t400 to t350

[WyattEarp18]

So I've got a 1979 K20 camper deluxe with a small block 350 and t400 and from what im told is a NP203 transfer case. I have a t350 and transfer case from my 78 K10 Silverado. I would like to swap the trans and transfer case for the t350 combo. I need the t400 combo rebuilt. Is there anything i have to do besides drop the t400 and swap in the t350? The NP203 I have now crapped out on me and is vibrating violently after 35mph and the t400 isnt picking up oil and kicks out of gear regularly. Any help and advice is greatly appreciated.

[MB84C10]

Should be a straight forward swap especially where you have matching tcase and all.. only real diference would prob be the kickdown (throttle valve) cable where the th400 doesn't use one and the th350 does. Are your tcases both np203? Usually the chain breaks or streches or the planatery lock ring blows up in the np203s causing vibrations ect..

[WyattEarp18]

So length shouldn't be an issue? And what would I have to do about the kickdown cable? Where does it go from the trans?

[WyattEarp18]

Also the t350 combo is from a 1/2 ton so will it have smaller ujoints than my 3/4 ton? Im having my buddy check to make sure my t350 transfer case is a NP203. Hopefully it is.

[MB84C10]

th350 and th400 are same overall legnth if they are both running a np203 you should be all set that way.. as far as ujoints they make the conversion ujoints for them any decent parts guy should know the numbers for the adapter joint run into it all the time swapping 3/4 ton 1 ton gear into half tons on mud trucks ect..

[MB84C10]

its like a 1310 to 1350 adapter u joint

[WyattEarp18]

And about how much is that gonna set me back?

[willett]

Those adapter joints aren't cheap, I think mine was about $75 cost. They can be a b*tch to find when you really need one. Your better to swap your yoke. If your going 203 - 203 it shouldn't be a problem trading yokes.


Why are you downgrading to a th350 anyways?

Ed.
Just read your 400 needs a rebuild.

Shouldn't cost more than a grand and its a far more robust trans

[WyattEarp18]

So if I understand that correctly I should be able to swap my current yoke onto the other 203 without a problem. My current trans and t case need to be rebuilt and i cant afford to have it down any longer than it is. I definitely plan on going back to the t400 once its rebuilt and working properly.

[willett]

As far as I know the output spline count should be the same. I'm not 100% though. You'll have a pretty good indication if this is the truth if the nut holding the yoke on is the same size on both cases.

Won't know for sure until it comes apart though. Haha

[WyattEarp18]

Thanks. Still waiting to hear back from my buddy on the other tcase with my other trans. Hopefully theyre the same tcase so I can swap 'em while my 400 is rebuilt. Next adventure is saving up to get some 3.43 diffs. This 4.10 **** is ridiculous. Cant do more than 65 without worrying about blowing the engine. Then on to lift, wheels, and paint then I can bore out my crate 350 and be golden.

[willett]

Run 35's and you will love your 4.10's. these trucks aren't made to win any races.

[wilkin250r]

I agree. If a lift is in your future, then I imagine bigger tires are also in your future, and 4.10 might be exactly where you want to be. I certainly wouldn't go through the hassle/expense of swapping them out, only to swap them back in later. What size tires and gears are you planning on running after your lift?

[andrewmp6]

If its not your daily driver take out the turbo 400 out get it rebuilt and throw it back in the truck.

[WyattEarp18]

I would like to run 37s so I was thinking at least a 6". I didn't know tires would affect the gearing. And I definitely plan on going back to the t400 once its rebuilt and working properly.

[nekkidhillbilly]

for all the money your talking to rebuild y not get a od some sort? just a though be nice with 410s.

[WyattEarp18]

Originally Posted by nekkidhillbilly

for all the money your talking to rebuild y not get a od some sort? just a though be nice with 410s.

Im not sure what you meant here but my plans are for the next year or two. The truck has been in the family since it rolled off the line so I figure I'll hand it down to mykids

[willett]

You know your going to have to trim your fenders to accommodate 37's right?

[WyattEarp18]

With an 8" lift?

[nekkidhillbilly]

Originally Posted by WyattEarp18

Im not sure what you meant here but my plans are for the next year or two. The truck has been in the family since it rolled off the line so I figure I'll hand it down to mykids

i meant if you going to spend a grand to rebuild a th400 why not get a 4l80e and a controller cost would be close.

[WyattEarp18]

I got a quote from a trans shop that'll do it for about 300

[nekkidhillbilly]

dang really...........thats nothing. hell the parts are that much.

[WyattEarp18]

I bought a rebuild kit for $50 and the shop is charging me labor and fluid.

[nekkidhillbilly]

dang son. i bow to you.

[andrewmp6]

300 bucks is about normal if you drop one off.Unless its a daily driver a over drive wouldn't be worth the time and money to swap to me.