Dana 20 or 18 0r 300 or...

[Grantshire]

I want to swap out my QT for either a Dana 20 or 18. I know I will need an adapter to mate to my TH400 but which way is the prefered direction? My WT has two tanks so I could pull the factory tank to take care of any driveshaft issues. Is it better to go 20 or 18? Won't the 18 "sing" at highway speeds (my Willys always did). Is there another TC that would work better?

Grantshire

[LRRH]

Dana300 would be a better choice in my opinion.....but each opf the cases you mentioned will have a weakness.

Also....finding a Dana300 with the appropriate bolt pattern might be difficult. I think they were only offered a few years.

[mandoneer]

if I remember right the QT has offset rear diff. and so you would need to go with the 18 if that is the case and you would need to also get the large bore 18 that was on 225 v6 jeeps and I think that the hubs are full time so you would need to do a hub conversion (this is all stuff I have heard about the QT and because I dont have one I really dont know also you will need the adapter , output shaft (short 2wheel drive version for the th400 )and the bull gear and intermediat gear from a D20 that was on an automatic (I think that the out put gears on the 18 are the same spline as the 20 but not sure and if your axle isnt offset than a 20 and hub conversion would be the way to go along with the stuff for the transmission ( make sure that the 20 is for an automatic though cause the standard and auto bull gears are diffrent and the splines on the intermeadiat shaft are diff (I think one is 19deg. pitch on the teeth and the other is 17deg.)

[jode]

Atlas :D ?

You'll also be needing a new tranny tailshaft in addition to that adaptor plate.

[scotty]

what tires do you run? ive broken 5 spicer 18s with 38s,at18 tranny,and a 258 smile.gif tth2 28 will not really hold up well in large vehicles like FSJs,especially f theyre running bigger than a 33" tire

i swapped in a d20,and have broken 1 tailsahft so far. but my driving style is pretty assertive at times ;) and in all fairness the 20 has held up muc,much better than the 18s

if you are talking about finding a factory adapter for your th400,youll be limited to a d20,or d20 gears and housing in a spicer 18 configuration,due to the odball 15 spline input gear.

if youre talking about buying an aftermarket adapter that will give your th400 as 6 spline tailsahft,you can use either a 20 or an 18 pretty easily

you cannot put a scout d300(shares d20 texas pattern) onto a factory th400/d20 adapter due to the 15 spline taislahft. the scout d300 input gears are either 23 spline(auto) or 6 spline(manual) if you get a d300 from a manual tranny,it would bolt to an aftermarket th400/d20 adapter with a 6 spline tailsahft smile.gif

confused? smile.gif heres what id do,depending on which is more cost effective,and within the relm of your "wrench-on-stuff-ability"

option 1:find a gm th400/205 and swap the tailsahft and adapter into your amc case th400. now you can bolt on the 205,wich is way stronger than the 18.20 or 300
option 2:find a jeep 727 tranny and swap that in place of your th400. a jeep d300 will bolt right to it,no adapters. the downfalls are not as strong,and the d300 will have limited clearance for a front drivesahft with the 727s big fat tranny pan. to put a d300 behind a 727 youll need at least 4" of suspension lift,and to extend the bumpstop on the passenger side to keep the sahft from contacting the pan. you may be able to gain extra clearance by re-clocking the d300 on the 727 adapter. rotate it so the front output is lower.

there are CJ guys on "jeeps unlimted" that actually run a 2 piece front drivesaft,with a carrier bearing to run a 727 in front of a d300. :eek: kind of clever,but i don t think id ever do it that way

whatever case you use,dont worry too much about the rear offset. lots of people run a center output tranfer case to the offset rear.the extra angle of the rear drivesahft doesnt hurt anything unless youve got a really big lift. dont listen to anyone that tries to tell you that "compound angles" exist and are bad

my $.02 on the 18/20/300 anyway