Tag axle pros / cons

msmith1199 wrote:

BigD629 wrote:
When I was looking for our DP, I asked a long time Cat Service Tech what he would recommend. He advised me to avoid the C7, as it is a non-sleeved block. I ended up with a 400HP Cummins ISL in a 36'.

Somebody can correct me if I'm wrong, but my understanding is the disadvantage to the "non-sleved" block is it is much more expensive come rebuild time. So after you've put two or three million miles on your motorhome the rebuild would be more expensive?

An engine with wet sleeves, such as the DT466 in my International truck, can be rebuilt with the engine still in the frame of the truck. The block doesn't have to go to the machine shop for boring the cylinders.

You pop the head off, drop the oil pan, remove the rod caps, pull the pistons and rods, pull the sleeves, and put it back together with new gaskets, pistons/rings, bearings and new sleeves.

Also with a wet sleeve engine, because the whole circumference of the sleeve is surrounded by coolant, the sleeve expands and contracts evenly, holding a constant diameter, which extends its usable service life.

With cylinders cast into the bock, there are hot and cold spots in various places on the cylinder. This causes unequal expansion and contraction, which makes the bore out of round, which wears it out sooner.