86 Comanche Project

[datruford]

I just picked up an 86 Comanche a few days ago. I intend to put a 5.9 Magnum in it or an LS one day. But for the time being, I'm tearing it apart to repair the rust it has. I'm new to Comanches so I'm going to need some help with this project. Any comments and suggestions are very welcome. Also, if I make any mistakes, let me know as I am new to this forum and restoring vehicles in general.

 

Here is what the truck looked like when I picked it up a couple days ago:

 

I need a tailgate (and maybe a bed) as you can see, so if you know where I can source one from, please let me know. I don't intend to waste time repairing this tailgate if I can get another one in decent shape.

 

The truck appears to have been in an accident or maybe it was used off-road. It has some dents all along the passenger side and some crappy touch up paint.

 

 

I just took out the seats and carpet. The transmission tunnel is pretty rusty. Thankfully the cab corners look clean to me, but the floor pans.... not so much. Here's the rust I'm dealing with:

 

 

Where can I get this part above the rocker panel? Maybe cut it out of an XJ?

 

I plan on taking the bed off pretty soon so I can bedline it and save it from rust.

 

Any suggestions for what I should start with or what parts I should pick up sooner rather than later?

 

Thank you for your help in advance!

[87MJTIM]

For floor pans, go with Key Parts. 
 

there’s a thread about repairing the tailgate. 
 

Depending on how bad the rear bumper is it may be straightened 

[yungupgrade]

If you think that bed is in bad condition you should see mine. Why do you think it might need to be replaced?

[datruford]

It probably doesn't need replaced. It just needs some body work on the passenger side. If I don't coat it with something sooner rather than later, it will rust through.

[87MJTIM]

Key Parts has bed wheel well patch panels, rocker panels, and bed floor panels on the website.

 

https://www.keypartsonline.com/comanche-mj/

 

On YouTube, Second Chance Jeeps has a series of videos about repairing a MJ - cab floors and rocker repairs.  He compares Key Parts to C2C floor pans.  Search for them and watch what he's done.

[datruford]

What about my transmission tunnel? What would be the easiest way to repair that?

[ghetdjc320]

For the tunnel, you could just cut some 20awg sheet metal and patch it. It’s important to remove the firewall pad as well as it tends to have a lot more rust back there. Also look carefully for any seam sealer that may be hiding rust. You’ve got quite a few areas to repair but it’s doable. Key parts has great replacement panels but their floor pan is not Comanche specific and it may not actually be long enough to replace rust through going up the firewall. Personally, I’d be inclined to replace the entire floor with another one from and MJ if possible. 

[datruford]

I plan on 97+ interior swapping. I'll end up getting an XJ to pull parts from soon. I might just cut out the floor from that XJ and use that. 

[Eagle]

On 6/16/2022 at 9:09 AM, datruford said:

What about my transmission tunnel? What would be the easiest way to repair that?

 

Cut one out of a Cherokee.

[datruford]

On 6/17/2022 at 9:08 PM, Eagle said:

 

Cut one out of a Cherokee.

Question. What is the difference between the MJ seat bracket and the XJ seat bracket? If I weld in new floor pans, can I use the XJ seat brackets from KeyParts?

[CrustyBoy]

28 minutes ago, datruford said:

Question. What is the difference between the MJ seat bracket and the XJ seat bracket? If I weld in new floor pans, can I use the XJ seat brackets from KeyParts?

 

I don't know the measurements but I saw this pic the other day. Looks like the XJ bracket is a longer with a different shape.

 

Picture is from Cruiser's Technical Photos

[ghetdjc320]

29 minutes ago, datruford said:

Question. What is the difference between the MJ seat bracket and the XJ seat bracket? If I weld in new floor pans, can I use the XJ seat brackets from KeyParts?

This is what’s unique about the MJ floor pan. This bracing is installed on top of the floor pan and is supposed to act as reinforcement to the bed frame which is sandwiched inside. 
 

 

[datruford]

2 minutes ago, ghetdjc320 said:

This is what’s unique about the MJ floor pan. This bracing is installed on top of the floor pan and is supposed to act as reinforcement to the bed frame which is sandwiched inside. 
 

 

Is this bracing necessary? Or could I just stick with what's in an XJ? My bracing is rusted out so I would need to find another MJ to pull them from, which is quite difficult. That's why I'm asking.

[ghetdjc320]

43 minutes ago, datruford said:

Is this bracing necessary? Or could I just stick with what's in an XJ? My bracing is rusted out so I would need to find another MJ to pull them from, which is quite difficult. That's why I'm asking.

I haven’t found too many places on these MJ’s that were “over engineered” from the factory. That being said, there are a few that have removed the bracing. I personally wouldn’t remove it without installing some alternate bracing

[datruford]

16 minutes ago, ghetdjc320 said:

I haven’t found too many places on these MJ’s that were “over engineered” from the factory. That being said, there are a few that have removed the bracing. I personally wouldn’t remove it without installing some alternate bracing

So essentially there isn't really any data out there about that bracing?

[Eagle]

8 hours ago, datruford said:

So essentially there isn't really any data out there about that bracing?

 

What "data" would you expect to be out there? The unibody (which the cab portion of the MJ is) was designed by a team of automotive engineers. AMC was in the business of building vehicles for a profit -- they wouldn't just throw extra pieces in there for no reason. The only "data" I need is that they didn't think the XJs needed the brace, and they did think the MJ needed it.

 

That's all I need to know.

[datruford]

48 minutes ago, Eagle said:

 

What "data" would you expect to be out there? The unibody (which the cab portion of the MJ is) was designed by a team of automotive engineers. AMC was in the business of building vehicles for a profit -- they wouldn't just throw extra pieces in there for no reason. The only "data" I need is that they didn't think the XJs needed the brace, and they did think the MJ needed it.

 

That's all I need to know.

I wasn't really expecting any data. I'll likely end up welding frame stiffeners along the bottom of the cab to solve that issue. ANYWAYS....

 

Can I use the KeyParts 1/2 floor pan for the XJ? Where does the back of the MJ floorpan end compared to the XJ?

[ghetdjc320]

3 hours ago, datruford said:

I wasn't really expecting any data. I'll likely end up welding frame stiffeners along the bottom of the cab to solve that issue. ANYWAYS....

 

Can I use the KeyParts 1/2 floor pan for the XJ? Where does the back of the MJ floorpan end compared to the XJ?

Have you had a chance to pull that firewall pad? You’re probably just going to have to tear things apart and see how far the damage goes to get a game plan. Iirc key parts was going to repop the floor brace as well. A quality spot weld cutter is priceless for getting things apart cleanly.

 

This thread has some fantastic detailed information and pictures on the overall design and some ideas on how to repair various degrees of rust damage: 

 

[datruford]

5 hours ago, ghetdjc320 said:

Have you had a chance to pull that firewall pad? You’re probably just going to have to tear things apart and see how far the damage goes to get a game plan. Iirc key parts was going to repop the floor brace as well. A quality spot weld cutter is priceless for getting things apart cleanly.

 

This thread has some fantastic detailed information and pictures on the overall design and some ideas on how to repair various degrees of rust damage: 

 

Thank you for the info! Much appreciated.

[ratrapp]

the cherokee rear pans will work but they require alittle cutting and bending.i just did this on my 86,take your time cutting the old floor pan out.it takes a little patience plus a good spot weld cutter or drill bit and a air chisel is nice as well.

[datruford]

1 hour ago, ratrapp said:

the cherokee rear pans will work but they require alittle cutting and bending.i just did this on my 86,take your time cutting the old floor pan out.it takes a little patience plus a good spot weld cutter or drill bit and a air chisel is nice as well.

Ok. Thanks for the info.

[Pete M]

frame stiffeners are unnecessary for MJs unless you're regularly jumping it or rock bouncing.  and even then they aren't really all that necessary.   

 

I wouldn't even bother replacing the floor pans if they are not rusted through.  just grind off all the rust and paint.   under the frame cap is another story and you will want to pull it to get to the rust underneath.  you can put it back, or not.  I've not heard of a single person having issues because it was gone. 

 

welcome to the addiction  

[datruford]

8 hours ago, Pete M said:

frame stiffeners are unnecessary for MJs unless you're regularly jumping it or rock bouncing.  and even then they aren't really all that necessary.   

 

I wouldn't even bother replacing the floor pans if they are not rusted through.  just grind off all the rust and paint.   under the frame cap is another story and you will want to pull it to get to the rust underneath.  you can put it back, or not.  I've not heard of a single person having issues because it was gone. 

 

welcome to the addiction  

You might want to see the pictures of my floor pans. Unfortunately, they are pretty much rusted trough fully on the driver's side and quite a bit on the passenger side. Too far gone for a quick paint job. But yes, the frame cap seems to be optional from what I've seen from others on this forum.

[ghetdjc320]

I wouldn’t go so far as to say that bracing is inconsequential. We have no hard data to know the actual results of removing the brace based on the usage of the truck. Kind of reminds me of the control arm reinforcement that is MJ specific. XJ’s don’t have this bracing and most likely any who remove it from their MJ will not notice any immediate ill effects. For the “floor bracing” It can’t be so critical that removing it will cause the car to fold in half, but the effects with a heavy load, a front end collision or even repeated off-road flexing haven’t been really determined as far as I know. It’s good to remember the purpose of that brace: stiffen the unibody rail due to the addition of the bed frame which starts inside those rails under the floor. And again, these trucks are not over-engineered by a long shot. There is a definite reason why amc choose to stamp out new sheet metal parts to reinforce that area. It is not an “optional” part that was only on a metric ton mj and so forth. You’ll find that bracing even on a little 4 banger 2wd short bed. If you’re going to remove it, assume that there very likely will be consequences in certain scenarios. 
 

If you have a press brake, forming that brace would be quite easy. However, spot welding it all the way through to the lower unibody will be a challenge for any who don’t have a high end long reach spot welder. 
 

To the OP, start removing your flooring and see how far the damage goes. Remove that dash pad and look carefully at all the seam sealer. Remove any sealer that is wet or loose. I hate to say it but you may find that the extent of damage is far worse than what is visible in the pics. Hopefully that is not the case. 

[datruford]

4 hours ago, ghetdjc320 said:

I wouldn’t go so far as to say that bracing is inconsequential. We have no hard data to know the actual results of removing the brace based on the usage of the truck. Kind of reminds me of the control arm reinforcement that is MJ specific. XJ’s don’t have this bracing and most likely any who remove it from their MJ will not notice any immediate ill effects. For the “floor bracing” It can’t be so critical that removing it will cause the car to fold in half, but the effects with a heavy load, a front end collision or even repeated off-road flexing haven’t been really determined as far as I know. It’s good to remember the purpose of that brace: stiffen the unibody rail due to the addition of the bed frame which starts inside those rails under the floor. And again, these trucks are not over-engineered by a long shot. There is a definite reason why amc choose to stamp out new sheet metal parts to reinforce that area. It is not an “optional” part that was only on a metric ton mj and so forth. You’ll find that bracing even on a little 4 banger 2wd short bed. If you’re going to remove it, assume that there very likely will be consequences in certain scenarios. 
 

If you have a press brake, forming that brace would be quite easy. However, spot welding it all the way through to the lower unibody will be a challenge for any who don’t have a high end long reach spot welder. 
 

To the OP, start removing your flooring and see how far the damage goes. Remove that dash pad and look carefully at all the seam sealer. Remove any sealer that is wet or loose. I hate to say it but you may find that the extent of damage is far worse than what is visible in the pics. Hopefully that is not the case. 

I've seen many different opinions on the top bracing. I'll add frame stiffeners to the bottom of the truck just to be safe. I will also be checking for rust further up the firewall shortly.