Gearing question
- Thread starter idaxj97
- Start date
88Xj
Banned
2200 rpm for the 4.0 is the sweet spot. Small things help but not much. Wanna know what's better since your already geared? Doing 1.7 Yella Tera rockers which are bolt on, not other mods needed. Gaining less wear, less noise, Moore mileage, more power, I will say those rockers felt like a regear when I did them. Cost about 450, 2 hrs worth of work, and can be done with hand tools in your driveway.
I have 4.56, 33x10.5 & a ax15. I'm pushing a smooth 2300 rpm @ 65mph, however I haven't driven it yet.
My mileage was around 20 highway. 3", 31 mudders, 3.55(auto axle swap for a cheap regear lol)..crusing around 2150rpm. Basic lift, kept it light, nothing on the roof, mild jeep. 20-24 on the highway pending how it was driven, weather, ac on, drafting ect ect. All variables! GPS verified hand calculated, every bolt on possible, tuned via. Safc II. I was on average pulling 20-21 highway. 18/19. Mixed. 17/18 city. I could improve that with how I drove & by drafting. Now I'll have a whole new motor, heavier axles(trussed), 33s, more lift, more weight. I'm hoping to stick to 20mpg..
Everything I've seen and felt in every mod I've done. The best so far to date was the rockers, followed by a ho head swap with horseshoe style manifold. Your an ho already, so get the newer style manifold, it helps down low noticeably. After that was a 2.5" downpipe...note downpipe not exhaust. The downpipe from the factory is necked down to under 1.75". Remake it with mandrel bends in 2.5". I did every bolt on. My advice for those is as follows.
Yella Tera 1.7 rockers. (Thread on naxja explaining them more...everyone's opinions are the same) its like going from stock gears on 31s to gears. Huge difference. Perfectly safe on stock valve train! I'd guess 20wheel horsepower gained across the rpm range.
99+ horseshoe intake manifold & drill/bore your stock tb to 60mm. It's 60 necking down to 55 if its still stock..open it up to 60...it's free. During this time since the manifold is out, do a intake heat shield. I used dei gold reflective blanket stuff. summitrcing, jegs ect..kept the intake cooler, cost 11 bucks. Worth it!
2.5" downpipe & exhaust if you want..downpipe made most difference, exhaust made it louder lol.
Relocating the iat sensor, its free takes but a few minutes.
If you don't have em yet, the 4 hole injectors help a bit, mainly in response and "LONG" highway trips! Idk what style injector clips you have but pm me, ill shoot you some good running 4 hole injectors for a couple expo stickers if you want em :smiley_drive: otherwise check your local yards or online jeep forums. They sell for 40-150 bucks.
After that there's not much. Headers aren't worth much, a apn header serves its purpose for under 200. Most intakes are trash, I have a cowl/hummer DIY style for a raised induction point. I did much more, but that "much" more didn't help much, gave me a bit more power, but nothing down low where I needed it. Those gains came from the 1.7 rockers, followed by the manifold, then downpipe. Each time 1 mod was added I could feel the difference. No need to adjust fuel trims either. I adjusted mine via a apexi safc II and ran on 91 octane. When you get into it, you can run a leaner afr on 91 then 87. 91 costs 5 bucks more to fill up my tank. 25 gallons, .20 cents more a gallon. 5 bucks even. I actually save about $1.65 per tank running 91 with more performance and a cleaner running engine. I have my "safe" tune for 87 incase I can't find 91 octane around when out wheeling. The 87 is consistently 1-1.5 mpg worse every time.
Now you can also look up high altitude CPS sensor. Or mod your own CPS to add in 6* of timing across the entire Rpm range. I did it but only once I tuned for 91. You could do it no issues, but I'd run 89 Minimum..If not you computer will pull the timing back out and you'll be back at square one. Add in the 6* was a very pleasant bump in low end again, but you need to run 89 to keep the timing their..87 it'll pull. It back out. Personally 91 is all the jeep sees unless I am forced to run 87. 5 bucks more per tank full...ya its worth it. Its 3.81 per gallon on 87. And 4.00 for 91 per gallon here..every station its 20cents more.
CPS mod write up. Works for any 4.0 jeep guy where the CPS is on the bell housing. Advances your timing 6*. You obviously need to reset your ecu when doing this and you need to run 89/91 preferably or the ecu will just pull the extra timing back out.
http://www.naxja.org/forum/showthread.php?t=1072456
I have 4.56, 33x10.5 & a ax15. I'm pushing a smooth 2300 rpm @ 65mph, however I haven't driven it yet.
My mileage was around 20 highway. 3", 31 mudders, 3.55(auto axle swap for a cheap regear lol)..crusing around 2150rpm. Basic lift, kept it light, nothing on the roof, mild jeep. 20-24 on the highway pending how it was driven, weather, ac on, drafting ect ect. All variables! GPS verified hand calculated, every bolt on possible, tuned via. Safc II. I was on average pulling 20-21 highway. 18/19. Mixed. 17/18 city. I could improve that with how I drove & by drafting. Now I'll have a whole new motor, heavier axles(trussed), 33s, more lift, more weight. I'm hoping to stick to 20mpg..
Everything I've seen and felt in every mod I've done. The best so far to date was the rockers, followed by a ho head swap with horseshoe style manifold. Your an ho already, so get the newer style manifold, it helps down low noticeably. After that was a 2.5" downpipe...note downpipe not exhaust. The downpipe from the factory is necked down to under 1.75". Remake it with mandrel bends in 2.5". I did every bolt on. My advice for those is as follows.
Yella Tera 1.7 rockers. (Thread on naxja explaining them more...everyone's opinions are the same) its like going from stock gears on 31s to gears. Huge difference. Perfectly safe on stock valve train! I'd guess 20wheel horsepower gained across the rpm range.
99+ horseshoe intake manifold & drill/bore your stock tb to 60mm. It's 60 necking down to 55 if its still stock..open it up to 60...it's free. During this time since the manifold is out, do a intake heat shield. I used dei gold reflective blanket stuff. summitrcing, jegs ect..kept the intake cooler, cost 11 bucks. Worth it!
2.5" downpipe & exhaust if you want..downpipe made most difference, exhaust made it louder lol.
Relocating the iat sensor, its free takes but a few minutes.
If you don't have em yet, the 4 hole injectors help a bit, mainly in response and "LONG" highway trips! Idk what style injector clips you have but pm me, ill shoot you some good running 4 hole injectors for a couple expo stickers if you want em :smiley_drive: otherwise check your local yards or online jeep forums. They sell for 40-150 bucks.
After that there's not much. Headers aren't worth much, a apn header serves its purpose for under 200. Most intakes are trash, I have a cowl/hummer DIY style for a raised induction point. I did much more, but that "much" more didn't help much, gave me a bit more power, but nothing down low where I needed it. Those gains came from the 1.7 rockers, followed by the manifold, then downpipe. Each time 1 mod was added I could feel the difference. No need to adjust fuel trims either. I adjusted mine via a apexi safc II and ran on 91 octane. When you get into it, you can run a leaner afr on 91 then 87. 91 costs 5 bucks more to fill up my tank. 25 gallons, .20 cents more a gallon. 5 bucks even. I actually save about $1.65 per tank running 91 with more performance and a cleaner running engine. I have my "safe" tune for 87 incase I can't find 91 octane around when out wheeling. The 87 is consistently 1-1.5 mpg worse every time.
Now you can also look up high altitude CPS sensor. Or mod your own CPS to add in 6* of timing across the entire Rpm range. I did it but only once I tuned for 91. You could do it no issues, but I'd run 89 Minimum..If not you computer will pull the timing back out and you'll be back at square one. Add in the 6* was a very pleasant bump in low end again, but you need to run 89 to keep the timing their..87 it'll pull. It back out. Personally 91 is all the jeep sees unless I am forced to run 87. 5 bucks more per tank full...ya its worth it. Its 3.81 per gallon on 87. And 4.00 for 91 per gallon here..every station its 20cents more.
CPS mod write up. Works for any 4.0 jeep guy where the CPS is on the bell housing. Advances your timing 6*. You obviously need to reset your ecu when doing this and you need to run 89/91 preferably or the ecu will just pull the extra timing back out.
http://www.naxja.org/forum/showthread.php?t=1072456
Last edited:
MtnClimber
Ready To Explore!
^^^ Most excellent info :bowdown:
88Xj
Banned
Haha thanks. try to help when and where i can. if you had a geared 4.10 or whatever ratio axle set already, I wouldn't regear unless I went to 35s or something. And at that I'd personally be looking for a d44/60 or something. If I ever go to 35s I've decided ill find Jk axles 44/44 and run theses. A 4.56 or 4.88 pinion in the d30 is terribly small, but it should and will hold up unless you beat it. I would do it mainly cause I want lock outs to gain some mileage and ease of parts. Stock unit bearings are a breeze and perfect for 35s or under if you we don't beat it. Nothing like 3 bolts to swap em out lol.
I just trussed my d30 with 4.56/trutrac and 760x shafts. Ill never buy chromos because 500 bucks into the 30 isn't worth it and usually the ujoints the weakness. The chromos and 760x shafts run identical shafts. The wj swap is a decent chunk of change into the d30 as is lol. Maybe 35s in the future...maybe.