Driveline compatability issues

[hgs_notes]

I am working on a first gen Jimmy without most of the driveline. Just has axles, thats it. I've been searching for transfer cases/tranny combos and I'm getting confused with the options available.

For instance, the NP205 that came in these trucks was also available several years later on other vehicles, including Fords and Dodges. Do they work with the right adapter, or are they set up different, like front output on wrong side, different spline count, etc?

There are figure 8 and round bolt pattern NP205's, whats the difference and will either one work?

I have read that there is a kit available to convert an NP203 to part time, anyone know where they are available? Is it even worth the trouble? Frankly, I don't really understand the full time/part time thing. Can't the full time transfercase be shifted to 2 high? I have lock out hubs, wouldn't that take it out of 4wd?

What is a divorced transfer case and would that work?

If I get a 73 and newer tranny, transfer case (NP203) and adapter, it will bolt right in, I think. But what will happen with the driveshafts? Would I need the original 72 version, the 73+ version, or some custom built driveshafts?

What are the differences in driveshafts between the first and second generation of blazers, other than length anyway? Is it something to do with slip yokes? Which vehicles have slip yokes and do I want them?

I don't have drive shafts now, but I don't want to get the wrong parts and end up spending more to make them work, than if I had just found the "correct" pieces to begin with.

The problem with getting parts, is that the first thing the junk yards do is pull the driveline out, so finding it all together is difficult. And the simple fact of the matter is that 2nd gen parts are just way easier to find and much cheaper.

I know this is a lot of questions, and not everybody has all the answers, but I need what ever help I can get.

[1969k10stepside]

Here is some info.I dont know about the driveshafts...

A ford t-case wont work with solid axle chevy axles (FORD has drivers side differential).There was 205s in some 73-87s.Most were behind 4spds though.And most (I believe) had slip yokes.Let's talk NP203s...all 4 tires receive power at all times. This was made possible through use of a differential in the back of the 203 that let the front and rear driveshafts turn at different speeds as just as a diff in an axle lets each axleshaft turn at a different speed. For off road use, the 203 had a "lock" position in which the differential was locked making the front and rear outputs spin at the same speed. Shift positions are: High, Lo, High Lock, Low Lock and Neutral.Like an open carrier,truck (jimmy) wont move if either driveshaft is removed.

Oh,if you need some parts,I will keep on the look out next week at the junkyard.Shipping on some stuff wouldnt be cheap though.Could probably get you a motor crossmembers,driveshafts,tranny hump,and a t-case if you would dare to pay shipping.

[LONGHAIR]

Frankly, I don't really understand the full time/part time thing. Can't the full time transfercase be shifted to 2 high? I have lock out hubs, wouldn't that take it out of 4wd?

In a word..........No.
The 203 is a "full time" case that has a chain driven front output. The "full time" part works essentially like an open differential. It puts power to the driveshaft with the least traction....so if you remove either one, the truck will not move. If you shift it into "LOC" this effectively locks the differential action and the truck moves, but you are then making the entire case "work" for nothing. This is a lot of extra drag. With the conversion kit, all of the chain and other internal workings are stopped until the thing is shifted into 4 wheel drive.

[CrashEd]

The divorced transfer case is separated form the trany by a short shaft. When there bolted together there called married. The divorced transfer case wouldn't work in your blazer it would make the rear drive shaft to short and to much of a angal.
The old trany transfer cases had the figure 8 adapters the newer ones are the round adapters which will work fine if you get the set witch would be trany adapter and case.
The TH400 took a 32 spline 205 case.
The Th350 took a 27 spline 205 case.
The sm465 took a 10 spline 205 case.
These are the figure 8 pattern up to like the 80s models
The new ones run the round adapters i know the newer sm465s took the 32 spline case along with the TH 400 trans not sure on the TH350.
I would stay away from the 203 transfer cases if you want a newer unit get the 208 case with matching trans.
If you get the older say TH350,adapter and 205 case then you should be able to find a set of shafts for that set up just measure the distance from yoke to yoke on the front and rear then you can use that distance to search the right shafts out just make sure you have the slip joint in the middle of its slide to measure it.
Hope my rambling helps.
Ed

[hgs_notes]

Excellent, this clears up a lot. NP203...bad (no 2 high). NP208...ok, but get the adapter with it for the correct tranny. NP205...best bet, but make sure it has the correct adapter.

I guess I just have a couple more questions then. Does anyone know or have a site bookmarked, that shows what vehicles came with a TH350 or TH400 and NP205 combo? I think all of the GM 1/2 tons and K5s came with the NP203 until 1980, then some NP205's were used again for a year or so, then they went with the NP208. But what about the 3/4 tons? Is there a difference in the output shafts between the 1/2 and 3/4 ton transfer cases where I would need the yokes or shafts with it?

Weren't the 208 cases aluminum? Anyone know if that has been a problem for breaking under moderate off road use?

CV joints, are these replacable on the front drive shaft or do you replace the whole drive shaft? How do you test the condition of a CV joint if you find one in the junk yard?

Thanks again,
Mike

[LONGHAIR]

Excellent, this clears up a lot. NP203...bad (no 2 high). NP208...ok, but get the adapter with it for the correct tranny. NP205...best bet, but make sure it has the correct adapter.

203 is not necessarily bad because of the 2high, there are conversion kits....most of them are already converted anyway. It is rare to see a fulltime truck anymore.

208 is a slipyoke tranfercase....not necessarily good for a Blazer becasue of the short wheelbase, especially if you intend to lift it.

205 yes best bet, smaller than either of the others and plenty strong.

Yes, CV joints are replacable/rebuildable....but it depends upon how bad it is before you start. If the joint is totally shot it can damage the bearing mount on the end of the welded-on side of the shaft. If this is the case it can be cut off a repaired but it will be cost prohibitive. Look for a better shaft to start with.
AS far as telling if it is bad.....you'll know. It will either be stiff and creaky or floppy and loose.

[hgs_notes]

Originally Posted by LONGHAIR

203 is not necessarily bad because of the 2high, there are conversion kits....most of them are already converted anyway. It is rare to see a fulltime truck anymore.

I found a good article on the 203, but was wondering how to ID a 203 that had already been converted? The kits cost about $250 for the shaft style, about $45 for the gear set style.

[LONGHAIR]

It would be hard to tell from the outside, since the shifter is a seperate external part. If you can get the levers to move, by hand/pliers or something, you may be able to feel the difference.

If it is converted, the input and rear output would be locked together and the front output will spin seperately. Then if you shift the lever it should lock the front to the others.
There are 2 levers on the side of the case. One shifts to lock/unlock the other shifts from high range to low range. The shifers on these units are a bit fussy though. Mud/sand/dirt in the grease will make them very hard to shift. They are very tough, but the internal parts have a lot of sliding surfaces. This causes them to act sticky. It is fairly simple to remove/disassemble and rebuild one though. It makes a world of difference.