HELP! Cracked tailousing/adapter SM465, NP208

[yakmastermax]

I pulled my SM465 to replace it with a used one I picked up in a trade. Pulled the top cover and the used one spins smooth and looks good aside from some rusty oil. The old one from the truck has a really hairy magnet which explains the noises it was making in 3rd and 4th so it will not be going back in the truck. Problem is, my original adapter/tail housing is cracked badly. It is in 3 pieces right now. My mechanic friend recommended having it welded but I have a perfectly good tailhousing/adapter on the used transmission I want to swap in however it is the later short mount design that was used on the 1985 and later trucks. What would you guys recommend? I'd prefer not to put the cracked and then re welded tailhousing/adapter back in. If I find a 1985 and later crossmember would it bolt to my frame and work with my drive shaft length? Would everything align okay? Is there any way to modify my current cross member so that newer style tailhousing/adapter fits?


Thanks a lot guys.

 

[yakmastermax]

went to the yard and pulled a cross member from a GMC Jimmy. There was an NP208 in the back and it had the same mount on it as the adapter that is not cracked. I'm going to see if it fits on the K5 frame and then possibly reuse the adapter that came on the used transmission.

 

[yakmastermax]

that crossmember does not fit. out 20 dollars. going to go to a different yard and narrow the search down to full size blazers and pick ups.

 

[6872xtc]

Could you explain why I did not fit? Is it because there are no holes drilled correctly in the frame? I know that drilling holes under the frame is not fun, but could that be easier than looking for a crossmember that fits both sides? (trans and frame) I remember seeing some crossmembers that one side bolts to the lower flange and the other to the side of the rail which is differrent than the '86 truck one I have here. I bolts only to the flanges.

 

[yakmastermax]

The jimmy cross member was a solid 1.5" too short. I could barely get more than half an inch of metal to overlap the frame on each side at the same time, nevertheless the bolt holes.

 

[6872xtc]

Have you found one yet then??? I will see about a measurment off my '90 Jimmy vs. the '86 k10 and see what that shows.

 

[yakmastermax]

nope and i still want one. it seems that the tall adapter is obsolete but that there are some new made short adapters as well as a healthy amount of fleabay short adapters. it is my priority to find a cross member for the short adapter that will fit my K5

 

[6872xtc]

I am very sorry that I did not get back to you sooner. I got my brain tied up with too many things!!!
Both '90 K5's I have here measure 32.75 overall width, which is the same as the '86 K10 and '85 K30 ones I have. The '85 and '86 were both SM465 while the K5's are 700R4's. So I am wondering what happened that you found one too narrow. I know these frames will flex, but that seems like that much would point to a bigger problem if it was in the frame??

 

[yakmastermax]

i think it was too short because i pulled it from a jimmy

right now my mechanic is having my tall adapter welded. we'll see how it holds up

 

[6872xtc]

I hope you get it done and back on the road!! Just to let you know, both of the '90 K5's I have here are Jimmys, same frame as a Blazer.

 

[yakmastermax]

stupid welder fell through, and i called around and no one seems to want the job or is book solid for 3 weeks with other work so it seems like the tall adapter is out the window. i'm going to try to focus on making the short adapter work. i've got two routes so far, make some sort of spacer or adapter so that i can use my stock crossmember with the short adapter, or find a different crossmember. does anyone know if a cross member from an automatic K5 will work?

 

[yakmastermax]

going to make an adapter to my stock trans crossmember, essentially a machined aluminum H block to extend the short adapter to the original rubber. I'll be uploading pics in the next couple days. i'll post dimensions as well for anyone interested.

 

[yakmastermax]

got the adapter in finished and in place. i'll post more pictures tomorrow once the tcase is one. if anyone is interested in the dimensions for the adapter i can email them. total cost for adapter was around 50 dollars but i did my own machine work, however the studs and nuts which were bought are grade 8 (a little over kill) and bought from a speciality bolt company. the aluminum stock was also purchased at a premium.

 

[yakmastermax]

it fits and is working well aside from my exploded rear end.

 

[bww3588]

Looks good, Fwiw, in my 89, I had both bolt patterns in the frame drilled from the factory. The 84 crossmember as well as the stock one fit just fine.

I too had my adapter crack in 3 places. One ear is busted off which I was going to have welded, but after putting it thru the hot tank, I discovered 2 more hairline cracks. So I ended up buying a different one to fit my later w crossmember.