Thanks NJT5573 for 903 info[now need help on vibration problem]

[Outback Man]

Well, I think I will give the pump shop a call tomorrow and see what we can do about the pump on my 903 Cummins. I sent an email to Bruce Dahl who works at Seattle Metro [the guy I talked to shortly after I bought the bus in '98] and he didn't think anything in the tranny would be causing the lack of speed so it must be what you described with them possibly not having the proper governor spring. I wil be better armed to discuss the matter with them now, thanks.

    I have two kids? [35 and 38] living in Seattle so I will be over that way later this summer and maybe I could get together with you about the governor situation. It would be very beneficial for me to get some first hand and hands on experience on the pump setup. I am a more than adequate mechanic but no experience with diesels. Just frustration at trying to find anything out about them. Most diesel men try to concince you that they're right up there next  to brain surgeons in the greater overall scheme of things.

    I wanted to pick your brain on another matter if I may, namely a vibration I have at about 40 to 55 mph. It feels like a u joint going bad, but they are tight so I don't think that is the problem. This began in April after the bus had been parked all winter in Arizona and when I went to go to the truck stop to fuel up before I headed to Tennessee the bus wouldn't move after I'd released the brake and put it in gear. It sat there for a short time and then something made a big BANG and it began moving. I don't know if a brake had frozen or what, only that something must have stuck and then finally released.  I am going to jack up the wheels and turn them to see if there is any funny noises in one of them. I thought maybe a piece of brake drum could've broken or the drum cracked.The drivers side brake makes a little clunk, clunk clunk sound when I'm going slow, almost to a stop. I don't remember it doing that until after the big BANG either. Doesn't seem to do it at speed. About 4 years ago when I pulled into Quartzsite from Idaho, that same wheel made a loud grunch when I pulled up to a stoplight. I was only 2 miles from my parking spot and it didn't make any more noise but the hub was quite hot to the touch. I had a trucker friend look at it before I moved it the next spring and he couldn't find anything amiss, at least visually and I had jacked up the wheel and spun it but it made no noise and seemed to be smooth. He thought that it had possibly picked up a piece of gravel or a small rock. I have probably only driven the bus 15 or 20,000 miles since that time and it never did anything strange since. I check the hubs every time I stop and sometimes the driver's side will be a tad bit warmer than the other but definitly not hot. I also had the back curb side tires balanced day before yesterday as I had blown a tire on the way down to Az. last fall and the only tire I could find to fit in Tonopah Nevada was a used recap and the service truck mounted it on the road so it didn't get balanced. I thought, grabbing at straws, that that could have been the vibration, but that was not the case. Hopefully it isn't something in the tranny or the dog bone. I have been reading up on the V730 and the bevel gears seem to be a weak point. Maybe something in your experiences might be helpful. Would appreciate any input for sure.

[TomC]

The transmission shop that overhauled my V730 said that converters regularly pump up the 8V-71 to 425hp through the V730 with good results.  Remember we are not doing transit service and are not flooring it all the time like transit drivers do.  My bus is turboed up to 375hp and 1125lb/ft torque, and the trans works great!  Good Luck, TomC

[Outback Man]

Thanks for the info on the V730 Tom. I am getting ready to crawl under the bus to check out that front wheel and do some greasing  and such. I called a truck outfit today in Jackson, Tennessee that was supposed to do work on Allisons and all they do is service work so I'll have to back online and find out the number of the shops in Memphis and Nashville and see what I can find out. The email I got from the head tech training guy in the Seattle Metro shop thought that the tranny wouldn't need any adjustments to get an increase in speed from more engine rpms, but it has been ten years since they phased out these old Flyers so they may have forgotten some of the stuff they used to do. Hope I can resolve the vibration issue and hit the road. Have to be in Dupree, South Dakota [my home town] by the 11th of July.

[NJT 5573]

Well thats a lot of questions! I can just guess on them. The bang was probably just a stuck set of shoes. On the vibration start at the front, is the balancer still on the crankshaft? Is the front motor mount in good shape and securely bolted? Do you have a loose rear mount on either side or a broken bolt on either side? Have you changed the ride height, there by changing the driveline angle? Is the driveline properly timed? Are the axles running straight under the coach? How full is the gear oil? Do you have a carrier bearing in your drive line? Is it OK? I think you should pull the wheel with the noise apart. Its probably just one or both return springs broken and they and the shoes riding around in the drum. Not extremely serious but easily fixed.

Another hard to detect vibration is an injector miss. My engines do not like the new fuel. In the old days of good fuel, an injector that was bad would usually seize and sound like a real bad rod in a car engine. (They would bang like hell). Nowadays with ULSD the injector just stops working! I recently chased a vibration on one of my trucks from one end to the other over several months. When we put Power Service in the fuel, the problem went away.

We used to run the fleet 903s at 2600 rpm all day every day. The best power trick (in the day) for a 903 was a stock 350 ntc pump with about a 1/4 inch of extra RMP shims.

The "something in my experiences" part of this tells me that you really do have a tire vibration. I don't like caps and I don't like to balance these tires. You can have a lot of irregular wear on a tire and not have any vibration. Most or all vibration in todays radials is going to come from innerliner/damage problems. Innerliner problems never get better. A tire with a vibration around my operation is not a candidate for a "balance", they go back to the dealer or in the garbage. (ASAP).

The Chinese tire recalls have sort of began. Problem is no one in America is rich enough to replace 500,000 tires at a time and the Chinese claim they were built to spec., and they don't speak good English anyway!

A cracked drum can be hard to spot. A crack will usually be visable if you have pressure on the brakes. A cracked drum has a sound all its own. Once you have heard one chewing up the brake shoes its hard to forget. A cracked drum is an out of service issue of extreme importance. If it is run it will come apart in 5 lb chunks and fly thru windshields.

[Outback Man]

Well, NJT, once again thanks for your input. I jacked up both front wheels today and spun them around forward and backward and watched the drum and the shoes and once again can't see anything that looks out of whack. I checked the rear end level and it is OK. Greased the U joints and they took grease well and didn't seem dry. I don't have a hanger bearing as it is a short shaft and there is a Telma electric driveline brake that is attatched to the front of the pinion shaft which makes the shaft fairly short. I am going to road test it tomorrow and see what goes on. I have been using an additive since I've owned the bus and more the last trip since I started having to buy the ultra low fuel. The engine runs smooth so I guess I'll just take off into the wild blue yonder and keep an eye on everything and see what happens.

     I called an Allison outfit in Memphis today and talked to a tech guy about the probability of the speed problem being due to the tranny needing to be reset or regoverned and he said no, if the engine runs more rpms, it should go faster. Then I called the guy here in Jackson who is the manager of the pump shop and he says that they did the calibration and he is going to have the guy who did the work call me in the morning and we can go over what he did.  Guess he wasn't in today. So the saga continues on that front.

     I will definitely keep an eye on that cap in the rear and see if I can get a deal on some new tires when I get somewhere else. No one has any of the 12R 22.5's in stock and I don't want to wait around as I have to get going soon. The sales tax here in Tennessee is exorbiant too, but then it is most places I guess..............Maybe I can get some online! Let's see, shipping would be very high........Nah, better just pay sales tax and quit whining.

     Thanks again for all your input. Very much appreciated.