SM420 is shot

[odog]

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.

[snj8198]

Obviously not with all the different fruit you have there. 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.

[odog]

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.

[snj8198]

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.

[odog]

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

[rcbildr]

Originally Posted by snj8198

this 221 is 10 spline.

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.

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?

[snj8198]

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.

[rcbildr]

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.

[odog]

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 side. Its been a long day, I will tackle this some more tommorrow.

Thanks Guys.
Erik

[snj8198]

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

[odog]

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.

[snj8198]

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?

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.

[odog]

Well I am adding to the fuit bowl. 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.

[odog]

Just an update. The guys at novak over in Logan Utah were a great help, they have new and used 420 parts, and machine everything in house. I have a mainshaft for a sm420 on its way, should be here tommorrow or Wednsday at the latest. Also have a collar for the adapter between the 420 and 221. Eric at Novak is including a blown up view of the trans so I can kinda see what I am doing when replacing this shaft. Lets hope this goes together easily.

[odog]

Allright, I got the output shaft and collar today. Got snowed out at work yesterday so I prepped the trans and we got rained out today so I took it all apart and put it all back together. Went pretty smooth. Only hang up was that on the rear of the shaft there is agroove for a snap ring that keeps the shaft from having to much endplay. On the new shaft there was no groove, I talked to the guys at Novak and asked if I could machine one in, they said sure if I have a lathe, and if I failed at the machining to send it back and they would send me another, no charge. SO the boss and I machined a groove, worked pretty slick too. Now that the trans is a ll buttoned up and ready, I will be putting it in the truck. Looks like we get a break in the weather tommorrow, so I have abunch of work to do, but on saturday I am hoping to get it in. All in all putting in a new output shaft wasnt too big of a deal. Everything was pretty straight forward, just put the things on in the same order you took them off in and you will be fine.

[amoscl]

Originally Posted by odog

Just an update. The guys at novak over in Logan Utah were a great help, they have new and used 420 parts, and machine everything in house. I have a mainshaft for a sm420 on its way, should be here tommorrow or Wednsday at the latest. Also have a collar for the adapter between the 420 and 221. Eric at Novak is including a blown up view of the trans so I can kinda see what I am doing when replacing this shaft. Lets hope this goes together easily.

Did you get both the mainshaft and the collar from Novak? I decided to pull out my sm420 and the rear output shaft is toast.

Thanks

Amos

[snj8198]

Good to hear it's coming together after all.

[odog]

I GOT IT TOGETHER!!! Went in yesterday and put trans and tcase on truck, then today got drive lines and everything on. It is driveable again. Thank you to everybody who helped and gave me advice on this little endeavor.

Erik

[snj8198]

Nope, wont believe it till we catch a beer and go for a drive

[odog]

THAT would be a good shake down run. I was relieved when I fired the truck up and backed out of the shop. No grinding, no hard shifting, just backed out, put it in 1st and drove down the road. Even made my girls happy when I came driving the old truck home. They had to ride along yesterday when I had my wife tow me to the shop.

Only thing is I wish I would have taken pics of everything, O well.