overdrive, hesitation

[davemaxx]

for the second time this week now while out on a long distance run and everything is up to operating temp, i have noticed that when my veichle is in overdrive or just about to change into overdrive the truck seems to feel that the engine is hesitating or a very slight misfire (as if it where a petrol engine) it only happens in overdrive because if i press the switch off and the revs lift its fine, it seems to happen just on the 50mph to 55mph as if its hovering to engage or not and can't make up its mind,

i have also noticed today that the speedo is sticking between 40mph and 60mph and jumps to where it should be if i tap on its cover (don't know if its related)

i drained off about 4.50 liters of atf and replaced it a few months ago and can't really say it was perticualy gungy but it was no longer any way near as red and clean as the new stuff. should i do this again? or is this problem down to something els,

[Wild Thing]

for the second time this week now while out on a long distance run and everything is up to operating temp, i have noticed that when my veichle is in overdrive or just about to change into overdrive the truck seems to feel that the engine is hesitating or a very slight misfire (as if it where a petrol engine) it only happens in overdrive because if i press the switch off and the revs lift its fine, it seems to happen just on the 50mph to 55mph as if its hovering to engage or not and can't make up its mind,

i have also noticed today that the speedo is sticking between 40mph and 60mph and jumps to where it should be if i tap on its cover (don't know if its related)

i drained off about 4.50 liters of atf and replaced it a few months ago and can't really say it was perticualy gungy but it was no longer any way near as red and clean as the new stuff. should i do this again? or is this problem down to something els,

Could be the lockup cutting in

[davemaxx]

thanks for such a rapid reply, i don't wish to sound daft but can you tell me a little bit more about this because, simply, i don't know.

[Wild Thing]

thanks for such a rapid reply, i don't wish to sound daft but can you tell me a little bit more about this because, simply, i don't know.

When you reach about 50 to 55 the torque converter locks up giving you direct drive from the engine until you either brake, drop the throttle back to idle position which then disengages the lockup so as not to stall the engine.
hope you can make sense of what I'm talking about

[davemaxx]

yes i can get my head round it, so it looks as if its down to me,
if i am driving at this speed, i am creating this kind of limbo of hovering between overdrive on or off,

[coolsv650]

When you reach about 50 to 55 the torque converter locks up giving you direct drive from the engine until you either brake, drop the throttle back to idle position which then disengages the lockup so as not to stall the engine.
hope you can make sense of what I'm talking about

Throttle position also make's a differance, if you have a very light throttle position it will try to lock up early, and then the road spead will try to fall, then the gearbox will drop back out of lock up

Its probably just more noticable now some fresh ATF is in, with mine the lock up used to get later as the oil thinned out

[andy]

yes i can get my head round it, so it looks as if its down to me,
if i am driving at this speed, i am creating this kind of limbo of hovering between overdrive on or off,

It's nothing to do with the overdrive, that will kick in at around 30-35 mph, and torque convertor lock up is a completely different thing.

Read this: http://en.wikipedia.org/wiki/Torque_converter

[davemaxx]

interesting reading, i think i'll change anouther few liters of the atf and see if it performs any different.

[davemaxx]

hi coolsv650, sorry i havent replied to this post sooner, i've only just read it, and your sugestion about,

Throttle position also make's a differance, if you have a very light throttle position it will try to lock up early, and then the road spead will try to fall, then the gearbox will drop back out of lock up,

are there any kind of adjustments i can make, i think that this is where i should be looking.