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NP203 Slip?

BizeeB65

BizeeB65

1/2 ton status
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Oct 12, 2005
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Louisville, KY
Ok, here's the setup. '73 K5 350/TH350/NP203. Just had the tranny rebuilt. Was slipping real bad in 3rd on the highway or at speeds 55 and over, for a length of time. Never slipped at lo speeds or in "lo range". The tranny fluid smelled like a local brush fire (very burnt), so I had the tranny rebuilt. Never looked at the T-Case, but prolly should have.

After getting it back from the shop, it still slips on the highway in 3rd gear, but I am suspecting the t-case because it also slams both driveshafts when you put it in gear, and wont turn front/rear shafts equally in lo-loc.

Does this sound like the T-case is bad? Or do I still have a tranny problem? I cant image in the tranny is bad after rebuild... I cant afford a doubler or a NP205 swap. I also like having full-time 4WD. And how much would u guys pay for a used NP203 that is "said" to be good, from '78?
 
Can you drive in 3d gear on a dirt road with the T-case in "loc"? The only "slip" you should ever have with a 203 is if the chain that drives the front driveshaft is slipping. I would expect that to make a significant amount of noise though.

One thought... Have you had this truck long? Is there any chance that the axle ratios aren't matched in both axles? Full time 4WD acts pretty strange if the gear ratios in the axles aren't matched.
 
thats almost what it feels like, like if the front hubs were unlocked trying to drive it. This truck has been a PITA since I got it. But I have gone thru so much that I dont wanna give up now.

I dont think the gears are different front and rear. I've had the truck for 8mo's. It did fine for a while until the tranny started to go. Thats why I did the rebuild, cause it would 'slip' in third down the highway, but not go back in once I let off the gas. Now it slips, but seems to 'catch' once i get off the gas. should I take it back to the shop and have them check the tranny? Any way to check a 203 inside the truck? (checking chain length from one of the access panel?)
 
There is nothing in the 203 to 'slip'. If the chain has stretched, it will jump teeth on it's sprocket. When theat happens, youl be hearing "bang......bang" as you drive it under a load. There aren't any clutches in the 203 to slip, so I'd say it's your tranny. Did you check the fluid, are you topped off? Take it back to the shop, have them take it for a ride until the 'slipping' happens, then make them fix it.

I don't know if the transmission kickdown cable has anything to do with it, but you might want to make sure it's adjusted properly. If you have a shop manual, there are good directions for doing this in there. If you don't have a shop manual, go get one.
 
yeah, if its only in 3rd, I'd suspect the tranny. If something was ****ed with the t-case, it'd happen no matter what gear the trans was in.

As far as 203 prices... a used one oughta be 100 bones or less. Try your local craigslist. The 203 is pretty much the least wanted tcase there is... especially the 27-spline input one.

j
 
Sounds good guys... Thanks for the help. I checked the tranny fluid level, and it was low, but topped it off and it still slipped on the highway. That was yesterday. Guess it's back to the shop monday to complain. I guess in a perfect world things would work right the first time.... Updates to come later.
 
Ok back to the top with this.

Seems that my transmission is fine. I drove the truck with the front wheel hubs unlocked and the T-Case in Hi Loc. ( Yes im sure it doesnt have a part time kit, and yes I know thats bad for the drivetrain, but it was for testing purposes.) Drove it about 10 miles on the highway with no slipping.

Came back, locked the front hubs, put er in Hi (no lock this time), and drove it again the same distance, and sure enough she slipped 4-5 times during the commute.

I am going to go ahead and say that my t-case has to be shot. It wont even loc in low range anymore. The shop that did my transmission has a t-case out of a 79 that he'll sell me for $200 and install for $195. I dont have the space, tools, or manpower to muscle a NP203 in and out. Think this price is fair? (I have checked out that t-case, and it seems the shifter is bad, but the rest is clean, no leaks, chain doesnt seem stretched.)

????
 
Yes the 203 can slip with no bad noises. I just went thru this with mine. A tranny shop here said in the tailend of a 203 it is almost like a rearend and it is baked. So I am switching to the 205. But a 203 is usually really cheap, I know I can get two for $100 canadian here right now.
 
i wouldn't pay $200 to install a t-case. Rent a trans jack (I just went ahead and paid $70 for a HF one) and install it yourself. All it takes is that jack and a couple of wrenches.

j
 
Ya the more I dwell on it the more I want to swap a 205 in. I would do the doubler, but if this goes beyond $400 I am a dead man. I dont really feel like dealing with a new driveline though. So perhaps a weekend and a trans jack is my answer. I've read most of the threads on changing out a T-case. You think I'll have any problems getting it down with 6" of lift on the truck?
 
BizeeB65 said:
You think I'll have any problems getting it down with 6" of lift on the truck?
Click to expand...

with the HF tranny jack I got mine out by myself... on gravel. You shouldn't have a problem, especially if you have access to a real driveway.

As far as the 203 goes, if you need any repair parts for yours, lemme know, I'd give them to you free, just pay for shipping. Like a lot of people, I took mine apart for a doubler... now I have the back half of a 203 sitting around collecting dust. ;)

j
 
jekbrown said:
with the HF tranny jack I got mine out by myself... on gravel. You shouldn't have a problem, especially if you have access to a real driveway.

As far as the 203 goes, if you need any repair parts for yours, lemme know, I'd give them to you free, just pay for shipping. Like a lot of people, I took mine apart for a doubler... now I have the back half of a 203 sitting around collecting dust. ;)

j
Click to expand...
Well I am considering going the doubler route... What was your total cost for that, if you dont mind me asking?? How would you rate the difficulty? I know there are writeups on it, and I have read em, but none really give an estimate total cost. Thanks man!
 
I have a guy right now trying to swing a deal on a complete donor vehicle with a 205 in it. Dont know about the doubler route yet cause of cost and the fact that I just moved into a house, which drained the budget for a few months. :( If the donor vehicle falls through, then I am planning of a rebuild of the 203 with a milemarker part time shaft kit. I'll update soon .
 
Sounds like a good choice. A couple of years ago I found a nice looking 205 behind a 350 in a blazer at a local junkyard. They wanted $450 for the case, adapter, crossmembers and both driveshafts.

I have a spare TH350 with a good 203, just like I have in the truck. Due to the fact that I could swap anything in relatively cheaply, I'm staying this way until its time for a doubler.
 
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