Hi everyone, got a new (new to me)300zx on sunday, car goes really well and excelerates really good, the only thing that did'nt seem right is when cruising at say 50 or 60 if i lift my foot off the gas the engine revs drop right down to an idle, then when i put my foot back down again the engine would rev up from idle and catch up to the speed of the car. Dont no an awfull lot about auto gearboxes just seems like theres a missing link between engine and gearbox ?

it wont over run if thats what you mean. when it senses less pressuer it will lift a gear from my understanding. try turning off the overdrive that little button on the stick and do the same, and also try it locked into second you shoudl get abit of over run.

Hi, drove her again today and tried the o/d button, made no difference to the engine rev drop. The only way i can describe what happens is imagine your in a manual car doing say 60 then taking your foot off the gas and pushing the clutch down, the engine drops to a tickover instead of staying with the rpm of the gearbox, then when i put my foot back on the gas the revs build up from tickover back to gearbox/car speed. Its not slipping because the revs never overtake the gearbox and excelleration is as it should be (quick)

not experinced that myself hrm.

That sounds healthy to me matey...

That sounds healthy to me matey...

Bloke at work says sounds normal to him, something to do with fuel consumption. Well i must admit i'm not to used to auto's and not to clued up on them. Like i say pulls strong changes nice and the oil in it is like new. So its sounds like its good news. Thanks, its put my mind to rest.:biggrin:

Mines the same, nothing to worry about.

Mines not!:wacko:

It could be a line pressure issue, but im getting mine converted soon, ( how many times have i said that lol, honestly it is soon) so im not going to worry about it. All i can say is, it has been like it for the past 3 years and still fine.

Mines not!:wacko:

 

lol i swear our boxes act different to everyone elses mate lol

Thanks to Willio for this.

 

Overdrive on an auto is the 4th gear ratio available (ie 4 speed auto) and to make it more complicated there is also a lock up clutch which by-passes the torque converter making it feel like yet another gear ratio. So overdrive in set off position leaves you in the same top gear ratio as a manual left in 4th gear. If you want to be pedantic about it a 5th gear on the manual is also overdriven in that the gearbox output speed is higher than the shaft input speed - so overdriven.

 

When crusing at speed in overdrive with the lock up clutch engaged you should be showing about 2750rpm @ 80mph

 

Cruising at speed on light throttle in overdrive should mean the least fuel consumption but for instant response on a country road leaving it off and letting the revs rise can be more enjoyable

 

Hope this helps, Paul

Sorted, loose throtal cable. Thanks.