all 4.0 cranks the same?

i looking for a 1990 4.0 motor and the salvage yard i called today said there is a difference between automatic and manual motor. he said the cranks were different. does anybody know if this is correct?

Cranks should not be different - but he might be selling the motor with the flywheel/flexplate in place - and those damn sure ARE different!

A flywheel is a thickish (about 1") cast iron disk that provides one-half of the friction surface for the clutch, as well as rotating inertia for takeoffs. Figure it for about 20# or so, and with a machined surface for the clutch.

A flexplate is a thin metal plate to which the torque converter is attached. You don't need as much rotating mass for a flexplate - since that is provided by the torque converter anyhow. And, you don't need a friction surface. Therefore, a flexplate is just a mechanical coupling.

As far as I know, the bolt patterns for both are the same. The key difference would be the presence of a "pilot bushing" for a manual transmission, which would likely need to be removed so the crankshaft would be able to accept the pilot on the torque converter.

5-90

alky350 said:

i looking for a 1990 4.0 motor and the salvage yard i called today said there is a difference between automatic and manual motor. he said the cranks were different. does anybody know if this is correct?

Click to expand...

The cranks for manual and auto trannies are the same for each year. The only change was from '92 upwards when the pilot bearing hole was made bigger.