sm420 in the flattie

im sure this has been covered, and i did a search and couldnt find what i was looking for, so here goes my question.
i have recently started a build on my 3b and came across a sm420. now i already have the chev 283 so going to that isnt hard but i want to adapt it to a dana 20( i have switched axles already, so i need a centered rear output). what im looking for are pics, specs, advice, warnings, ect. to get this all put togather. im worried that replacing the t-90 with the 420 i will move the tranny forward too much. the engine cant come back anymore. so give me what ya got!

 

I'm doing it right now with mine. 283, SM420, Dana 18, etc.... Give me a week or 2 and I can tell you about it
It's already adapted to the Dana 18. I needed to cut my mainshaft down and machine the main shaft for Advance's snap ring. Otherwise, it's pretty straight forward.

 

you got your adapter from advance?
im looking at novaks or a used one. just cant seem to find one.

 

I ended up getting the blem one Advance had listed in their "junk yard" for the low low price of Too Much .99
Aka $430
The blem one was .005" short of the specified 4.00 inch in their plan. I guess that's their tolerances... They should have went 4.000 +.005/-.000
None the less, the spud shaft would bind up against the T90 to Dana 18 bearing retainer it used, so I cut my mainshaft down to make it work.
I looked for used adapters, no such luck

 

Uhh, could you clarify this:? The SM-420 is longer so if anything you want to move it forward along with the transfer case for more rear driveline length and to ease the u-joint angles, especially using the 20 transfer case that has the rear output up high. You certainly don't want to move the engine back any, if anything you want it as far forward as possible....

 

okay, my t-90 is 9" long, and i have a 2.5" long adapter from the chev v8 to the t-90. the 420 is 10.4" long and i lose my adapter onthe engine and gain a 4.4" adapter on the tranny. so it looks like im gonna be about 3" different. i was thinking my engine adapter was more like 6" long... had to go out and measure it to see. so im not as bad as i thought. looks like its gonna fit like a glove. now just to find an adapter.

 

my 420 as it sits in the garage with Novak adapter awaiting it's installation sometime this summer.

 

*******, I have a 465 with a AA adapter and a 20 already hangin on it. Before you buy a adapter for 500 give me a call.

 

i just bought the 420
im thinking to hold onto it for a while. will probably try to build a whole combo. something with fi... i might give ya a call, see what we can do. thanks D!

 

I will be doing a tranny swap also this summer using the np435 (good deal) on mine for more drive line length, I moved the rear axle back 1" by redrilling the perchs and the u bolt plates 1" with no issues about year ago and plan on moving motor forward 2" when I do the swap (v6), still a daily driver now

 

Well mine's a '55 CJ5 so not a flatty, but I'm working on converting the 134/T90 to a 225/SM420. So this thread has interest to me. I'm going with Advanced Adapter's spud shaft kit as well. I couldn't find used one without buying an entire Jeep, so I am getting mine from Herm. I'll let you know how it works out.

 

ya dude i talked to herm about one of his deals and about the 420 and im bummed about the fact that i cant rebuild it if i have to... i will most likely be getting rid of the 420 and buying a 465... probably daryls'.

 

Why can't you rebuild it? Easier than an SM 465....

 

hay DARYL could you please give me a shout about the adapter thanks yancy:v6:

 

no one makes parts for them any more. seals and bearings and little things to overhaul them but no more gears and the other major components.

 

Yup, I'm aware of that. They also came in 3 different versions with different guts BUT if all it needs is a rebuild that is do-able. A rebuild is simply replacing soft parts, bearings, blocking rings, seals, etc. If it needs hard parts then that is a different matter. Have you looked at the condition of what you've got to see if it is rebuildable?

 

the guys that have been rebuilding these and working on them for years and years will have hard parts, new or used; just have to find the right guy/shop.
the shop that rebuilt mine had a small room full of OEM sm420 parts collected and scrounged over the years. No, I didn't need any for my rebuild, as my hard parts were deemed a-ok.
getting him to sell them might be hard; he's hoarded for his own use.

 

ya i talk to a couple guys in the business of rebuilding them and said it took 6 or more trannys to get one. also your paying them to rebuild it for the exact reason you stated... they dont want to part with parts. i'd rather have a 465 that they still make everything and it can be rebuilt by myself if and when its necessary. it the long run it makes more sense for me to save my cash and throw the dana 20 on the back of the t90 and get a combo or piece a set togather over time. or just buy daryls..

no nick, i havent even cracked the top loose... for all i know it could be perfectly fine inside. i do plan on opening it up and seeing what condition it is in. im just at the point where is it worth investing almost 500 bucks into an adapter for a tranny that if i had to rebuild it, it would be exspensive.

 

push comes to shove i'll open it up and check it out, if its good i'll throw it in the corner and sit on it. save money for the adapter and for now run the t90/dana 20. if its junk, then im out the 100 bucks and it goes to scrap or wherever.

 

I have a 3 speed rat box that you can have if all you are looking for is a stronger trans.