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Old 04-14-2020, 11:31 PM   #1
dmoz
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Default Rear end recommendations

I am looking for recommendations on upgrading the rear end in my 1950 mercury. I am in the process of rebuilding the flathead. Its a 3 on the tree manual trans. I plan to keep it that way but adding overdrive to it. Not looking to build a race car; just more of a more capable restoration.


Thanks in advance for your recommendations.
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Old 04-15-2020, 12:22 AM   #2
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Default Re: Rear end recommendations

Can’t go wrong with a Ford 9”.
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Old 04-15-2020, 01:28 AM   #3
richard crow
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Default Re: Rear end recommendations

1951 lincoln auto matic trans rear. 331-1 bolts right in has 5x5 1/2 bolt pateren on the axle& the brakes are a bit biger no prolbem hooking up the hand brake. & it,s strong
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Old 04-15-2020, 09:36 AM   #4
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Default Re: Rear end recommendations

Considering the weight of the rear axle determines the rid quality of the vehicle, I'd probably go with a dana 35 for the Flatherd or 44 with SBC, 3.73 gears for the OD. The 9" belongs behind a 400 hp plus engine or a PU.
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Old 04-15-2020, 09:41 AM   #5
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Default Re: Rear end recommendations

A 1971-73 Ford Mustang 9 in is the exact same wheel mounting surface to wheel mounting surface measurement as the stock 49-51 Merc - 61 1/4 inches. Bolt pattern is different however. Here's one in a 51 Merc. If you find a rear and need the two axles, I have them. Oh, last photo is of a 51 Merc rear. Here's a helpful chart of rear end widths. Open and scroll down.
https://www.jalopyjournal.com/forum/...-chart.302774/
Attached Images
File Type: jpg car #11.jpg (48.2 KB, 55 views)
File Type: jpg car#15.jpg (48.1 KB, 54 views)
File Type: jpg car#19.jpg (48.4 KB, 52 views)
File Type: jpg DSC00208 (Small).JPG (37.1 KB, 181 views)

Last edited by 19Fordy; 04-15-2020 at 11:29 AM.
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Old 04-15-2020, 09:59 AM   #6
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Default Re: Rear end recommendations

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I'm with Ol' Ron. It is not just that the nine inch is more beef than you would need. The result is a lot more unsprung weight. Any imperfect roadway can be a 'pain in the kidney' (read PIA) Others will say "not that much more weight." It is hard to control or ignore. Larger softer tires can help. So can smooth roads.

If there no need for it why drag it around.
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Old 04-15-2020, 09:59 AM   #7
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Default Re: Rear end recommendations

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Originally Posted by Ol' Ron View Post
The 9" belongs behind a 400 hp plus engine or a PU.

Ah, but you're forgetting that by using a 9", it's easy as pie to retain that all-important 5 X 5-1/2" bolt pattern. 19Fordy offers some pretty savvy advice in post #5, and outfits like Curry can send ya a pair of axles with the proper bolt pattern in a heartbeat! That would be my choice, and for those reasons, but WTF do I know? DD
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Old 04-15-2020, 01:33 PM   #8
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Default Re: Rear end recommendations

Why change it there's nothing wrong with them. I have a 60 over flathead 3 carbs potvin cam. Overdrive car and I drive it hard alot. Never had a problem. I think 2nd gear will break before the rear end
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Old 04-15-2020, 02:01 PM   #9
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Default Re: Rear end recommendations

lonewolf is correct. Merc rears are very strong. You won't blow it up with a modified flatty. If you start changing the rear, other problems arise and your wallet gets emptied.
I only changed my 51 Merc rear because I stuffed a 354 Hemi in it. Otherwise, would have left it alone.
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Old 04-15-2020, 02:08 PM   #10
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Default Re: Rear end recommendations

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Why change it there's nothing wrong with them.



…..until you break a tooth on a ring gear or a spider gear, or an axle snaps....on a Sunday afternoon, about 175 miles away from the house, and none of your friends have a trailer to come get ya. And the guy that owns that junk yard you just passed (which has a chain around the gate...Sunday, remember?) is gonna laugh at ya Monday morning after you sleep in the back seat overnight as he remembers that his dad crushed the last '50 Mercury they had in the yard back in about 1978. That's one of the things that "ain't wrong with it"! You can find 9" stuff almost anywhere in the USofA...one thing that keeps America great! DD


OOps...I digress! 19Fourdy just above has spare parts a waitin'!
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Old 04-15-2020, 05:35 PM   #11
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Default Re: Rear end recommendations

9 inch rear sucks up a lot of horse power tho.
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Old 04-15-2020, 05:45 PM   #12
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Default Re: Rear end recommendations

I'd ponder the Ford 8" rear with 28 spline axles in your car -- lighter, takes less horsepower, parts availability up the ying-yang and plenty of aftermarket parts (like gears), drum/disc brake options, available all over the place. In the end, it will cost a similar amount to a 9" . . . but a good solid rear end that will take all the flathead horsepower you can throw at it.
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Old 04-15-2020, 07:14 PM   #13
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Default Re: Rear end recommendations

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9 inch rear sucks up a lot of horse power tho.

True statement because of the geometric relationship between the ring and pinion on a 9". The 8" would be ideal except for the fact that it's tough to get that much-desired 5-1/2" bolt circle one desires to match the front of a '50 Merc. MAYBE if you had a disc conversion on front with a 4-1/2" bolt circle, a matching-patterned 8" would be a natural, hands down! DD
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Old 04-15-2020, 07:20 PM   #14
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Default Re: Rear end recommendations

Has to be 30 yrs ago, I put a 1970 Mustang rear in my '51 Merc with no overdrive. Drove it for years and never thought twice about my choice. Went in rather easily, from what I remember.
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Old 04-15-2020, 10:37 PM   #15
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Default Re: Rear end recommendations

I think h
the use of an ( or) ich Ford rear is not the issue here. WE all have a favorite and so be it. My suggestion is based on bring the vehicle up to later standards at a minimun of cost. Having owned several 40/53 Fords and Mercs I can say they didn't ride bad handled well for their time, but the brakes were marginal even then. I have access to several junk/scrap yards and worked for one for 7 years druing the late 90"s. So I go shoping for the best (cheapest ) way to solve a problem. At present i'm running a late 90's rear spicer 44a rear from a Jeep grand cherokee. THis has 373 rear with posi and fits nicely under my 47 International pickkuo cost 150. New brake pads and EB cables anothe 50 shocks from a nid size GM car and the ride back there is quite nice. The fron suspension is from a 42;48 Ford with a Speedway disk conversion. Agan the cost was minimal . The trans is an RTS behind a 280 flathead with a modified steel bellhousing using the stock clutch . It stops pretty good I use 236/15 wheels from a ford ranger PU.

Very few of these Items are very expensive to the yards because there is very little demand for then (except the trans) and if the yard has one ready for the crusher , they'll probably cut itout for a few bucks. However, I try to improve the vehicle aswell as make it rideand handle better, probably comees from a racing background
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Old 04-16-2020, 02:18 AM   #16
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Default Re: Rear end recommendations

Quote:
Originally Posted by 19Fordy View Post
A 1971-73 Ford Mustang 9 in is the exact same wheel mounting surface to wheel mounting surface measurement as the stock 49-51 Merc - 61 1/4 inches. Bolt pattern is different however. Here's one in a 51 Merc. If you find a rear and need the two axles, I have them. Oh, last photo is of a 51 Merc rear. Here's a helpful chart of rear end widths. Open and scroll down.
https://www.jalopyjournal.com/forum/...-chart.302774/

Man, you just have to appreciate a guy SO serious about his hobby that he builds a dedicated, roll-around stand and fixtures to display and store his "take-out", no-longer-needed parts. DD


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Old 04-16-2020, 02:26 AM   #17
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Default Re: Rear end recommendations

Not sure if you can add the later 3 on the tree with od from about 50-53 on. Had a 53 with a I6 and tree od. 70mph all day.

https://www.fordbarn.com/forum/showthread.php?p=821706


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Old 04-16-2020, 10:05 AM   #18
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Default Re: Rear end recommendations

If your 1950 has the Dana 44, I see no reason to change it. If it has the older Dana 41, then changing it to the Dana 44 is a direct swap. Ford used these same axles in the F1 pickups and later in the F100 pickups. They can take anything a flathead V8 can put out. Parts are still available with exception to the 19 spline axles but I haven't worn one out yet. F100 rear brake drums are still available and can be modified to work on the front as well. If a person wants to change the suspension, there is all sorts of stuff out there but the ride of the Mercury & Lincoln cars was top notch for the time and they ride better than a lot of modern stuff.

A lot of Mercury cars came with overdrive so installing the original type OD would be a bolt it. There are still plenty of 49 thru early 51 transmissions out there since folks like to take them out when building the lead sleds. The Ford car ones are different and would require a late 1951 Merc bell housing to bolt one in.

Mac VP has a step by step set of overhaul threads on the Mercury R10 overdrive that is very recent and should be easy to search out. The standard trans is the same length and uses the same mountings as the overdrive trans in the 49 thru early 51 time frame.

Last edited by rotorwrench; 04-16-2020 at 10:18 AM.
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Old 04-16-2020, 12:19 PM   #19
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Default Re: Rear end recommendations

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Originally Posted by Art Newland View Post
9 inch rear sucks up a lot of horse power tho.

Oops! Double post
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Old 04-16-2020, 12:20 PM   #20
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Default Re: Rear end recommendations

Quote:
Originally Posted by Art Newland View Post
9 inch rear sucks up a lot of horse power tho.



Is there a dyno tested answer to how much HP loss, or is this a bench racing myth? Any lost horsepower would be due to excess friction (from the sliding action of the extreme hypoid gear design). Excess friction causes excess heat. Excess heat can soften gear teeth and cooks the lube, causing rapid wear. Yet millions of 9" rears outlasted the vehicles they lived in! Plus, the racer's differential of choice is overwhelmingly the 9".
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