T-150 Upgrade?

[BajaEdition]

The D 18 and Dana 20 transfercases are closely related, and the first to use a Dana 20 case with D 18 parts was Jeep, It is called a Super 18 as the case is stronger. If you do want to do this you need to get the gearing for the D 18 with a 1 1/4 intermediate shaft, strongest one they offered. also check on the input shaft spline count. One other place you need to check is if the hole of the input on the Dana 20 will work, if not they make a smaller adapter for it.
The Warn Overdrive unit you put in the thing will really start you rocking and rolling as it is a 25 % unit, grat for Hwy speeds and like said, effectively gives you double the gears you have multiply that by 2 for the lowrange and you can really get a lot of gear choices however it unit does not work with the LOW LOW gear ranges you can put in a D 18, The unit works in the PTO port so you cannot use it on regular Dana 20 .
And as said, a D 18 has a passenger side offset to the rear output, which can give you a problem if you have a short rear driveshaft
Still need pics ?

 

[LongHorn]

The D 18 and Dana 20 transfercases are closely related, and the first to use a Dana 20 case with D 18 parts was Jeep, It is called a Super 18 as the case is stronger. If you do want to do this you need to get the gearing for the D 18 with a 1 1/4 intermediate shaft, strongest one they offered. also check on the input shaft spline count. One other place you need to check is if the hole of the input on the Dana 20 will work, if not they make a smaller adapter for it.
The Warn Overdrive unit you put in the thing will really start you rocking and rolling as it is a 25 % unit, grat for Hwy speeds and like said, effectively gives you double the gears you have multiply that by 2 for the lowrange and you can really get a lot of gear choices however it unit does not work with the LOW LOW gear ranges you can put in a D 18, The unit works in the PTO port so you cannot use it on regular Dana 20 .
And as said, a D 18 has a passenger side offset to the rear output, which can give you a problem if you have a short rear driveshaft
Still need pics ?

Yes.

 

[BajaEdition]

Yes.

OK what of?

 

[LongHorn]

The backside of the Transfer Case for one. Do you just move the output shaft in the other hole & pop the O/D in the original output hole. I use to run a D18 with the Saturn O/D when I was last a flattie pilot.

 

[jarbidge09]

Yes that is the basic difference between the Dana 20 and D18

 

[BajaEdition]

the output hole of the Dana 20 is the output port for the D18, the D18 uses a strait through for the rear output.
The Saturn,Warn Overdrive fits in the PTO output.

Dana 20 , notice the output on left and the port on the right is covered

this is a D18 simular view
the output is on right and the pto port is on the left

notice the cases are very simular, the D 29 can take the parts from a d18 however I believe the parts for a Dana 20 need more clearence to fit in the D 18 case

 

[LongHorn]

So how do you get the O/D to work in all gears, including 2 wheel high with the straight through setup.

 

[BajaEdition]

the OD fits in the PTO port and uses a planatary gear setup. you take off the cover then remove a gear and replace it with the assembly

here Installing an Overdrive

 

[Petescj]

Now that the "house cleaning" was done I'll offer my opinion. C.W. is right. As far as an upgrade and cost effectiveness the T-176 is probably the way to go. You get the Dana 300 with a bit lower range and a lower first gear which was covered here a few times as the T-150s biggest shortcoming. The only thing you'll have to change out are the driveshafts.

I believe his best overall choice, and the easiest most cost effective would be a T-176 / Dana 300 direct bolt in.