RD4 engine serial number question

I do know that the 7U block won't work, that is a completely different engine

The 9S is also a D315 engine where your 4G is a D4400.

STEPHEN and OLD MAGNET thanks for your help. I figured it was to good to be true.

I'm not sure if you can put a 315 in place os 4400 but I have a 7U tailseat that the guy I got it from put a 4400 in it and seems to all work well

WILLIE, are you saying that a 315 "might" work in place of my 4400?

WILLIE, are you saying that a 315 "might" work in place of my 4400?

Tomorrow in the light I will look mine over good and take some pics, like I say its a 4400 taking place of 315, if you can change 1 way I wouldnt know why you could change the otherway after all Cat used many of its crude designs for 30 or more yrs if you look at a parts book from the 70s and 80s youll see many part numbers that start with A - S and L from the 20s

CR and WILLIE, Thank you for the info.

Found this insert in one of my Parts Manuals😊 😊

I don't know if there is a limit to the serial numbers that will interchange or the insert reflects the period it was published in. (Article found in a 5T Parts Manual)

Seems later units would interchange also.
Edit: Did some checking 7U28232 is where the block changed to the balancer engine along with the bell housing.

Looks like either your 7U18236 or the 9S6461 (using tractor change over parts) are candidate replacement engines.