NP203/NP205 Doubler Kit

4-to-1 (4:1) transfer case gearing in an NP205/203 package strong enough for big block power and full size trucks.... Or any other really abusive application you can come up with - Chevy, GM, Dodge, Ford or custom!

The Doubler is an all gear, dual transfer case system uniquely suited to full size trucks or other heavy duty, high output/abusive applications because of the durability of its components (all massive helical gears and large input/output shafts).  Basically, the Doubler consists of the gearbox section from an NP203 transfer case coupled to a complete 205 transfer case.  It's a 3 speed transfer case system, it has options for the 1:1 and 2:1 options that an NP205 would normally have plus a double low range gear of 4:1 with both cases in low range.  

**This is a build-to-order part and does have a lead time. Please email us for an estimated timeframe.**

As low as $925.00
NP203 NP205 Doubler Kit
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Adding lower transfer case gearing gives you huge improvements in off road control and torque without affecting your highway gear ratios. Adding the extra gearbox also allows you to run in your normal 2:1 reduction or in super low 4:1 reduction for best performance in any situation. We use a combination of bulletproof and easy to find factory parts with a minimum number of modified components to give you easy bolt together gearing options. Our baseline kit is just the parts to adapt YOUR 203 to YOUR 205, we can also ship complete 203 and 205 units if you like.

The doubler shaft that couples the NP203 to the NP205 is 100% new and US made from 8620 chromoly heat treated steel.  The Doubler is only available in 31 or 32 spline which eliminates any weak link in the transfer case system.  Very early on we experimented with 10 and 27 spline input gears in the NP205 and they simply didn't hold up. We don't want you to have to buy the kit again when you find the limits of the smaller input gears!

Our doubler adapter is a one piece billet 6061-T6 aluminum adapter housing, we've never had a failure on our doubler adapters.  We supply studs for the front face of the NP205 which makes the t-case easier to install and more secure than a bolted connection. 


Need a range box for your doubler? We have them HERE



Doubler Crossmember Pictures

Here are some pictures of a custom Doubler crossmember built by one of our employees for a GM-GM Doubler with the 2" up rotation. It hangs between 1.5" and 2" below the '83 K5 frame with the 3/16" AR360 skidplate.

This shows the centered mounting on the adapter between the NP203 and TH350. This vehicle uses a TH350 to NP208 adapter with a re-drilled NP203. The single center mount lets the Doubler adapter and the motor mounts control all the torque while the single mount between the 203 and trans helps keep the drivetrain from bouncing and breaking. We HIGHLY recommend a heavy duty poly motor mount set, we keep them in stock!

This is the piece that makes the high clearance setup work. It's shaped just like you see with the entire back plated in to make it stiffer. It uses a urethane mounting puck (available from ORD) on top and bottom of the mounting bracket. The bolts are either tightened into the adapter or running a locknut to allow a preload adjustment on the pucks. This 2 puck arrangement puts a little more "give" in the mounting system and spreads the load over more pucks.



(Click to expand)

NP203 make

NP205 make


NP203 ID guide

NP205 ID guide

Adapting a TH350 to the NP203 range box

Adapting a 700R4 or 4L60E to the NP203 range box

Adapting a TH400 to the NP203 range box

Adapting a 4L80E to the NP203 range box

Adapting the GM SM465 to the NP203 range box

Adapting the GM NV4500 to the NP203 range box

Adapting most Ford transmissions to the NP203 range box

Adapting most Dodge transmissions to the NP203 range box

Icon Label Description Type Size Download
pdf NP203 NP205 Doubler Instructions pdf 1.1 MB Download