How Common is Rear End Separation in '70s Overlanders

[dbj216]

I'm looking for my next project. It might be a 70s Overlander 27. I have shied away from the 70s trailers due to the "beatrice" effect. In other words, corporate cost reductions. "Space age materials" they say. Yeah, right. I read about a lot of rusted, buckled frames in the 70s trailers. Less so in 60s and 80s trailers.

It seems to me the longer trailers are plagued with this more than the shorter ones. The Overlander 27 is a shorter longer trailer (21, 23, 25, 27,29,31 were the lengths in the 70s.) How's that for good english; shorter longer.

So if you were eyeballing a 75 Overlander, would you just assume it has rear end separation. I should sharpen my welding skills, huh.

What is the cause of this failure? Subfloor rot (many trailers have this) frame weakened by rust, lousy frame steel, frame steel too thin, or something else? Maybe you can point me to a thread that explains it.

Thanks,

David

[garry]

Problem is prevalent in rear bath models due to weight.
Longer units are more likely to have the rear bath.

One way to test is to step on rear bumper and if it moves independent of the body you probably have frame separation.

Forget about welding repair that won't work.

[AnnArborBob]

Garry is spot on in terms of the cause and likelihood of rear end separation on a 1970's model. If you detect rear end separation in a unit you are considering purchasing, know that you are going to need to do a full frame off restoration to make a lasting repair. That isn't necessarily a "deal killer" but just be prepared for the hassle (if DIY) or cost if having this done professionally.

[TennTex]

The primary cause of the rear end problems is the infamous rear deck that ran from the bumper trunk forward and ended up under the plywood subfloor. A line of sealant was the only barrier to this acting as a funnel directing water to the most vulnerable part of the trailer. Eventually the floor rots, the rear crossmember, hold-down plate, and their fasteners rust through, and there is complete loss of the structural integrity of the rear end. The length and weight (especially the battery as far back as possible) only accelerate the process; in my opinion, I don't think they are a problem in a structurally intact trailer.

So, unless a trailer of this era has had very little exposure to the elements, it will need at least some attention to this issue.

I added aluminum to extend the rear wall down to the level of the belly pan, eliminating the problem for good. BTW, the rest of my frame, except for the steps, was rust-free.

Alan

[dbj216]

Thank you folks. There is bath weight right at the rear. I suspect there is a black tank close to the rear along with the battery. The infamous rear body to bumper deck seal is probably the root cause. Moisture rots both the wood and the steel.

As we say on the Forums, semi monocoque construction means the frame holds up the subfloor and the body holds up both of those. Lose one of the three, and the egg shell breaks. Some owners talk about buckled frames behind the axles.

But the problem seems worse on the 70s trailers as compared to the 60s or the 80s. Both of these decades had a rear decking between the body and bumper too.

I was wondering if the frame steel or paint in the 70s trailers was somehow different.

David

[casey0672]

I rebuilt and have a 1971 27ft Overlander. The drain on the tub had separated from the sewer line and as a result tub water drained (for years I suspect as the home was permanently in a Florida Park) in into the frame area and the black water tank and enclosing sheet metal tank. The damage was a rotted out section of floor and a severely rusted right rear main frame member.
The frame was straightened and gussetted, the floor was replace as well as the black water tank, black water tank encasing sheet metal pan and related supporting angle iron members. Overall the frame was in excellent condition with the structural damage restricted to the area of the separated tub drain.
We have over 20,000 miles on my rebuild and it has served us well with no further deterioration of the frame.