Author Topic: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT  (Read 7198 times)

Offline jfkelley

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NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« on: March 29, 2019, 06:08:13 PM »
I purchased an 1976 Chevrolet K10 4X4, 350/TH350/NP203 transfer case, The transmission is smoked ...It has No Reverse and drive in every gear...Purchased a rebuilt TH350 Transmission ...My question is when replacing the transmission should I pull Tranny & Transfer case all together, switch tranny's out and put back in as one unit   ?...Thanks in advance
1976 Chevrolet Scottsdale 4x4 ,K10 33” BF Goodrich All-Terrain .. in the middle of an LS swap LM7/4l60e/NP241C

Offline Captain Swampy

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #1 on: March 29, 2019, 07:25:35 PM »
I would do them separately the 203 is heavy. They can be balanced on a jack, but it isn't easy. Make sure you flush the lines and the cooler or you will contaminate the new one. Flushing the torque converter isn't acceptable and voids most warranties. There are too many places for dirt to be caught and work loose later. You need a rebuilt or new torque converter.
1987  350TBI 700R4  4X4  4.56 gears  33" BFG All Terrain


http://forum.73-87chevytrucks.com/smforum/index.php?topic=32209.0

Offline Rapid Roy

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #2 on: March 29, 2019, 08:00:42 PM »
Welcome
1974 Cheyenne 10 LWB STOCK 350 W HEI /TH350/AC/4 BBL Quadrajet
Mopar by Birth
Chevy by Choice

Offline Irish_Alley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #3 on: April 01, 2019, 10:30:06 AM »
x2 what capt said. take them out in two pieces makes the unit lighter
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Offline JohnnyPopper

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #4 on: April 01, 2019, 12:57:46 PM »
Welcome from SoCal!

Did you make sure your NP203 is not in neutral?

Also, is your replacement for a K-type 4X4 and not a standard TH350?

The Longer output shaft will not be your friend...
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline jfkelley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #5 on: April 01, 2019, 06:46:06 PM »
On the Side of the Transmission Casing it does say K , came out of an 85 Blazer ..Is that bad ?
1976 Chevrolet Scottsdale 4x4 ,K10 33” BF Goodrich All-Terrain .. in the middle of an LS swap LM7/4l60e/NP241C

Offline Irish_Alley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #6 on: April 01, 2019, 07:16:15 PM »
k just a little thicker trans casing for the 4x4s. youre all good
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline jfkelley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #7 on: April 01, 2019, 07:29:34 PM »
Thank Goodness ! You skeered me! Lol
1976 Chevrolet Scottsdale 4x4 ,K10 33” BF Goodrich All-Terrain .. in the middle of an LS swap LM7/4l60e/NP241C

Offline jfkelley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #8 on: April 01, 2019, 09:35:11 PM »
Thanks to everyone that has chimed in ...Just to be clear the TH350 K transmission I purchased will fit with no modifications ...Correct?
« Last Edit: April 01, 2019, 09:49:33 PM by jfkelley »
1976 Chevrolet Scottsdale 4x4 ,K10 33” BF Goodrich All-Terrain .. in the middle of an LS swap LM7/4l60e/NP241C

Offline Irish_Alley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #9 on: April 01, 2019, 10:29:20 PM »
yes, the two trans should swap with no issues. as long as theyre both 4x4 its pretty straight forward. its when you get into 2wds or going from ones style of trans to another that you might run into some problems
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline jfkelley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #10 on: April 03, 2019, 05:18:02 PM »
Irish Alley I have manual locking hubs on my truck ..With the NP203 being full time ..What Position should my transfer case in for city driving and Highway “Hi? ” ..This is where I show my newbie colors ..Thanks !
« Last Edit: April 03, 2019, 05:38:20 PM by jfkelley »
1976 Chevrolet Scottsdale 4x4 ,K10 33” BF Goodrich All-Terrain .. in the middle of an LS swap LM7/4l60e/NP241C

Offline Irish_Alley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #11 on: April 03, 2019, 08:10:12 PM »
if you have manual hubs and theyre unlocked you shouldnt be able to drive the 203 just in "HI'. you should only be to drive it in "hi Loc" with the hubs unlocked. which isnt too bad but if the hubs are unlocked and you can drive it in "hi" then you have a part time kit installed 
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline JohnnyPopper

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #12 on: April 07, 2019, 10:44:42 AM »
Hey man, sorry for the late reply, was gone all last week

It sounds like you got the answer to the THD question.

I have the same drivetrain, and it was full time 4WD until I installed a "Miles Marker 501" part time kit. It removes the internal differential so you can switch between 2/4 WD.

The difference is incredible! It separates the front drive shaft and axle. The hub locks separate the front wheels from the front axle.

You lose the 'loc' feature. It changes from shifting pattern, front to back,  4/Low - 2/Low - 2/Hi - 4/Hi.

You may already have one installed because there's no reason for locking hubs if you don't. Driving in 4 Loc doesn't make sense since your entire drive train is engaged except the fronti tires.

Worth looking into if you're already this far down the road!

1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline jfkelley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #13 on: April 09, 2019, 11:50:48 AM »
I had to have the shop install transmission between work and my two boys baseball season I have no time ..The shop called said with the K transmission I have to get the driveshaft lengthen 4 inches ..I was under the impression they would interchange ..? You guys have any input
1976 Chevrolet Scottsdale 4x4 ,K10 33” BF Goodrich All-Terrain .. in the middle of an LS swap LM7/4l60e/NP241C

Offline Irish_Alley

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Re: NEED ADVICE -1976 K10 / TH350 TRANSMISSION REPLACEMENT
« Reply #14 on: April 09, 2019, 12:05:18 PM »
the yokes/t-cases will interchange but the th350 is about 2" shorter. unless its a different adapter/t-case. but they should have to shorten your shaft, which is easier (you could almost do it yourself with a cutoff wheel and welder) and cheaper sorry didnt think about this detail as being redundant as the 700r4 is pretty much the th350 but is longer due to the OD. the shop isnt lying but i would look for a driveshaft from a scrapyard or the donor the 700 came from.
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes