4-cylinder build plan advice needed

[The4bangertj]

I have a 2.5l with the ax5 that I love dearly. The tub and frame have no rust and this being my first and only car since the age 16 (couldn’t afford a 4.0 from cutting grass money growing up) and have taken it to 38 states, I want to keep it and the 4cyl motor. I have 33s with 30/44 with 4.56 gears and I enjoy driving it. I can do 70 on the highway here in Idaho and get around 20 mpg doing so. It’s slow as crap every where else but it’s tolerable.

The goal is 35s (regear to 5.13) and outboard with Currie 4in springs as a fun around town Jeep but also a very capable rig. I don’t plan on doing trails like starky does but I would like outboards mostly for the better shock rather than just travel and the stock rear location is a pos. I would also like a deeper crawling gear as I often have to bump things, burn my clutch some, or end up stalling on steeper very technical spots but would hope the larger tire diameter would help a little.

What’s the best plan of attack to achieve a capable but daily rig that I can also do it in steps as this is still my daily and likely will still be for another few years. Am I crazy to want to ax15 and atlas 2 with a 5 to 1 low range? If that needs a body lift and a new skid to fit why wouldn’t I also mid arm rather than trying to rebuild my re arms I have now or spend money on all savvy arms just for them to be swapped out. How easy would I be able to install it in a drive way? Would the 5 to 1 help with the AS hops enough for me to not need the mid arm?
I feel like I’d have to swap everything for even a low hp ls swap and a 4.0 swap is just as much work so I might as well just start all new but I really like the 4cyl. I know this is kinda blabbering but still curious to see what others would do or have done in this situation as my suspension is getting worn and I’d like to replace it with what ever I’ll actually keep.

 

[Tob]

Lower gearing will allow more control over over your drivetrain, but will not fix any geometry issues. That said, you can still have a very capable rig on a short arm setup. And later when you go to chase that last 10% of performance with a midarm setup, maybe it won’t have to be a weekend driveway project. Correct me if wrong, but I believe you wouldn’t have to do any rework if you did an outboard now and decided to do a midarm later on. An engine swap is an ambitious weekend project for a daily driver in a driveway in my opinion.

 

[PNW_LJ]

x2 to what Tob said. Find and maximize the limits of the short arm setup first.

The way I see it, your biggest improvements will come from bumping up to 35s (with appropriate lift and gearing), and outboarding. The midarm can happen later, and will not affect the outboard.

I'm one of those lucky folks that rushed into a midarm, earlier than I was supposed to. Had I started with a quality short arm, I would have appreciated the midarm's benefits more later on. It's also likely that I might've found that I'm better suited in a TJ, than an LJ.

 

[BlueC]

I want to keep it and the 4cyl motor. I have... 30/44 with 4.56 gears... It’s slow as crap every where else but it’s tolerable. The goal is 35s (regear to 5.13)

In your situation, I think I’d find a 44 front so I could gear to 5.38. That 4 cylinder needs all the leverage it can get, especially on 35s.

After that, I'd consider a transfer case or forced induction, depending on if you want better performance on-road or off-raod at that point, or both if your pockets are deep.

 

[The4bangertj]

Lower gearing will allow more control over over your drivetrain, but will not fix any geometry issues. That said, you can still have a very capable rig on a short arm setup. And later when you go to chase that last 10% of performance with a midarm setup, maybe it won’t have to be a weekend driveway project. Correct me if wrong, but I believe you wouldn’t have to do any rework if you did an outboard now and decided to do a midarm later on. An engine swap is an ambitious weekend project for a daily driver in a driveway in my opinion.

Ya I do believe others on the forum were saying (possibly telling jmt) that outboarding on short arms then upgraded to mid arm is totally fine just make sure you have enough space inside the shock and frame for axle swing on both sides going from the track bar to single tri so I totally could just do that step of short arms then outboard. The only reason I’d do an engine swap is the market for parts on my 2.5 were harder to find than say an Ls and I could simplify it. Which I don’t think will happen.

 

[The4bangertj]

x2 to what Tob said. Find and maximize the limits of the short arm setup first.

The way I see it, your biggest improvements will come from bumping up to 35s (with appropriate lift and gearing), and outboarding. The midarm can happen later, and will not affect the outboard.

I'm one of those lucky folks that rushed into a midarm, earlier than I was supposed to. Had I started with a quality short arm, I would have appreciated the midarm's benefits more later on. It's also likely that I might've found that I'm better suited in a TJ, than an LJ.

Ya I get jealous of all you guys with mid arms and seeing the trails you just walk up without a hick up. Definitely want gearing and tire size to stop bumping and burning over everything.

 

[The4bangertj]

In your situation, I think I’d find a 44 front so I could gear to 5.38. That 4 cylinder needs all the leverage it can get, especially on 35s.

After that, I'd consider a transfer case or forced induction, depending on if you want better performance on-road or off-raod at that point, or both if your pockets are deep.

I never even thought about going with a 44 front for that reason. If assuming the final gear ratio is around the same with 35s and 5.13 as it is with my 33s and 4.56 now but with the added diameter to roll over just a bit more rather than drive up things, I think it would be ok. If it is less then maybe I’ll look into a 44 front before I re gear again if that gearing jump will make a noticeable difference.

 

[The4bangertj]

Does anyone know if i could use my existing or aluminum ucf skid with an atlas 2? As far as I know they’re the best aluminum skid for early model jeeps as savvy doesn’t make early model skids and I’d hate to swap my current 2in deep steel skid with a 1in deep aluminum then have to swap that if I did an atlas.
Edit : I am also assuming I would need to do an ax15 swap to get an atlas 2 mounted but I’m also under the impression the ax15 mounts and length are the same as an ax5 but with different bell housings and output shaft spline count.

 

[Wildman]

Being a former 4 popper owner I can tell you I miss my 4 angry squirrels now & then.

As far as rebuilding your 4 cyl I'd start looking for a stroker crankshaft if there is one available anymore. 505 Performance hasn't been a reliable company for a while now and I don't know of any others.

I had a TeraLow 4:1 kit in my t-case and it made a world of difference in how well I was able to get around off-road in 4WD. I also installed the 2Lo kit when I installed it.

If you were looking at a Dana 44 front & regearing then I'd seriously look at the 5.89 gears for a LP Dana 44. With your 4 cyl & 35" tires on the road that should allow you to actually use 5th.

Edit: You'd be turning about 3200 RPM's at 70 MPH with 5.89's & 35" tires if they measured out to 34.2"

 

[The4bangertj]

Being a former 4 popper owner I can tell you I miss my 4 angry squirrels now & then.

As far as rebuilding your 4 cyl I'd start looking for a stroker crankshaft if there is one available anymore. 505 Performance hasn't been a reliable company for a while now and I don't know of any others.

I had a TeraLow 4:1 kit in my t-case and it made a world of difference in how well I was able to get around off-road in 4WD. I also installed the 2Lo kit when I installed it.

If you were looking at a Dana 44 front & regearing then I'd seriously look at the 5.89 gears for a LP Dana 44. With your 4 cyl & 35" tires on the road that should allow you to actually use 5th.

I’ll try looking into some motors. I just was planning on throwing a Jasper motor in once this one goes and calling it good.
I wish the Terra low kit still existed bc I think that with 5.13 would be enough. One of my best friends here with a tj has one ( 4.0 with the Terra low) he didn’t even know he had it and bragged about his slow speed since he never stalled on anything but I would.

I’m currently in the process of swapping everything I can to aluminum with going back to soft top and half doors when I can and really trying to lighten the jeep up. Even rn with all the steel, hard top, and steel targets in the back for shooting I can still cruise 70 on the idaho highways and that’s perfect for me. I’ll soon be moving back east where the speed limit is not 70 and I will not be at 5k feet of elevation so I’m not expecting it to be good by any means but if it can hold 65 with35s and 5.13s I’ll be happy with the on road. Also hoping to run some lighter method wheels in 17in and a lighter 35 like a bfg.
Their really isn’t another option for case gearing besides an atlas since the terra low is discontinued, the rubicrawler is only for a specific auto, 241 still needs a new trans and is basically the same cost as an atlas, and finally the atlas which is more than what I originally got this jeep for.

 

[Wildman]

I’ll try looking into some motors. I just was planning on throwing a Jasper motor in once this one goes and calling it good.
I wish the Terra low kit still existed bc I think that with 5.13 would be enough. One of my best friends here with a tj has one ( 4.0 with the Terra low) he didn’t even know he had it and bragged about his slow speed since he never stalled on anything but I would.

I’m currently in the process of swapping everything I can to aluminum with going back to soft top and half doors when I can and really trying to lighten the jeep up. Even rn with all the steel, hard top, and steel targets in the back for shooting I can still cruise 70 on the idaho highways and that’s perfect for me. I’ll soon be moving back east where the speed limit is not 70 and I will not be at 5k feet of elevation so I’m not expecting it to be good by any means but if it can hold 65 with35s and 5.13s I’ll be happy with the on road. Also hoping to run some lighter method wheels in 17in and a lighter 35 like a bfg.
Their really isn’t another option for case gearing besides an atlas since the terra low is discontinued, the rubicrawler is only for a specific auto, 241 still needs a new trans and is basically the same cost as an atlas, and finally the atlas which is more than what I originally got this jeep for.

I was going to do the AX15 swap on mine when I still had my 4 popper. I had a supercharger I was going to install also. I was running 35" Toyo M/T's at the time and got convinced to do the V-8 swap instead.
I only had 4.88 gears back then because that was as low as they offered.

And yes an Atlas isn't cheap. Keep you eyes open for a TeraLow. There was one about a month ago on FB for $1200.

 

[Wildman]

If I see another TeraLow I'll let you know. It was for a 23 spline (AX15) but since you want to swap to one anyway.

 

[PNW_LJ]

Ya I get jealous of all you guys with mid arms and seeing the trails you just walk up without a hick up. Definitely want gearing and tire size to stop bumping and burning over everything.

The way I see it, the midarm solves a narrow set of problems. There are more gains to be had with the other mods you've discussed here.

 

[The4bangertj]

I was going to do the AX15 swap on mine when I still had my 4 popper. I had a supercharger I was going to install also. I was running 35" Toyo M/T's at the time and got convinced to do the V-8 swap instead.
I only had 4.88 gears back then because that was as low as they offered.

And yes an Atlas isn't cheap. Keep you eyes open for a TeraLow. There was one about a month ago on FB for $1200.

I like being a small light Jeep and while I know I’d enjoy the building aspect of a swap I don’t want financially to swap my axles to tons. I’ll definitely be looking for them since I havnt and even more so when I get to the east coast since parts available are a lot more than idaho.
1200 for a terra low isn’t bad at all.

 

[The4bangertj]

The way I see it, the midarm solves a narrow set of problems. There are more gains to be had with the other mods you've discussed here.

Glad to hear it’s a smaller jump honestly. I read too much on this forum and it’s gets in my head. Seeing how a mid arm just never doesn’t anything weird but I don’t watch enough short arms do almost all the same trails.

 

[Wildman]

I like being a small light Jeep and while I know I’d enjoy the building aspect of a swap I don’t want financially to swap my axles to tons. I’ll definitely be looking for them since I havnt and even more so when I get to the east coast since parts available are a lot more than idaho.
1200 for a terra low isn’t bad at all.

What SUCKS is that I bought my TeraLow NEW off Ebay for around $1K in 2005. And when I was doing my first build of my TJ I gave my t-case to a friend for her 4popper YJ. She's still rocking it too.

 

[Blackjack]

As a current four popper owner on 35s let me give some of my thoughts.

The AX15 is worth considering if your AX5 is showing signs of old age or fragility.

5.13s will give you some of your gearing advantage back but it will never be the same as being on 33s as the rolling diameter and weight are higher and gears alone cannot make up for all of that. Even though my 33s that I replaced were heavier the rolling diameter is still there. So count on mileage loss and being even a bit more of a pig than it is now.

Since you plan to stay with a manual I would not go with the Atlas and look at going with a Northwest Fab Black Box I https://northwestfab.com/products/blackbox-integrated married to a Bronco 20 with a Wild Horses upgraded output https://www.wildhorses4x4.com/early...uty-transfer-case-output-system-1350-complete or a flipped Dana 300 (many ways to achieve this) with upgrades. This is more cost effective, lighter than the Atlas and you do not lose you 2.72 low range which you will regret for milder trails you do not need the 5.0-1 for. Gollywomper did it with a 300 check out his build https://wranglertjforum.com/threads/“thought-it-was-done”-build-blog.18708/

If you do Rockjock coils you will want to use the 3 inch coils up front as the 4 inch will give you way more than 4 inches of lift. Trust me on this one.

Outboarding the rear shocks (and most likely modding the front towers) is a worthwhile endeavor if you really want to get into a completely different class of shocks.

Mid Arm helps with certain bad behaviors that happen in certain terrain situations. I would invest in the other mods first and if the bad behavior rears its head then worry about going down that road then.

Show me pics of your RE arms. Depending on which ones you have there are some tricks to get more out of them and I have a few spare to service them in my collection.

 

[bty34]

I believe Blaine did one where he slid the motor forward and left the transfer case in the stock location and added a crawl box in between. There is quite a bit of room in front of the 4cyl before the radiator.

 

[Wildman]

I believe Blaine did one where he slid the motor forward and left the transfer case in the stock location and added a crawl box in between. There is quite a bit of room in front of the 4cyl before the radiator.

JP magazine did one with the old Klune-V which is like the Black Box that Blackjack was talking about years ago where they moved the engine forward.

 

[The4bangertj]

As a current four popper owner on 35s let me give some of my thoughts.

The AX15 is worth considering if your AX5 is showing signs of old age or fragility.

5.13s will give you some of your gearing advantage back but it will never be the same as being on 33s as the rolling diameter and weight are higher and gears alone cannot make up for all of that. Even though my 33s that I replaced were heavier the rolling diameter is still there. So count on mileage loss and being even a bit more of a pig than it is now.

Since you plan to stay with a manual I would not go with the Atlas and look at going with a Northwest Fab Black Box I https://northwestfab.com/products/blackbox-integrated married to a Bronco 20 with a Wild Horses upgraded output https://www.wildhorses4x4.com/early...uty-transfer-case-output-system-1350-complete or a flipped Dana 300 (many ways to achieve this) with upgrades. This is more cost effective, lighter than the Atlas and you do not lose you 2.72 low range which you will regret for milder trails you do not need the 5.0-1 for. Gollywomper did it with a 300 check out his build https://wranglertjforum.com/threads/“thought-it-was-done”-build-blog.18708/

If you do Rockjock coils you will want to use the 3 inch coils up front as the 4 inch will give you way more than 4 inches of lift. Trust me on this one.

Outboarding the rear shocks (and most likely modding the front towers) is a worthwhile endeavor if you really want to get into a completely different class of shocks.

Mid Arm helps with certain bad behaviors that happen in certain terrain situations. I would invest in the other mods first and if the bad behavior rears its head then worry about going down that road then.

Show me pics of your RE arms. Depending on which ones you have there are some tricks to get more out of them and I have a few spare to service them in my collection.

I’m not opposed to an auto swap if the auto would be competent at not just the low end torque converting but gearing for on road too. I havnt heard of good things for the autos that came in the 2.5 or even the 2.4 but if I could swap a 32rh and it be as good as everyone says it is on a 4.0 then I would be willing. I actually just got a new to me ax5 in the jeep bc I was dumb and burnt it out on a 16hr trip. The ax15 was just to get a stronger case behind it.

I figured I’d never get exactly the gearing to tire size back just bc of the diameter and weight but I ran these 33s and 5lb lighter 32s with 4.10 for 6 years and it was dog, I was still happy just to drive it but the jump to 4.56 made a massive difference so I’m optimistic mostly bc I won’t be driving west coast 80mph highways anymore. I’ll have to look into those case options bc I have never heard of either.

Dude that’s perfect I’ve always wondered that height especially with the hope of me swapping to an aluminum front bumper making it even lighter and right now I’m running 3.5in metal cloak coils and I’m getting just a hair over 4.5in of lift but oddly enough I’m also getting that out of the rear still too and if I run a soft top I goes up to over 5 so would you think I should run the 3in front and rear? That would just limit my outboard length to prob 10in travel with a 50/50 split.

Realistically once these arms actually have slop I’m going to savvy’s right away. They’re loose but no play. Infact one of my jj on my savvy rear uppers does have play where I can hear it so I’ll need to rebuild those. ( I believe those are the 2in skinny joints so correct me if I am wrong)