Is the factory TJ frame electrically grounded to the body?

My 98 I have only ever found the two you have mentioned. Ideally with no electrical items on the frame something for static is probably all that is needed.
Curious about the little one up front. Gotta be a reason why it is there and not on the later ones.
 
Are both the frame and the body galvanized under the paint? If one is but not the other I could see electric isolation being added by design to minimize galvanic corrosion.

On mixed-metal vehicles like the new F150, the builder's manuals strictly forbid any grounding to the frame or any electrical connection between the body and the frame. Though I've never seen a similar warning on an all-steel vehicle. Though that may also be because aluminum-steel corrosion is a much higher risk than steel with zinc plated steel.
 
Are both the frame and the body galvanized under the paint? If one is but not the other I could see electric isolation being added by design to minimize galvanic corrosion.

On mixed-metal vehicles like the new F150, the builder's manuals strictly forbid any grounding to the frame or any electrical connection between the body and the frame. Though I've never seen a similar warning on an all-steel vehicle. Though that may also be because aluminum-steel corrosion is a much higher risk than steel with zinc plated steel.
There is no galvanizing on the frame whatsoever.
 
Do you remember what year that ground went away?
I have a 97, you have a 98 and I'll check my 99 later today but I don't recall seeing it on the 99 and I've worked in the area of the mounts on it a fair bit. The way it is tucked in next to the mount on the 97, I'm not sure I would have always noticed it though.
 
There is no galvanizing on the frame whatsoever.
If the body is galvanized but not the frame I could see that being a reason to isolate the two.

Theoretically if they were connected, the galvanization on the body would protect both the body and the frame at first, assuming enough paint has chipped to expose the galvanization.

However, if the paint only chips in a small area on the body, the larger area of the frame could result in the galvanization at the chip being lost very quickly, resulting in significant corrosion at the paint chip.

The total overall amount of corrosion of steel would be the same regardless of whether or not they are isolated, but by isolating them you sacrifice frame metal to save body metal. Maybe they assumed a small amount of frame corrosion is less damaging than an equivalent (by weight) amount of body corrosion. Which would make sense given that the frame is much thicker.

If neither are galvanized I’m not sure there would be a reason to isolate the two.
 
If the body is galvanized but not the frame I could see that being a reason to isolate the two.

Theoretically if they were connected, the galvanization on the body would protect both the body and the frame at first, assuming enough paint has chipped to expose the galvanization.

However, if the paint only chips in a small area on the body, the larger area of the frame could result in the galvanization at the chip being lost very quickly, resulting in significant corrosion at the paint chip.

The total overall amount of corrosion of steel would be the same regardless of whether or not they are isolated, but by isolating them you sacrifice frame metal to save body metal. Maybe they assumed a small amount of frame corrosion is less damaging than an equivalent (by weight) amount of body corrosion. Which would make sense given that the frame is much thicker.

If neither are galvanized I’m not sure there would be a reason to isolate the two.
The tub has a layer of what appears to be galvanic protection. I don't know specifically what it is but there is a layer of plating under the primer that you can see if you know what to look for when prepping for welding. It also makes welds pop and blow holes in the sheet metal like galvanizing does with the accompanying white smoke curls and distinctive smell.
 
The tub has a layer of what appears to be galvanic protection. I don't know specifically what it is but there is a layer of plating under the primer that you can see if you know what to look for when prepping for welding. It also makes welds pop and blow holes in the sheet metal like galvanizing does with the accompanying white smoke curls and distinctive smell.
That would make sense then.

The engineers may have decided to isolate the tub from the frame to reduce visible tub corrosion at the cost of a small amount of additional frame corrosion.

How effective that really is is debatable. It would depend upon the quality of the isolation as well as the actual means of corrosion, which isn’t necessarily all galvanic.
 
That would make sense then.

The engineers may have decided to isolate the tub from the frame to reduce visible tub corrosion at the cost of a small amount of additional frame corrosion.

How effective that really is is debatable. It would depend upon the quality of the isolation as well as the actual means of corrosion, which isn’t necessarily all galvanic.
We've pretty much figured out that the brake lines aren't very well isolated so it is likely they gave it no thought or not enough to make it completely isolated. The stock front flex hoses mount with a tab that is attached to the metal hose end. The hardlines screw into that. The hard lines run to the metal combination block that is bolted to the booster studs which is bolted to the firewall.

1638197635875.png
 
Short answer: I don't know. Slightly longer answer: I couldn't find any reference to an "official" tie in, so I installed this:
View attachment 292983
In addition to beefing up the battery negative connections to the block and firewall. Maybe un-necessary, but I don't know and it was cheap and easy. #2 wire with star washers used.
Plus side is in some states that'll be the only thing holding the Jeep together. 😁
 
That would make sense then.

The engineers may have decided to isolate the tub from the frame to reduce visible tub corrosion at the cost of a small amount of additional frame corrosion.

How effective that really is is debatable. It would depend upon the quality of the isolation as well as the actual means of corrosion, which isn’t necessarily all galvanic.
I can't imagine the Jeep engineers of the day giving a damn about corrosion of any type, much less esoterica like this. Kinda like putting screen doors on a submarine - they OBVIOUSLY didn't care about corrosion of any kind.
 
I can't imagine the Jeep engineers of the day giving a damn about corrosion of any type, much less esoterica like this. Kinda like putting screen doors on a submarine - they OBVIOUSLY didn't care about corrosion of any kind.
If they did, we wouldn't have so many damn rust problems.
 
I can't imagine the Jeep engineers of the day giving a damn about corrosion of any type, much less esoterica like this. Kinda like putting screen doors on a submarine - they OBVIOUSLY didn't care about corrosion of any kind.
Flawed attempts at minimizing corrosion don’t necessarily mean they tried to ignore it altogether.

Perhaps it was part of the original design, but at some point the brake line design was changed and the change was overlooked in review. It is very strange that only the brake lines would be a ground path between body and frame.

There are quite a few other things on the TJ that are designed to minimize corrosion. The fact that the frame is painted inside and out, the galvanization on the body, the lack of stainless fasteners and aluminum components, etc. Those are all done with corrosion in mind.

When it is done really badly, it goes south very fast. Take a look at all the Toyota frames from a decade or two ago. Many of them rusted through far faster than almost any TJ, and the frame would literally give up and “taco the Taco”.

Granted, the design for corrosion on TJs is far from ideal, but to claim it simply doesn’t exist I think is incorrect.

BE2E10E6-9E45-4B28-845F-724C862D1BB3.jpeg


F792C67E-7399-40EE-9C37-991B8DF0CDA3.jpeg


A32BB150-266F-4198-ABA8-F3CB5D941D58.jpeg
 
I can't imagine the Jeep engineers of the day giving a damn about corrosion of any type, much less esoterica like this. Kinda like putting screen doors on a submarine - they OBVIOUSLY didn't care about corrosion of any kind.
If that were true, the frame would be bare metal like the driveshafts, steering knuckles and other bits. They also would not have used a 5 or 6 step coating process on the sheet metal. They may not have cared as much as you want them to but they did spend a fair bit of money on corrosion prevention which shows they did care.
 
Flawed attempts at minimizing corrosion don’t necessarily mean they tried to ignore it altogether.

Perhaps it was part of the original design, but at some point the brake line design was changed and the change was overlooked in review. It is very strange that only the brake lines would be a ground path between body and frame.
The brake lines are the same ground path on all TJ's. The only thing that changed was the coating. They went from zinc plated to plastic coated but the ground path is still identical.
There are quite a few other things on the TJ that are designed to minimize corrosion. The fact that the frame is painted inside and out,
The frame is actually dipped. On many we've done you can see the paint runs down the length of the frame from being hung by the front crossmember area.
the galvanization on the body, the lack of stainless fasteners and aluminum components, etc. Those are all done with corrosion in mind.
Not only that but they put a sheet of lead or similar material under the rear aluminum hinges to slow that down in that area.
Granted, the design for corrosion on TJs is far from ideal, but to claim it simply doesn’t exist I think is incorrect.
Very true.
 
  • Like
Reactions: Steel City 06
This might be part of the reason some people have difficulty tuning bumper mounted antennas, brake lines are probably not an ideal RF ground path. It also might be why my fuel pump is so noisy with respect to RF, the skid isn't really well grounded.
 
  • Like
Reactions: Necro