Allison AT545 gearbox

[Rmachines]

Does anybody remember the old merc vario busses, they had the automatic gearbox that would chirp and squeal between gears.. Was fitted to various other busses too,  not used these days but i remember them well.   Anyway, i have been offerd one cheap, was going to make it a summer project to convert.   anyway, the auto boxes make this weird chirping between gears... and since test driving it, i have been racking my brains as to what would make the noise.   

Its a standard planitary 4 speed box with clutch packs rarther than bands,  and conventional torque convertor,  i just cant imagine whats going to make this noise and its doing my head in, i cant rest untill i know 


http://www.youtube.com/watch?v=JEbFVnlyjaA

Any ideas??

[Khare]

I always though the chirp on the change was the turbo.

[PenguinGTI]

Yep sounds like the turbo to me. Look up turbo flutter.

[Thom89]

Sounds like a Rootes type blower to me, but also sounds like large heavy duty straight cut gears...

Thom

[Khare]

Sounds like a Rootes type blower to me, but also sounds like large heavy duty straight cut gears...

Thom

I always though they had automatic straight cut gears. Sounds like a dogbox.http://www.youtube.com/watch?v=asFwDpLe1xo

[Rmachines]

Its not a turbo thing for sure, the manual doesnt do it,  Its well known to be the gearbox and only the allison AT545 for some reason.  The dennis darts with the 5.9L cummins engine,  and the merc vario with 4.2L 4pot engine does it as well as some others,   to prove its not a turbo thing, the bluebird american busses with the V6 petrol non turbo lumps do it when fitted with the AT545.    And they are helical cut planitary gears,  its not a particularly heavy duty box compared to the  ZF and VOITH

Also... a brand new box/overhalled will not chirp or squeal much or at all,  I have a feeling its to do with the pressure diffrence on the TC/pump