Hey everyone, I currently have a d4 7u that the motor has had an extremly rough life and needs extensive repair. Im currently looking for a replacement option found this parts machine in the attached photo. Owner says its a d4 3T, My thought is the 3t has the d4400 engine and not the d315. Serial number plate is extremly hard to read and cant make anything out in it. If someone can Id it from the picture that would be great. Thank you!!

Yes thats a D4400 from a 5T series D4, it would be a downgrade from the D315. I'd locate another 315

As Rome says, engine is a no go, but my understanding is the D4 5T shares basically the same transmission housing and final drives with the 6U / 7U, so if your machine might need back end parts too, that donor machine might be handy for things like sprockets or bottom rollers, bullgears or transmission gears.

For example I used the upper transmission shaft and later model helical cut crown wheel and pinion out of a D4 6U/7U to save a early D4 7J built in 1939 that has the D4400 engine, and straight cut crown and pinion gears.

The best way to be certain is to look at the Parts Number book for each model, and I think they will be found in the Technical Library in the forum though accessible only to ACMOC financial members, so think about joining ACMOC, its cheap relative to the cost of saving a dead Cat, maybe $30 or $40 a year, that wouldn't even buy you 10 minutes talking to a Cat Dealer Mechanic who probably has never worked on a early D4..........

Either a 2Txxxx or 5Txxxx D4  would have the D4400.
A 3Txxxx s/n is for a D7.
D4400 engine can be interchanged with the D315 but your going backwards with power and parts availability.

Subscription to ACMOC ...
.Well worth the money ... I bought "A" ( as in one - singular) gasket that cost a lot more money and worth a lot less the esperance and info provided here on ACMOC.
The D315:
Don't over look 955C-955E (12Axxx), Industrial (stationary), Gensets or Marine D315's .. The Marine applications, I believe, run at a little lower rpm and are probably not the best replacement options (I think the marine models have brass journals as well).

Been looking a little closer and find the D315 sears engine are not as interchangeable as I had thought.Though it can be done just keep an eye on clearances.
 
 

Thank you everyone for there help!!