TJ frame swap questions (need some input from those that have been there)

glowell222

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Hello everyone.

New to this forum, and I posted this question on another Jeep forum, with no replies. Hopeful to gain some insight before I jump in.

The frame on my '98 Sahara has succumbed to O2 poisoning. Time for a swap. Just picked up a reconditioned, rust-proofed, painted 2006 TJ frame. I have several questions, and hopefully the gurus can offer some answers. Thanks in advance for all of your excellent support.

My Sahara is stock as a block, except for the Borla 2 piece header that I installed at 57,xxx miles back in the way early 2000's. I use the Jeep for camping/kayaking/hiking and sometimes as a daily driver for weeks at a time. 5 speed manual, original clutch. Ordered in the late fall of '97, picked up on 10 Jan '98. Some parts are '97 specific, some are '98 and never really know which I will need.

I will do a write up as I am performing the swap, with pics and a view of the actual costs. There is a famous (?) vid on youtube where 3 pros do a complete swap in 5 hours. My timeline is eleven days working 10 hours a day. I will have help here and there but nothing I can count on for long periods of time. Advil and whisky on standby for those intense days.

Now the questions. If there are any suggestions for reasonable upgrades, I would love the advice. Trying to have as much of the replacement/upgrade items on hand so I can roll as fast as possible.

'06 FRAME vs '98 FRAME
Anything that is different between the two other than the steering box and steering box mounting?

STEERING:
I understand the steering box is different from '98 to '06. If I switch to an '06 box, will my hoses and linkage still work? Is it better to modify the mounting and stay with the '98 box? I will be replacing the box either way.

CLUTCH:
Still on the original clutch. Time for a replacement. I have all the bits to do the replacement. Anything else I should be doing while I have the driveline apart? Engine main seal? Should I do the replacement with the engine/trans in the old chassis or in the new chassis? I am thinking in the old.

BUSHINGS:
Should I replace the old suspension and body mount bushings? If so, I will stay with original rubber bushings. Is there a kit? Haven't seen one for the original rubber bushings, seen plenty for poly.

FUEL TANK:
Skid plate is mostly rust and I will install a new skid plate and new straps. Any advice or tips or gotchas? Anything i should do to the tank while I have this level of access?

BRAKE LINES:
I plan to use new stainless lines. Any vendor or brand suggestions? What about mounting clips-is there a kit? Front disc/rear drum, and already have new rotors/discs/shoes all around, plus a new e-brake splitter is already installed.

SHOCKS:
I plan to replace the shocks with stock items. Any suggestions for reasonable upgrade or brands?

CONTROL ARMS:
Can I re-use the originals or should I replace? Upgrade suggestions? I have seen where you can spend *a lot* of money here. Worth it?

EXHAUST/INTAKE MANIFOLD:
I have a leak in the exhaust manifold gasket, and I will replace the gasket. Any tips/gotchas/suggestions here?

ENGINE:
Any other suggestions while I am in there? I have already proactively replaced all of the engine management sensors, and the exhaust is new as well, including the cat, all the way back.

A/C:
The system has a leak. I need to replace the dryer and the o-rings. Not a big fan of the way the hoses connect. Suggestions here on the system?

SUSPENSION:
Stock, and I will keep it stock. Any suggestions or tips for minor upgrades here or maintenance items I can do while it's all accessible?

RADIATOR:
Not overly fond of the plastic in the OEM item, and this is the second radiator. Suggestions for an upgrade here? I will likely not stay with stock.

INDISPENSABLE TOOLS:
Suggestions here? I don't have an impact wrench, do have a pancake compressor. Still need to get a cherry picker and some spring compressors. Have torque wrenches and pulley/pitman/ball joint pullers, and a good collection of tools, both metric and SAE. Have oxy/acetylene and propane torches, vacuum pump and refrigerant gauges and refrigerant.

TORQUE SPECIFICATIONS:

Where do I find the detailed torque specs for each of the systems? What is the best system to visually ensure I have torqued everything to spec-a dab of white paint on the bolt upon successful torque application?

ADDITIONAL INFO:
Any other suggestions or advice will be most welcome. I am just a home mechanic. I will treat this like any other large project-as a series of smaller projects, logically completed in series until overall project finalization.

Here is my plan:
Run the fuel down as low as possible. Liquid Wrench the hell out of the entire underbody for about a week. Drain engine oil, coolant, refrigerant, brake and ps fluids. Lift the Jeep and lower onto the wheel dollies, using chocks for brakes and leaving the trans in neutral. Remove the battery. Remove the soft top, rear seat, doors, spare, and any other extraneous weight. Unbolt and disconnect all systems and bolts between the chassis and the body (it's a bit of a list). Raise the body off the chassis with the lift and leave body lifted for the duration. Roll the chassis to the open garage bay and next to the replacement chassis. Disconnect the exhaust at the downpipe. Replace the exhaust/intake gasket. Replace clutch. Pull engine/trans/transfer case and move aside. Begin moving systems from the old chassis to the new (not sure of the order I should do this and would appreciate advice). Should I do brake lines first or last or somewhere in the middle? Should I do fuel system first or last or in the middle? Suspension and axles first, last, middle? Which way makes most sense? Once all systems are replaced and all bolts are torqued and double checked, will install the engine/trans/transfer case and axles into the replacement chassis. Will roll the completed chassis under the lifted body and reinstall the body to the chassis and reconnect all systems. Bleed and fill brakes. Bleed and fill clutch. Bleed and fill ps. Bleed and fill coolant. Vacuum and recharge A/C. Replace battery.

Sorry for the long post, and again I thank you all in advance for any and all suggestions, support, tips, and advice.

Garrett
 
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'06 FRAME vs '98 FRAME
Anything that is different between the two other than the steering box and steering box mounting?

See this thread:

https://wranglertjforum.com/threads/what-years-of-tj-frames-are-interchangeable.8298/
STEERING:
I understand the steering box is different from '98 to '06. If I switch to an '06 box, will my hoses and linkage still work? Is it better to modify the mounting and stay with the '98 box? I will be replacing the box either way.

97-02 uses a different steering box than the 03-06. The 03-06 unit is much more expensive, and often times when people's 03-06 unit goes bad, they'll modify the frame to fit the 97-02 unit, which can be had for much cheaper. I wouldn't switch to an 06 box, I'd stick with a 97-02 box, that's the smart choice.


CLUTCH:
Still on the original clutch. Time for a replacement. I have all the bits to do the replacement. Anything else I should be doing while I have the driveline apart? Engine main seal? Should I do the replacement with the engine/trans in the old chassis or in the new chassis? I am thinking in the old.

I'd replace the clutch while you have the engine out. I'd also do the rear main seal, oil pan gasket, etc.


BUSHINGS:
Should I replace the old suspension and body mount bushings? If so, I will stay with original rubber bushings. Is there a kit? Haven't seen one for the original rubber bushings, seen plenty for poly.

Yes, if they are old and worn, replace them. Use rubber replacement bushings. I've never seen a complete kit, but you can piece it together. Polyurethane bushings don't belong on primarily street driven vehicles IMHO. They make too much noise and are much less forgiving than rubber.


FUEL TANK:
Skid plate is mostly rust and I will install a new skid plate and new straps. Any advice or tips or gotchas? Anything i should do to the tank while I have this level of access?

Make sure you thoroughly inspect the frame where the skid plate mounts after removing it. There likely will be surface rust there, as it's there on even the most clean TJ frames. Take care of it with a wire wheel, paint over it, and you'll be good to go.


BRAKE LINES:
I plan to use new stainless lines. Any vendor or brand suggestions? What about mounting clips-is there a kit? Front disc/rear drum, and already have new rotors/discs/shoes all around, plus a new e-brake splitter is already installed.

Stainless lines offer no benefit over stock rubber lines on your TJ, it's a waste of money. I defer to @mrblaine (the brake expert) on the rest.


SHOCKS:
I plan to replace the shocks with stock items. Any suggestions for reasonable upgrade or brands?

Rancho RS5000X are my favorite off-the-shelf shocks. They ride excellent.


CONTROL ARMS:
Can I re-use the originals or should I replace? Upgrade suggestions? I have seen where you can spend *a lot* of money here. Worth it?

If you're going with the stock height, keep the stock control arms. If the bushings are worn and beat up, replace them with a set of new stock control arms. Here's some with bushings already pressed in: https://www.amazon.com/gp/product/B01MPVWEBY/?tag=wranglerorg-20


EXHAUST/INTAKE MANIFOLD:
I have a leak in the exhaust manifold gasket, and I will replace the gasket. Any tips/gotchas/suggestions here?

Make sure the gasket gets seated properly. Since both the intake and exhaust manifold share a gasket, it can be tricky to get them seated properly. It's certainly easiest to do it when the engine is out.


ENGINE:
Any other suggestions while I am in there? I have already proactively replaced all of the engine management sensors, and the exhaust is new as well, including the cat, all the way back.

My only suggestion is to use Mopar engine sensors and NGK O2 sensors (or you'll live to regret it).


A/C:
The system has a leak. I need to replace the dryer and the o-rings. Not a big fan of the way the hoses connect. Suggestions here on the system?

Can't answer this one.


SUSPENSION:
Stock, and I will keep it stock. Any suggestions or tips for minor upgrades here or maintenance items I can do while it's all accessible?

If you're going to keep it stock height, I would say just throw in some better shocks than factory, such as a stock height Rancho RS5000X.


RADIATOR:
Not overly fond of the plastic in the OEM item, and this is the second radiator. Suggestions for an upgrade here? I will likely not stay with stock.

There is no "upgrade" for the stock radiator. Do some reading and you'll notice a pattern very quickly. The majority of the TJ experts have found that there is no suitable upgrade for the stock radiator. @mrblaine has tested many of the aftermarket ones and found all of them to be garbage.

If the stock Mopar radiator lasts 10+ years and well over 100k miles, you're going to have to explain to me how you "upgrade" something like that. And don't say it's to make the vehicle "run cooler", because that is not an upgrade at all. The engine is designed to run in an optimal temperature range. Messing with that is pointless and a waste of time unless you have some very, very specific use case (i.e. an LS swap with 500 HP)..


INDISPENSABLE TOOLS:
Suggestions here? I don't have an impact wrench, do have a pancake compressor. Still need to get a cherry picker and some spring compressors. Have torque wrenches and pulley/pitman/ball joint pullers, and a good collection of tools, both metric and SAE. Have oxy/acetylene and propane torches, vacuum pump and refrigerant gauges and refrigerant.

Don't forget a good set of torx bits, Kroil or Liquid Wrench (not PB Blaster, it pales in comparison to these two), and lots of anti-seize for re-assembling.

TORQUE SPECIFICATIONS:
Where do I find the detailed torque specs for each of the systems? What is the best system to visually ensure I have torqued everything to spec-a dab of white paint on the bolt upon successful torque application?

Here: Jeep Wrangler TJ Factory Service Manuals (FSM) & Technical Documentation

And here: Jeep Wrangler TJ Torque Specs (1997-2006)

I also HIGHLY suggest checking out the TJ Resources and TJ How-to Guides sub-forums. There's treasure troves of information in there you're missing, that I curated and organized for TJ owners. Trust me on this.
 
Go with new control arms with the bushings already installed. New clutch, pressure plate, throw out and input bearings. Check rear main seal while you are in there. Any seeping then replace now. Have A/C drained at a shop equipped to do it properly. Replace as many bushings and mounts as possible at this time. No polyurethane. Stick to new rubber. I would replace all the brake hard lines with SS if I could, but if you haven't rotted the original ones then regular lines are fine. Replace all soft lines. SS or stock, either are fine. I'd consider a new clutch master cylinder assembly now too for the same reason.
Get every speck, every hint of rust NOW. This is the most important part. Every possible spot. Drill holes in new frame for proper drainage and be sure it is whistle clean inside. Give it a good heavy coat of cosmoline. You can get it in a spray can and use a wand to get inside the frame. I'd recommend no type of hard coating. Eastwoods frame coat, POR 15, paint inside any place that you can't get it back off if rust appears. You won't see it till it's too late. Fluid Film or Cosmoline on everything (obviously not exaust) under the body. That way you can still get nuts and bolts off without having to scrape off a coating. Never use undercoating. That gooey mess is a nightmare to work with later on and can hide rust until it turns into cancer.
Your plan sounds solid. Take lots of pictures and document the whole journey. It will surely help the next guy. Good luck.
 
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'06 FRAME vs '98 FRAME
The front most steering mount hole is up higher in the frame on newer TJ's by about 1/2". Also the center skid mount holes are further back in the frame by about 2". The old skid will not work on the new frame, and the transmission mount will not line up with the new skid, so you'll have to custom fab the trans mount or cut and reweld. Everything else is the same.

STEERING:
Try to retain the old saginaw steering box if possible, better unit.

CLUTCH:
If you have it torn apart now's the time to replace it.

BUSHINGS:
Crown has a body mount kit with all new body bushings and bolts. Also get new upper pads for the springs.

FUEL TANK:
Nothing special here, but if you've been planning to replace the fuel pump now's the time. Delphi is about the only complete pump available now that's worth anything since the oem Bosch quit making complete pumps. You can still get the Bosch motor but that requires some delicate rebuilding of the pump.

BRAKE LINES:
I got some SS lines from classic tube, haven't installed them yet but they look to be decent quality. Pay close attention to your rear axle type and if you have abs or rear drum/disc, because they have about 5 or 6 different sets depending on your vehicle specs.

SHOCKS:
No opinion yet, but rancho rs5000x seem to be the go to shock.

CONTROL ARMS:
Might as well get new moog or mopar arms while it's apart.

EXHAUST/INTAKE MANIFOLD:
Get an exhaust manifold that has expansion bellows in the #1 and #6 exhaust tubes.

ENGINE:
Just new gaskets as you see fit to replace.

A/C:
No opinion on this.

SUSPENSION:
As suggested might as well get new arms, and depending on miles might get some new track bars and steering linkages, also a good time to do the ZJ steering upgrade. There is a detailed writeup in the resources forum section.

RADIATOR:
My oem radiator spewed at 50K, bought a CSF copper radiator that leaked in short order, got a second CSF that has been good for 50K. But I'm going to give the oem pastic tank radiator a try again and if it pukes then it'll get an all aluminum radiator.

INDISPENSABLE TOOLS:
Floor jack, plenty of jack stands, air comp, engine cherry picker, couple of furniture rolling dollies.

TORQUE SPECIFICATIONS:
Available in the FSM in the resources section.

ADDITIONAL INFO:
Understand that there will be seized bolts, broken bolts, you will find hidden rust, rubber and plastic parts will be cracked and brittle, all these things will eat up massive amounts of time and waiting for parts will cause major delays. Good luck.
 
Hey Garrett,

I tackled this same project this past summer and would be glad to give you any advice or answer any questions. Mine took me 21 days, working 6pm to 2am monday - friday. 9am til 10pm saturdays and sundays.

There is a lot of good info from the people above. The first I would say which is most important is get the rust out of the frame now. Take your time because you wont have the opportunity to get in all the cracks and small enclosures as easily as you can right now. Treat it right. Do your research.

CLUTCH:
Replace
Engine main seals, oil pan gasket, Clutch, flywheel, throw out bearings, do it all now because why would you want to have to pull it all apart again and now you know everything is new and will last. preventative maintenance

BUSHINGS:
I would replace any bushings that have severe wear cracks, marks, etc. Some of my body bushings were rotted dust.

FUEL TANK:
Give the top a real good cleaning. Make sure you clean the connections before you try to pull them apart (will save you from snapping them)

BRAKE LINES:
I plan to use new stainless lines. Any vendor or brand suggestions? What about mounting clips-is there a kit? Front disc/rear drum, and already have new rotors/discs/shoes all around, plus a new e-brake splitter is already installed.

Suspension: If you have any plans to do upgrades now would be the time. Including if you want to replace the control arms

INDISPENSABLE TOOLS:
Engine hoist will be your friend. the ability to move the pieces by centimeters will be your friend.
A buddy to help. When you pull the body it will really help to have a friend/spouse/kid just another set of eyes.

ADDITIONAL INFO:
Understand that there will be seized bolts, broken bolts, you will find hidden rust, rubber and plastic parts will be cracked and brittle, all these things will eat up massive amounts of time and waiting for parts will cause major delays. Good luck. (THIS THIS THIS THIS THIS THIS) I put the whole jeep back together then realized a hub was bad so I replaced that. Took her for one test drive and my ps high pressure line hose sprung a leak as soon as I parked it. Just know that there will be things to delay the process.

TORQUE SPECIFICATIONS:

There are factory service manuals here like GASSnBRASS said that tell you how to take everything apart/ put it back together and what the torque specs are and even what special tools you'll need.


Here is my Suggested plan:

FIRST::: HEAT HEAT HEAT HEAT HEAT: Heating bolts will be your friend, a propane torch from any hardware store will save you so much time and so many broken bolts. It works much better than any rust penetrant and works quicker. just remember to not touch the bolts or nuts without gloves after.

Second get a set of paint markers. and mark the connections with different colors before you pull them apart. That way you know if you see a pink line, it goes with the pink line or blue and green goes with blue and green.

Now to start

Run the fuel down as low as possible. Drain engine oil, coolant, refrigerant, brake and ps fluids. Liquid Wrench the hell out of the entire underbody for about a week. (heat them as you go to take them apart if they dont go through rubber bushings) Lift the Jeep and lower onto the wheel dollies, using chocks for brakes and leaving the trans in neutral. (Remove the battery, soft top, rear seat, doors, spare, and any other extraneous weight before you lift the jeep) (TAKE THE FENDERS and HOOD OFF BEFORE YOU start pulling apart the systems) This will help you really understand everything that is going on around the engine plus will make taking the ac system apart so much easier. Unbolt and disconnect all systems and bolts between the chassis and the body (it's a bit of a list). Raise the body off the chassis with the lift and leave body lifted for the duration. (It is a lot easier to remove the body if it is just the tub and tail gate. Taking the fenders, hood, grill off greatly reduces the chance of damaging the engine and transmission and less weight makes the body easier to manipulate once its in the air . Roll the chassis to the open garage bay and next to the replacement chassis. Disconnect the exhaust at the downpipe. Replace the exhaust/intake gasket. Replace clutch. Pull engine/trans/transfer case and move aside. Begin moving systems from the old chassis to the new (not sure of the order I should do this and would appreciate advice).
The order I did things that I found to be the easiest.

1) Suspension and Axles, control arms (If going after market, now would be a good time to try and set your pinion angle accordingly)
2) Engine
3) Trans and T-case
4) Driveshafts
5) Brake lines and Fuel system (makes sense to run all lines going to the rear at the same time)
6) Steering

As you take things off the old chassis, put them right onto the new chassis. Do it in sections and take your time.

If you find yourself screwing around with something late at night like 1am for instance and its not working.
STOP AND GO TO BED!! , You'll come back at it in the morning and be like wow I was tired cause that was so simple.

As you install things, torque them down to spec and witness mark them with a paint marker (Purple for example) Then when you go to recheck, use red or orange. That way you know that all have been double checked.

The reason for not having the rear axle in during these pics was I was doing a stretch so I had to wait until I had the gas tank in and wanted to measure everything twice before I cut the frame. I also kept the whole body as 1 unit and I DO NOT RECOMMEND doing it like that at all! Take the fenders, hood and grill off. YOU WILL THANK ME LATER. The last pic explains why I needed a new frame, That's all the rust and dirt that fell out of my center sections near the skid plate holes when I cut my frame in half after i transferred everything over.
IMG-0080.JPGIMG-2202.jpgIMG_2195.jpgIMG_2196.jpgIMG-5761.JPG58067110680--A42C9323-574C-4E19-B8A1-EFE8E86E148C.JPGIMG_2199.jpgIMG-5865.JPG58067555765--75EDFAFA-01C4-4E5F-A203-33AB665411CF.JPGIMG_0623.jpegIMG-5698.JPG
 
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I will add that I had the tub rocker seams resting on 5 foot lengths of 4"x4" wood beams up on cinder blocks, removed the hood fenders and grill, removed the rear axle, and disconnected all of the fuel and electrical connections. Rested the gas tank on a dolly and slid the whole frame out from under the tub, engine, trans, tcase, and front axle still on the frame. Also any of the torx bolts you take out (other than the outside body hinges), just get regular grade 8 hex head bolts and washers of the same length and thread pitch and chuck those torx in the trash can where they belong.

IMPORTANT TIPS!!!!! Take lots and lots and lots of photos from multiple angles and even a video pan of an area so you can see what goes back where. You can never have too many pics. When you take off a part, bag all the fasteners for that part and label the baggie (masking tape and a sharpie) or if possible thread the bolts back into their original location on the part. I've got probably 70+ baggies on my bench from when I tore mine apart 5 years ago and if it wasn't for bagging and tagging everything I'd be screwed. I actually learned this the hard way when I tore apart an old VW and then had to put it in storage for many years and dumped all the bolts and parts into one box. Felt sorry for the guy I sold it to, still torn apart. Spent an hour going "I think this is for that, and these are for those, or was it for them?"
 
Chris, Goatman, GasnBrass-thank you! I greatly appreciate your advice, the links, and the use of your experience.

Just ordered the Rancho shocks, control arms, coil spring pads, standard OMIX non-abs brake lines, and some tubing frame clips.

I will just use the stock radiator for now. It leaks a tiny bit, same as the first one, but I have dealt with it for 21 years, so... No problem at all with cooling, just an annoying leak.

For the exhaust and intake manifold gasket, should I use a heat-proof gasket sealant? Should I replace any of the studs or bolts/nuts? Not sure if these are reusable.

I have both the '98 and '06 steering boxes. The '98 is ready for a replacement, but man-more than $500: unexpected. I will look up this ZJ upgrade and see if it's worth doing.

For the coil springs, there is surface rust. Is there a flexible coating I can apply?

I am still thinking about the AC lines and the dryer.

Thanks again. When I am ready to start, I will keep track of costs and time and will provide the forum with vids, pics, and lessons learned.
 
Just use a standard oem manifold gasket, it will have a silver graphite type coating on it. Hopefully your manifold bolts don't snap in the head.

I'm not sure if the late model steering box will mate up to the early steering column shaft, test it first.

ZJ upgrade is a beefier steering link and tie rod end from the left wheel to the drag link.

Just use a flexible bumper spray paint.

Don't try to re-engineer the a/c routing. I was actually happy with the routing on my '98 cause everything was on the top side of the motor, so I was able to just unbolt the dryer/compressor/condenser and just hang them from the ceiling on ratchet straps and move them slightly out of the way to roll my engine and frame out. No evac or recharge needed.

remember you may need to sort out the transmission mounting difference on the new skid plate (depending on transmission), but on the plus side you will have a clear view of where things need to go to make it fit.
 
Kevin Bright and GasnBrass-thanks! Excellent suggestions and thanks for the listed order. I will follow that advice.
 
As I am currently in the middle of a frame swap on my 99 I can tell you that you are overthinking the process a bit. Ultimately what are you trying to accomplish, just a frame swap or a complete restoration. It helps to know what direction you want to proceed. I am removing, repairing, restoring and re-finishing just about every part of the chassis except for engine, axle and trans internals and this will take a bit longer and cost more.

Initially you want to get the body and chassis separated so you can perform a complete inspect then formulate a plan of attack. There will be a few curve balls thrown at you.
 
TJ4Jim, agreed. Not really going for a full resto, but don't want to do a quick and dirty either. I am trying to spend my time/money where it makes sense while I have the access.

Do you have a thread for your resto?
 
I'll second the evaporust suggestion. Stuff works great at dissolving rust without harming the base metal. Only downside is it takes a long time to work (24-48 hours). Small parts can be soaked in it, for large areas like sheet metal you can lay towels wetted with evaporust on it and keep wetting the area with a spray bottle (capillary action will help keep the towel clinging to the metal).

Short picture montage of my resto:
 
Nothing much to add that hasn't already been said after having swapped many frames and parts in all year TJ's.

The two things that are true are the steering box and skid plate or belly plate.

The newer steering box starting in 2003 that Daimler spec'd for the TJ sucks and is really expensive comparatively to the old Saginaw style. I'd want to mod the frame and use a Saginaw style earlier box as they are stronger and cheaper for the rebuild or replacements. Especially in extreme wheeling builds, I have seen the late model boxes sector shaft snap clean off at the seal area in the box and when that happens on the trail, you're done.

The main skid plate or belly pan is different and has different holes to line up. Many aftermarket tummy tuckers or up-armored skid plates have BOTH patterns punched in them and both transmission mount patterns laid out so you can fit to either generation TJ. I'd recommend going with one of these aftermarket armored and tummy tucked skids that will fit either or you can customize the transmission mount to fit the later skid that goes with the 2003+ frame.

My .02 cents worth.

Ideally, it would have been nice to find a west coast or desert area 1996-1998 TJ frame for your swap as they are gussetted a little better than all later frames and need no modifications to fit your 1998 but hey, you got what you've got there.....

Good luck with your swap.

Note: P-Blaster will remove some zinc and plated finishes off of bolts and parts if left to soak too long as it has a chemical like carburetor cleaner in it along with the penetrating oil properties. While restoring 50 year old antenna rotors I discovered silver balls of some substance hours or days later in the remaining liquid and discovered it was the zinc metallic coating attacked by the spray that had totally come off the gears and small parts. This may be an issue if you re-use these parts afterwards because they may rust really bad in areas of high humidity or salt roads etc....... FWIW.
 
Never knew that! Good information to have.🍻 Yet another reason to have quit PB Blaster for liquid wrench for light duty and Croil for the really stuck parts.