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th-350 trans case swap ? w/ pic

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mudrunner78

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ok heres the question a while back I had my th-350 rebuilt, the case cracked, while I had less than 50 miles on the rebuild, so I went to a local tranny shop and had them look it over. the internal parts were of course in great shape. So I had them swap case's and well they swapped my K code case for the thinner case. Now for the question I just bought a th-350 np-205 setup. I would like to swap the case's again but this tranny is different theres a plug in this case and a different input shaft can I still use this case.
http://coloradok5.com/gallery/album90/aab
 
that is a 350-c case out of a 81-82 .the plug is for lock-up t-converter.the front input shaft should also look different unless some one swaped in regular 350 parts .
 
its a different shaft I know, but its not a C case, its a K case I see the big k plus it uses the thick 6 bolt cover not the thin little tin cover.
 
i think you should be just fine. i converted a 2wd truck case with a big L on it to 4wd by just swappin the output shaft. just swap all you internals over to the case you want to use. what i want to know is what is so great about these K cases. i see that the casting is thicker where the inspection cover goes but is it thicker anywhere else? and what good does it do to have that case thicker at the inspection cover? i guess you get a stronger inspection cover. but is the case any stronger where it bolts to the engine or anywhere else that would be relevent? from the trannies i've pulled i've seen no diffence in thickness around the bellhouseing which, to me, would be better. someone correct me if i'm off line with this or knows the real deal with the big bad K case.
 
Stay away from the G series case, I just broke one. With it broken apart it was easy to see just how thin it was and how even the smallest structural defect could promote breakage under heavy load. I was in a similar boat getting a thin case from a trans builder and wanting to transplant the internals. Ended up making an Ultra Bell modification, but it was a lot of work.
 
well from what I know(not much) is that with the thicker case around the inspection cover, you then use the two supporting rods to the motor mounts. this gives you a better supported driveline. I can tell the difference in the thickness also between the two different case's bellhousings. Jesse
 
just asking are you saying I have a G series case? I don't know if I could afford or would need the stregth of an ultra bell case. Jesse
 
Yep I would have to agree, it sure looks like a TH350-c. Now I wonder if instead of that guy asuming he knows every thing from the responce he gave to your post if he would like to know that yes it still has a K series case. The K designates its a TH350 for a 4x4 truck. The "c" designates it as a lock up converter just like you said but isn't cast into the side of the case like the K is in the designation. Yes C's have appeard on the sides but were not talking about that are we? Nahhhh
The clutches are the same but the pump, converter and valve body are different. You might be able to run a nonlock up pump in that housing. I know you can run a lock up pump in a non lock up case because I'm running it that way. For what you would have to pay somebody to swap the guts you could buy the parts to rebuild that tranny yourself. B&M sells a kit to make the lock up work in a truck that was not originaly equiped with it. Then sell the TH350 he has to cover the cost of parts.
 
so what we are saying is this is the thinner cast case.If I posted wrong then by all means I will applogize. I have three th-350's in my garage right now, one with a big C on it. I know this is fron a 2WD C-10. and two K case's. I was just wondering if the swap could be done. I would like to rebuild the other K case. Is there alot of specialty tools required to rebuild a th-350. And any recommend rebuild kits. Thanks Jesse
 
Hell I don't know if the way I post is offending anybody but I am not acting like I know anything. I f I knew everything I sure wouldn't need to ask so many questions. I can see how I write things down might be mis-understood. I would just like to clarify that I am not second guessing anyone. Jesse
 
I'm not sure what you have, but I mistook my G series case for a C series for a long time. Be sure of what you have before making and decisions. Treat your tranny like the bottom end of your engine and spare no expense, it will be worth it in the long run. I would hope you don't need to go the Ultra Bell route, there are a lot of variables to overcome durring installation.
 
I have the TH350 with the lockup converter plug, but it's not connected. but I have an 80, so what tranny should I have?
 
In response to the case thickness and thick inspection cover, I don't think there are any significant thickness differences in the cases. The reason for the thicker inspection cover is to add support and structural rigidity to the bellhousing. With the thick cover installed the bellhousing acts like a single body around the converter thereby making it stronger. The same principle holds true for the thick aluminum pans, all these things work together to make the overall assembly much stronger than the standard duty cases with the flimsy tin covers and pans.

Also, as previously stated, the 2 torque bars that tie the cover to the motor mounts help to the assembly to act as one stronger unit.
 
As for specialty tools to rebuild, the only extras I needed were 2 large C-clamps and the spring compressor for the low-reverse piston. The compressor cost like $30. And a good manual, I used the Haynes GM auto trans overhaul manual. Hope that helps.
 
No. we are saying it's a TH350 with lock up converter known as the TH350-c in parts books.
The K on the side of the case does mean it's the strong housing. That case came out of a 80-82 truck. ALL the 4x4 trucks with the TH350 got the K cases from about 76ish up. ALL TH350-c's out of a 4x4 have the heavy duty K cases. The light duty cases were only available as a 2wd but yes they can be made into a 4wd by changing the output shaft. That's what you have to be carefull for is some shop doing mix and matching parts like you had happen and put 4x4 outputs into 2wd cases.
The TH350-c is the parts book designation for the lock up torque conveter feature. Other than the plug to control lock up you would not be able to distiguish it from the non lock up converter TH350 with the K series case.
If your ordering a rebuild kit you would need to tell them it's a TH350-c so they will get you the right converter. The rest of the parts that will come will be the same. If you need a replacement for the pump, converter and valve body you would need TH350-c parts not TH350 parts. This is the predocessor to the 700R4.
 
I am confused about case's but I will take your advice in the tranny department, unless I find a 700R4 soon i will be rebuilding my own tranny. thanks for the help jesse
 
you have helped alot, again I guess I came across bad, but I was just going off what I have been told the simple C case is a case with a C cast on it, and K is the other model, well again GM has proven to confuse the heck out of me. Oh well, thats the way it goes with me, now I have a TH-350 out of a 78 blazer should I use this case instead for the rebuild. I belive I should be able to do it, It seems that theres not a whole lot of speciality tools required. Any suggestions on rebuild manuals other than the Haynes. I figure a large clean work space and I should be ok. I just don't want to rebuild it and mess it up and end up wasting money. Thanks again Jesse
 
Well depends on what you want. The "c" version with the lock up converter came about to try to ge some economy out of them and loose the Auto typical loss of 250-500 rpm at hwy speeds. It will give you better cruising but still not OD like a 700. As for ease of Rebuilding...TH350 doesn't get any easier. If you can build and engine you can Rebuild a TH350. As for special tools. what you need is a tool for compressing the clutch pack springs. You can home brew one with a harmonic ballancer puller and three 3/8's x 1.5 inch bolts and a couple big flat washers and a peice of 2 inch by 6 inch long 1/4 plate. Then you can make the puller into a compressor. The other thing you may need is if it's a fairly freash tranny the pumps tend to be difficult to yank free. The O-Ring holds it in pretty good.
Do a search for Delta Automotive. They are a tranny parts supply house. They deal mostly with shops but they will take parts orders. Total parts to rebuild a TH350 including a rebuilt converter, book and a cooler flush kit is in the $125 range if it's not got any major problems. Little more for a lock up converter. I have looked at what's different as far as rebuilding a C and regular 350 and it's not much. Where the expense will come in is if you have bad pumps or a blown forward sprag. Then your into hard parts. I picked up good used pump, forward sprag and forward drive drum used from the local small shop for $50. Also plan to heli coil the pump retaining bolts and the 4 bolt holes for the output.
Have plenty of bench space. When you dissassemble the tranny you want to lay it in a line the way if comes out to keep it all in order. Other than the first gear clutch located in the very end of thetranny the rest of the work will all be done on loose parts till you put them in the case. Really not a bad job if you stay organized and pay attention to who it comes appart. I'll tell you this much.... I will NEVER pay anybody to rebuild a TH350 after doing one. It's easy enough to do. Takes about a day taking your time. A shop can rebuild one in a couple of hours.
 
just what I needed, I think, heck I know I am going to rebuild my own, I will use the non-lockup model. I don't drive on the highway much. I wanted OD but don't want to have to try and find a 700r4, and rebuild it. I belive your homemade compressor will work great I am trying to picture in my head so I can make my own. Thanks for the great info Jesse
 
<a target="_blank" href=http://community.webshots.com/album/33075803dViTNh>http://community.webshots.com/album/33075803dViTNh</a>
some 350c info
 
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