E30 320i Auto Gearbox

Post Tue Oct 21, 2014 9:10 am

I have a 1990 BMW 320i Convertible with ZF4HP22 Autobox and wonder if it is possible to make some adjustment to make it change from 3rd to 4th a little earlier than normal. The gearbox works fine, but it does not change to 4th until over 50mph is reached. I believe it does this because 4th gear with a ratio of 0.73 is treated as an overdrive. If it were to change to 4th at say 40 ”“ 45mph (with gentle acceleration) the engine would be less noisy, more comfortable on the ears and possibly more economical, I’m sure there is more than enough power to pull away in top gear at this speed. I would be grateful for any help and advice you can offer.

Post Tue Oct 21, 2014 1:59 pm

Are you sure thats not the torque converter locking up? It locks up at about 53mph iirc.

Post Tue Oct 21, 2014 9:47 pm

Could be, but engine revs drop noticeably and the effect is just like the upward changes between the other gears. You're right though, it does happen at about 53mph. Is this drop in engine revs normal when the torque converter locks up?

Post Wed Oct 22, 2014 6:43 am

Yep, happens in mine. Its just the lock up clutch engaging to give you better economy.

Post Thu Oct 23, 2014 8:45 pm

Thanks Darkchild, puts my mind at rest, at least there's nothing wrong.
Many thanks
Mel.