Transmission choices/ road manners

OK after crawling for days on end for a transmission I have come to the conclusion that I am officially confused. I need some professional help to decide.

The transmission that seems like a obvious choice is the t18 but then there is the overall brute strength of a 420 that will not require a front adapter.

The question is road manners I am seeing that the 420 has a gap that most note and there is a debate about it being hard to shift(but probally linkage that a hyd clutch will eliminate).

Now I do plan on running 4.11 in the rear and later switching to a 4.88(if i can convenience a buddy to sell his 8" HP 3rd member).
With either unit I would want to install a warn/saturn. This is really needed to save the motor. Not a option it is a necessity. As for a transfer case either a 20 or 300(i want to twin stick just something i always wanted to have).

What will work best with a daily driver. The drive train will be a(231 in prep) 225 to either a 420 or a 18 (running a od) to a 20 or a 300 to a yoda 8" with 4.88. oh and running 35's.

I am sure there are a few members that have the 18 or 420 with a OD. I am simply looking for what will drive the best as a daily driver.

Also after pricing and pricing and pricing. It seems I am going to come out having between 2500 and 3500 in the transmission/transfer case between the two choices using AA as Novak seems to get some bad responses.

Between the rebuild/adapter/od/hydraulic slave(pedal)/clutch/flywheel I am going to set aside 4k(yes I am dumping cash into this pos).

I want to know what will have the best road manners as this will be a daily driver in the long run. Toss your preference of a transfer case behind said transmission also. Once again I plan on using a 85-89 yoda 8" with a hp 3rd member as axles.

Thanks for all your help in advance. You all hold a level of respect that someday I hope to mimic which is why I come to you with such a important decision.

 

I assume the overdrive you are talking about using is the warn/saturn OD if so it will only work on a dana 18 transfer case.

 

Assuming that you're build prospect is an early 81" wheelbased CJ.
Consider that the Jeep will not handle well at speeds above 65/70 mph.
That fact alone helps trendously in determining the ideal gearing.

1st) You will be hard pressed to improve upon a V-6 powerplant.
See Jim Allen's excellent torque formula :
http://www.film.queensu.ca/CJ3B/Tech/EngineDyno.html

2nd) You need a good clutch rated for the engines torque output.

3rd) You will be hard pressed to outperform the T98/T18.
This transmission ranges (gear splits) very well with the Warn O.D.

4th ) Warn 25% O.D. This will get you up to hiway speed without excess fuel wasted due to overly high drivetrain velocity.

4th) The Dana 18 TC is the overall best choice for a short wheelbase Jeep.
The offset drop down design is a huge plus for short wheelbased CJ's.
You might want to build a twin stick D-18 in a D-20 case.

5th) HD propeller shafts and not some skinny 4 cylinder parts.

6th) 4.88 final drive will put your engine near optimum crankshaft velocity.
No sense in hiway cruising the engine at the wrong crankshaft rpm.

This is just one quick example of a complete synchronous system.

 

If you plan on using toyota axles, you wont be able to run the D18/OD combo as it is off set

 

Here is my take on it and what I am building with; T18 (because it is the smallest truck 4 speed), Dana 20 (because it is quiet) and I got a Scout Dana 20 twin stick that looks just like a Dana 18, this is so cool, it looks like a stock Dana 18, but is a Dana 20. I also have a centered Dana 44 so I can run the Dana 20 with (tera low gears in the Dana 20). I picked this set-up so when going down the road it is quiet, and I do not want an extra gear box (with an OD) to have problems with. And, when off road I have a granny first gear if I need it, and a low geared Dana 20 to pick up the slack. Just my view of things,

 

With the 4.88 and 35" tires at the .75 (5th gear) the engine will be running around 2500 rpm at 70. Without the warn it is around 3300 at 70.
Realistically I don't see myself getting over 65mph or running anything larger then 33's on the road. Just going with the what if scenario.

So going with the T18.

I know herm specializes in them and that was the major factor in the debate over whether to use a 420 or not.

I know about the offset. I am really set on using that HP 3rd member though. They come with 4.11's. I was only factoring the 4.88 if I happened to fall into a pair as the best and worst case scenario.

Thanks for all the great info. Better to ask these "interesting" questions now then find out after I rebuild a 420 or something. Be going with the t18 and doing more research on what t case to use with the yoda's.

 

why do you HAVE to have 4.88's and 35's? Same with the Toyota axles? IS it because "everyone else" is running them?

 

I have a 225/sm465/dana 20,and 4.27's &33" M/T's.I can cruise comfortably at 50-55.If I have to pass,65 isn't awful.I'm very happy w/it.My rear drive shaft isn't that straight.I swapped in a flanged dana 44 for use w/the dana 20,but could have used the offset 44.Oh yeah,mine is my daily driver.Good luck

 

Lets see, a Scout twin stick dana 20 has the same shift tower that takes dana 18 shifters, I have a transfer case E-brake on it and the only difference in looking at my Dana 20 and a Dana 18 is where the output shaft comes out. But, if you where to take a quick look at it you would think is was a Dana 18. My point is that I have a Dana 20 that has the same twin sticks as a Dana 18, but is on a Dana 20. I bet you have not seen one very often, and it keeps that retro look I wanted in my Jeep.

And, I beg to differ that a sm420 is smaller. The T18 is not as fat, has a cleaner shift tower that fits in the floor hole with out cutting, and does not have that extended adapter. The T18 in my view is the cleaner package when the transfer case is bolted up.

And, as I said in my post it is my view as to how I wanted my Jeep to be built and was offering up a different set up for someone to think about. And, one more thing a Dana 20 is alot quieter than a Dana 18 and will not wear out the intermediate shaft as fast.

 

Well in Patrick'ss defense the sm420 is smaller than the t18. Its 1 1/2" shorter in length, 1/2" shorter in height and is 10lbs lighter. Now with the adapter the t18 is a cleaner more compact fit overall due to it being narrower but the transmission itself is smaller than a t18.

 

Why is quietness an issue on a CJ anyway? Unless you have a fiberglass hardtop and a fully carpeted interior, it's gonna be noisy anyway.

 

yep
i insulated the bejabbers out of my floor and 1/2 cab.
now it's only kinda noisy.

 

Here is the axles setup I plan on using.

http://www.greatlakes4x4.com/showthread.php?p=2397502

Why will it not work with a dana 18?