If the Jeep body was in real rough shape, then you can just imagine what the frame will look like.
Not all is lost though.
If this discussion was more towards older Jeeps such as CJ's and older then we would have to worry about thin, C-channel frames that have their own unique issues and strength problems.
I'll deal with those in another article.
Our beloved YJ or Wrangler Jeep frames however are boxed rectangular and much stronger.
Starting from the front of the Jeep frame and moving towards the rear we will now go over a few trouble areas.
Front Cross member The front of the Jeep frame has a round cross member hidden underneath a plastic cap between the front bumper and the grill.
This area has a few trouble areas.
First to check is the frame area on the driver side just behind the cross member.
This is big stress point where the steering box mounts to the frame.
Mud, salt and general crap gets caught inside the cross member and/or gets into the frame via drain holes or tow hook mounting points and can rot the frame from the inside out.
This problem is amplified by the forces applied by the stresses of the steering box.
Add heavy, large offroading tires and extra stresses of offroading to the list and you could have a recipe for disaster.
This is the first place I look and will give you a good idea of how well the Jeep was maintained.
Body Mounts While looking at the Jeep body, you have seen the body mounts, but have you taken an real good look? Take time here to get underneath and even tap around with a hammer.
These mounts are a trouble spot if the Jeep was not well maintained.
Body mounts are a catch all under the Jeep.
Not only do they catch, but they hold on to the crud and mud.
There are 11 mounts on a Jeep, the 6 prominent ones on the sides of the frame which are move visual, 1 in the front just under the grill, 2 under the rear cross member just before the gas tank and lastly 2 more at the rear cross member.
The rear mounts on the rear cross member just before the gas tank are the most susceptible to rot.
Skid Plate Jeep skid plates are another catch all for mud and crud.
Maintenance of a Used Jeep will show here the most.
If the Jeep was well maintained, the skid will not be rotted out and be structurally sound.
The skid plate is also the support mechanism for your drive train; transmission and transfercase mounts.
The other trouble error for skid plates is the frame mounting points.
There are 6 mounting points for the skid plate, 3 per side.
If the frame was never cleaned out after compounding mud trips it will cake and rot these mount points to the point where skids have fallen out or bolts have snapped as they seized.
The skid plate is holding up the heart and soul of the Jeep so if you see anything booty fab or rotten here run away.
Rear Cross Member The rear cross member just before the gas tank is another catch-all.
It is the mounting mount for the gas tank skid plate and support 2 inside body mounts to stabilize the rear of the tub mounted to the frame.
There is a curled lip where the cross member meets the frame where, you guessed it, mud and crud gets caught and will rot it out.
Although this is a beefy piece of metal it can substantially reduce the structural strength of frame twist.
Fuel Filter Mount/Skid The fuel filter is mounted on the driver side frame behind the rear cross member.
It is held to the frame using 3 metal screws which will snap off if you try and remove them, without a doubt.
Although this little skid protects the fuel filter from debris and rocks it also catches mud and crud and will rot the frame as well as the filter if it is not cleaned and properly maintained.
During your used Jeep search you might find some interesting ways at which previous owners have located the filter after snapping the screws.
One way to address this is to get rid of the skid mount and relocate the filter and gas lines on top of the frame.
This will require a minimum 1" body lift, but will keep your filter and lines out of the way.
You will need that space to run dual pipes out the rear after the V8 swap anyways ;o) Rear Cross Member/Bumper Lastly is the rear cross member/bumper.
If the YJ still has the little designer bumperettes you will have a good view of the rear cross member that ties together the rear of the Jeep frame.
The rear body mounts are at the far corners and usually don't cause much concern as the rear cross member is basically a stamped piece of flat stock so there isn't any place for mud and crud to accumulate.
One spot that is worth checking is the lip underneath the cross member where the gas tank straps and skid plate bolts up.
This is especially true if there is an aftermarket bumper or rear hitch.
Leaf Spring Mounts Another area to look at, although not as susceptible, is the leaf spring mounts on the frame.
They create a location where mud can catch as well but usually pretty easy to get at during regular cleaning.
One item to check for in this location is frame cracks.
Rot and stress will create cracks here and this will also show any tell tales of hard impacts.
In conclusion, take your time to look at each of the trouble areas listed.
If you check out a Jeep and it's just been freshly undercoated ask questions.
I'm not against undercoating, but it's also used to cover up trouble spots, rust and possible cracks.
Next we will cover the engine and drivetrain check points.
This part two of a six part series I'll write.
Check out: - How to buy a Used Budget Jeep: Body Check Stay tuned for: - How to buy a Used Budget Jeep: Engine & Drivetrain Choices - How to accessorise your Used Budget Jeep - How to build a mild offroading Used Budget Jeep - How to upkeep your Used Budget Jeep Hope this was informative and helps you discover the Jeep addiction.
Keep it Jeep!