Re: How much overbore?

Posted by Owen_Dyneto On 2010/12/28 18:38:49

I don't understand this. Standard shift cars don't generally have a reputation for eating main bearings, and in high or OD they're no different in that respect than an Ultramatic or other automatic with a locked converter. IF that was a cause of Packard's bearing wear (a BIG IF), it might be attributed to lockup occuring at such low road speeds, like 22 rpm. I would probably have my 34 Eight in 3rd gear by then, but it has 4.69 gears. With a more "normal" rear axle ratio and standard shift, I suspect you are rarely in high gear at 22 mph as you accelerate.

My own opinion is that a good driving habit with Ultramatics is to use the throttle when possible to delay the lockup to 30 mph or so. Or have the governor reworked to accomplish the same thing. I try very consciously to avoid lugging, for example up a hill, at low road speeds in lockup. Just tick the throttle and kick back into converter when you're at such low road speeds to avoid lugging.

I doubt modern automatics lockup at road speeds in the 20s. At least none that I ever drove.