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January 26th, 2008, 11:00 AM
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 |  Unanswered: NP203 to TH350? Hi all, I'm sort of new to the 4x4 world so take it easy on me, I have a 73 Chevy pickup long bed, that used to be a two wheel drive,three on the tree. I bolted in a 86 chevy blazer front end lifted it and changed the three on the tree to a TH350. I know why did I go through so much work for that?, because I could not find a 73 Chevy long bed 4x4, so I had to make my own.(btw) a few months after all that work was done a long bed 4x4 was for sale down the street!!!!!!!.....He wanted to much anyway!!!?#$@! So my question is I want to bolt up the NP203 transfer case that I have. What are some things I should know or do before? What size tail shaft is right to bolt it up too? Thanks  | |||||||||||
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January 26th, 2008, 11:18 AM
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| Moderator
 Name: Colorado Crew Joined: August 2006 Location: High Desert Plains
Posts: 2,792 (#5) Tech Points: 6 | I guess the first question to ask is if the TH350 you bolted in came off a 4x4 or a 2-wheel drive. There's a difference in output shaft length. If it's a 4x4 trans the next concern would be spline count. Did the tranny originally have an NP-203 behind it or an NP-205? TH350 mated to an NP203 should have 27 spline output shaft if I remember correctly. If your output shaft is the correct length with the correct spline count it should bolt up. You'll have to remove the crossmember support (currently bolted to your NP203) and attach it to the transmission first, there's a large O-ring needed on the transmission side and a full size paper gasket o the t-case side. Other than that you'll need to get the correct length driveshaft s for front and rear. If I missed something someone else correct me. | |||||||||||
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| The Following 2 Users Say Thank You to James For This Useful Post: | cbbr    (January 26th, 2008), VegasBruce (January 26th, 2008) |
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January 26th, 2008, 11:21 AM
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| The tranny came out of a two wheel drive car. It has the short tail shaft. I have the front drive shaft out of the 86 blazer, the only other thing is I will have to fab up a crossmember to hold the transfer case in the truck, unless I can find one somewhere. | |||||||||||
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January 26th, 2008, 11:29 AM
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Name: Colorado Crew Joined: August 2006 Location: High Desert Plains
Posts: 2,792 (#5) Tech Points: 6 | If you look for a Chevy crossmember there are two styles. One is flat across and the other is stepped. You'll want the flat one. How are salvage yard pickings in your area? There's always Craigslist. | |||||||||||
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January 26th, 2008, 11:38 AM
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| Pickins are slim around here, but I can always Fab up somthing, just takes time.....One more thing that comes to mind is differential size. The front came out of a 86 blazer, I have no idea what gears are in there. I need to make the 10bolt in the rear a posi, so I need to match the gears in the front.  | |||||||||||
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January 26th, 2008, 11:52 AM
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Name: Colorado Crew Joined: August 2006 Location: High Desert Plains
Posts: 2,792 (#5) Tech Points: 6 | It sounds like you have a good idea of what to expect.  By the way welcome to 4x4 Mecca, I'm sure some of the others will chime in over the next couple days. Enjoy your stay here and stop by the Introduction area if you get a chance. | |||||||||||
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January 26th, 2008, 04:24 PM
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 | Welcome Aboard! Cool truck.
__________________ 1990 Chevy Suburban Specs There are many ways to lose your life that don't involve dying... Blue Ribbon Coalition - working hard to keep public lands open. And remember, no one ever laid on their deathbed wishing they had spent more time at the office. | |||||||||||
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| The Following User Says Thank You to cbbr For This Useful Post: | Bigblue (January 26th, 2008) |
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January 26th, 2008, 11:13 PM
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| Moderator
 | Welcome  Nice truck.
__________________ 1974 Chevy K5 fulltop Specs  Bruce  When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. Henry Ford (1863 - 1947) Nice! I love primered trucks. Looks agressive like that... almost like the back alley thug. 4x4 Mecca http://www.tbucketeers.com/ | |||||||||||
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January 27th, 2008, 03:10 AM
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 | Welcome. Good job on the SAS. Here is a Link that tells you one way to figure out what ratio you have. Depending on what size tire you plan to run it may be good enough but more than likely not. If you plan on running a 35 in tire you are going to want somewhere in the 3.73 to 4.56 range depending on type of use. If it is more surface street and highway a 3.73 or 4.10 will probably work if its more off road then i would go with 4.56. The best thing to do is figure out what the ratio is currently and then figure out what you need to get the RPMs in the speed range that you will spend most of your time. If you are like me and daily drive as well as wheel it then its going to be a comprimise. I have 90 suburban with 4.10s in it and i would like 4.56s but i drive it 40 miles a day on the freeway and the revs would be way to high.Oh and by the way we really like pictures.
__________________ 1990 / 1986 Chevy V2500 Suburban / K 2500 truck Specs to err is human.... To blame someone else shows good management skills. | |||||||||||
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February 2nd, 2008, 07:38 PM
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 | with the small 27 spline shaft in your 203 you will need a short 4x4 output in you th350. the short shaft you are mentioning in your post is a 6inch car/van shaft , the 4x4 shaft sticks out of the trans 1in.
__________________ old guys rule ! | |||||||||||
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February 4th, 2008, 07:21 AM
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| Thanks Darryl, I have decided to go with a NP205 and a rebuilt TH350 from a 4x4. I will post pics when I get them. | |||||||||||
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