frame question third generation

[mats1985gmc]

I have a 1985 gmc 2wd 1/2 ton. I was wanting to buy a frame to prep as I drive my truck. An educated guess tells me that the 4x4 frames are different, right? 73-87 are all third generation trucks. do all those 2wd frames work? or only later 80ish years? thanks for the help.

[slammed79]

The frames between 4x4's and 2wd are mostly the same as far as I know, the differences are the steering boxes are different and the engine crossmember, and of course the front leaf spring mounts.

Are you looking to for a short bed frame or a long bed frame?

[mats1985gmc]

Honest I cant decide. I have a long wheel base now and I like it. If I would have started and had to pick I would have went short. I like to be a little different to, I go back a forth.

[thirsty]

The frames between 4x4's and 2wd are mostly the same as far as I know, the differences are the steering boxes are different and the engine crossmember, and of course the front leaf spring mounts.

This has been coming up alot lately. There are many differences between the two. When the weather breaks here I should bring my project in and document all the stuff.

[KY..Rob]

Yes there are differences in the frames. Decide on what you want to build, 2x4 or 4x4 Short or Long wheel base, and then find the frame you want.

In general, all the 73-87 frames are the same. besides the differences in 2x4 vs 4x4

[mats1985gmc]

I need a long bed 2wd frame for a 1985. how far back can a guy go in years till the frame changes (or do they). I was told the early frames are different.

[Blazin]

Only frame that will bolt up is 73-87, or 91 with Blazers, Burbs, and 1 tons. The front rear spring hangers are taller on a 4x4 as well.

[bake74]

     You can make a 4x4 frame work, but best bet is to find a 73-87 2wd frame, less work and you wont have to drill out the riviots to bolt the 2wd stuff on to the 4x4 frame.

[mats1985gmc]

I dont want to beat a dead horse here but if I am buying a frame I want to make sure it work for what i have. I was told by a guy who seemed to be knowledgeable  that the frame is different from 73-80 and 81-87. He said the mount for bumper and suspension is different. I also want this to be an easy swap not having to drill hole for bracket on an older frame etc. Is there any truth to what this guy is saying?

[thirsty]

The frames are different 73-80 and 81-87. Either will still work. He was also right about the bumper mounting area. I'm not sure about the 2wd suspension. On 4wd frames they changed stuff like e-brake brackets, the way flexible brake lines mount, transfer case crossmembers, ect.
Safest bet is using the same year.

[mats1985gmc]

Thank you very much!

[mats1985gmc]

I have a couple frames I am going to check it out. Any advice with what to look for? tell a tale sign that a guy should look for? any advice would be great. You guys are a lot of help. Thanks again

[slammed79]

Check for cracks near the steering box, and make sure the front crossmember (the one the brake proportioning valve mounts on) is still tight. Those two things have been my biggest bane with these trucks.

[thirsty]

Rust is the biggest issue in NH.

[Captkaos]

The overall frame rails are identical on these.  To covert you would have to have every bracket from whatever you are wanting to go to, so it is much easier to get the frame you need than to convert one, but it can be done, but you would have to have the donor.

Frame horns changed in 1980, to a cut off end and a bracket for mounting the bumper, prior they were bolted straight to the horns.  All the crossmembers changed to the "lightened" versions this same year.  All the body mounts changed at this time also so if you are using a 73-80 from you have to use body supports for the same year.  Same goes for the 81-87(91)