So sitting here in quarantine and thinking about strength of parts on my 1975 440 powered TrailDuster. I think that year is a NP203 and looks pretty stout underneath, though I have heard other models have good and bad to them, depending on years and cases. I have thought about not converting it to a drag truck mainly because of weight and costs, but do more of a hotrod street truck. Any weak points or upgrades that are worth doing when the time comes to rebuild it?

The NP205 t/case is the strongest from a factory. Now if you want ultimate strength then the aftermarket Atlas is the one to get.

205 is gear-to-gear whereas a 203 is chain-drive.
Atlas would be about the top of the line but really overkill for a stock, street-driven truck.


Tim

I have never had a problem with any NP203 transfer cases, but maybe I've been lucky? The last few years (77-79) of the NP203 had a better chain, so that might be an upgrade. I've always liked the AWD of these (all the rage these days), even though everyone seems to want to part time them. If you do change to a different transfer case, I believe the output shaft in the transmission is shorter when coupled to a NP203. You'll need to change the rear shaft in the transmission to hook it up to anything else. A part time transfer case, you'll probably want locking hubs too. That's changing from the knuckles out.
So, here's an idea for you. My project truck has a 203/205 doubler transfer case. It uses the NP203 range box, an adapter, and a NP205. This way you don't have to do anything to the transmission, and you get 1:1, 2:1, and a 4:1 ratios. You already have the NP203, so you just need the adapter and a NP205. This combination is only 1/2" longer than a NP203, so you might not even have to modify your driveshaft.

How can it only be 1/2 inch different. I vision it more. Got any pics of it?

I LOVE overkill

to be honest, this truck would never be used for off-road or severe use, so if the 203 is upgradeable, I'm fine with that. I don't think I will add jumbo tires on it, probable under 31" all terrain. If there are no real weak spots, then I could assume just freshening it up, maybe a source for a stronger chain, better bearing and such? Appreciate the info.

Quarantine???

I don't have any pictures of the 203/205. The chain case part of the NP203 is pretty big, similar size of the whole NP205. You just have to swap over the gear reduction section, and add the adapter thickness. It may be a little more than 1/2", but it's very minimal.
migsBIG, I think a rebuild of your transfer case would be good enough, for your application. They are pretty tough.

yup.

Thanks for the info.

I've pushed snow for a lot of years, and drug car trailers around for even more years on the standard mid 70s Dodge transfer case equipped trucks, many went well over 100,000 miles, a couple over 200,000 miles, without a single transfer case issue. In fact, none were ever taken apart. The only one I ever had that ever had any damage was the one where the transfer case got busted in a crash that totaled the truck.

I think a freshening up will be all it would ever need. Gene

I agree the 203 is a tuff one. upgrades I did to mine were the mile marker adjust a chain kit to keep it from excessive slop as they do wear/stretch start slipping/break & bust cases (DAMHIK!) the other mod was adding the mile marker part time kit in the 203 rear output differential housing. the full time bearings still turned the shaft/diff but it was not under any power in 2-hi

that's the other cool thing about the 203 is it has a differential built into it so it turns with out binding the front & rear can spin independent of each other (this why it does not drive off jack stands with 1 axle up- power goes out axle off ground) and when in hi-loc or low loc the front & rear output shafts are locked together = front does not turn without the rear turning (this will drive off stand with 1 axle up and has been a big safety problem when working on them)

but IMHO the w350 435/205-D60/D70 IMHO is the best bone stock & toughest units.

and yes the adapter for the 203/205 doubler is awesome behind the 435 even better is the nv4500 5 speed with the 205 or 203/205 doubler. awesome rock crawling and tuff as nails.

when I had my 79RC I swapped in the w350 running gear 360/435/205 D60-D70 4.56 lockers with a 6" lift & 17/40/15 ground Hawgs. only real issue I had was the short rear shaft and pinion angle. but rolling pinion up and a double cardan joint at each end of rear shaft fixed it.

Also GM used the 205 married to the 435.

Well tickle my transfer case, that some great info there guys, thanks again. Since this truck has alot of mile on it, probaly going to need to rebuild it. Any sugestions for kits, video's or services? Never even taken one out of a truck before.

I built a jig to support the case in the funky angle that it is in while in the truck. I welded a peg to the bottom so it would fit in a floor jack.
A few years ago when I converted my 4 speed Power Wagon to a 727, I used the car lift and transmission jack.
I now wish that I kept the 4 speed in it.

Check if you can change the shift in the 727 with an appropriate kit that works with the trucks gearing. Alot of automatic car/light truck transmissions get swapped in and that makes for improper shifting. Torque converter could need to be swapped too. I've seen it a dozen different times while helping my buddies at their transmission shops.

There is nothing wrong with the 727 or converter. Its just that since I converted my Charger to a 5 speed, I enjoy manual transmissions a LOT more.

Ok, got it.