Transmission Crossmember compatability?

[corgus]

Anyone have any information on compatible trans crossmembers for my truck? I've been searching for ages, it seems like, haven't found much at all. Is there an aftermarket option available?

1985 GMC K1500 w/700R4 and (I think?) NP208
1/2 ton;single cab; long wheelbase, if that matters.

I've got a lead on a couple possibilities, but they're for 3/4 ton. Would that work on a 1/2?

[Jason S]

There are a few differences through the years.  What style do you have?

You should be able to swap around parts from the different style of NP208 crossmember.  You may have to drill new frame holes.  In a salvage yard,  81-87(91) Chevrolet/GMC 1/2 & 3/4 ton pickups, Blazer/Jimmy and Suburbans. 

There are others with more experience on the 80's trucks that should also chime in.

If all else fails, you might try eBay. I just typed "85 Chevrolet NP208 crossmember" into eBay and there's a couple listed...

[corgus]

Well, mine does have the double hump crossmember on it, would that mean I have an NP205 maybe?

edit:
like the lower crossframe in the picture

[Jason S]

Well, mine does have the double hump crossmember on it, would that mean I have an NP205 maybe?

edit:
like the lower crossframe in the picture

The NP205 is cast iron, the NP208 is aluminum.  If you're looking to replace the W crossmember with single piece mount, I 'think' the '85-up Blazer, Suburban and pickups had those style.  The '84-back had the flat crossmember with the 4-piece mount...

I would wait for someone else to confirm this... I could be way off on this one...

Also, forgot to say welcome to the site!

[Engineer]

Yes, '85 is when they went to the W crossmember. You will need an 85 or newer transmission/transfer case mount to match.

If using the older trans crossmember you will need an 84 and older mount to match your set up.

[blazing816]

Yeah I have an 86 that had the "W" crossmember and had figured out the TH350 was from a pre-84 truck and had to switch out crossmember and drill new holes in frame rails for it.

Here's my story that took me awhile to figure out, because PO did not know anything:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=26887.msg225189#msg225189

[corgus]

anyone know where to find a double humper?

[fitz]

Where do you live? If your in Mass I will give you one.
If not I would go to the junkyard or look on craigslist for someone parting out a truck.
 Any 85-87 pick up or 85-91 blazer/suburban with a 700R4/208 (technically 4L60/241 in 89-91)will work.
Whats wrong with your crossmember?

[roundhouse]

We just swapped a 1977 Sm465 4 speed / 205 combo for a 1985 NV3500 5 speed /208

The cross members are different
We just used the one that came with the 1985 208

Had to redrill some of the holes where the member bolts to the frame
Easy to do

And I think the 3/4 and 1 ton crossmembers are the same

The 1 ton uses a taller adapter mount that's sandwiched between the trans and tcase since the 1 ton frame is taller

Is yours missing?