Diesel tech help needed from the UK

[rambo19]

Hi guys.
I'm a london bus driver.

We are having a problem with one of the buses I drive and the company mechs are having difficulty working out what it is.

It's a diesel auto, voith autobox with push button gear selector-D-N-R. Volvo engine.

Start the bus and touch the gas=instant responce.
Put the bus in drive and touch the gas= about a 5 second delay before the bus pulls away. If you put it in drive and don't touch the gas, the tickover will move the bus.

If you put it in drive and leave the handbrake on, then rev it up to about 1000rpm and release handbrake, the bus pulls away quickly, but with a jerk.

Once the bus gets moving she flys along with plenty of power. It's just intial pullaway thats very slow.

A tech from voith came down last week and hooked up his laptop to the bus whilst I drove it, he is adamant there is nothing wrong with the gearbox.
There is a boost gauge on the dash, but this does not start moving until the bus hits about 1000rpm.

I'm not a autobox expert, but I reckon the torque convertor is the problem.

Your opinions?

 

[kamesama980]

I work on diesels but for another company and R&D not troubleshooting. I do have some experience (and my education is in) automotive repair. If it were a car I'd say check the transmission fluid, sounds like it might be low.

So (just to reiterate and make sure I have this right:
-Idle while in gear and it creeps (normal)
-Throttle while in neutral it revs OK (normal)
-throttle while in gear delay before going anywhere
-throttle while in gear with brake on, goes just fine when brake is released

In scenario #3 (in gear given throttle) do the engine revs go up without moving the bus, then the gears engage and you move or is there drag on the engine like it's actually in gear but no power/acceleration for a few seconds?

in scenario #4 (in gear given throttle w/ brake) does the jerk happen before or after the brake is released?

For now, I'm not sure I'd worry about the boost gauge. it takes a certain amount of exhaust flow to get the turbo spinning enough to push more air than the engine can ingest. It takes a load, engine revs, and time (and help from the turbo) to get to that point.

 

[rambo19]

Number 3= revs don't go up for about 5 seconds.
Number 4= jerk happens after I release park brake. But only after ive built the revs upto 1000rpm.

I did think that the oil may need changing, i'm going to ask the mechs if they have done that.