Transmission gear identification

I

Ingram 33vicky

Senior Member
I have a cluster gear that is a 68-7113-A. Has 4 notches at rear, uses cage rollers, tooth count is 28-24-18-14.

I am having trouble finding and installing the proper input shaft and gear. I have found one that has Ford part number 8M-7017. This input will work very well, and has a gear diameter of 2.342 inches. HOWEVER, I have two more input shafts that when installed will lock up the gears. The problem is that the gear diameter measures 2.451 inches on these input shafts. Looking at Mac's book it appears that any of the 3 input shafts (48-7017, 81A-7017, and 8M-7017 will interchange Tooth count, caged bearings all the same.

What am I missing?

Thanks for any help or input on the input.

Paul
 
You need to study Mac VanPelt's book very closely and know what part numbers you have. The 49 through early 51 Mercury transmission uses very similar gears to the early Fords since they still used the 1 3/8" 10-spline input. You can use the 68-7113-A cluster with it but you need the correct thrust washers to work with that cluster. The Mercury 8M-7113 cluster will work with the older input but it needs its own thrust washer set up for the back end of the case. Some use rollers with cages and some use loose roller bearings too so you have to watch for that.

If you have any transmission parts from the 1951 model year on then you need to segregate those parts from the early stuff. They have different gear tooth shape and tooth count than the older stuff.

There are four different ratios common to the early FoMoCo transmissions. Two of them are the Lincoln Zephyr ratios and two are Ford & Mercury ratios so you need to have the correct tooth counts for each ratio.
 
The gears that measure 2.45" are the 1951-52 main drive gears (1C-7017) which will not work with the 1936-50 type 28-24-18-14T cluster gears. The larger diameter of the 16T gear is why the cluster is jamming tight when you try to install the countershaft.

The early main drive gears (b-7017 and 48-7017) may have 16 teeth but are NOT useable with the late style synchros with the separate bronze synchros. Different overall length and different tapered cones.

The 81a-7017 and the 8M-7017 are essentially interchangeable as 16T gears working with the 28T cluster gears. You'll notice a slightly longer "shoulder" on the 8M gear....just in front of the section where the ball bearing rides. This was made to help control oil leakage when used with the 8M-7050 (Mercury) front bearing retainer, which had the funny spiral groove inside.

Keeping all this straight in my mind took years...... Still learning too.
 
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