T-150 Upgrade?

[BajaEdition]

The D 18 and Dana 20 transfercases are closely related, and the first to use a D 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 D 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 D 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 D20 transfercases are closely related, and the first to use a D 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 D 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 D 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.

D20, 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 D20 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 / D300 direct bolt in.