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np203 crossmember

guz71

guz71

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I bought my 89 with a th350/203 in it. I had a 700r4 swapped in with the 203 behind(used the 2 inch spacer/adapter). since then I have had the seal on the 2 inch spacer replaced 3 times because of leaking. This new transmission shop is saying that I am missing a crossmember so the transfercase is wanting to pull away due to its weight. I have the factory 203 crossmember that goes directly under the tcase but they are saying there is another one I need. I just wanted to see if anyone had a picture they could show me of how there 203/tranny is supported etc.? any input would be great...thanx
 
na the shaft wasnt cut unless someone did with out telling me. They wanted to swap in the 2 inch shorter output shaft from advanced but I decided to run the 2 inch spacer because I saw where a few people had driveshaft/trans pan clearence issues.
 
The 2inch spacer will work fine, I havent had any issues with mine anyways. The downfall to it is that with the short wheel base of a K5 and the girth of a 203 it makes for a pretty steep driveshaft angle. I dont think mine is all that bad really, I havent had any issues with it either and I regulary run down the highway at 70+. With a suburban I do not think that would be an issue at all.

If your doing a swap, make sure you run a 2nd crossmember or the factory one that runs from the transfercase to the tranny. The single crossmember that bolts on to the trans/tcase adaptor isnt enough to keep the 203 from jumping around in 4wd.
 
From the factory on the trucks that used the 203 they only had one crossmember that was bolted to the t-case adapter. Some trucks had a second crossmember mounted behind the first one but that was only to mount the factory skid plate and it did not mount to any portion of the tranny or t-case.
 
when i had a 700r4 in my blazer i put in the advance adaptors output shaft so get away from the any spacer. i didnt have any leaks.
 
So I'm confoosed!
My TH350-203 has a 1" adapter.

My 700R4-208 has a 3 1/4" adapter. Advance wants me ta buy a $$$ output shaft to install the Full Time 203 transfer case on a 700.

What adapter do I need, and do I really need the Advance output shaft if the 700 has a 27 spline output shaft ta match the 203's 27spline input?

The 1st 4 pix are the 203, then the 700-208, then the TH350-203

12 15 07 Transfer Case Inches 002.jpg

12 15 07 Transfer Case Inches 003.jpg

12 15 07 Transfer Case Inches 006.jpg

12 15 07 Transfer Case Inches 007.jpg

12 15 07 Transfer Case Inches 012.jpg
 
In order to install a 203 behind a 700R4 you either need the AA short shaft with the TH350/203 adapter or use the 1 7/8" spacer along with the TH350/203 adapter.
 
Why all the fuss with using an NP203? Why not use an NP241 in the truck?

The later year NP203 crossmembers were actually very complex, the crossmember was like an L shape on the end of the frame on the passenger side, there was a small little angle bracket for the driver side and then there was a mount from the side of the case to the frame on the passenger side.

That case is an anchor and I would look to dump it.
 
I did all this for a doubler, I just used the stock 208/241 adapter that came with the 700r4 tranny and redrilled a pattern into the face of the np203 to match, then tapped it and cleaned out the range box full of metal pieces. Plugged the factory holes that were not being used and bolted it in there.
 
I have seen the factory peice that runs from the rear passenger side of the transfercase and mounts to something further up.Maybe it was not standard but I have seen them before and the tranny shop that rebuilt my tranny even showed some pictures.

Either way, I would run two because with just the one crossmember under the adaptor, the tcase moved enough to stripp out the bolts that go into the trans in 4lo. I forgot to add that, you still have to use the th305/203 adaptor and the 1-7/8" spacer to run it the 203 behind a 700r4.

I think the short shaft is good for a doubler but with just a stock 203, there can be driveshaft clearences with the pan, so I have heard anyways.
 
uglytruk said:
Now more TH350 thin adapter and more 203...
Click to expand...

this is the mounti have in my blazer, when i out the 700 in i used the AA shaft in the trans. i dont nknow if any other adaptor could be used or not, but my issue was driveline length. going from a t350 to a 700 shortened the driveshaft enough, and at the time i had a 6 inch lift so i didnt want to have too severe of an angle on the u jiont at the t case.
 
What's a 241?
I've already paid $450 ta rebuild the 203. I want a center diff for dry pavement use, then I'm ALWAYS in 4wd. Good for plowing and hitting snowdrifts at speed on the interstate. Ug


yunit said:
Why all the fuss with using an NP203? Why not use an NP241 in the truck?

The later year NP203 crossmembers were actually very complex, the crossmember was like an L shape on the end of the frame on the passenger side, there was a small little angle bracket for the driver side and then there was a mount from the side of the case to the frame on the passenger side.

That case is an anchor and I would look to dump it.
Click to expand...
 
wow this thread is going all over the place, back to topic: I have read that when using that 2" spacer u need to grind a little off the transmission output shaft.
 
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