Just bought a '51Merc

51 MERC-CT said:
Sure looks like the the inner axle/bearings are moving quite a bit in the vid.
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My understanding is that there is not an "inner" axle bearing. Only an axle bearing at the backing plate, and then Carrier bearing at the differential. The diff carrier itself is not showing any play. (Prying up on the ring gear)
 
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The side gear appears to be moving a good bit in the differential carrier case. It would certainly be something to look into. The axles would have to come out to remove the differential case for tear down & further inspection. I'm not sure the side gears will come out if you remove the spider pinions but they might. A person has to keep very close track of the shims for the differential case bearings in order to get it back into a good position for the ring & pinion backlash in case the differential carrier case is still serviceable. If the case has to be replaced then a person should consider a complete overhaul to get everything back up to snuff. You can reuse good bearings but with a new case, they won't be able to take the preload that the new bearings have to have. The gear pattern & backlash may also need adjustments. All this stuff is covered in the Lincoln Mercury overhaul manual for the 49 thru 51. Dana 44 generic information can also be used unless it differs with the older 19-spline type axle procedures.


If you go the salvage yard search, there is a chance you may end up with a dog. The carrier for the auto trans ratios and the 19-spline side gears are available in the link from Randy's R&P. He has several pages of stuff there for the 19-spline axle assemblies.
 
My gut feeling is that it is worn, but not worn out. To be more specific, hopefully it will just continue to go down the road without actually failing. It will clonk, but should keep going until you find a suitable replacement. Do not compromise with a lower (higher numerical) axle.

Just my 2c worth.

Mart.
 
Mart said:
My gut feeling is that it is worn, but not worn out. To be more specific, hopefully it will just continue to go down the road without actually failing. It will clonk, but should keep going until you find a suitable replacement. Do not compromise with a lower (higher numerical) axle.

Just my 2c worth.

Mart.
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Thank you. All of you have been very helpful. I'm going to drive it a little this summer, and then I will remove the whole rear end in September and bring it to a driveline shop for rebuild.
 
If you take it easy on it hope it will last the summer for you.

I had a 1953 Ford with a flathead vs in it with a 3 speed I switched the whole rear end with a newer one with higher gears
 
I had a '51 Ford in high school. The rear end howled like a banshee from when we got it in the summer of '57 until I junked it in '61 (because of rust issues). In the interim, the engine was rebuilt once, and the transmission replaced twice. The rear end was still howling when it left our place for the last time "on the hook".

You'll probably make it through the summer. (And then, there's always a handful of sawdust.)
 
Keep your eyes on Craigslist and Ebay as 49-51 Merc rears show up now and then.
I sold mine for $150 5 years ago. It was a 4:27
 
I did some checking around the internet for information on the side gear fit in the case for Dana 44 axles. The Dana Spicer information lists no specs it just states "the case bore for the side gear should be round". Perceptible elongation should be minimal at best. Other folks that have rebuilt them and done the measurements on the side gear and the case ID bore all agree that the clearance is about .005". My best guess is .005" to .006" for clearance. Someone will have to measure them to see what the clearance and out of round might be. If they are not out of round or tapered, the surfaces are not scored or burned blue, and clearance is reasonable, then they are good to go. This is a semi floating rear axle so the stuff has to be free to move in there.


If you haven't already, remove the brake drums and inspect in there. Check the axles for smooth movement and play. If brake parts are secure, everything moves OK, axles are smooth to turn, and doesn't have much play, I'd run it. Clicking in a rear axle usually means a broken gear tooth or a bad bearing. Whining under torque load indicates a loss of preload on something and it's moving around too much under torque. If your not seeing any of this, you may have a problem somewhere else.


The only reason I would buy a junk yard axle is for the hard parts like the axles or housings. The gears might be good and they might be worn out.
 
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It looks nice and looks very familiar too. I think I know that car. I see you are from Minnesota. Are you part of the Early V8 Ford Club? Join them and our Twin Cities chapter.
 
Yeah I ain't buying one of those. I inspected it and put in some thick gear oil (85w140)+ some Lucas and it's quiet now.
 
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