Rating: N/A |
Not the ones that I drove. I think that you have to be class 5 or less to get synchros. GMs have the big axles while the Flxibles have small axles. It might make a difference. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 325 Registered: 10-2003 Posted From: 74.244.14.221 Rating: N/A |
Thanks Tom. The manual I have for the spicer lists syncros but I still have to double clutch going down. Going up it isn't necesary just shoft at 2100 and it slips right in. This is the first heavy duty trans I have handled so I don't know if what I am describing makes any sense or not | ||||||||||||||
| Glen Rice (Rgrauto)
Registered Member Username: Rgrauto Post Number: 3 Registered: 2-2006 Posted From: 98.18.111.247 Rating: N/A |
Tim, Your dropbox description sounds like the MCI 5a that I own with the exception that the driveshaft is offset to the drivers-side, over the d-box. I think the 6-series allison is the only trans. that will fit for length in the 5a,maybe the the same for you. Is Lake Lanier full pool? I have not been on lake since drought. (Habersham Co. Ga.) Glen Rice | ||||||||||||||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 326 Registered: 10-2003 Posted From: 74.244.14.221 Rating: N/A |
Glen, Lanier is getting closer every day only about 5 1/2 feet below full pool now | ||||||||||||||
| Kevin Black (Kblackav8or)
Registered Member Username: Kblackav8or Post Number: 124 Registered: 8-2005 Posted From: 24.152.162.226 Rating: N/A |
I like my RTO-14615. 15 speed with a .78 OD. I turn 1550 at about 60. It really is a 10 speed overdrive with an underdrive section. So think of this, you only use the underdrive for getting into your spot or tight confines, the rest of the time it is just a 10. A 13 speed is really a 4 speed plus low that you go through 2x with an option to split the top four. Truckers love 13's because you can take that half step by splitting if you start up a grade without moving the lever. 8LL's are also supposed to be pretty decent for RV / Hobby use. Now for a 6/71 mentioned the 13 speed would be a better choice, understand you aren't shifting 13 times unless very heavy or very steep. The drawback to 13's is when the 12xxx series and older wear out, then they howl like the dickens. 15speed: http://www.youtube.com/watch?v=r0UljDne4xU&feature=channel_page 13 speed with worn out overdrive: http://www.youtube.com/watch?v=16-e26yXRjw&feature=channel_page For some odd reason some people seem to like that sound. (Message edited by kblackav8or on May 15, 2009) | ||||||||||||||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1475 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
Nice thing about the 9 speed is that you can use low in high range to avoid having to go back into low range. Can save hassle at times. Normally, low is only used in low range. Low, 1, 2, 3 ,4, shift to high range while moving shifter back to 1, which is now 6th, then 2, which is now 7th, then 3 which is now 8th, then 4, which is now 9th. The trouble with the older ten speeds is that they have about a three hundred RPM spread, if you think about it would keep you busy in your coach. I believe the 9's are about 400 to 450 rpm spread, should be better in a coach, since you aren't hauling 80,000 lbs. gross. You CAN add the splitter, but it will lengthen the trans about ten more inches. |
