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Swap help: All TH350/205 combos alike???

78-K5

78-K5

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Murrieta, Ca
First of all let me introduce myself as I'm new.

Just bought a 78 K5 with 18k on GM 350 crate motor, rebult TH350 and the 203 (with 30yr old part time kit) needs work.

Both driveshafts need to be rebuilt so I was intending to just get new ones. Then I noticed I'm getting a rather loud, metallic "clunk" when I shift back and forth between "R" and "D." The outputs on the tcase spin about a 1/4 turn.

Took it to a local reputable tcase shop and am told it's more than likely the needle bearing set that came with the part time kit more than likely desintigrated, allowing play and a gap between the splines inside. Additionally, I was told they need to drop it, open it up and if it's the set of bearings in the front half of the case, then I got quoted $900+ to fix.

Rather than have this thing opened up onlyto find out I may be spending a ton, I decided I should find a 205 and do the swap as I plan on keeping this truck for a long time. I also figure I can drive my truck around and feel more comfortable opening up a 205 than a 203 based on my internet research.

I have a few questions for you experts:

I found a TH350/ 205 combo for sale locally for $300.00. Will this t-case fit MY TH350?

Also seller says it has no yoke in the rear output (so just a hole in the housing where it should be), should I be concerned about this?

Lastly, when I go check it out, i've read there's a panel or plate I can unscrew to look inside at the gears... where is this located so I can check some of the internals?

I've searched andsearched and so far know I'm gonna need new drive shafts. Other than the T-case and the mounting "shaft," this should be all I need right??

Sorry for the lengthy post but I don't want to be one of those that gives limited info. Thanks for the help.
 
$900 is way too much to pay. I swapped a 205 into my 76 to replace my 203. Yes you need new driveshafts. Yes the the 205 you're looking at will fit your tranny. Your crossmember will work. $300 is a good price, the 350/205 adapters aren't easy to come by. Would not be real concerned about the rear yoke missing. You can get parts from ORD or HAD to fix that. Also you can get a rebuild kit from ORD.
 
78-K5 said:
Nice! I love this site. Anyone else have input?
Click to expand...

Yes the hole in the housing means you have a slip yoke 205, which is very common.
And yes the $300 is a good price for the combo.
I sold a couple of sets for $300 just the 205 plus adapter. and I have one more that I will not let go for less than $300.
 
imiceman44 said:
Yes the hole in the housing means you have a slip yoke 205, which is very common.
And yes the $300 is a good price for the combo.
I sold a couple of sets for $300 just the 205 plus adapter. and I have one more that I will not let go for less than $300.
Click to expand...


So when I go check this thing out, is there a simple way to unbolt something to get a peek at the internals? I heard there's a plate, or cover I could remove with a few bolts.

My only concern is could water have gotten into where the slip yoke goes iinto and damaged the internals??
 
78-K5 said:
So when I go check this thing out, is there a simple way to unbolt something to get a peek at the internals? I heard there's a plate, or cover I could remove with a few bolts.

My only concern is could water have gotten into where the slip yoke goes iinto and damaged the internals??
Click to expand...

Well there is the PTO cover 6 bolts and you can see inside.
 
BE SURE and check the foot on the adapter between the case and trans.I have saw more than one that has been broke and rewelded and while not too big of a deal if done correctly it would be a bargaining point.Also check to make sure the shifter bolt is not broke off on the adapter.
 
Check the adapter for cracks, it is common that they crack and break when abused. You will need the splined sleeve in the adapter, sometimes they are missing on the newer ones. If it is from 1980-81 it will probably have a long aluminum slip yoke on the back that can be swapped over to the better fixed yoke style. I have good used parts for these if you need something.

Take a 9/16" wrench to take the pto cover off to look inside.
 
FYI the same Spicer yokes are used on 205s and 203s, so if it's missing a yoke, just steal it off your 203.

The 203 is retardedly simple to rebuild too, don't let that intimidate you. I would not blame you for moving to a 205 though, even if just for the sake of not lifting that heavy damn 203 more than you have to haha.
 
Yes... the "adapter." The guy at the t-case shop told me to make sure it had that. The t-case and tranny are still mated. Where do I check for the splined adapter to make sure it's still there?

The guy at the shop told me that if it doens't have the adapter then it's not worth it because they're difficult to find. Is this true?

9/16" wrench... check. Now where is the PTO cover? The circular plate facing the rear of the truck, next to the rear output shaft I'm guessing?

My fear is spending $ on this thing to find out I can't use it!
 
The PTO cover is on the driver side of the case. It is sheetmetal and about 4"x6" with 6 bolts holding it on, it can be seen in the right side/middle of this picture. The drive sleeve is removeable on the newer adapters and is also in this picture (bottom/middle), it will have 27 internal spines on both ends and it is smooth on the outside.

131_9809_03_o+131_9809_an_np205_in_your_future+fine_spline_205_gear_and_sleeve.jpg
 
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GreenieK30 said:
The PTO cover is on the DRIVER side of the case. It is sheetmetal and about 4"x6" with 6 bolts holding it on, it can be seen in the right side/middle of this picture. The drive sleeve is removeable on the newer adapters and is also in this picture (bottom/middle), it will have 27 internal spines on both ends and it is smooth on the outside.
Click to expand...

There, fixed it for you. :D

To the original poster, make sure you also get the shifter as it is not the same as a 203 shifter.
 
78-K5 said:
Yes... the "adapter." The guy at the t-case shop told me to make sure it had that. The t-case and tranny are still mated. Where do I check for the splined adapter to make sure it's still there?

The guy at the shop told me that if it doens't have the adapter then it's not worth it because they're difficult to find. Is this true?

9/16" wrench... check. Now where is the PTO cover? The circular plate facing the rear of the truck, next to the rear output shaft I'm guessing?

My fear is spending $ on this thing to find out I can't use it!
Click to expand...

In order to check for the sleeve you'll have to split the trans and case it goes inside the adapter and joins the two splined shafts.The pto door is on the ds of the case and will have 6 bolts holdin it on and look like this.
IMG_1979.jpg
 
Awesome thanks everyone. That PTO cover is in a pretty obvious location. I'd be blind not to see it!

Now if this thing doesn't have the adapter, can I find it somewhere else besides a junkyard?? Also... anyone have a photo of what this thing looks like/ where it is?
 
You can find them on ebay. But, the best bet would be to become a paying member here and you can use the classifieds. We've got a pretty good little group of people. Lots of guys have extra parts and you don't have to worry about getting screwed over.
 
78-K5 said:
Awesome thanks everyone. That PTO cover is in a pretty obvious location. I'd be blind not to see it!

Now if this thing doesn't have the adapter, can I find it somewhere else besides a junkyard?? Also... anyone have a photo of what this thing looks like/ where it is?
Click to expand...

If it doesn't have the adapter, don't bother buying anything.
For the same price I will sell you my setup complete and in good shape.
But if you say it's all together then it does have the adapter and the sleeve, I am sure.
 
I'm definitely going to become a member as I'm just getting started on this project.

The seller told me the tranny and tcase have never been apart s sounds like I'll be okay there.

I appreciate all the feedback! I'm definately not new to auto enthusiast forums and this one is the most helpful with a bunch of useful tech info! I'll be asking a lot more questions when I can't find the answers on my own.
 
78-K5 said:
I'm definitely going to become a member as I'm just getting started on this project.

The seller told me the tranny and tcase have never been apart s sounds like I'll be okay there.

I appreciate all the feedback! I'm definately not new to auto enthusiast forums and this one is the most helpful with a bunch of useful tech info! I'll be asking a lot more questions when I can't find the answers on my own.
Click to expand...

You're welcome.
ANd there are a bunch of guys in your area, specifically in Murieta I know of at least one guy.
 
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