Author Topic: 4speed to TH350 swap in 76 4x4  (Read 7437 times)

Offline 1976 4x4

  • Newbie
  • Posts: 10
4speed to TH350 swap in 76 4x4
« on: October 21, 2003, 11:55:00 AM »
Ive been reading all kinds of different information this morning on this subject. So what i want/need are some straight answers.  I know of all the other parts i'll need as far as shifter, cooling lines, different radiator etc etc. What I need to know is: are there any special parts or adaptors I'll need? The truck currently has the granny geared 4spd and I believe a 205 T-case.  The TH350 is mated to a T-case that is chain driven, but thats all i know about it. If the T-cases are the same is there anything special i need? Thanks. Im sorta knew to all this stuff and will very much appreciate any and all help i can get.

Thx!!!!


Offline aprice

  • Registered Users
  • *
  • Posts: 185
re
« Reply #1 on: October 21, 2003, 11:37:00 PM »
first check your radiator to see if there arent plugs in it where the tranny lines should be. other wise consider getting a tranny cooler instead of a whole new radiator. you will need a new flywheel and the torque converter. also you'll need to remove the bearing in the cam shaft. (cant remember the name of it) but fill it with grease and push like a socket extention in to it to push it out from shaft  


Offline 73K20

  • Registered Users
  • *
  • Posts: 228
Re: re
« Reply #2 on: October 22, 2003, 08:48:00 AM »
About 3 weeks ago i swapped from a TH350 w/ NP205 to a 465 w/ NP205.  

First thing to consider is that the chain driven transfer case is probably a NP203 which is longer than a NP205.  In my swap since i was using the same t-case the drive shaft lengths were the same so I didn't need new ones made.  Because the NP203 is longer you will need the rear shaft shortened and the front one lengthened.  Also the crossmember that supports the tranny and t-case will not mount up in the same location so you will need to drill new holes into the frame to bolt it up.  

Second, if the t-case you are swapping to is indeed a NP203 you will want to get the part-time conversion kit for it so that the front driveshaft isn't turning all the time, you already have part-time hubs in the front so you might as well take advantage of them.  

Third, you will of course have to swap to an automatic tranny steering column and if you're that far you might as well swap the pedals as well for auto ones.  The backup light switch on an auto is located at the base of the column near the firewall and should plug into the wire that currently exits through the firewall and goes to the SM465.  

Fourth, I wouldn't bother switching radiators for one that has a tranny cooler built in.  These don't cool overly well in heavy use condtions and swapping radiators is more expensive than buying an external cooler. Here is the one i recommend from Summit Racing.  A year ago I disconnected my tranny from the stock radiator cooler and installed this one in front of the radiator.  I use my truck to plow with in the winter and this cooler worked excellently to keep the tranny in good condition.

1973 K20 - 350/465(as of 10-04-03)/205


Offline 1976 4x4

  • Newbie
  • Posts: 10
Re: re
« Reply #3 on: October 22, 2003, 01:32:00 PM »
Thanks for the replys--- 73K20,  what if i was to use the T-case I have now.  I beleive it is a 205. If i did that I wouldnt have to worry about all the changing/swapping/shortening/lengthening etc etc.  If I can just drop the 4spd and reinsert the 350 That would be awesome.  you did the opposite of what im doin, was that the case??? Drop and swap???


Offline 73K20

  • Registered Users
  • *
  • Posts: 228
Re: re
« Reply #4 on: October 22, 2003, 03:12:00 PM »
That would work fine...........Except that the SM465 uses a 10 spline output and the TH350 uses a 27 spline output.  The 205 you currently have is a 10 spline input to match up with the SM465.  To put a 205 behind the TH350 you need to find one that has a 27 spline input.

1973 K20 - 350/465(as of 10-04-03)/205


Offline 1976 4x4

  • Newbie
  • Posts: 10
Re: re
« Reply #5 on: October 22, 2003, 03:20:00 PM »
73K20,  would u take a look at this link and let me know what u think.  this guys seems to have done the same thing I want to do but he mentions a Transmission adaptor and power sleeve. If I have to sheel out an exytra $250 then forget it.

your version /  method seems so much easier.  Thanks again for ALL the advice.

www.geocities.com/spencer...s_swap.htm


Offline 73K20

  • Registered Users
  • *
  • Posts: 228
Swap Info..........
« Reply #6 on: October 23, 2003, 08:47:00 AM »
I think that you are getting confused here.
 
First, when i swapped from an auto to a manual, I not only swapped transmissions but transfer case as well.  There is no way to simply put a TH350 in place of the SM465.  The transfer cases are identical EXCEPT for the input shaft which is a 10 spline to match the SM465 and a 27 spline to mate with the TH350.  To make your current NP205 work with the TH350 you would need to swap the input to a 27 spline shaft.

Second, the adapter between a SM465 and TH350 is not the same.  The bolt pattern that mounts the the transfer case is the same but is not the same on the tranmission.  The SM465 uses a figure 8 bolt pattern with 8 bolts while the TH350 uses four bolts in a square pattern.

The adapter on the left attaches to a TH350 while the one on the right goes with a SM465.  If your concerned about the cost of the TH350 adapter, it is only that expensive because he bought it from the dealer.  If you are interested in keeping a NP205 transfer case the best thing to do is hit junkyards in your area and get one with a 27 spline input and adapter.Here is the adapter and coupler you need on ebay.  There is a day left on the bidding.

Swapping out the input shaft is not that difficult in the t-case but is time consuming and going to cost a little in a new gasket kit (about 18 dollars).  Then that leaves finding a new input gear for the t-case with 27 splines, which at worst case can be obttained from the dealer.

What you have to consider is that using the NP203 that you have will require new driveshafts.  If you get them from a junkyard they will not be very expensive, but getting two custom made will set you back 300-400 dollars which could be better used getting the parts (or whole t-case for that matter) to make your NP205 work with the TH350.  

dang that was long, I hope that I didn't confuse you even more.  When swapping drivetrains it is never an inexpensive task.

1973 K20 - 350/465(as of 10-04-03)/205


Offline 1976 4x4

  • Newbie
  • Posts: 10
Re: Swap Info..........
« Reply #7 on: October 23, 2003, 09:45:00 PM »
OK,  well I do REALLY appreciate everything you have done / explained. As for now I think I'll just keep what I got. I crawled underneath it this morning to see if i could determine what T-case I had for sure and couldnt tell. SO  Im sticking with what I got. For now.....Thx again


Offline 73K20

  • Registered Users
  • *
  • Posts: 228
Re: Swap Info..........
« Reply #8 on: October 24, 2003, 08:48:00 AM »
Here is the easiest way to tell if you have a NP205 or not:

First there is a round cover on the rear with 3 bolts in it.


Second, on the front of the case there is an identification plate that states the model, low range gear ratio, serial number, and assembly number.  The circled box gives the model number.

1973 K20 - 350/465(as of 10-04-03)/205

Edited by: 73K20 at: 10/24/03 8:01 am

Offline Blazin

  • Blazin new trails!
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6130
Swap
« Reply #9 on: October 30, 2003, 06:19:00 AM »
Mabey you could find a parts truck? with all the right parts. Sounds like this is a preference swap. You can still drive what you have right?  

Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline 1976 4x4

  • Newbie
  • Posts: 10
Re: Swap
« Reply #10 on: October 30, 2003, 04:35:00 PM »
yeah,  theres absolutely nothing wrong with the stuff i got now.  It would just be easier for me to have an automtaic.  and so that when the snow is 3 feet deep my wife can get to work, b/c she cant drive a stick.  Ill just have to see what's out there.


Offline Blazin

  • Blazin new trails!
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6130
Stick
« Reply #11 on: October 31, 2003, 06:13:00 AM »
Or teach her to drive a stick! I think every one should know how. I taught my stepdaughter when she was 12. Since then her mother let her drive her car know she dosn't want to drive my ugly truck, but at least she knows how. She starts driver ed next month.

Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline rck20

  • New Users
  • Posts: 2
trans swap
« Reply #12 on: January 24, 2004, 11:37:00 AM »
i have a 76 k20 with a th350 np203 wolud love to swap the whole shooting match for good sm 465 np 205