sansabarJ wrote: ↑Wed Mar 17, 2021 12:58 pm
I m not at all sure about that statement on a late model frame on most vehicals produced today .
My J4000 really is only heavier due to the flat steel the be Tory welded to the bottom of the frame between front and rear leaf springs . I've yet to hear or see any post or other comment regarding weak frames . The FORD Raptor Chevy Colorado and others use thinner light weight frames and while we are talking a JKU I'd look at it and see the differences in the steel thickness number one that is heavier gauge. Second most all late frames have holes in them to lighten them up .
So Again I digress the JKU frame is in no way stronger .
A JKU frame is fully boxed with seven cross members. I have owned both a Cherokee, J-Truck, a JK, and a JKU. And I have been all over all of them. While J-Truck frames were stronger than say, GM c-channel frames of the 70-80's (Which were notorious for flexing and cracking), the J-Truck frames are very much inferior to trucks made today, which all use boxed frames except for the Tundra.
A JKU Rubicon also weighs more than an FSJ. Which makes sense as it has to pass safety standards, and durability testing is much more stringent now.
There have been posts here of J-Truck frames (no cab/bed) on three jack stands with a weight on the fourth corner, showing how much the frame flexes. And then show the same test after boxing the FSJ frame.
A JKU frame has almost no flex until it is put under extreme forces. With my Cherokee, if the suspension was crossed up, and you opened the tail gate, good luck closing it. Because the whole body and frame would twist. This is not the case with a JKU. Boxing a frame and giving it a lot of cross members makes a GIANT difference.
sansabarJ wrote: ↑Wed Mar 17, 2021 1:03 pm
I'm you g to add here , this does not mean you cannot perform your conversion. The J trucks are far heavier than anything late model built today . Heavy steel body's and beds . Lots of weight .
Consider this when deciding to change out a vehicals designed frame onto another vehicals been
Built as a complete AS designed vehical . Guys do put dodge frames under these like a Cummins platform and similar . Those frames are designed for heavy engines and payloads and are more appropriate for such a conversion . At your own risk on all of these modifications though .
Consider this as well .
J-Trucks are definitely lighter than almost any full size truck made today (2wd, single cab short bed F150 is a bit lighter, but its also aluminum). A new Jeep Gladiator weighs more than a J-Truck, it tows more than a J-Truck, and it uses a frame that is partially based off a Wranglers with some Ram bits tossed on in back.
While early FSJ's used thicker sheet metal than later FSJs, it was not enough to greatly change the weight.
Anyway, we all love FSJs. They have amazing style and character. But they were never really known for amazing build quality. Kaiser and AMC did what they could with what they had. And if they could take a short cut, they did. Even if it did lead to things like dash fires.
So again, I think Copper204 going with a JKU frame is a fine idea. Its strong, TONS of parts available for it, and he will end up with a nice riding, capable Jeep with modern brakes, power train, and suspension.