Old to New Swap - Questions?

[1999 MJ]

   What hiccups did you run into?

Truck is currently a 1988 2wd, 4spd, Long bed.

Plan:  Make this a 1999 4x4 5spd, 2 inch lift, 30 inch tires, DAILY DRIVER.

- I have a complete 1999 2dr, 5spd, 4x4 XJ.  Pretty rusted body.

 

I see a lot of people “piece” in the firewall.  Has anyone actually cut the firewall out of the XJ & welded / grafted it into the MJ?

 

Everything appears to be straight forward bolt in, except the door jamb latches.  Sounds like an easy welding project, for anybody that welds.  I don’t weld, unless I’m playing with wrenches around the battery.  Haha. 🤣 🤣 🤣

 

Questions:

- 1).  Did you end up doing a bolt in exhaust?  Fabricated exhaust?  I’m looking to put a performance header on the 1999 engine.  Probably a “Banks” or a “Gibson”.  I’d like to continue to run a “Quality” exhaust all the way to the back.  Recommendations?

- 2).  Hard to source parts, that I should start looking for now?

- 3).  What would you have done differently?  Why?

- 4).  What transmission mount / cross mount did you use?

- 5).  Any non MJ / XJ parts I should seek out, to install on this build?

- 6).  FYI’s I should be aware of?

- 7).  Things I should consider?

 

Some of my plans:

I do plan on doing the “Brown Dog” Engine Mounts.

I’m probably going to do a 2 or 3 row radiator, WITHOUT the internal transmission cooler.  I think this is a custom unicorn part.

Cooling products from https://hesco.us

Disc brakes onto the C8.25.  Should I / do I relocate the lower shock mounts?

BDS - https://bds-suspension.com/products/2-inch-lift-kit-jeep-comanche-mj-86-91

 

 

[AZJeff]

If you install Brown Dog motor mounts, DO NOT use the ones with urethane in them, unless you only do trail riding.  The amount of vibration that is transmitted by the urethane for street use will be QUITE noticeable.

 

There is no need to try to source a rad without a trans cooler line embedded.  The cooler line only travels up the one end tank, and thus not rob the rad of any fins and tubes.  Just cap the two ends of the line on a 3 row rad, and you will be good to go.

[TurboedMJ]

As far as radiators go, check these guys out. Just ordered one and have heard good things about them. Plus, 60 day return and 1 year warranty. 

 

https://www.alloyworksplus.com/products/4-row-radiator-fan-shroud-kit-for-1984-2001-jeep-cherokee-xj-comanche-2-5-4-0l

 

[ghetdjc320]

17 hours ago, 1999 MJ said:

   What hiccups did you run into?

Truck is currently a 1988 2wd, 4spd, Long bed.

Plan:  Make this a 1999 4x4 5spd, 2 inch lift, 30 inch tires, DAILY DRIVER.

- I have a complete 1999 2dr, 5spd, 4x4 XJ.  Pretty rusted body.

 

I see a lot of people “piece” in the firewall.  Has anyone actually cut the firewall out of the XJ & welded / grafted it into the MJ?

 

Everything appears to be straight forward bolt in, except the door jamb latches.  Sounds like an easy welding project, for anybody that welds.  I don’t weld, unless I’m playing with wrenches around the battery.  Haha. 🤣 🤣 🤣

 

Questions:

- 1).  Did you end up doing a bolt in exhaust?  Fabricated exhaust?  I’m looking to put a performance header on the 1999 engine.  Probably a “Banks” or a “Gibson”.  I’d like to continue to run a “Quality” exhaust all the way to the back.  Recommendations?

- 2).  Hard to source parts, that I should start looking for now?

- 3).  What would you have done differently?  Why?

- 4).  What transmission mount / cross mount did you use?

- 5).  Any non MJ / XJ parts I should seek out, to install on this build?

- 6).  FYI’s I should be aware of?

- 7).  Things I should consider?

 

Some of my plans:

I do plan on doing the “Brown Dog” Engine Mounts.

I’m probably going to do a 2 or 3 row radiator, WITHOUT the internal transmission cooler.  I think this is a custom unicorn part.

Cooling products from https://hesco.us

Disc brakes onto the C8.25.  Should I / do I relocate the lower shock mounts?

BDS - https://bds-suspension.com/products/2-inch-lift-kit-jeep-comanche-mj-86-91

 

 

     Here is my .02: Use only rubber mounts as mentioned above if you go brown dog. The poly’s are quite horrible. Remember that you need flex at the transmission mount as well so stick with the one rubber mounts here. Personally, I went back to one rubber mounts for the engine as well. 
     As for the radiator, same as others posted. The tank doesn’t diminish cooling by any significant amount. Keep in mind it’s plumbed through the radiator to also pre-heat the tranny fluid not just to cool it. 
BDS suspension is a nice company to deal with. You will have to mod their add a leaf to fit the MJ spring pack correctly but it’s not difficult. Rebuilding a spring pack is a task though, especially when it come to removing the factory bushings. 
Hesco is the opposite of BDS imo. Clifford is similar. Once great companies. I’ve had nothing but horrible experiences with them. Perhaps hesco can build a nice stroker engine still but who knows. 
KJ disk brakes are an easy swap on the 8.25. Possibly worth swapping. There is a thread on brakes in the DIY section that may help you decide. 
The firewall is pretty integral to the structural integrity of the body. If you did swap the entire firewall, you’d want to separate it at the factory seams and secure it exactly the way they do or even better. The better approach is to graft in the panel sections that are needed. You will need to have these welded by a competent welder. They could be mig welded but tig would be preferred, again to maintain as much structural integrity as possible. 
I’ve ran a variety of 4.0 headers and ultimately ended up using either the Gibson ceramic coated one or the late style one manifold with the flex connection for the front and rear cylinders. 2.25” single exhaust is easy enough for any shop to fab. Be sure they add a hanger or anchor point near the crossmember as well to relieve the weight of the exhaust on the header. If the header supports too much weight plus the heat, it will likely develop cracks. 
 

The next questions would be, are you swapping to the entire 99 powertrain and electronics? If so, you will need to sort out an appropriate fuel system among many other items. This is often overlooked in these swaps. You’ll need a way to run a turbine style pump and return less style fuel delivery from the MJ tank. You could also swap over the transmission, transfer case and axles but keep your jeep Renix. No dash swap either as that 99 receives a canbus signal from the ecu for gauges. The doors and front end could still be swapped if you like. Just some food for thought. 

[1999 MJ]

13 hours ago, TurboedMJ said:

As far as radiators go, check these guys out. Just ordered one and have heard good things about them. Plus, 60 day return and 1 year warranty. 

 

https://www.alloyworksplus.com/products/4-row-radiator-fan-shroud-kit-for-1984-2001-jeep-cherokee-xj-comanche-2-5-4-0l

 

Good to know.

[1999 MJ]

7 hours ago, ghetdjc320 said:

     Here is my .02: Use only rubber mounts as mentioned above if you go brown dog. The poly’s are quite horrible. Remember that you need flex at the transmission mount as well so stick with the one rubber mounts here. Personally, I went back to one rubber mounts for the engine as well. 
     As for the radiator, same as others posted. The tank doesn’t diminish cooling by any significant amount. Keep in mind it’s plumbed through the radiator to also pre-heat the tranny fluid not just to cool it. 
BDS suspension is a nice company to deal with. You will have to mod their add a leaf to fit the MJ spring pack correctly but it’s not difficult. Rebuilding a spring pack is a task though, especially when it come to removing the factory bushings. 
Hesco is the opposite of BDS imo. Clifford is similar. Once great companies. I’ve had nothing but horrible experiences with them. Perhaps hesco can build a nice stroker engine still but who knows. 
KJ disk brakes are an easy swap on the 8.25. Possibly worth swapping. There is a thread on brakes in the DIY section that may help you decide. 
The firewall is pretty integral to the structural integrity of the body. If you did swap the entire firewall, you’d want to separate it at the factory seams and secure it exactly the way they do or even better. The better approach is to graft in the panel sections that are needed. You will need to have these welded by a competent welder. They could be mig welded but tig would be preferred, again to maintain as much structural integrity as possible. 
I’ve ran a variety of 4.0 headers and ultimately ended up using either the Gibson ceramic coated one or the late style one manifold with the flex connection for the front and rear cylinders. 2.25” single exhaust is easy enough for any shop to fab. Be sure they add a hanger or anchor point near the crossmember as well to relieve the weight of the exhaust on the header. If the header supports too much weight plus the heat, it will likely develop cracks. 
 

The next questions would be, are you swapping to the entire 99 powertrain and electronics? If so, you will need to sort out an appropriate fuel system among many other items. This is often overlooked in these swaps. You’ll need a way to run a turbine style pump and return less style fuel delivery from the MJ tank. You could also swap over the transmission, transfer case and axles but keep your jeep Renix. No dash swap either as that 99 receives a canbus signal from the ecu for gauges. The doors and front end could still be swapped if you like. Just some food for thought. 

Are you still on Guam?  I’ve seen a few XJ’s here, on this island of Toyotas.

 

I do plan on making this 1988 Comanche as much as a 1999 Comanche as possible.  So, yes I will be swapping over the 1999 XJ drivetrain, wiring, dash, etc…. I’m currently collecting parts, my projects are stateside and I’ll deal with them, once I return to the states.

[ghetdjc320]

45 minutes ago, 1999 MJ said:

Are you still on Guam?  I’ve seen a few XJ’s here, on this island of Toyotas.

 

I do plan on making this 1988 Comanche as much as a 1999 Comanche as possible.  So, yes I will be swapping over the 1999 XJ drivetrain, wiring, dash, etc…. I’m currently collecting parts, my projects are stateside and I’ll deal with them, once I return to the states.

I am! Are you on island? 

[1999 MJ]

1 hour ago, ghetdjc320 said:

I am! Are you on island? 

Currently on vacation in Thailand.  Returning to Guam for work on Monday.

[ghetdjc320]

32 minutes ago, 1999 MJ said:

Currently on vacation in Thailand.  Returning to Guam for work on Monday.

Nice! Just sent you a PM

[gogmorgo]

Just a heads up you know the MJ uses the 4-dr XJ doors, not the 2-dr ones off your donor, yes?

[1999 MJ]

46 minutes ago, gogmorgo said:

Just a heads up you know the MJ uses the 4-dr XJ doors, not the 2-dr ones off your donor, yes?

I know.  Kind of a shame.  I always wondered why, because it’s a lot easier for me to get in and out of the 2 door XJ’s than the 4 door XJ’s.  I’m usually hitting my head on the upper door frame of the 4 door, if I haven’t driven it in awhile.  Also, this 1999 2 door 5spd 4x4 fit the bill, for what I’m looking for, other than the fact it didn’t have 2 more doors.  I’ll also be able to graft the 2 door power window switch controls into a drivers front 4 door panel.

[JZLAJeep]

51 minutes ago, 1999 MJ said:

I know.  Kind of a shame.  I always wondered why, because it’s a lot easier for me to get in and out of the 2 door XJ’s than the 4 door XJ’s.  I’m usually hitting my head on the upper door frame of the 4 door, if I haven’t driven it in awhile.  Also, this 1999 2 door 5spd 4x4 fit the bill, for what I’m looking for, other than the fact it didn’t have 2 more doors.  I’ll also be able to graft the 2 door power window switch controls into a drivers front 4 door panel.

Unless you can be as cool as this guy

I'll never sell my '95 2 door, 5-speed XJ. Owned it since 2001.