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MOPAR Crankshaft's Automatic vs. 4-Speed Transmissions

Paul Cotton

Paul Cotton

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I heard something this week that I have never heard before. I was told that Mopar made crankshafts/engines that were specifically for either a 4 speed transmission or an automatic.

The difference was relief being cut in the end of the crankshaft for a pilot bearing for a manual transmission, vs no relief being cut in the crankshaft for an automatic.

Any comments on this?
 
I've seen both, you would think they all would be cut.
 
This is def true for the 60's and early 70's stuff. Alot of the cranks were rough drilled but not finished sized for the input shaft on the automatic cranks. I know even on my 78 Powerwagon, I had to specify the crank was for a 4 speed truck when I ordered a reman so I'd like to think this is the case for quite a large chunk of cranks through the late 70's or early 80's.
 
I had to get a new crank for my rr motor I picked up wasn't drilled for a stick.
 
Paul Cotton said:
I heard something this week that I have never heard before. I was told that Mopar made crankshafts/engines that were specifically for either a 4 speed transmission or an automatic.

The difference was relief being cut in the end of the crankshaft for a pilot bearing for a manual transmission, vs no relief being cut in the crankshaft for an automatic.

Any comments on this?
Click to expand...
Yep, you were told correct. A lot of guys just cut off the tranny shaft when putting a 4-speed in an automatic car. You can then use a pilot bearing instead of the bushing. Not the best way to go about thing though imo.
 
BB and RB needs a 5/8" deeper hole sized to fit which ever bushing purchased.
Drill to deep and hit the oil galory creates a wasted crank
 
Its my experience that you never know whether a factory crank from a automatic is machined and bushed or not. When they ran low on auto cranks they just used the other?
 
cryplydog said:
Its my experience that you never know whether a factory crank from a automatic is machined and bushed or not. When they ran low on auto cranks they just used the other?
Click to expand...
Ever try to install a converter into a 4 spd crank? On a /6 it will not work. Maybe on others it will but would not count on it.
 
I've used both the 727 crank, not drilled r bushed for the 4 spd and the bushed 4 spd crank. I also had one crank drilled for the 4 spd but didn't have the bushing. Mopar apparently was thinking that one less machining operation was a cost saver.
 
Hi fellas,
As I recall NAPA used to have a bushing that was sized to fit the automatic crank and work with a manual transmission.
Mike
 
The auto crankshafts that I have were not drilled to the same depth as the 4 spd cranks. My observation.
 
Paul Cotton said:
I heard something this week that I have never heard before. I was told that Mopar made crankshafts/engines that were specifically for either a 4 speed transmission or an automatic.

The difference was relief being cut in the end of the crankshaft for a pilot bearing for a manual transmission, vs no relief being cut in the crankshaft for an automatic.

Any comments on this?
Click to expand...
used to be that the cams were just a tad different also.
 
The auto crank in my 440 was drilled deep enough but not finished out to accept a pilot bearing. In this case you can use a bearing for a Dakota pickup which friction fits the crank flange perfectly.

images?q=tbn:ANd9GcTVUCt4Meu-0gHosm5XERDZg9_lx9693U0TT_INbZlIaWSSq8UH.jpg
 
Was a common practice, think about the money they saved. If they saved even $2.00 per car in machining x's say hundreds of thousands of motors. Lots of Dinero.
 
Yes its true, some were drilled and some were not. ran into this a few times over the years. mopar actually made a bushing for some of the engine that were not bored out for the 4spd. use to have to get them machined down myself to fit the crank. I even came across a hemi 4 spd were someone had cut the input shaft down to make it fit....uggggg.
 
Sorry to revive this but does anyone know the specs to tell a machine shop how to drill out an auto crank to accept a 4speed? My crank is sitting at the shop right now and I cant find any specifics online. Answers seem to range from, a pilot bushing will work to you need to drill the crank out more.
 
FYI, my crank is forged. I dont know the # or year.
 
I have two steel 440 cranks in front of me that appear to be drilled and machined for the bushing, but no bushing. The machined depth is about .980 deep with about .875 - .880 machined diameter with the drilled, (not machined depth) another .750 to the drill point. I presume these were factory machine for the bushing. My recollection of the 727 cranks without the machining was shallower & didn't have any machine diameter. Good luck.
 
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