Hello ya'll. I'm in a freakin pickle? Should I use a th400 or sm420? I like manuals but woinder if it will live behind it. Lets just say my caddy motor is a long way from stock:D Length is any issue also. Which ever goes in a 4-h atlas will be behind it. Let me know the pro's and cons of each. Thanks

OMG Newset member already posting. Let me be the first to say..... Search!


And welcome newest NEWBIE!:flipoff2:

yep been searchin. One question though, on the 2-wheel drive sm420 with the 35 spline output is the output shaft long enough with the 3 inch novak adapter to mate to the atlas? If not is the ten spline output on the 4x4 version strong enough? I just don't want a weak link in the drivetrain.

Depends on how much work you want to do. You can go with the 400 and swap in a 4wd output shaft and have a nearly bolt in swap. Or you can go with a manual tranny if you don't mind machining the end of the crank to accept a pilot bushing. No 500's came with a manual tranny so none of 'em have a hole to put the pilot bushing in.

Well auto vs manual question sounds you are the answer!

I have an SM420 and the only drawback I see is the unsynchronized 1st gear. The SM465 would be better and the 1st gear ratio difference is minimal.

SM420 is a awesome transmission, but if you wanna have fun in the dunes, mud, have a bottle or kick some ass on the strip, better turn for the auto :rolleyes:

The SM420 has a 10 spline output, I have it with an Atlas II and you need the coupler or so shaft. The Novak adaptor is 2" shorter than the AA, wich is around 6".

I needed a rev cut rear axle with my 350V8 / SM420 / AA Adaptor / AA Atlas II, rear shaft is 22" long running at 23°

Thanks to High Angle Driveline no problems with the 1350CV but still a step angle there ;)

The Caddy 500 / SM420 / Atlas / KluneV is still in my dreams tho'.

Good luck!

Yup I'm thinking I'm gonna use the 400 and just beef the hell out of it. 32 spline output on the 400 right? Yes I do have NOS and love the mud and dunes and the occasional mustang beating:D

lol.. lets think on this..
cad 500 stock 500 ft/lb
sm420 7.whatever 1st gear
atlas tcase...
:nuke:
scatered parts come to mind..

LOL.. Hehe jus think I have close to 700 ft/lb without the juice!! I was just trying to give myself a sane rear driveshaft length. That is why I was looking into the sm420(or 465)

acording to aa's website the have durability tested the atlas to 900 ft/lb input. so you would be right up there in 3rd gear. first gear at wot would be over 5000 ft/lbs.. :eek: that ought to make a nice mess..

that can't be right....

if 900 ft*lb is it's limit on the input, then the weekest v8 w/ a 420, 435, 465, t18 etc would easily exceed that......


--Berne
its not ft/lb.....:flipoff2: :flipoff2:

i know.. i thought i had read somwhere that it was rated for something in the ballpark of 1700 ft/lbs input.... but im at work and cant spend to much tilme looking. but any way you look at it.. 700+ ft/lbs at the flywheel thru any trany is guna be hard on stuff.. even a 205.. not to say it wouldnt work.. just got to use the brain more than the right foot..

Damn maybe I've out done myself on the motor :( I thought the atlas had like a 2500 limit. Hehe maybe that nitro needs to be removed! I am conservate with the gas...sometimes:D

What's you wheelbase?


Oh, :flipoff2:

just dont juice it until you are in like 3rd or 4th.

Over a hundred, jus haven't decided if I want to stretch the frame or jus move the rear axle back alittle more. The front has been moved froward about 4 inches. The tank is already gonna be in the rear of the tub jus haven't had time to screw with it yet. Any ideas on wo far I should move it back

700+ ft/lbs at the flywheel thru any trany is guna be hard on stuff.. even a 205..

that is definately not a problem for the 205.

Jeepaholik: Get the 400 if you do ANY mud. Shifting a manual in the middle of a mud hole is a no no, whether or not you have 600/700 lbs of torque.