51 Merc driveshaft

nellis003

nellis003

Senior Member
Strange thing happened when I put the drivetrain back together on my 51 Merc Coupe.

I pulled the engine that I bought it with (Ford Flathead) and replaced it with a completely rebuilt '49 flathead. Used the same trans and bellhousing, but I had pulled those out as well to rebuild trans. It's a manual with overdrive.

I just put the driveshaft back in, and it barely reaches the trans spline shaft. It just makes it inside the transmission rear seal.

So, it's connected, but definitely not as far in as I'd like. I don't see where I could make up the space - the engine mounts look to be right, and everything else hooks up fine. This really stumps me, because I figured the blocks would be exactly the same.

Any thoughts?

Nick
 
All the 8BA type 239 and 255 Merc blocks are the same. There is a difference in water pumps with the Merc though. Does yours have the later Ford type trans like the 52 & 53 Merc or does it have the half bell like the 49 though early 51. Early types had the 1 3/8" 10-spline input and the later ones had the 1 1/8 10-spline input like the 49 to 51 Fords did. You make just need a longer drive shaft.
Kerby
 
It has the 49-51 Half bell and stock trans, so that's why I'm so surprised that it's not lining up the same way. If the blocks are the same, then the driveshaft should fit like it did before.

Putting in a new driveshaft is no problem, but I just can't figure out why the old one suddenly isn't long enough.
 
When you had everything apart, could the rear axle have moved backward? Bad shackles or shackle bushings? Probably not too likely but just a thought. Good Luck!
 
Is the car jacked up from the frame with the differential hanging down?

Does your rear ****** mount line up? Is your fan and radiator installed to check the clearance? The front motor mounts swivel into different positions, so I'd line up the ****** first.
 
If you have the 49 through early 51 Mercury transmission with the Borg Warner R10 Tail shaft (these also had the rail switch that sticks out in front of the speedometer cable attachment) you should have the single biscuit mount set up between the tail housing and the crossmember. These mounts used the same biscuit parts that the waterpump front mounts utilized. If this is the case I can measure my tail shaft housing and driveshaft. They should compare to be the same. If you have something different they won't. I'll see if I can measure them during my lunch hour.

Kerby
 
rotorwrench said:
If you have the 49 through early 51 Mercury transmission with the Borg Warner R10 Tail shaft (these also had the rail switch that sticks out in front of the speedometer cable attachment) you should have the single biscuit mount set up between the tail housing and the crossmember. These mounts used the same biscuit parts that the waterpump front mounts utilized. If this is the case I can measure my tail shaft housing and driveshaft. They should compare to be the same. If you have something different they won't. I'll see if I can measure them during my lunch hour.

Kerby
Click to expand...

I disagree with Rotorwrench on the biscuit ****** mount.
Part # AD 6068-D is the transmission tailshaft mount.
 
I measured the tail shaft housing from the rear face of the mounting flange to the aft face of the seal with a tape measure and came up with near 12 7/8" to 12 15/16". Since this is with a tape measure it is only approximate but will be in the ball park. I measured the drive shaft tube length from the weld joints of each u-joint fitting (tube length only) and came up with very near 53 inches. The front drive shaft yoke is only 4 inches long on the OD area of the machined portion of the slip joint and the last 5/16" has a larger OD than the first 3 11/16" does.

Now, my old sport sedan is sitting with standard body weight and only 5 gallons of gas in it and the slip joint is only half way into the tail housing. If this is where yours is sitting then it is normal. With full tank and extra passengers it will go in another 1/4 inch maby more but thats about it.

Kerby

PS: Mike51merc - You are correct to a point. Many 49 & early 50 mercs had the 8M-6068-B mount that became unobtainium when Ford discontinued them. They came up with a kit to convert them. However the late 50 and early 1951 Mercury cars had the 1M-6054-B mount that uses the rubber biscuits I mentioned before. Late 1951 and on used a different mount since thay basically changed over to the same transmission that was used in the Ford cars with the big bellhousing and arm type clutch release mechanism.
 
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if every thing is the same and every thing lines up now, basically the only thing that would make your drive shaft to short is the tail shaft was changed, did you rebuild the trans or have it done?:cool:
 
I think I figured it out, but could still use some help from the forum.

I think I have the mounts done wrong. I've attached pictures of the mounts as I have them (apologies for the poor quality, I took them with my phone), so if anyone can tell me if this is the wrong configuration please let me know what the right way to do it would be.

If anyone has a picture of how this style mount is suppoed to sit, I'd be grateful.

Thanks,
Nick
 

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I don't have a way to get pictures easily but I think I can explain how the "U" shaped mount adapters work. They were set up to get the proper engine height and move it back farther in relation to the center of the pump mount vs. the center line of the biscuit mount. This also helps to get the nuts and cotter pins in the top of the biscuit bolts. The top or open side of the "U" shape of each adapter mount is to be pointed toward the front of the car. As your U mount adapters are mounted in the pictures you should be able to just turn open ends of the U forward toward the front and they should line up. I think they are already correct as to right and left sides. The engine may have to go back a little to line things up from the look of it.
 
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Will these pix help?
 

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Yahoo!!!

Guys, thank you so much for the help. Going by the pictures and drawings, I finally got the engine lined up the way it should be, and the driveshaft fits like a glove.

I say this so many times that I sound like a broken record, but I really don't know what I'd do without the group here. You all are the best. I wish I could roll you all up into one gorgeous woman.

Thanks so much,
Nick
 
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