Help With Crankshaft

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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dpcd67
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Help With Crankshaft

Post by dpcd67 » Wed May 09, 2018 6:24 pm

I have a problem; installed the front cover on RMC 56789 today; all parts are installed per TM 9-1804A. Not my first L134.
Problem is that I only have 5 threads for the nut to engage. Should have about 7 or 8. The crank nose has not been shortened.
So, does anyone have the thickness of the Spacer, 7741414? That and the pulley are the only things that could make that difference.
The timing gear is in the right place.
I have ,400 space between the pulley and the cover. That seems like too much.
So I need help.
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Re: Help With Crankshaft

Post by Joe Gopan » Thu May 10, 2018 3:22 am

Spacer in backward? One side is cupped, and the cup goes toward the gear. And remember, the bevel in the thrust washer faces the crank shaft.
It's in the manuals.
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Re: Help With Crankshaft

Post by dpcd67 » Thu May 10, 2018 5:49 am

Yes, that is exactly how I have the spacer, IAW the TM.
The thrust washer was installed by the machine shop; I'll double check that.
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Re: Help With Crankshaft

Post by Joe Gopan » Thu May 10, 2018 6:10 am

Check to see if the woodruff keys are not jammed.
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Re: Help With Crankshaft

Post by dpcd67 » Thu May 10, 2018 7:20 pm

The key is not jammed; what I need is the thickness of the spacer to make sure mine is right. My engine came out of an MB; it was set up for that from the beginning; it has the studs for the coil, and had the front engine mount for the MB on it. I suspect the spacer might not be the same as an M38; I don't know but that is the only thing that locates the pulley. So if someone has the correct thickness for an M38 spacer, I need that dimension.
The crank gear matches the face of the cam gear. The oil slinger is thin of course.
My pulley thickness is exactly one inch.
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Re: Help With Crankshaft

Post by Joe Gopan » Fri May 11, 2018 3:01 am

Don't have the Spacer handy, Gear type is 641281, Chain type is 630727.
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Re: Help With Crankshaft

Post by dpcd67 » Fri May 11, 2018 6:24 am

Ok, thanks. I will make it work; I will make a new spacer on my lathe that makes it all fit correctly.
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Re: Help With Crankshaft

Post by Joe Gopan » Fri May 11, 2018 7:30 am

I grabbed one quick like off the shelf. Not sure if it is the gear type, can't mike it for a couple ro three hours.
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Re: Help With Crankshaft

Post by dpcd67 » Fri May 11, 2018 10:09 am

Hmm; if the gear type and sprocket type are different then maybe that is my problem. I can't find another one but I had another gear type here; lost.
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Re: Help With Crankshaft

Post by dpcd67 » Fri May 11, 2018 11:26 am

My spacer is .483 thick. The distance from the gear to the end is 1.9, same as on another M38 crankshaft I have, so that is correct. My pulley is 1 inch thick, and the nut is .5. The oil slinger is .040, so if you add all that up, it leaves .377, much less than .5 inch for the nut, which is why it does not screw on all the way. Maybe the nut is too thick?
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Re: Help With Crankshaft

Post by Joe Gopan » Fri May 11, 2018 3:51 pm

The Spacer I grabbed has a major thickness of 0.4802" and a minor of 0.3334". Will try to measure the style 638513 nut used on the M-38. They usually go on flush.
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Re: Help With Crankshaft

Post by dpcd67 » Fri May 11, 2018 4:41 pm

Ok, good; my spacer is the correct one. The nut is .5 inch thick. Maybe the pulley I have is wrong; it didn't come on the engine. It is one inch thick.
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Re: Help With Crankshaft

Post by Joe Gopan » Fri May 11, 2018 6:04 pm

1" through the Pulley is OK, the thickness of the nut will have to wait till Saturday.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
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Re: Help With Crankshaft

Post by dpcd67 » Fri May 11, 2018 6:18 pm

Ok. thanks. Everything is checking out so far so maybe the nut is thicker than normal. It is one with the round portion on one end; hex the rest of it.
I found some pictures of the nuts and they have 8 threads, like mine does.
I never noticed this before because all the nuts i used had cranking bars on them. So thread engagement is not visible. Maybe I should just tighten up this one and forget about it. Or get a nut with a crank bar in it and it will look fine.
Last edited by dpcd67 on Fri May 11, 2018 6:35 pm, edited 1 time in total.
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Re: Help With Crankshaft

Post by Joe Gopan » Fri May 11, 2018 6:34 pm

There are two types of Nuts, Long with pin for hand crank, other is short like used on M-38/M-38A1.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
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COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO


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