| Author | Message | ||
| Jim Sanders (Sandy)
Registered Member Username: Sandy Post Number: 67 Registered: 1-2011 Posted From: 69.199.96.250  Rating: N/A |
Hey guys i appreciate all the response i have gotten on RPM rato...A bunch of good info...Iwill try to settle for a RPM around 1300 I think a Over drive tranny would be better than a change in the rear end. As far as i know Allison has never made a auto tranny????????? I have been told that With a electronic control tranny one is availilable?????? Cost verses a ease of operation ???? I am not sure that i want to go that way????? I think that the tranny i have now is a 731??? Comments please Thanks BBBBBunches | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 520 Registered: 3-2006 Posted From: 216.198.139.38  Rating: |
Jim If you have a V731 you have no other option but a rear end change. No O/D tranny available for the V configeration. 1300 is a low rpm for highway use. Ideally you want about 1600 rpm at 65 mph. Good fuel economy and in power range. If you try to use a rear end that lowers the rpm too much you will have no bottom end power. The V731 isn't great on soft ground at the best of times. I run a V731 with a 4.56 - 1 rear end with a home made O/D but complicated to do. My top speed is 68 mph at 2100 rpm without the O/D. With the O/D it is 88 mph. My friend runs a V730 with a 4.10- 1 on a 35' coach and has a top speed of 71 mph at 2100 rpm. Bill | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 312 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
If this is for your Flxliner, then you have a T drive. You do NOT want a 1300 rpm cruise speed. Simple to low for the 6-71, or any 2 stroke engine. The aim is to have a comfortable 1800rpm cruise-this is where the engine is rated as continuous operation. If you have a direct transmission and want to go 75, that would be a 2.96 rear end. 65 at 1800 would be 3.42 ratio. The Allison World transmission has both a .75 and .65 (3000 series) overdrive and can be used with a mechanical engine with throttle position sensor. The 3000 series transmission is rated to 1100lb/ft torque, or 1250lb/ft torque in gears 3-6. When I changed my Kenworth from a 13spd single overdrive transmission to automatic, the HD4060 (like a B500) electronic transmission would have cost exactly twice what a HT740 4spd Allison cost. Hence I installed the HT740. With 11R-24.5 and 3.55 rear gears that gives me 1690rpm at 60, 1830rpm at 65, 1971rpm at 70, and 2112rpm at 75. Hence I'm not doing any gear changes. I cruise at around 58 most of the time with my bus and that on my truck will be around 1633rpm-which will give me as good fuel mileage as possible (with my Caterpillar 3406B). On yours'-please don't gear to big-you might loose startability that would get you stuck on a steep hill. Good Luck, TomC | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1264 Registered: 8-2006 Posted From: 99.37.28.23 Rating: |
Jim, Does your engine sit straight in line with the bus? Or does it sit crosswise with the fan on the left? From what you are telling us by saying "731," your engine would have to be crosswise, also known as a VEE drive, with left hand rotation. If you have a TEE drive, the engine, transmission and differential form a tee, then you can't have a 731, you've got a 740, or one of the smaller T drive Allisons, like a 643. Tom and I both think you have a T drive, but anyhow, all three of us answering you so far are really concerned about your proposed axle ratio choice! "No bottom end power" is Canuckian for a sluggish bus, especially in traffic or in the hills, not to mention the mountains! Although your ratio choice is in the high part of the torque curve, its also in the LOW part of the horsepower curve. Not only that, but optimum fuel consumption is from about 1400-1600 if I recall correctly. Please, tell us which way your engine sits, and we'll be glad to help with the trans, and the gearing. G | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 521 Registered: 3-2006 Posted From: 216.198.139.38 Rating: N/A |
George "Canukian". Thats a new one. At least you knew what I meant. My Mak bus ID chart doesn't tell me the type of drive so I assumed Jim had read the model number from the tranny when he said V731. Bill | ||
| Paso One (Paso_1)
Registered Member Username: Paso_1 Post Number: 192 Registered: 11-2004 Posted From: 142.165.246.240  Rating: N/A |
Thats interesting your friend is running a 4:10-1 rear end along with the V730 as that is exactly what i'm going to end up with. Is he using the 6 V71 ?? 2100 @ 71 is not bad for me.  | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1265 Registered: 8-2006 Posted From: 99.37.28.23 Rating: N/A |
Bill, My mother was born in Scotland, and her 6 brothers and sisters were born in BC. My parents were married in BC, and I have 20 some cousins there, so it can't be called Canadian bashing! On a serious note, I get just what you mean, and so does Tom. We've all just put it differently, but with those proposed gears, that engine couldn't get that bus up to cruising speed, because it would take more horesepower to do it than it could produce at that low RPM! Interestingly enough, almost the same thing is being done by someone else here, to the same brand of bus, and he wants to tow a boat! I have expressed my concerns, so we will just have to wait and see? I feel that his trans will spend most of its time in its lower gears, and be very hard on its torque converter. KUTGW, G | ||
| Jim Sanders (Sandy)
Registered Member Username: Sandy Post Number: 68 Registered: 1-2011 Posted From: 69.199.96.250 Rating: N/A |
Hey guys I bought this Flxliner last year from a man N.J, Checked it over the best i could. Drove the bus to houston. The only trouble i had was busted air line.(NO BRAKES) Put it up on blocks went to work on it..Found RUST RUST RUST. I am still cutting out rust. I am starting to give a little thought to other problems.I had to open my drop box. Found 1 gear tooth with 30% gone??????? HOW WHERE WHEN???? Drained the grease from the 3rd member was full of ground up gear tooth New Rear end....... From NJ to houston was running 65mph @ 1750rpm. Cruse at the Torque curve 1250 to 1350 now is the time to change gear rato if possible.I dont like the idea of haveing to change rear end rato. BAD NEWS?????? Tranny with O/D Good....Not avaible????? Running a DD6/92 With auto tranny.So i came to BNO see if somebody new a better way to do the same thing. I LIKE the feed back i am getting Thanks Thanks Jim. | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 522 Registered: 3-2006 Posted From: 216.198.139.38 Rating: N/A |
George Maybe you should apply for dual citizenship with that many cousins from here. Then again maybe not as we are taxed much higher then the USA. 13% sales tax plus everything else hurts. Paso 1 Joe runs a 4.10 - 1 with the V730 and an 6V92TA DDEC IV. He is limited to 2110 rpm and 277 HP because of the DDEC computer. He runs 12R22.5 tires. His bus is a GM 4107 35'. Jim It sounds to me that the ratio you have is about right other then replacing it due to wear. Do not lug the engine. They like to run in the range you mentioned. You still never clarified the drive set up for us that are unfamiliar with the Flxliner. Looking in the engine commpartment is the engine going from side to side (across the bus) or is it straight in (forms a "T" with the rear end). Bill | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 619 Registered: 10-2003 Posted From: 66.165.176.62  Rating: |
Bill, The Flxliner is a Tdrive with a drop box. Not sure of the dimensions of a 730 but I know with my 5 speed spicer my driveshaft is only about 18". Here is a shot of my engine bay for reference http://members.tccoa.com/timb/Flx/100_5831.jpg | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1559 Registered: 10-2006 Posted From: 76.195.74.7  Rating: N/A |
ON a 2 stroke running at lower RPM to obtain "better" fuel mileage at the torque peak will never be worth the cash. However some folks install De-fuller injectors for a tiny HP increase. The DD rule is you need to use 60% or more of what the engine was set up for, and the economy will be normal. The other concept is these were 1800 RPM engines in commercial (genset , water pumping) operation and will only get good fuel burn there ,1800,or at a max 10% higher . WE use 1950 on our sports car , 70 mph works out to over 9mpg mostly for over a decade with an 8V.. 16 HP works out to 1 GPH at good cruise speed , so you can inspect the injector tags , Da Book and see if an upgrade (more rational size)is in order with the next set of injectors. Using the torque peak id GREAT on a modern 4 stroke , on the MB bus the tach is back lit at 1200-1300 in green , but requires a 6 speed stick tranny to operate with efficiency. At the usual 10,000 miles of bus camper use , there isn't much that is worth the effort, except a repair if it caused low mileage. FF | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1196 Registered: 8-2006 Posted From: 74.33.48.167 Rating: N/A |
If that is true Fred why did DD build the fuel saver 8v92 TA engine a 1800 max rpm engine for transportation use ? I have built dozens of 8v92 in the 450 hp range with 1450 # of torque at 1300 rpm and got 7 to 8 mpg in a 32,000 + lbs coaches not that big of a deal,Don Fairchild can do better with mileage on his engines than I do fwiw good luck (Message edited by luvrbus on July 18, 2011) (Message edited by luvrbus on July 18, 2011) | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 2109 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
Fred's coach is basically an empty shell as far as weight goes. If he runs at 1950 with standard timing, he is running too fast, should have advanced timing. Probably because of the 4.375 rearend. Have a DDA Silver series brochure with a 8V-92 rated at 350hp @ 1600.1250 peak torque @1000rpm-600 rpm operating range.Also, a 8V-92 400 hp @1800. 1250 peak torque @ 1300- 500 rpm operating range. So,SOME 92's can run slower than we might think. | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 525 Registered: 3-2006 Posted From: 216.198.139.38 Rating: N/A |
Tim With the flxliner being a "T" drive then the V730/VS2-6/VS2-8 are impossible to use. They are only used in "V" drives. He now has a lot more options with it being straight in. Bill | ||
| Jim Sanders (Sandy)
Registered Member Username: Sandy Post Number: 69 Registered: 1-2011 Posted From: 69.199.96.250 Rating: N/A |
George I am running A 4 speed tranny( the P/O said allison)????? I have not spent any time on the bus Other than rust Still a way to go.... Since i have found ground steel in the 3rd member. I know that i can not put that back in... A man (James Seagraves) from BNO Has a complete axle &drop box out of his 69 flxliner. I will not put in my bus until it is checked out...Take it apart check all gears ( every thing in it) Now would be the best time to change rato... So pros and cons I still lean towards Torque curve... If i need power i can allwase drop a gear but still cruse around 1250 to 1350...Save both fuel and wear.... Now the best way to do that????? Thanks Bunches Jim | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 1480 Registered: 3-2007 Posted From: 76.4.118.153  Rating: |
Jim I know about trying to save wear and tare along with fuel mileage,However a DD runing at that low rpm will not perform like you think. It will always seem to be booged down and then when you need a little omph you will have to downshift. I would try to get the rpm around what has been said. You will be better satisified with the all around results. I GARUNTEE LOL Gomer | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1266 Registered: 8-2006 Posted From: 99.37.28.23 Rating: N/A |
Jim, How do we get you to listen to us? I'm sorry if this makes you mad, but there doesn't appear to be another way! All engines have TWO curves, torque, and HORSEPOWER, which you are ignoring. It takes horsepower to do work! As you see, maximum torque is produced by most diesel engines from about 1200 to 1400 RPM. Maximum horsepower is produced right at about maximum governed speed, or about 2100 RPM. From memory, at 1300 RPM, that engine won't be producing much over 150 horsepower, which won't be enough to get you to cruising speed. Best fuel economy starts about 1400, and continues thru about 1600. Your cruise RPM wants to be at the closest spot to all three curves, or ABOUT 1800 RPM. There is a reason bus and truck makers gear them the way they do. If one maker could gear the same engine 500 rpm slower at cruising speeds than everyone else, and get lots better fuel mileage, they would have done it a long time ago. You can't "drop a gear" you can't get up to! I have done four gas to diesel conversions in Ramchargers and 3/4 Ton pickup trucks, with and without lockup torque converters, and with factory overdrive, and with Gear Vendors O/D on behind. Considerable research went into final drive ratio, which includes tire size. I'm done. G | ||
| Jim Sanders (Sandy)
Registered Member Username: Sandy Post Number: 70 Registered: 1-2011 Posted From: 69.199.96.250 Rating: N/A |
George Beleive me whin i say I want you guys openion. All of you has had more experiance with these older busses than i have as far as i know the flxliner came from the factory with a 3,56 rear end in it. Or that is what the tag says under my dash. Yes i would like to lower the cruse RPM BUT If i could find a tranny that would give that to me and leave the low alone I would have less misgivens about the Installing it | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 1483 Registered: 3-2007 Posted From: 76.4.118.153 Rating: N/A |
Jim I forgot to add last night that I drove a Flex that originally had a 6-71 in it and [history lesson] was used by the Hopper Brothers and Connie in their Gospel Music. The new owner installed an 8V-71 in it and never changed the rear ratio the tranny. It would top out at about 80 but we always ran it around the speed limit[?] and never had any pulling issues with it or git up an go. I believe you are on the right track to stay around 1600-1800 rpms. Gomer | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 315 Registered: 1-2006 Posted From: 66.218.33.156 Rating: |
Jim- Please take the advice of many and myself that ran 71 and 92 series over the road for hundreds of thousands of miles. DO NOT GEAR THE BUS TO CRUISE AT 1250-1350 RPM. I don't know how much louder I can shout this out. You'll loose your startability, the power will only allow you to cruise at that rpm on the flatest of roads, and you'll be constantly down shifting. Once a mechanical 92 series gets below 1500rpm, it doesn't have much power left. Electronics are a bit better. PLEASE-take my advice-gear to run in the 1500-1800 rpm range. That's what the 2 stroke engines are made for. If you want a 1250-1350rpm cruise speed, you need to change to an electronically controlled 4 stroke engine. What appears on paper to be a good idea sometimes just doesn't work in real life-like running a 2 stroke too slow. Good Luck, TomC | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1835 Registered: 12-2000 Posted From: 71.195.124.20  Rating: |
Jim - The overall message being sent to you from everybody who's responded regarding regearing is this: "IF IT AIN'T BROKE, DON'T FIX IT!" It's that simple. FWIW & HTH. . . | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 318 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
The 8V-92TTA "Fuel Squeezer" engine was rated at 365hp at either 1800 or 1950. It was a flat horsepower engine from 1500-1950. I had that option on my first truck-didn't like it and had the shims removed from the governor. The increase of power to a regular 435hp @ 2100 was quite noticable. And with driving habits, the mileage stayed the same. The biggest determining factor in what fuel mileage you're going to get is the loose nut behind the steering wheel (LOL). Good Luck, TomC |
