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December 2010 Techline

Steering Component
Willie Worthy | Writer
Posted December 1, 2010

Reading a 14-bolt axle, Super Duty steering wander and more

Wants Turbo 475 for SM465 Swap
Q I have a tough manual transmission in my Jeep, an SM465, and an NP205 transfer case. I want to replace the manual with an automatic TH475 from an '81 Chevy Van C60. Is there an adapter on the market to match them? If so, could you tell me what manufacturer (Advance Adapters, JB Conversions, or Novak) could have it (serial number, etc., so I can order a kit)?

Is the TH475 similar to the TH400 automatic? (I mean length, bolt pattern, etc.). I know the 475 is for towing and usually found in GM heavy duty '80 trucks. Does the TH-400 to NP 205 adapter work for the TH-475?
Jorge Beecher
Neuqun, Patagonia

A Yep, the TH475 is very similar to the TH400. It's kind of the heavy-duty version, with more clutches, straight-cut gears in the planetary unit, perhaps a slightly lower First gear, and a few other changes. They also have one of the nice heavy-duty aluminum bottom bellhousing covers with built-in brace bosses that connect to the sides of the engine for more trans support, just like some of the 4x4 versions have.

I spoke with Advance Adapters tech guy Steve about this, and he said that their standard TH400 adapter will work just fine. They sell quite a few to guys using the Cummins BT4 engine/TH475 combination out of delivery trucks in 4x4 conversions.

I don't think that it is necessary for you to go to the extra effort to locate one of these transmissions, but if you have access to one, go for it. Only Advance Adapters ( offers this adapter, and the part number is 51-3202.

Drivetrain Swap Tips for Wrangler YJ
Q m looking into a complete drivetrain upgrade for my '94 Wrangler. I have an '84 Blazer donor truck. The small-block 350 is an easy answer. However, the NP208 transfer case and GM 10-bolt 8.25-inch differentials are another matter. Is it worth buying gears, lockers, and disc brake kits for these axles? As well as spring pads, etc.? How strong are they really?

Should I scrap the '84 Blazer and find a Dana 44 or 14-bolt rearend instead? I already have installed a Skyjacker 6-inch monolinear suspension lift, rear disc brakes and a transfer-case output shaft shortening kit.
Cliff Roundtree
Raeford, NC

A Well, let's start with the small-block first. Generally speaking, engine swaps are not emissions-legal unless the engine is from the same model year or later than the vehicle it's going in. Being in the military, you may end up being stationed in a state with emission checks, and you may not be able to license the Jeep.

I don't think that you're really gaining anything by going to the GM parts other than a lot of work. The track will be considerably wider, with the tires hanging way out of the fenders. (Some states really frown on this.) You will also have to buy new wheels, as the GM axles use a six bolt pattern. With all the work you have done to your Jeep at the present time, why make the axle swap? The present Dana 30 frontend and (hopefully) Dana 44 rear can handle 33-inch tires with no problem under reasonable use, and 35s with an axleshaft change. I think that you would be money and time ahead if you keep your present drivetrain and upgraded it with better axleshafts, true locking differentials and such.

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