1973 J4000 body on a 1976 J20 frame

[xabn82]

Ok, I'm doing a frame off on my 1973 J4000, but I have a 1976 J20 donor truck that came with it. I know there are differences in the two, but how much? I was just planning on using the front/ rear axles from the J20 since they have disc brakes and they don't have the closed knuckles and put those under my J4000. Or should I put my cab and bed on the J20? What would be easier?

[trickc]

The body mounts should be the same to swap the cab and bed. You'll need the later brake booster/ master cylinder to work those brakes anyways. The springs would be different if swapping axles cause the 73 has post mount and the later ones would be the more standard aka easier to get parts for style. If I remember right the 73 has a spring over on the front axle in stock configuration but because the post mount springs sit up on the side of the frame it sits lower like a stock height later model.

Neither will be "easy" either way.

[xabn82]

Neither will be "easy" either way. Dang. That what I kinda expected. Yeah it just seems like more stuff available for 1976 and up plus I remember as a 16 year old driving this truck it took a 10 acre field to turn around. I'd like to have disc brakes, but understand that CJ disc can go on the 73, but you loose even more turning radius.

[NeverKnowsBest]

Not sure about 76 having the same mounts but I know for sure a 77s cab mounts are not the same from a 73 as that's the swap I did l. The bed was the same though.

[xabn82]

I'll do a ton of measurements and see what I come up with. Maybe just a glutton for punishment?

[xabn82]

I was thinking the 73 bed was 2" shorter or longer???

[NeverKnowsBest]

There may be differences that i don't know about i can only account for a 73-77 swap, but heres some pictures if they help any


my truck and old frame


only the front cab mounts moved


closer view, ignore the wire coming out of the old cab lol. I haven't decided how i want to permanently fix my problems just yet


i'm no body man by any means, but overall it looks straight enough for me for now.

[xabn82]

Thanks for those pictures. I should have both truck frames side by side in the garage soon. I need to figure out how to load pictures.

[darylb]

Neither will be "easy" either way. Dang. That what I kinda expected. Yeah it just seems like more stuff available for 1976 and up plus I remember as a 16 year old driving this truck it took a 10 acre field to turn around. I'd like to have disc brakes, but understand that CJ disc can go on the 73, but you loose even more turning radius.

Check your wheel size first. The J4800 has 12 1/8 inch brakes and hubs, not interchangable with anything as far as I can find.

[NeverKnowsBest]

i do have some frame by frame pictures as well, the only other noticable thing was the back hump in the frame near the gastank was in a slightly different location, even with it being different it didn't interfere with anything bolting up.

Good luck on your project !

[airman]

I did a 1982 bed to a 1969 truck and the only item I found was the front bed mount was offset to the outside of the frame and the n69 the mount was on top of the frame. so only had to make a little adaptor.

Now the bed on the 69 was a 126 wheel base and the 82 was 132 wheel base . So I had to move the axle back 6". the frame was the same on both.

Andrew

[xabn82]

I'm thinking, but could be wrong, that my bed is 131". Does that sound right?

[xabn82]

Neverknowsbest, I might like to see those frame by frame pictures. Thanks

[darylb]

I was thinking the 73 bed was 2" shorter or longer???

I too have heard that the 73 bed is different than later years. Since it is also different than 72 and previous in both tailgate design and lights I suspect we have a one off year bed? Anyone know for certain if the 73 interchanges with anything else?

[xabn82]

Darylb
That's what I've heard also. Is that what makes the 73 "rare" or simply a PITA?