| Author | Message | ||
| John (172.168.238.12) Rating: N/A |
Is it bad to coast with the trans in neutral? | ||
| Mike Eades (Mike4905) (206.148.164.184)
Rating: N/A |
Oh Yea" | ||
| RJ Long (Rjlong) (24.127.74.29)
Rating: N/A |
John - You are "pulling our leg", aren't you??? RJ PD4106-2784 Fresno CA | ||
| John (64.12.101.171) Rating: N/A |
No, I read somewhere that coasting a trans in Neutral for long periods of time is bad. Something to do with extra wear on the clutch or something like that. | ||
| RJ Long (Rjlong) (24.127.74.29)
Rating: N/A |
Are you asking about pulling a toad? Or coming down off a mountain in a bus?? Help us help you - fill in the blanks a little better. . . RJ | ||
| john (64.12.101.156) Rating: N/A |
In general. Lets say driving on a level steet. | ||
| Buswarrior (Buswarrior) (64.229.213.47)
Rating: N/A |
The new Allison World Transmissions are specifically forbidden to be coasted in the literature. I don't know why. I do know that you'd be best to bring the engine revs back up before you push the shifter back into gear after a bit of Newfie Overdrive (Yes, that is NO by the initials!) HT740 and 8V71 It wasn't my bus, and it kept going, but wow, what a bang! Thought for sure something must be behind us out on the road. Be careful what braggin' and tall tale tellin' you do around a young 'un. They don't know the difference yet and they might just go out and do it! happy coaching! buswarrior | ||
| jmaxwell (66.42.92.9) Rating: N/A |
Just how far do u think u are going to coast on a LEVEL street? At best, I would have to say that coasting a bus is a dangerous practice. You should not have sealed your house up so good with the duct tape; your experiencing oxygen deprivation! | ||
| John (64.12.101.156) Rating: N/A |
Yes, why is coasting a bad practice? About 1000 feet or so. Like Buswarrior said, why does allison and other state "Never coast transmission in Neutral"? Does it damage the trans? That is what I would like to know. | ||
| Edgar Jewett (Kristinsgrandpa) (65.134.220.96)
Rating: N/A |
I had a '55 Ford that I used to kick up into neutral and let coast. A few times doing that it blew a seal in the transmission. Cost me $12.95 to get it fixed. The man at the garage told me that the pressure builds up when doing that. Years later the subject came up again and I was told that new (late 60's) transmissions had a vent on top of the housing to relieve the pressure, then all you did was spray trans fluid all over the underside of the car and onto the pavement. I don't have a coach and I don't know a lot about them BUT I do have a Service manual for Allison Transmissions Series HT 740 (hydraulic controls). In the operating instructions section on pg. 1-7 the very first thing it says (with the word CAUTION  Quote "failure to lift the driving wheels off the road, disconnect the driveline, or remove the axle shafts befor pushing or towing can cause serious transmission damage" unquote. I would say it is probably something like what happened to my '55 Ford. HTH Ed | ||
| Peter Broadribb (Madbrit) (65.37.89.205)
Rating: N/A |
It is because you are basically towing an automatic with the wheels down and as we all know, most trans can't do that or we wouldn't be having great discussions about which 'towed' we can flat tow or not. I did coast my 91 Ford diesel dually down a local 10 mile hill on a fairly regular basis, when the motor was bad, to save on using so much oil. I lost the overdrive sprag and the shop told me I had contributed to the failure of an already worn transmission by starving the trans of lubrication. Peter. | ||
| DaveD (64.235.198.76)
Rating: N/A |
The difficulty may be that with the engine at idle speed, the transmission pump which is usually driven by the input shaft may not be turning fast enough to provide enough oil circulation for adequate cooling of the transmission. Overheating can be a major factor in transmission failure. I'd could be wrong, but if memory serves me correctly, coasting is prohibited under various highway traffic regulations for safety reasons. FWIW Dave Dulmage | ||
| Jack In KC (65.28.19.120) Rating: N/A |
Towing the bus: This all raises an interesting question: Are there limits or recommendations on towing the bus? I saw a passenger bus being towed on the interstate a few weeks ago. It looked like this HUGE tow truck had a hydraulic arm that lifted the front wheels. This would leave the transmission spinning as they went down the road. | ||
| Scott Whitney (66.82.9.13) Rating: N/A |
Still can't figure form the orginal question whether John is talking about towing a tow vehicle, towing a bus, coasting a bus down long grades or what. If talking about coasting a bus on level ground, you won't get very far. They slow down in no time when level. Granted, I've never thrown my VS2 automatic into neutral when I was moving. I don't see what the point would be. I certainly would NOT throw my bus in neutral going down a hill. On a similar note: Why are auto trannies not lubricated by the output shaft? Seems like it would save everybody (mechanics, owners and tow truck operators alike) a lot of headaches on cars, trucks, busses with auto trannies. I am sure there must be some design factor I am not aware of, but it seems like the equipment would be a lot more foolproof if anytime the rear axle was spinning, everything was being properly lubed. I guess the output shaft could be spinning very fast, so the pump would need some sort of clutch or govnerner to keep RPMs reasonable. Guess it would complicate the inner workings a bit. Maybe an electric lube pump on all trannies would be better? Scott | ||
| jmaxwell (66.42.92.26) Rating: N/A |
Jack in KC: About 99.9% sure that they either pulled the axle shafts or the drive shaft. If not, some tow operator was in the process of buying a 15-20k trans. Aside from the cost of that tow truck, preping a big bus for towing is one of the factors involved in towing bills of $750 and up for short hauls. | ||
| Jason Windecker (198.81.19.49)
Rating: N/A |
The trans definatly dont like to be towed, One of our avis buses had a turbo line failure and the engine cought on fire and they brought a lobboy in to take it back to the lot, only about 1.5 miles so that just goes to show that they disliek being coasted/towed. anything like that | ||
| Phil (24.195.248.213) Rating: N/A |
Older car automatic transmissions (1960s and older had rear pumps as well as front pumps. The rear pump was turned by the output shaft and the fromt pump by the outer housing of the torque convertor. These cars could be push started and most recieved adequate fluid circulation under most circumstances. This wenr away with newer designs. Don't know if this is true with bus trans. | ||
| Tom Caffrey (Pvcces) (64.114.233.188)
Rating: N/A |
Phil, you've got it exactly right, and as far as I know, it was just a matter of saving the cost of the pump and necessary plumbing. I think it was a lousy idea, like a few others that they have had over the years. The rear pump did not turn fast enough to give any trouble because the driveshaft never turns faster than ordinary hydraulic pumps run. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher | ||
| Tom Caffrey (Pvcces) (64.114.233.188)
Rating: N/A |
In the early 60s, a friend of mine and I hand pushed a 1951 Packard with the small engine and the Ultramatic transmission over a small knoll near his house. We got it up to about 8 mph, as far as we could tell. He jumped into it and shifted it into low range and the engine started right up. But what I *didn't* know at the time was that there was no battery in it! I guess that when the engine rolled over, the generator spun over fast enough that it made enough ignition before the engine slowed down, so it just started running. In this day and age, what do you think of the chances of doing something like that now? Just food for thought. Tom Caffrey PD4106-2576 Suncatcher | ||
| DaveD (64.235.198.76)
Rating: N/A |
I think some earlier automatics had a rear pump as well as a front pump on them, so push starting was effective. DaveD | ||
| Jim Stacy (32.101.44.27)
Rating: N/A |
Most states prohibit coasting with the trans in neutral. Michigan motor vehicle code does not state auto or stick. I don't know if this is a holdover from non synchro days. Can you imagine coming down out of Eisenhower pass with your Spicer in neutral and gaining speed rapidly while you tried to double clutch into gear? Seems I remember an old Ford T truck transmission made by Warfield that had the only vehicle brakes on the trans and often if you coasted it in neutral it wouldn't go back into gear. No compression breaking and no brakes! Maybe that's where the law started. Jim Stacy | ||
| Dave Wheat (24.197.182.248)
Rating: N/A |
Recently a Greyhound broke down on the road with alternater problem. Bus was towed to our facility for repair. Rear axles were pulled prior to towing and capped off with special cut piece of plywood to temporarily seal off axle housing. That, I have to assume, is the correct way to tow a bus. | ||
| DaveD (216.18.113.69)
Rating: N/A |
Phil, That the front pump is driven by the torque converter is a subtle but important distinction. It slipped my mind. DaveD | ||
| Mike Stabler (Docdezl) (64.255.109.188)
Rating: N/A |
FWIW to keep from burning up the center bearing on the main shaft in a stick you pull one axle OR the drive shaft. If it was towed in with them still hooked up you made a BIG note on the work order. Almost all automatics are now designed to free wheel or "coast" ie for better fuel milage. The Allisons will pull out of "lock-up" and coast. I have pulled vehicles 4-down with the engines at idle (didn't have time to put in driveline spliter) wanted to go play! I have always be told that if the engine was running it was pumping enough oil to lubricate. There is an after market electric pump for "toads" that plumbs into the cooler lines and does a good job (never seen a trans warranty with tow hooks). So coast or, freewheel or,glide but don't shut off that engine. Done some "downhill" in the Smokies for miles , never touched that fuel pedal. She was doin real good at idle!!! Smoke,rattle&,stink.....docdezl | ||
| smoky (12.222.48.5) Rating: N/A |
Guys, I rebuild automatic transmissions for a living and outside of trying to isolate a noise or vibration complaint I can't understand why anyone would want to do this on a regular basis this is why you spent more money for your bus so it would be less work to drive. as far as the mechanics go when ever you shift to neutral all clutch packs go to released posistion for example lets say you're going highway speeds so foreward and direct clutch pack are applied then you shift to 3rd so direct (4th) release 3rd clutches come on and stop direct drum and foreward clutch stays on the whole time but thats ok because this is normal operation but lets say you,re going highway speed in 4th and shift to neutral direct clutch releases and also foreward (imput) clutch releases the foreward clutch was not designed to be used in this manner this clutch comes on in first gear and stayes on in all foreward gears the only time its not on is neutral and reverse so what happening when you shift to neutral while under way is first even though you can't feel it foreward clutches are being sliped as they disengage besause they have no release pressure the just use spring pressure to retract piston because under normal conditions this is all it needs also while the foreward drum is turning at high rpm (same as engine) centrificual force keeps fluid behind foreward piston making it even more difficult for piston to retract and fully release clutches also heres the other problem once the foreward cluches release foreward drum is turning at apromx engine rpm (depending on stall speed) as are also the steel plates that are splined to the inside of the drum now the foreward frictions are sanwiched between each steel plates and splined to the output shaft via a hub and planatary sets which are turning at road speed which is creating a lot of heat in the transmission. I could ramble on for hours about automatic transmission power flow but I'll stop before I put anyone to sleep. Happy shifting , Smoky | ||
| Neo/Russ (216.148.244.38)
Rating: N/A |
Smoky, I'm looking for an Allison B-500. You sound like you're connected, any ideas? Thanks, Neo/Russ | ||
| Henry R. Bergman, Jr. (Henryofcj) (65.194.145.54)
Rating: N/A |
Smoky: Actually, I found your detailed explanation very comprehensive and knowledgable. Thank you. Henry of CJ. | ||
| Steven Gibbs (12.148.43.7)
Rating: N/A |
So that's why there are so many parts inside that thing! Steve G. | ||
| smoky (12.222.48.5) Rating: N/A |
sorry Neo/Russ all the one we have have already been parted out Smoky |