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Discussion Starter #1
Have aTj with the AX15 thinking of putting in a granny tranny.

You hardcore guys. Which one would you go with, the sm420 or np435

thanks
 

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choosin btw those 2 id go with the 420 only because its lower and its all cast...where the 435 has the aluminum top....but good luck finding a sm420..
 

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i've got a SM465 in one of my wagoneers. I like it. Lower than some of the 435's (rarer), more plentiful than the 420. Mine is one of the later 465's that has the aluminum shifter top. But to be honest, I wouldn't bother with any of it unless you've got other plans for your TJ
 

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Hey, kinda hijacking the thread, but I was going to post the same question, only for my '67 CJ-5. You can see what it has on it in my signature below, except I was wrong about the tranny, it's a T-86, not a T-18, so thats why I wanna swap, get a low gear instead of the 2.79 crap I have now. I was thinking NP435 because it's shorter for my CJ-5, is this a good assumption, or should I look elsewhere/at something else? Let me know, sorry for the hijack, but still comp-ing trannies, so I think it should be okay...
 

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Need more info on what else you are planning on doing. If your not swapping out the rest of it I'd just leave it alone. Both are good xmissons but unless you already have a 420 located good luck finding one. They are shorter than the 435. Don't bother with anything but a Ford NP435. I have always heard that the Sycronizers on the 435 are troublesome but I ran one behind a built 304 with a Dana 300 hard for 5yrs with no problems.
 

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Discussion Starter #7
SEEJAY7 said:
Need more info on what else you are planning on doing. If your not swapping out the rest of it I'd just leave it alone. Both are good xmissons but unless you already have a 420 located good luck finding one. They are shorter than the 435. Don't bother with anything but a Ford NP435. I have always heard that the Sycronizers on the 435 are troublesome but I ran one behind a built 304 with a Dana 300 hard for 5yrs with no problems.
Right now have dana 44 F/R with alloy shafts, all the body armour, hy-steer cross over steering, ARB's F/R. Stock 4.0 L , AX-15, Np231 w/sye. Have Tera flex short arms, will be building something similar to Clayton Long Arm

Pretty much a trail rig but I do drive to the trail.

Reason for tranny swap is to get better crawl ratio. With the sm420 or np435 I can get to 83,86:1. Later maybe an Atlas or Stak tcase.

Really looking to get lower crawl for the least amount dollars to spend. think I have a sm420 to rebuilt. Still figureing out what the total cost to buy,rebuilt, and adapters. think this would be most cost effective way.
 

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Mr. Personality
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Either one would be a good choice for your rig.. the 420 is slightly shorter in length , and has a slightly lower first gear , 7.05:1 versus ford np435 6.69:1.

I have a ford np435 in my TJ , behind a 4.0L with the AA bellhousing and hydraulic clutch. It works great , never had a problem with this setup.
 

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blackbeauty said:
....but good luck finding a sm420..

Sorry, but ................ :laughing: :laughing: :laughing:
There's 2 SM420's for sale on PBB right now and Novak sells rebuilt ones.
Also, patman's in San Diego and M.I.T. in El Cajon sells rebuilt SM420's.
There's NO problem finding them.
.
 

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I have a sm420 matched with a dana 300 and the only problem is when you break something on the 420 parts are few and far between I have to replace my main shaft and am having a hard time finding one so in the mean time I am buying a 465/205 setup from some one for $100.00 and still looking for parts but good luck on what ever you decide
 

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To me the above is the tie breaker. Strength is equal, ratios close but edge to 420, both noisey in 3rd, but 435 parts are more available and generally less $$. While there are GM, IHC, and Dodge 435's, the Ford applications outnumber them15 to 1 at least and are very available.
 

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Maybe it's just the junkyards or east coast that is lacking in SM420's.. I've been unable to find one at a reasonable cost over about 6 months of looking.

Curious, couldn't you make up a good bit of the costs toward a NV4500 by selling the AX15?

Why exactly are you wanting to swap, anyway? The AX15 doesn't completely suck. You may be better off putting money towards transfer case upgrades.
 

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I think the decision maker is does any of the 4 (NP420, NP435, NP465, or T-18) come with the correct input length for your bell housing? I think that would be my decision maker there.
I know the 420 and 465 have the same length input but the retainer flange is larger around for the 465.
I am running a T-18 and am very happy with it for offroad use. A Ford T-18 input shaft length is equal to GM so I found one and redrilled my bell housing to fit it. Only 2 lower holes were off.
Novak is pretty helpful with finding out what would and wouldn't fit.
 

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Discussion Starter #15 (Edited)
fullygruntled said:
Maybe it's just the junkyards or east coast that is lacking in SM420's.. I've been unable to find one at a reasonable cost over about 6 months of looking.

Curious, couldn't you make up a good bit of the costs toward a NV4500 by selling the AX15?

Why exactly are you wanting to swap, anyway? The AX15 doesn't completely suck. You may be better off putting money towards transfer case upgrades.
Good points !! I have been evaluating every possible way for lower crawl ratio and it keeps pointing towards a TCASE upgrade. Would like a NV4500 but have also been taking weight into the decision . I believe the nv4500 weighs about 60 lbs more than the sm420 and np435, dont know if 60 lbs is a big deal, also nv4500 are more expensive

I like the ax15 not sure I could get that much for it. Runs good.

Short on funds and trying to save as much as I can $ wise to get lower crawl.
 

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Once you figure in adapters, crossmember mods, etc., upgrading the tc is the obvious choice. 4:1 gears and a SYE kit would probably run you $700-900 or so. Slightly more expensive but easier, get a junkyard 241OR for about $1400. Atlas runs about $1800.

Comparatively, you'll have maybe $200 into a granny 4-speed, plus ~$500 for the bellhousing adapter at minimum. That puts you roughly even with the 4:1 and SYE, and you haven't even begun to deal with crossmember, clutch, shifter, and tunnel modifications, modifying BOTH driveshaft lengths... and at the end of it all, you're still out an overdrive gear.
 
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