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Transfercase Tech |
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Discussion
Board Caribou
Hills 6-03 |
NP-205
The NP-205 is smaller and shorter than the NP-203. It is easy to distinguish by its small round 3 bolt cover over the intermediate shaft. (green arrow) I drilled and tapped the freeze plug holes for 1/16 Pipe plugs. If you look close at the first two pictures you can see some serious corrosion damage to the aluminum covers. That t-case was scrapped for another 205 that was behind an SM-465.
Above you can see the modifications that need to be made to convert your NP-205 to Twin Stick operation. The notch in the middle of the shaft needs to be lengthened and have a gradual slope. The notch on the end needs to be lengthened and have an abrupt slope. I did not include dimensions for these modifications because it is not exact science. I used a 1/4" carbide burr to make the necessary modifications. I also had to make a few adjustments after my first bit of grinding. Don't take too much though, you will be able to get the thing in High and low at the same time!
Here you can see four of the different kinds of 205 input shafts. One the very left is the 27 spline Th-350 version. The next one over is the 32 spline Th-400 version. Then the SM-465 shaft and coupling sleeve. And on the right is the 31 spline Ford input shaft that I used with my Dual T-case setup. If you want to run the BEEF, you will need to buy a new front output shaft for the 205, and bore the case to fit the larger bearing if you have a half ton case. You will also have to order a larger seal housing (cheap) and seal for that shaft. Machine work should be about 1/2 hour for boring the case. If I remember correctly, I did mine in about 35 min.
Compare the stock 1310 End Yoke that came on my 205 to the 1410 that I ordered from High Angle Driveline.
If you want to upgrade a 1/2 ton NP-205 to heavy duty yokes such as 1350 or 1410 you will probably need to get a different front output shaft. This shows the difference between the stock, 1/2 Ton 10 spline 205 front output, and the Ford 1 Ton 32 spline. Also notice the difference between the seal diameters.
Th-400 Np-205 Broken front output 30 Spline. Took out the shifter, broke the transmission and put a large dent in the frame!
NP-203
B.O.P. Th-350 to a NP-203
Rear of 203, notice the lack of a cover over the intermediate gear? That's because there is no intermediate gear, the 203 is a chain drive t-case. The NP-205 will have a 3 bolt cover where the 203 just has a fill plug.
The shaft on the top is the stock 203 shaft that is machined to look like the one on bottom. It is turned down and re-splined to what ever female 205 input you have. I used a 31 Spline Ford. Next time I will use a 32 spline Chevy that was from a 205 behind a TH-400.
This is the back of the 203 range box, and the stock shaft before machining. Notice the anti-rotator tab that is protruding from the front of the aluminum cover. This needs to be machined off prior to installation into the WMS adapter.
Here is a top view of the NP-203 Range Box, the shaft sticking out of the right side is the female input that accepts the TH-350's output shaft.
The picture on the left shows the measurement from the top of the tranny directly in front of the 203 adapter. With a 3" body lift it should just clear. Keep in mind that I don't have a Chevy motor in my truck so I'm not sure where the motor sits in relation to where the OEM motor would have as far as height goes. Front to back has not changed. I didn't have to trim the floor to fit the 203, I trimmed it to fit the shifters, but ended up changing the design when I decided to stick with the bench seat for the summer. I have a leak between the 203 and the tranny, but don't know why. I'm running ATF in both cases and the 203 does not leak out the shifter. No frame clearance issues. Your very likely going to have to re-do your exhaust if you have headers and duals. I had to get block huggers and completely re-route mine. Drive shaft angle will be more of an issue now. As will clearing the side of the transmission pan with your front shaft. I would only use one x-member and just make torque rods and maybe chain the motor down as well.
Transmission and T-case SpecsNP-203 - 195 lbs 2wd Th-400 short housing - 4" from back of 6 bolt flange
to end of housing, .625" shaft stick out NP-205 front output shafts
Courtesy of Petersons 4-Wheel & Off-Road, August 2001, pg 127
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