M939 engine and trannie removal

[Stevepala]

I'm almost ready to remove the stuck motor from my dump truck and replace it with a big cam. It looks like the best way is to remove the motor and trannie in one piece. I have everything disconnected except for the upper rear trannie mount and the pto. Is there an easy way to get at that trannie mount, it's in such a tight spot under cab and seems like it should be easier.

Anybody out there pull there trannie that can give advise.

 

[markmontana]

Are you sure there is a tranny mount? When we pulled the 8.3, we separated the tranny first, then pulled the motor. The tranny came forward several inches as we tugged on the motor. All that was holding it was the fluid and other control connections. Maybe the NHC250 is different- if that's what you have.

 

[Stevepala]

It looks like the rear mount might not be directly bolted togather but has a rubber puck that sit on a steel plate. I'm going to put a jack on it tomorrow and see how it moves. It's just so tight above the trannie it's hard to tell.

How about the PTO on the 3 o'clock position on the trannie. Does it only have 5 bolts? Or is there a sixth that I'm missing. I removed the 5 bolts(2 studs and 3 bolts) but its still tight. Just thought I would ask.

 

[Csm Davis]

Six bolts on pto, looong one goes through the pto body. Also the rear mount is on top of the transmission but can be undone from under the trucks, what model are you working on?

 

[Csm Davis]

Okay a dump you should be able to sit/kneel after you take the pto and short shaft out and get to the bolts and yes it's a pain.

 

[Stevepala]

It's a 939.

 

[Csm Davis]

Thought the dumps were 929?

 

[Stevepala]

Sorry, 929 your correct.

Well, the motor and trannie are out. Surprising how simple it was, just a few things in question were solved. First was the rear trannie mount. One short half inch bolt attaches to a rubber puck which is what attaches the trannie to the cross member. I ended up using a hole saw to drill an inspection hole in the battery box right above the bolt, which made removal very easy.

Because the pto was so close to the frame, when I lifted the motor, I turned it to make more room. At that point the pto fell out.

The big cam cummins should be here on Friday.

 

[Csm Davis]

So what gives have you got new motor in yet?

 

[Stevepala]

I did get a Big Cam motor from Matt over in Massachusetts. Matt said it was a recent rebuilt 350HP motor and when I removed the rocker covers it was very clean inside. I did check the serial number on the motor and it turns out it is actually a 400HP motor from 1980. I needed to locate a different style front motor mount which I found but received the wrong one on Friday. So I'm going to send that one back in hopes to get the correct mount next week. After I get that mount on the motor I'm going to start it up on the ground to make sure it runs ok. Then bolt on the tranny and drop it in place. It came out real easy by myself, going in should be the same.