SM420 is shot
 

Ok a couple of weeks ago, I went to leave work and the truck went bang. Has an SM420 tranny and a t221 tcase. Today I finally got a day off and pulled the tcase out. The output shaft on the tranny has splines that are worn to a knifes edge. The input side of the tcase has NO spline, they are worn off, I assume the final striping was when I heard the bang. So here is my dilema, do I do the NV4500 swap I have been talking about on my NV4500 will it fit thread, or do I find an output shaft for the tranny and an input collar for the tcase. I think the less expensive route may be to rebuild the sm420, but not sure. Any thoughts??? This was my daily driver, firewood hauler, but now its lawn art. Truck is a 1/2 ton 4x4 69 chev with 327'

Re: SM420 is shot
 

Easiest and cheapest route is probably just finding another SM420/T221 or SM465/NP205. I bought my 465/205 combo for a hundred bucks last year.

Re: SM420 is shot
 

I agree, SM465/NP205 would be the most fast and economical way to go from the sounds of things.

Re: SM420 is shot
 

there should be a coupler between tranny abnd acse. i have the same setup and replaced the coupler before it sheared. So, you may just need the tranny shaft. i can get a pic of the coupler.

Re: SM420 is shot
 

67 mater you are right there is a coupler between tranny and tcase, however the splines in the coupler are gone on the tranny side. The output shafts splines on the tranny are sharp, almost nonexistent, and the couplers splines are nonexistent. However on the tcase side of the coupler they are fine. So I need the coupler and the output shaft on the tranny.

Redcap I think I may have found a SM465 bolted to a 396, but not sure what tcase it has. What year were the 465s found in? The truck I found is a late 70's early 80's. The guy said I could have the motor and tranny if I come get it. Everything is supposed to run well. so we shall see

Re: SM420 is shot
 

Hi odog,

The '70's to early 80's sm465's had the np205. The 465 granny gear is not quite as low as your 420 (7.0 v.s. 6.55) but regardless it's tough to beat. If you could get your hands on the assembly for a couple hundred bucks ish it would very take little maintenance before slapping it in. I forget the length difference between your 420/221 and the 465/205 combo. You may want to figure that incase you need to address driveshaft length differences.

-steve

Re: SM420 is shot
 

Thanks Steve,

I looked at the truck last night and it didnt look like a 205 tcase, but Im sure its a 465 tranny, its got the granny low then 1st 2nd 3rd on the shifter. But I am not sure, I need to do more research. I have a fresh 205 sitting in the shop if the one on it now isnt any good (the one on it looks tiny). I am kinda excited about the 396 that comes with the tranny. I probably will take it regardless, its kinda nice having extra stuff laying around. The guy I got my frame from when I built this truck had a 454 with an auto trans and the 205, with the drive lines. When I got the frame, he gave me the tcase and drive lines too, so maybe I will get lucky and have the right drive line.

Re: SM420 is shot
 

the only other tcase behind the 465 was the np208 later in the 80's. I dont remember if the 203's ever got slung behind the 465's in the early '70's but it's possible. You don't want that. I think I heard of the Rockwell 221 behind them too but don't remember. I have a complete 221, keep that in mind. I sold my 465's and used my last good 205.

Re: SM420 is shot
 

I know its not a t221, thats what I had behind the 420. Its a good tcase, strong, but after 44 years of hard use, its finally said uncle. I will look into the tcase on this one, is the 203 chain driven? I dont want that. how about the 208?

Re: SM420 is shot
 

ya that 203 is chain driven and it's a full time unit. You don't want that. The 208 is chain driven and aluminum cased but tends to hold up well unless you are pushing it hard in the back country. really you want the 465/205 as you know they are stout and plentiful.

Re: SM420 is shot
 

Ok when I looked at it, the truck is not full time, it has locking hubs, the tcase is aluminum, but not as big as a 205, so most likely a 208?? Also will a 205 bolt up without an adapter if it is a 465? I am leaning more and more towards this.

Re: SM420 is shot
 

If it's an aluminum case then it's an np208. They started that combo somewhere about 1985ish. You will need an adapter for the 205. It's about 6 inches long, has the boss for your shifter, and has a a figure 8 bolt pattern.

Re: SM420 is shot
 

Didn't they switch to a 32spline output shaft on the sm465 when they started putting the np208 behind it

Re: SM420 is shot
 

http://www.novak-adapt.com/knowledge/sm465.htm

http://www.advanceadapters.com/tech-...l-information/

Re: SM420 is shot
 

I don't remember if they did or not. They definitely used the 32 spline shaft with the 205 starting in late '88, as they also switched to the round bolt pattern. But I don't remember what shaft they used for the 208 when they started that combo a couple years earlier.

Re: SM420 is shot
 

Red cap thank you for the links, that provided some good info. I think I am looking at a 465 with a 208 in which case I will go that route. Now I just need to get another day off to take it out and swap it in.

Re: SM420 is shot
 

I would bet you money you are looking at a 465/NP208 combo. It will get you going, but keep your eyes out for a 465/205 combo to replace it. I don't think very much of the 208 case as I've destroyed a few of them.

Re: SM420 is shot
 

Just an update, I got today off and I finally pulled the sm 465/np208 out of the donor truck today. Didnt go to bad, But I decided I am going to put my 205 on the 465. The 465 has a 32 spline output shaft and my 205 has a 32 spline female end that should fit, I guess now I just need an adapter that has a figure 8 pattern on both ends. Tranny looks in good shape, took the top cover off and everything visible looks good. Curious about the tcase though, it was filled with ATF, is this normal? I seperated the tcase and tranny and the output shaft on the tranny is long, about 8 to 10 inches. I will keep working on it, and updating as I go.

Re: SM420 is shot
 

Alright, Appernetly I am a dumba$$. I got a 465 to 205 adapter, put a new seal in the tcase side, then got busy at work and didnt get any farther. Today I had time so I went and tried to bolt it all together. Well the little short shaft on the tcase side, (calling it a shaft, its about 1 inch long with female splines) is bigger than the seal on the adapter. They dont make seals this size come to find out. So I says to myself both tcase and tranny run on 80-90 so oil mixing should be ok. I try to bolt everything together and the tranny side of the adapter fits great, the output shaft slides right into the little shaft on the tcase, BUT the adapter WILL NOT fit on the tcase. The bolt pattern is the same, the little shaft fits inside the adapter, but I guess its the bearing? that sticks out about 1/4 inch will not fit int he recessed area on the adapter. The recessed area is too small. This explains why there is no seal. Do I have the wrong adapter? Is there more than one adapter for this setup? Im not sure what year tcase this is. I got it off a 72 with a 350 or 400 tranny, but it could be from any year I guess.

I dont need this running tommorrow or anything, but I would like it eventually. I guess I could do another option, but I have questions about that as well. Can I bolt a T221 to an SM465? My 221's power collar is shot and it is only 10 spline. Is there a 32 spline to 10 spline converter/adapter? The tcase is 10 spline and the tranny is 32.

What a pain this is turning into. Anybody have any thoughts.?

Re: SM420 is shot
 

sounds like you have a coupler for the 32 spline 205 that came later but you are needing the 10 spline for the earlier years 205. I gota have another one somewhere here, I'll start looking tomorrow.

oh, went back a reread further back, maybe im wrong. lemmie know what I can do to help.

Re: SM420 is shot
 

Steve, Maybe you are on the right track. Is there an adapter for the 32 spline 205 and 32 spline tranny, and one for the 10 spline tranny and 205. If so maybe I have the 10 spline version. I'm gonna do some research and see what I can find.

Re: SM420 is shot
 

Well the difference between the two versions was the early year adapter was the 8 bolt "racetrack" shape and used the 10 spline female coupler. The later combo had a round pattern 6 bolt pattern and used a 32 spline female coupler. The input shaft on the 32 spline was larger iirc as the case opening was larger making room for the larger input bearing and again the larger diameter shaft. So just as long as you have the right bolt pattern adapter to case and the proper splined coupler you should be in good shape. Snaps some pics if you get a chance. Again I can snoop around as I bet I can find what you need if you indeed need different parts. I know I have an 8 bolt adapter but not sure about any more couplers.

Re: SM420 is shot
 

I will try to get some pics after work tonight.

Re: SM420 is shot
 

If you decide to rebuild the 221 I have 2 spares I can pull parts from. I only have 1 TC outout shaft as I just sent 1 to another member for his rebuild. Just cover shipping and you can have what ever parts you need.

Re: SM420 is shot
 

ok here are some pics of the tranny, tcase and adapter.Attachment 855319

Attachment 855320

Attachment 855323

Attachment 855324

Attachment 855325

The ist pic is of the tranny side of the adapter. The second pic is of the tcase side of the adapter. the 3rd pic is of the tcase with the "short shaft" wih 32 internal splines. The 4th pic is of the output shaft on the tranny, 32 splines. the last pic is of the 465 to 205 adapter with the seal and the adapter that was on the tcase with its seal. Both adapters showing tcase side. Notice how the 465 to 205 adapter is smaller on the tcase side than the other adapter.

Re: SM420 is shot
 

That looks like the short 32 spline input gear. I thought those were only used behind the TH400 when that case still had the 8 bolt pattern. Stout set up but looks like we are searching for the right adapter now. I thought the adapter on the right in your pic was the correct one. Now you got me scratchin my head. Sorry odog but I'm stumped too. Im searching the internet.

Re: SM420 is shot
 

This tcase came off an auto tranny, so probably was a TH400. I took the adapter on the right off the tcase, it has the round bolt pattern. Am I trying to mate an apple to an orange here?:lol: I though about machining a new recess in the adapter to fit the bearing and the seal on the tcase, but by the time I mill it out to accept both seal and bearing, there will be nothing left. My boss and I poured over this after work and there just isnt enough metal in the adapter to do it. I searched and found a few adapters on ebay, but they all are the same as what I have. I looked on advanced adapters and the search I did there just took me to a 465 to 208 adapter. Is it possible to even mate a 32 spline 465 to a 205? or were the combos both 10 spline originally?

Re: SM420 is shot
 

I have 1 last hope. We blasted a basement for a guy a few weeks ago and he had a late 70's early 80's chevy 3/4 ton sitting in the weeds. Motor and tranny are gone, but the tcase is still there with the drive lines. I talked him out of it, cause I wanted the 3/4 ton axles, and kinda forgot about the rest of it, but maybe it will have the right adapter.

Re: SM420 is shot
 

Obviously not with all the different fruit you have there:lol:. I knew I should have kept my complete combo for a time like this. That trans pictured is what you had in the truck? and the left adapter in the pic came from it? If this becomes a big pain for you to swap I could just swing you down the complete Rockwell 221 I have so you can get back to driving your truck.

Re: SM420 is shot
 

I agree, I have a whole pile of mixed fruit here. No the trans I have in the picture came out of a 80's model. The original in mine was a 420, but the output shaft is worn out, the splines are worn to a knifes edge. The left adapter is one that I had bought from a board member that came from a 465/205 combo, but I am thinking it came from a 10 spline combo. Does your 221 have a 32 spline coupler? Mine is a 10 spline deal and it has no splines left on the trans side. If there is a 32 spline to 10 spline coupler, I would use the rockwell. I have no problem with that, I was just looking at the 205 cause I thought it would be easy.

Re: SM420 is shot
 

this 221 is 10 spline.

ok we started down this path...

you have an 80's trans with funky long output shaft, early style 465-205 adapter, and 32 splined early pattern 205 from a th400. Something's not right but im not sure what. I'll keep searching. I dont recognize that output shaft on the trans.

Side not: whatever you do don't lose that transfer case even if you don't use it in this project.

Re: SM420 is shot
 

I agree with you, that transfer case is a good one, and I wont get rid of it. I may get rid of the trans though. I have a message into Novak to pick their collective brains over there, but since they are mainly jeep guys they may not be able to help. I might have a tranny that isnt compatible. I am going to keep researching and see what I can figure out. I appreciate your help.

Thanks

Erik

Re: SM420 is shot
 

I had an SM-465 with an output shaft just like that. IIRC the t-case adapter for my application (sm-465 to np-208) was a huge piece of cast iron...makes those np-205 adapters look small. Somebody correct me if I'm wrong, but didn't the 1 ton trucks 82 and newer get the sm-465 to np-205 combo?

Re: SM420 is shot
 

Ya you're right rcbilder, during the 80's the 1/2 and 3/4 tons used the np208 behind sm465 which used 2 different adapters, a tall, and a short. I don't know why and for what purpose though. The 1 tons had the np205 then in '88-92 they switched to a round 6 bolt pattern.

odog- As rcbilder states, you may have a 465 with output shaft for the np208 tcase but not the right adapter and of course not the tcase. Too many mismatched fruit like we said. Tho I am surprised that wide mouthed adapter on the right in your pic didn't fit the tcase. Tomorrow I'm visiting a friend and I'll dig through our pool drivetrain parts. I'll let you know what I find.

Re: SM420 is shot
 

IIRC the tall or short adapters were dependent on the crossmember. The short was used on the W shaped x-member and the tall was used on the flat one.

Re: SM420 is shot
 

Just checked my email. I sent a message to Novak conversions last night, looking for some options. I got reply from them, and the guy says hes not sure how he'd handle this problem if he was in my shoes. I could go with the later style 205 with the round bolt pattern and use the later style adapter, but that brings in the expense of another tcase. Then he through out the way to go would be to put the 10 spline 4wd shaft into the 465 and run the coupler to the NP205. He said they carry the parts for around $160 ish. Thats not too bad, except I have to tear into the tranny to replace the output shaft. I dont know, maybe I can find a 208.

Oh, the wide mouthed adapter DID fit the tcase, it was on the case when I got it, but it has the round six bolt patter on the other sideAttachment 855913. Its been a long day, I will tackle this some more tommorrow.

Thanks Guys.
Erik

Re: SM420 is shot
 

yeah that adapter is for the later 80's round pattern 205's which are really tuff to come by.

Re: SM420 is shot
 

Ok so the Novak guy said to replace the output shaft on the 465 with a 10 spline affair and then the input gear on the 205 wih a 10 spline. Why not replace the output on the original sm420 that wore out, and avoid all the swapping BS. If the shaft and collar are reasonable to replace that is.

Re: SM420 is shot
 

I totally agree. It would have been nice to trade up but if things are working against you swap the parts.

Yay we can start a new snowball effect! Since your replacing the output shaft you might as well...

...do a frame off resto? :mm:

I'll be digging through the parts shop today regardless. If i run into something that may be of use to ya i'll let you know.

Re: SM420 is shot
 

Well I am adding to the fuit bowl:lol:. We shot a basement for a guy a few weeks ago and he had an old rusted out chevy in the weeds, said I could have it if I hauled it away. Front clip was gone, no motor or tranny, only 3/4 ton axles that I am after, and possibly a tcase. Well today we went and got it. I knocked down all the weeds around it, it's bed sides are gone, but no big deal. I jacked it up an put wheels on it, and sitting in the dirt on the crossmember under this truck is a 10 SPLINE NP205!!!!! Both drive lines are still attached. So I tie the tcase in place, pull the truck on the trailer and head home. The truck is a 76 Scottsdale, Big 3/4 ton rear and big hubbed front end. Assuming the front is a 44 with big hubs, hoping the rear is a 60, but not sure yet, cant wait to tear into it and see what I got.

Now I am waiting to see what price a output shaft on the 420 is going to cost from Novak. I am probably going to rebuild the 420/221 combo, but its cool to have another 205, especially one with a 10 spline input.

Oh and I dont see a frame off resto in my future, my wife would like to see this truck running again before I so anything else to it.