BW Autobox hot and cold

[HersnotHis]

Following on from the discussion of oil coolers in another thread I would like to know why there is a significant difference when engaging forward or reverse between hot and cold running?

When cold even though the idling speed may be higher engaging forward or reverse results in the merest snatch in the transmission. However when hot engaging forward or reverse results in a perceptible jerk and thump.

Can anyone explain why this is and if there is a way of improving this ?

Although 1973 my Stag was later fitted with the later BW65 box. My Daimler has a BW35 which also behaves similarly.

Cheers

H

[rac]

same here bw35 seems to be a thing with em-trouble is you tend to compare them with a modern auto which are invariably electrically controlled with solenoids and so are a different kettle of fish--I think getting the tickover as low as possible is a great help

[roverv8stag]

its probably to do with oil viscocity. Hotter oil allows the hydraulicy bits in the gbox to move more quickly...clunk...cold oil give a bit of resistance so more smooth
..i guess its a bit to do to do with wear of older moving parts too.

[GDPR]

Poor brake band adjustment will also do it