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203 Transfer Case in Early Bronco

Tech article by admin and filed under Transfer Case

Tech article by Mike Mussett (jonylost)

Well, I said I would do a bit of a blow by blow account of the fight to install a 203 so here goes….. Got the Dodge 203 from a salvage yard in WI. Had it shipped to me in TX and saved a bundle still. (really shows the ass of most yards here in TX) Anyway, I already vented about that a while back. The 203 came out of a 78 Dodge 4×4 and are very abundant. Should have no probs finding on…..check www.carparts.com. I had to wimp out a bit when it came to adaptors due to the fact that the machinist that was going to work with me landed a HUGE contract and didn’t have anytime for the foreseeable future, so I ordered up the Wild Horses Kit that Advanced Adaptors made. GREAT KIT.

Very inclusive and complete, and hell even has pictures on the directions for me! Gotta love that! I will be calling WH and speaking with someone in management that this is a good job.Here’s what I got done today…..
Took apart the 203…..it is two pieces for the most part and all I will be using is the gear reduction half. The chain drive 4×4 part is official anchor weight. BE SURE YOU KEEP TRACK OF ALL ROLLER BEARINGS! As usual, I spent too much time chasing these things around. You will need to keep the bearings that occupy the 203 output shaft. Everything from the aluminum keeper back, off the 203 is transferred to your new set up. I was lucky enough to have two 435 setups so I could go ahead and put together the entire new 203 to D-20 shaft assembly. It consists of:

  • New 203 to D-20 Output shaft (kit)
  • Original 203 2:1 (large) gear
  • Original spacer
  • Original Output shaft bearing and carrier (big slotted aluminum thing)
  • New D-20 Bearing Retainer and sealer (you will recognize this from a 435 set up)
  • Original D-20 input gear assembly.

Keep all of your snap/retainer rings! You will need these. Tomorrow (if time permits) I will get the tranny and stuff out of the rig and get the New NP435 Output shaft in the tranny. That will pretty much take care of the hard stuff…Well its tomorrow and that wise crack the hard stuff is over is all CRAP. These things weigh a ton all put together!!!!!! Here is the account today…….

Got the 435 out of the rig and the D20. Pulled the cover off the top of the 435 to see what I am up against and found that my tranny is also a great water catcher. The milkshake goo that I found in there is quite amazing.

Anyway, finished cleaning that out and put to work taking the main shaft out of the tranny for the new main shaft swap. Steps:Take the rear output bearing off as well as the front input bearings off. The front will come apart and the shaft will be in two pieces. You have to have that rear bearing out of there also so you can tilt the shaft enough to get it out of the case. REMEMBER…there are roller bearings in that front input part. PITA trying to get those out of the bottom of the case. Here is a pic of the new main shaft (one with NO gears) and the old main with all of the gearing still attached. That’s the rear bearing as well lying there. Shorter is the main difference and a new output spline count.

Take a note on how your gears go on the shaft when you transfer them to the new shaft. There is really only one way, but if you remember and note in the first place then you will save a bit of time.NOTE: When the large gear comes off…..it only comes off the front of the shaft. There are two metal …….”things”. Because I tilted the shaft just so the large gear slid off and I didn’t take note of where these *&E(%&($(# ! things went. Took me quite a long time to figure that one out with no manuals to refer to!

Anyhoo…….now reverse the process with the new shaft and reinstall back into the 435. There will probably be a bit of resistance with bearings and stuff like that due to new parts, so things my fit a bit tighter than they came off. I had a press for things like bearings (rear bearing specifically) to put it on the new shaft. You may or may not need this, but always be careful with your bearings. YOU WILL ONLY WANT TO TAKE THIS THING IN OR OUT ONCE! I promise! Here is a pic of the gears bearings ( the evil roller bearings as well) with the old and new shaft.

The adaptors are pretty much simple on the hows and whys. There are supplied allen bolts that are counter sunk for bolting to the 435 and d20.

Its hard to see from this pic above, but on this adaptor at the 6o’clock position you have to preinstall this bolt, due to the fact that the 435 reverse gear bearing housing bumps out a bit from the tranny case. Having this bolt in first is the only way to get it in.

Here is the 203 gear redux box. Top pic is the side that will mate to the d20 and that adaptor. Second pic it the 435/203 side . Again, you will use some parts from you existing 435/d20 set up right now, like the aluminum housing that fits into the D20 with the seal….

Above are the fully assembled shaft gears and bearing that runs between 203 and D20. Left side to 203, right side to d20.

D20 and 203 together. The POR 15 was pristine for about 15 minutes until I touched it again and drug things all over the concrete.

My helpful daughter Andi!

This kit does not have any gaskets so liberal use of silicone was the SOP on all mating surfaces.

For the install back into the rig, I did the 435 first by itself and then the 203/D20 assembly second. In hind sight, I would have probably left the 203/D20 apart just for sheer weight factor and difficulty in handling. I have the entire top of my tranny tunnel cut out anyway so that helped me in that I ran rope around the 203/D20 up to my roll cage for assistance. If you do a 3 part install, again WATCH YOUR ROLLER BEARINGS in the 203 on the d20 side. The 203 is a snap bolting it to the 435, then you get to do the roller bearing fight when installing d20 to the 203, but with good amounts of grease and patients, you can get them together.

The cross member of old is just that, old now! Your new and improved cross member runs across the top of the assembly and bolts to the 203/D20 adaptor. It uses the same cross member perches that the old cross member bolted to and the kit supplies bushings for this area.

Shifters…………

There is a new D20 shifter mount. It now bolts to the top cover of the 435 using supplied bolts. The new shifter site about 4 inches back from the previous position that mine used to site in. HOWEVER, yours may differ because mine was not stock to begin with.

For the 203, when you get your 203 from the donor vehicle there should be a Z shaped bracket on passenger side of the gear redux box. WH supplies shifter for both the D20 and the 203. The 203 shifter, I welded to the Z bracket and then bolted it the shifter mount. Unfortunately I didn’t take any pics of the modern art master piece but it’s described well in the direction.

Measure positions, and cut as necessary your floor board to accommodate all of these neat things and you are just about at the end of the project.

The kit lengthened my driveline a bit over an inch, but my driveshafts were able to absorb this with no mods. Your call on yours!

If you have any questions, I am glad to help.

by Mike Mussett

One Response to “203 Transfer Case in Early Bronco”

  1. daniel hart Says:

    I was reading through your install (nice work), and noticed you weren’t going to reuse the chain and diff from the 203. I’ve been trying to find the back half of a 203 for awhile, if you could contact me that would be great.

    Thanks, dan

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