Detroit 371 blower shaft replacement?

[Rod R]

Hello,
First post, as I have scoured the net for an answer, and the closest I came was on this forum, but I didn't want to necrobump an old thread.

Anyhow, today I learned that one can break the shaft to the blower on a 371 inline DD. Apparently, a little water found its way to the bottom of my blower and froze, leaving the rotors stuck. The motor wouldn't turn over, and I figured it was just from being so cold, and the battery just not putting out the CCA it needed to get the old girl (Austin Western Super 88 from 1954) grinding oil. Of course, once the shaft (assumed) sheared, she cranked just fine. But I knew something was way wrong, as the exhaust flapper wasn't lifting, no unburnt fuel smoke, and ether couldn't even coax a burp of power.

I removed the cover from the intake of the blower and cranked the motor to confirm no movement of the rotors. I did see a little water down in the bottom of the blower, and the rotors were stuck, which I freed with a wooden hammer handle. Being free, further confirmed they are separated from the geartrain.

So, the question I am trying to find is, what disassembly will be required to replace the shaft? I am kind of hoping the whole blower doesn't need to come out. I think it may be as simple as removing a cover, removing a spring clip, and extracting the shaft. But my other concern is, if the shaft is sheared, how do I fish out the piece back inside, or if the splines are stripped, do I need to do a more thorough teardown to clean up pieces of spline?

Any help would be greatly appreciated, as while ignorance may be bliss, it sure can be costly!

Rod R

 

[Vetech63]

In 30+ years doing this work, Ive never seen a blower shaft break. Its more than likely the splines on your blower drive coupler. Remove the accessory drive cover on the back of your flywheel, remove the retaining ring and slide your blower shaft out. You will then need to remove the blower from the side of your engine, remove the drive coupler cover to access the drive. The drive is attached by 4 bolts. Be sure to check the splines on the drive gear also at your accessory drive. Reverse all above to reinstall.

 

[farmboy555]

When I had my 6-71 I stripped the splines on one end, but also have seen them break. Can't remember which engine it was. But the shaft broke and I made a tube to catch any metal pieces and pulled the broken back part of the shaft with a magnet, it's been 40 years ago

 

[Rod R]

Thanks guys. I feared that you would say I'd have to pull the blower off, along with everything else associated with it. However, I got incredibly lucky, as the shaft did in fact shear cleanly as it appears it was designed to do, and was able to extract it with relative ease.

What a relief, as I didn't really want a fairly big project this time of the year, here in the snowbelt of central Pennsylvania. (I have more than enough heavy iron projects going on as is)

I was half tempted to weld it back together, but bypassing the designed weak point, not to mention any tempering of the splines, I figured it best that I simply get another one. ;-)

Thanks again for the responses.

 

[kshansen]

I too have seen one break like that but I believe it was on a 12V-71. That engine has a pair of 6V-71 blowers so it is transmitting a bit more load than your 3-71!

I assume you have made sure your blower is turning nice and free and nothing damaged in there from the ice. I have seen where ice can crack the housing or rotors on a 3-71 that ran a water pump we had at the quarry years back.

 

[Rod R]

Thanks. Yeah, everything in the blower looks good. It was so little ice and water, I'm amazed it was stuck. (and freed so easily, though I suppose, some may have melted off in the time I removed the inlet cover and diagnosed the issue) I'm guessing that the water got in there from a loose hose clamp on a rubber coupling right above. Despite a fairly snug fit of the coupling over the tube, I wouldn't have thought rain/snowmelt could squeak by, but it did. Made sure that's all tight again, part ordered, and hopefully I'll have her back to grinding oil before the next snowstorm.

 

[kshansen]

I maybe a little paranoid but one thing I would do while waiting for the new shaft to show up would be to make sure that flapper valve in the intake housing to the blower is working nice and free. Just want to be 110% there is nothing else wrong and you have a easy way to kill it if it starts to run away on start up!

 

[Rod R]

Heck yeah. The flapper was stuck and disconnected when I bought the grader a couple years back. It was one of the first things I fixed. Also reconfirmed it's still working smooth while I had the cover off.

 

[old-iron-habit]

Always a good idea to put a socket on the crank pulley and give a Detroit at least one full turn by hand before starting them when they have been setting. I had a rotor break a year or so ago on a 3-53 from ice after a bit of moisture that must have got in during a bad windy rainstorm, Had I cranked it, things could have been much worse.