Time to bring this thread back to life...
I recently got a set of the front and rear Timbrens for my '04 FG649. The rears got installed pretty easily, but as you can see below, they don't quite line up with the center of the axle. Is this a big deal?
View attachment 682382
I should note that the rear end is sagging a decent amount at this point, which I assume is what's causing the top of the axle to not be parallel to the frame -- notice how the U-bolts aren't on quite the same line as the Timbrens). I'm getting the rear leaf springs dealt with soon, and hoping that once the truck is leveled out, this will be corrected, the result being that the Timbrens will then hit closer to the center of the axle. Sound plausible?
On the fronts, the OEM bump stop is on the frame side of these older FGs, so that gets permanently removed, and the Timbrens get mounted on the leaf spring side, underneath the u-bolts. As a result, the frame itself becomes the new landing pad for the Timbrens, whereas newer FGs have an actual landing pad up there (since the OEM bump stop is on the leaf spring side). So to those who have installed these on '04 and older models, are there no issues with using where the old bump stop was as the landing pad? I wouldn't think so, as the forces shouldn't be any different from before, but this is the only possible wrinkle I can see with using these Timbrens on the older FGs, so figured I'd make sure.
Timbren's support email hasn't been too helpful, btw. After approaching them with the above issues, they've basically told me that there is no application for my '04, and I should return them. I know there are several people on here who have gotten these springs working on trucks even older than mine though.