Inliners International Forums General Discussion Drive Train Does anyone here know about transfer cases? Top secret project question.

Anyone? I need one for a top secret FL Mopar based Bonneville project. I need to know about the NP 208 transfer case, and what breaks in'em when you have too much HP. I also need to know about why the cases crack under stress. I need to put 700 HP through one in a very space limited environment, and have it last. Thanks for the info.

-Jeff

The 208 isn't a particularly strong transfer case, although they are available.

The strongest transfer case is the NP-205, which came in GM, Ford-left hand drop, Dodge, IHC, etc., both in attached and divorced positions. They are easy to find with lots of variations.

They are CI, so a bit heavier than the AL ones, but the strength more than makes up for the weight, especially on a Bonneville vehicle.

Some truck guys make their own with a roller chain and pillow blocks-very light. For your application you would need to provide a drip oiler.

Ed Pruss
Longmont, CO

The problem with the NP 205 is that the case is physically to big. It won't fit where I need it to. The weight isn't really an issue. How strong is the gear reduction/rear wheel drive part of the 208, or the full time 203? I'm not overly concerned with the front wheel part of it, just the gear reduction and rear wheel drive for now. Thanks.

-Jeff

The 203 is much larger in length than a 205 because of the low range section and interaxle differential.

The output of both T-cases is straight through. Both are strong. I'm not sure if you want a trasfer case for the 4WD feature, the reduction gear, or ? Do you want an offset driveline?

Ed Pruss
Longmont, CO

Ed,
I'm mainly concerned with the gear reduction. I want about a 2:1 reduction, and the 1.9:1 in the 205 is just about right. It will not be a 4WD car, and I will probably take the chain and front drive gears out, leaving me with just the gear reduction unit it's self.

I looked at the bolt on under/overdrive units, but they're way out of my price range. Used transfer cases are cheap and plentiful.

Where and why do the cases typically crack? Is it because the chain is exerting to much force, pulling the two sides together? If that is the case, I won't need to worry about it, just the strength of the gear reduction. Thanks for the info.

-Jeff

Jeff, 205's use gears only, no chain. If you just want gear reduction, could you use a truck 4 speed with a granny low to get started? The NP-540 5 speed has a granny low, plus a close ratio 4 speed on top, if you need close ratios?

Otherwise, use an NP-241, 271, etc, which has a planetary reduction in line w/ the rear output shaft, whatever you can find, and you could even remove the chain and front output gears, but don't remove the oil pump.

Ed Pruss
Longmont, CO

The problem is that I don't need the rear reduction all the time, only when I'm racing. For normal every day driving, I'd be using the high range. That's why I can't just use a low rear end ratio, or granny geared trans. It'll kill my highway distance driving ability.

-Jeff

Basically, I want to have really high gearing for land speed racing/highway driving, and low gearing for dragstrip racing. The best of both worlds so to speak. A quickchange rear end would be nice, but won't handle the HP in a vehicle as heavy as mine. The Gear Vender Under/overdrives are nice, but way out of my price range, plus I like to be different.

-Jeff

Check out offroad designs web site. They make a adapter to mate the range box off a 203 onto the back of popular transmissions. This would give you your reduction without the rest of the weight of the chain etc. The range box on a 203 is really strong on that note. here is a link.
http://www.offroaddesign.com/catalog/doubler.htm