4L SOHC jackshaft question

[rango88]

Hey guys doing some random research i found out that the cologne 4L SOHC doesnt use a camshaft but actually a jackshaft? I never heard of a jackshaft, can anyone clarify the differences between a jackshaft and a camshaft and how it works?

 

[rwenzing]

... the cologne 4L SOHC doesnt use a camshaft but actually a jackshaft?

The 4.0 SOHC doesn't use a single camshaft; it has two overhead camshafts, one for each cylinder bank.

This engine evolved from an earlier 4.0 OHV design that had the single camshaft in the vee above the crank. To make the conversion, a plain shaft (the jackshaft) was substituted for the original camshaft and it delivers the cam rotation to the front and rear of the engine. Each of the new overhead cams is turned via a chain from the jackshaft - driver side is driven from the front chain and the passenger side from the rear chain.

In general, a jackshaft is a shaft that transmits rotation from a power source to one or more 'user' devices. In the case of the Ranger 4.0 SOHC, the jackshaft is powered through a chain from the crankshaft and, in turn, sends power through the front and rear chains that turn the two camshafts.

With the three chains, the tensioners and the other hardware required just turn the 2 cams, it's not difficult to see why Cologne had to revise this system a few times to get it to work without self destructing over the long term.

(Some year 4x4 4.0 SOHC engines also have a counterbalancer shaft running parallel to the crankshaft driven by a fourth chain - this is for NVH control and has nothing to do with the cams.)

 

[rango88]

i really appreciate the in depth reply, it helps a lot