73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: jfkelley on March 29, 2019, 06:08:13 PM
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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
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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.
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Welcome
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x2 what capt said. take them out in two pieces makes the unit lighter
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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...
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On the Side of the Transmission Casing it does say K , came out of an 85 Blazer ..Is that bad ?
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k just a little thicker trans casing for the 4x4s. youre all good
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Thank Goodness ! You skeered me! Lol
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Thanks to everyone that has chimed in ...Just to be clear the TH350 K transmission I purchased will fit with no modifications ...Correct?
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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
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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 !
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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
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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!
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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
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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.
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I will go and look for a donor Drive Shaft ..When I’m looking for one should I look for an 700r4 Drive Shaft or TH350 ..Sorry for the questions I’m new to this but you Guys teaching me so much as I go along ..TIA !
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700r4 but same bed length as yours. only the 208 came behind them. so if you find a 1982+ 4x4 1500 it should be the one youre looking for
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IRISH ..Shop said needs to be 4” shorter ..I’m going to try and do this myself like you said in the last post
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Really confusing!
Your original post said you were replacing a THD 350 with the same...
Where did the 700r enter the picture? :o
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I did replace the 1976 TH350 with an 85 K5 Chevy Blazer TH350 4x4 Transmission it has an K on the casing for I assume HD ..I’m a newbie so I assumed it would be a drop in with no drive shaft mods
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Really confusing!
Your original post said you were replacing a THD 350 with the same...
Where did the 700r enter the picture? :o
Thought we sent him on the wrong road lol. Glad you picked up on that I was feeling bad for missing the post about the 700r4 lol
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So I’m good ? ..I can take the 4” inches out of the rear drive shaft myself and weld it back together correct ? Anyone have steps in shortening a drive shaft ?
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now when i say you could do it yourself its not something thats going to be real easy. you have to carefully cut the weld on the yoke where its welded to the driveshaft but you cant go too deep as theres a tapered end on the yoke that goes on the inside of the driveshaft.
(https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSXwrXT0YRXLxN8AvfDBvGSeJ1OvEypESFhxj_t3DXoy8Agt85e)
(https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSpkkJ22BUFfjIHHyZcxxTsWqay_1lrYF4GUZaqIBLxQvwyqj9gkw)
now i would cut the side thats farthest away from the weight on the driveshaft itself. the 4" you cut off wont bee too much to effect the balance of the shaft but the less you cut off the better.
then comes to welding it. if i have to walk you through that im going to say not to weld it and take it somewhere or find a donor
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Can anyone weigh in on whether there is a difference between a 76 and 85 TH350 K model?
Did you remove the NP 203?
If not, why are you not having to adjust the front Drive Shaft?
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think hes working on a new truck or a different setup
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I replaced the original TH350 transmission in my 76 K10 , with an 85 TH350 K Series Transmission ..Sorry If I confused anyone
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where does the 700r4 come into play?
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Irish I have no idea where the mention of 700r came from ? ..Guess I'm gonna have to go back and look over my previous post
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The saga began in a galaxy far, far away...
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.
;)
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yeah i think i goofed lol. think i mixed up a few post BUT if youre only working on the th350 you shouldnt need a new driveshaft.
as they say on the streets "my bad"
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The shop that’s installing my transmission said the 1985 TH350 K Series was longer than my previous transmission..?
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So they had to move the NP 203 toward the rear of the truck, and that would have made the Front Drive Shaft shorter, yes?
Can someone weigh in on whether there is a difference in a 1976 K type TH350 and one from 1985 please?
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theres no difference, the only difference in the lengths is when youre dealing with a 2d trans.
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That's what I though Irish!
Is JFKelly being scammed by some imposter?
The world is so full of them today... :-\
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I’m starting to wonder if this shop knows what they are talking about ..I had the rear driveshaft shorten ..So if it’s wrong looks like I will Be buying a new driveshaft @ $300 + more
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did they move your transfer case back?
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I haven’t heard from the shop in a couple days ..I will follow up with them on Saturday
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did they shorten the shaft or you?
im terribly sorry about throwing in the 700r4 into the mix and im guessing between you mentioning they have to lengthen the shaft which is wrong as the th350 only uses one case between all 4x4 and 4x2 applications and only changes the tailshaft for the 2wd. they should of never needed to touch the shaft if you google th350 length you will see theres only one
http://forum.73-87chevytrucks.com/smforum/index.php?topic=32506.0
theres the list ive compiled and you will also see theres only one adapter plate the th350-np203 uses.
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So the shop called me and says the sleeve between the transmission and Transfer case is too long?...it wont fit..Why is the 1985 K series Transmission not fitting to my 1976 K series NP203 Transfer Case
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alright so apparently the th350 uses two different outputshafts one for the 203 and 205 and another for the 208. the th350 and 208 were only out for a few years together so its a little more harder to find. im not doing so hot with information for you. you cant cut the longer shaft down due to the splines not covering the whole outputshaft. you might be able to find a spacer but then youll be looking at new driveshafts. i hate to say it but you might want to try and sell that long outputshaft th350 and get your rebuilt or try to find a good donor from the same wheel base as yours that has a 700r4/transfercase and driveshafts.
(https://www.monstertransmission.com/assets/images/content/techinfo/turbo-350-4x4-output-shaft-1-5.jpg)
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Ok so that I understand you correctly the 85 K series will not work with my existing set up ...So I will need to take the Old TH350 that came out and have it rebuilt...? Correct
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yes the K one will not work with your t-case and driveshafts. you could get the np208/adapter that came off it and front driveshaft and just have the rear driveshaft shortened. or just get your old one rebuilt, which in the long run might be better because you dont know how much life is left the the "K" trans
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Thanks Irish ☘️ For all your help ..The K Transmission was just rebuilt ..I may put it up for sale and have the old one rebuilt ..What if I get the Quick Adapter GM 700R 4WD to replace the GM TH350 adapter ? Will that work
https://www.advanceadapters.com/products/50-8505-adapter-to-replace-gm-th350-with-gm-700r4/
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that adapter is to make the 700r4 work with your adapter/transfercase
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Any idea to find an adapter to make that transmission work with my Transfer case ? The mechanic says he puts on the Transfer case adapter from the previous transmission the shafts not long enough ..What if I take that Adapter and have it Milled Down to where I need it to make it work ?
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Any idea to find an adapter to make that transmission work with my Transfer case ? The mechanic says he puts on the Transfer case adapter from the previous transmission the shafts not long enough ..What if I take that Adapter and have it Milled Down to where I need it to make it work ?
Any idea to find an adapter to make that transmission work with my Transfer case ? The mechanic says he puts on the Transfer case adapter from the previous transmission the shafts not long enough ..What if I take that Adapter and have it Milled Down to where I need it to make it work ?
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im kind of in unknown territory right now so i cant really say what will work or not. so the mechanic put the old adapter on and the outputshaft is too short?. doesnt make sense.
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First, your shop is incompetent, look for someone else if you can find them. Don't pay them a dime, they are liars!
Second, the problem you're having is the output shaft is not the right length. Don't spend anymore energy on it.
Get your original rebuilt and sell the other.
Done and done!
"the world is full of imposters" T. Khoury.
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First, your shop is incompetent, look for someone else if you can find them. Don't pay them a dime, they are liars!
Second, the problem you're having is the output shaft is not the right length. Don't spend anymore energy on it.
Get your original rebuilt and sell the other.
Done and done!
"the world is full of imposters" T. Khoury.
I was starting to wonder if they knew what they were doing after the 1st week ...They already have the Transmission installed and I paid 1//2 down ...I feel so embarrassed because i thought it would be a easy replacement
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im with johnny, either rebuild your old th350 OR replace it with a 700r4 (for the OD)
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Well, you can make lemonade from lemons...
If I were in your shoes I would try this:
(And this is on the assumption that you are dealing with a transmission rebuild outfit)
Gut your original TH350, and transplant the good parts of your replacement transmission into your original housing.
You will need to use the original output shaft, as that matches your transfer case.
If they are not a transmission outfit, have them take out the transmission and find a shop that can do the work I listed above.
Mr. Kelly, in either case, you have the wrong transmission in your truck at the moment. These guys should have spotted it right away.
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10-30w or SAE30 Non-Detergent for the 203