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SM 420 and NP205 in a CJ-5

1030 Views 3 Replies 1 Participant Last post by  GreenMachine
I am going to attempt to put a SM420 mated to a divorced Np205 into a 75 CJ-5. I know that it sounds like a long combo but i have done some figuring and I think it might just work. I made a short little driveshaft that measures 4.5 inches from end to end (which is about the same length as the adapter to mate a 420 to a NP205). I will gain a little in putting in the 420 as the bellhousing is shorter (I don't know how much yet as the adapter housing hasn't got here yet). My driveshaft length now is 19 inches center of cup to center of cup. The T-15 and SM420 are about the same length. I will add about 6 inches with the yokes and little driveshaft but I get to suptract about 2 inches for the shorter bellhousing and input shaft. So I think that will leave me at about 15 inches for my rear driveshaft. Does anyone run one that short? I can put in a shortened cardigan (spelling?) type shaft out of the front of an Bronco if need be. I guess if it comes down to it I can move my rear axle back a bout 3 inches and trim the sides and possibly some of the back of my glass tub out to accomidate the axle being further back.
If anyone has any ideas or insight let me know. I would also like to maybe see some pictures of how you bolted the 420 down. The one i pulled out was sitting on a cradle type crossmember and then bolted from the frame to the bellhousing. I have some ideas on this but it depends on how the adapter Bhousing is made. This tranny also had the old heavy duty drum brake on the back which is gonna save me from having to put a line lock in and run brake lines into the dash (not to mention the brake lever looks really cool).
Thanks for any info

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15 inches would be ok as long as you dont have some killer travel suspension in there. you should run a double cardan (cv) driveshaft, as it will help with the short length. the thing i would look at is how low that 205 hangs compared to what you have now. 205s are big units.

best wishes this turkey day.
why is there no mazda thread?
I feel left out.:p
Unless you are running mega horsepower you would be better off running a model 20 transfercase. They
are lighter, more compact, easier to rebuild and get parts for, and will allow you to run a driveshaft that won't
limit suspension travel. Also, the low range in the 20 is slightly better than the 205. Nickmil.

I'm not running mega horses (a pretty much stock execept headers, no emmisions 360). However I operate on the whatever I have laying around principle. I wouldn't mind keeping the dana 20 but I don't want to shell out the money to buy the adapter for it as well as the bellhousing. I got the NP205 out of the 3/4 ton dodge I bought when I did my axle swap so it is laying around (doesn't cost me a dime to use it). The SM420 I purchased for 50$. I have found the bellhousing for $322 so if I use the 205 I am looking at $372 versus about $772 to convert to the dana 20. Otherwise I would follow your suggestion...

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