HUP restore in Sask

[ahleeds]

So it isn't a sm420 but the earlier 31-48 predecessor.
Normally I would buff up the gears and carry on ,but the rust ate 3 teeth off third and the rest don't look much better.
If I was to run this pitted up gear set it would be so loud in the cab you'd need good ear plugs .
Anthony

[Tony Smith]

Although the CMP parts books list the transmission casing as being Pn 590524, it seems that 590474 is a common alternative.

I have 2 Chev CMP gearboxes with the casing number 590474.

The mainshaft 3rd gear is pn 590493, while the countershaft 3rd gear is pn 590502, both available NOS from a variety of sources.

[Phil Waterman]

Hi Anthony

I would not give up on this box, rust on gears often looks far worse than it is. Two of my CMPs had transmissions as bad or worse than this, and they both clean up and have many thousands of miles on them after going back on the road.

I started by removing the bearings then polishing each gear tooth with 3M rowloc pads, used old wheels with most of the abrasive worn off, with a very light touch, object remove and smooth the surface. I didn't try polish out the pits, leave the pits alone.

Take a look at the photos http://canadianmilitarypattern.com/C...ansmission.htm it shows, primarily, the transmission in my C60S as I started 1990 and then 2008 and 12000 miles later. When the main shaft got noisy and had to be replaced, new shaft and it ran for another 10,000 miles before breaking a tooth. http://canadianmilitarypattern.com/3...ansmission.htm

That time I got lucky and found a NOS gear box, can we say scarce as hens teeth. Yes, I did find a replacement gear and rebuilt the first transmission, which with three CMPs on the road sits on the shelf full of gear lube ready to go in.

Back to my point, if the gears and bearings areas clean up it will probably give many thousands of miles.

Keep us posted on your progress.

Cheers Phil

PS I'll look to see which of my photos need to be moved to MLU.

[Jordan Baker]

When I rebuilt mine i put all new bearings in it and also a new rear seal. The rear seal has the sheet metal tabs spot welded to it. I also replaced my shift forks as they were worn. I found all of the parts on ebay.

[Harry Moon]

Originally Posted by ahleeds

So it isn't a sm420 but the earlier 31-48 predecessor.
Normally I would buff up the gears and carry on ,but the rust ate 3 teeth off third and the rest don't look much better.
If I was to run this pitted up gear set it would be so loud in the cab you'd need good ear plugs .
Anthony

Loud is normal, at highway speed I use a com set just to talk to the passenger. Straight cut gears in the transmission and transfer case will do that!

[ahleeds]

Looks like this gear was on the meth pipe

[Phil Waterman]

Originally Posted by ahleeds

Looks like this gear was on the meth pipe

Yup those are definitely past the polish and put it back together.

Though back in the day my brother had a Model A where the teeth looked like that and some mechanic had carefully brazed and filed each tooth back to shape. But boy was it load, he replaced the gears.

That photo is a classic "it ran when parked"

Cheers Phil


Is that the only gear that is bad? Interesting because that looks like the 3rd gear lower cluster gear which is the same one that my C60S broke a tooth out of, which I was able to find a NOS gear and replace it.

[maple_leaf_eh]

Originally Posted by ahleeds

Looks like this gear was on the meth pipe

Hmmm? In your situation, maybe you want to invent a jig to hold the rotten gear and then stock up on good quality welding wire? Or, pause the project until you can source a better looking gear.


BTW, I visited Moosomin many times when driving East/West on No. 1. The namesake of my street in Regina, Harry Mullin VC, is buried south of town.

[Bob Carriere]

Hi Anthony

Gear clusters are available....maybe not new but in good shape. I have opened more than one tranny over the years and although the box was half filled with water and bearings might have been pitted the gears were always good. Seals and bearings should be available from industrial dealers like General Bearing Services by size...OD and ID. A complete tranny from a junk yard may be much cheaper than a single gear retail....just remove the cover and spin the gear around for inspection. Easy to mail but expensive by weight. Sometimes the gears can be chipped or worn from lack of synchros but if not too bad can be dressed up with a grinding wheel. I have some available if you get desperate but postage from Ottawa, when they work, would be high.

Yours are beyond recovery and will no doubt chip and cause further damage to other gears.

Good luck and keep us posted by photos of your progress.

[Jordan Baker]

Just buy the individual gears NOS off of ebay. The MB-C2 manual gives a great run down on how to replace the gears. its very easy to do.

[Phil Waterman]

Hi

In your search for a replacement gear check the number of teeth, if memory serves there are two different 3rd gears with different diameters and different numbers of teeth so you need the one you have to match the upper gear cluster.

Cheers Phil