Kickin’Chicken Posted January 23, 2020 Share Posted January 23, 2020 as the 4.0 in my old ‘99 Tj. Both have manual transmissions (‘99 had ax15, rubi has nv3550) so that’s pretty even but at low rpm this rubi doesn’t have the umpf that ‘99 had. Did Jeep reduce the exhaust ports or something in the later model 4.0s? Seems like I’ve read that here somewhere. BTW, still working on my MJ. The damn fuel pump isn’t pumping anymore so looks like I’ve got to drop the tank again (thinking seriously about cutting an access hatch in the bed to get to it easier.) Link to comment Share on other sites More sharing options...
Pete M Posted January 23, 2020 Share Posted January 23, 2020 congrats! what size tires? Link to comment Share on other sites More sharing options...
mjeff87 Posted January 23, 2020 Share Posted January 23, 2020 What's the curb weight of the new pig compared to your old one? Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted January 23, 2020 Author Share Posted January 23, 2020 Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted January 23, 2020 Author Share Posted January 23, 2020 15 minutes ago, Pete M said: congrats! what size tires? 36” on both. And I’m not sure of the weight differences but I’ve probably got less weight on this rubi. The ‘99 had a heavy rear bumper/spare tire carrier and a highlift on the hood as well as a warm upright winch with cable. Rubi has stock rear bumper, smittybuilt winch with nylon Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted January 23, 2020 Author Share Posted January 23, 2020 Link to comment Share on other sites More sharing options...
FrankTheDog Posted January 23, 2020 Share Posted January 23, 2020 What gears are in the axles? Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted January 23, 2020 Author Share Posted January 23, 2020 7 minutes ago, FrankTheDog said: What gears are in the axles? 4.10:1 in Rubi 4.56 in ‘99 rubi has 4:1 low range ’99 has 2.73:1 Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted January 23, 2020 Author Share Posted January 23, 2020 Does anyone know much about the locking diffs in the ‘04 rubicon? my rear locker Indicator light blinks momentarily then stays lit. The front one just blinks (never stays lit.) They both lock the axles fine but just wondering what the difference is. Link to comment Share on other sites More sharing options...
Pete M Posted January 24, 2020 Share Posted January 24, 2020 barring anything actually wrong with the Jeep, 4.56 is definitely better than 4.10. Link to comment Share on other sites More sharing options...
FrankTheDog Posted January 24, 2020 Share Posted January 24, 2020 4.56’s will definitely feel like more power than 4.10’s. Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted January 24, 2020 Author Share Posted January 24, 2020 1 hour ago, Pete M said: barring anything actually wrong with the Jeep, 4.56 is definitely better than 4.10. It is with 2.73:1 low range but with a 4:1.....4.10 gears are more than enough low. Link to comment Share on other sites More sharing options...
Pete M Posted January 24, 2020 Share Posted January 24, 2020 oh, I guess I assumed we were talking about on-road performance. Link to comment Share on other sites More sharing options...
87Warrior Posted January 24, 2020 Share Posted January 24, 2020 I bought my TJ Rubi (4.0) with a blown motor, so I stuck a WJ motor in there while I rebuilt the stock motor. When I got around to installing the fresh motor, I expected to gain a seat-of-the-pants improvement in power. Actually, the opposite occurred, I could clearly feel that the fresh motor (built to stock specs) was not as peppy as the WJ motor. The machinist and myself discussed and researched what the difference was, and it turned out the cam in the TJ 4.0 was different. Both the WJ and TJ 4.0's felt way under powered in comparison to a HO XJ or MJ 4.0. I blame updated emissions system and coil on rail design. On 1/23/2020 at 10:35 AM, Kickin’Chicken said: Does anyone know much about the locking diffs in the ‘04 rubicon? my rear locker Indicator light blinks momentarily then stays lit. The front one just blinks (never stays lit.) They both lock the axles fine but just wondering what the difference is. Does the front compressor keep running or does it shut off? Are you sure the front is locking? If the front diff fill plug is tightened too much, it can prevent the locker from locking or unlocking. There is no stopper on the diff cover for the fill plug, so you just wrap the threads with Teflon tape and screw it in a little ways. There is also a switch on the locker that sends the 'locked' signal to the dash light. This switch is probably not working if the axle is really locked. Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted February 4, 2020 Author Share Posted February 4, 2020 On 1/24/2020 at 3:54 PM, 87Warrior said: I bought my TJ Rubi (4.0) with a blown motor, so I stuck a WJ motor in there while I rebuilt the stock motor. When I got around to installing the fresh motor, I expected to gain a seat-of-the-pants improvement in power. Actually, the opposite occurred, I could clearly feel that the fresh motor (built to stock specs) was not as peppy as the WJ motor. The machinist and myself discussed and researched what the difference was, and it turned out the cam in the TJ 4.0 was different. Both the WJ and TJ 4.0's felt way under powered in comparison to a HO XJ or MJ 4.0. I blame updated emissions system and coil on rail design. Does the front compressor keep running or does it shut off? Are you sure the front is locking? If the front diff fill plug is tightened too much, it can prevent the locker from locking or unlocking. There is no stopper on the diff cover for the fill plug, so you just wrap the threads with Teflon tape and screw it in a little ways. There is also a switch on the locker that sends the 'locked' signal to the dash light. This switch is probably not working if the axle is really locked. Has anyone tried using a ‘99 motor distributor in place of the coil rail? Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted February 4, 2020 Author Share Posted February 4, 2020 On 1/23/2020 at 8:54 PM, Pete M said: oh, I guess I assumed we were talking about on-road performance. On road the engine doesn’t seem as peppy either but I really notice hill climbs and letting it crawl under its own idle. The ‘99 wasn’t as low but seems like it had more torque. Anyway.....my questions centered on the engine performance and not on gearing. Link to comment Share on other sites More sharing options...
Pete M Posted February 4, 2020 Share Posted February 4, 2020 engine performance and gearing cannot be fully separated. what your butt feels is a direct relation to torque applied to the ground. Link to comment Share on other sites More sharing options...
87Warrior Posted February 4, 2020 Share Posted February 4, 2020 4 hours ago, Kickin’Chicken said: Has anyone tried using a ‘99 motor distributor in place of the coil rail? While not impossible, it's not really feasible. The camshaft position sensor functions very different than a distributor. You could do it, but you would need to gut the engine bay and replace all wiring and computer with parts from a TJ with a distributor. Kind of like going from Renix to HO in the MJ. Link to comment Share on other sites More sharing options...
FrankTheDog Posted February 4, 2020 Share Posted February 4, 2020 The power difference between coil packs and distributor is non existent. They are rated the same and feel the same between my stock 99 XJ and stock 00 XJ. The gearing will make a difference on how the power feels. With 4.56’s it will feel like you have more power because you have a larger lever in the gear case. Link to comment Share on other sites More sharing options...
75sv1 Posted February 4, 2020 Share Posted February 4, 2020 I've have/had two '98 XJs, both autos. I kid of feel there was a power difference between those two engines. On my present one I have it lifted 31's not 32's. I did bore out the TB to 60mm. That gave it more power. Then I installed a 62mm. Seemed not as powerful. It notice it on my WV travels. I went from Ford 4 holes to Bosh 12 holes. Not real change. I picked up an '00 over the summer. I have not had it on the open road, just around the block. It seems to have as good as power as either of them. I think what ever power they might have lost in the exhaust ports and cast exhaust manifolds, they made up elsewhere. Some say the distributor less ignition adds a bit of power. There is a Viper Coil replacement. I do have the parts. But have not replaced that yet. I am forgetting who I bought it from. Edit: K Suspension Link to comment Share on other sites More sharing options...
FrankTheDog Posted February 5, 2020 Share Posted February 5, 2020 I did have a 96 XJ that felt more powerful than all the others. It was a noticeable difference. I couldn’t see anything different about it. Link to comment Share on other sites More sharing options...
strictlyxjs Posted February 8, 2020 Share Posted February 8, 2020 When i swapped in a 7120 head 95 block into my 2000 xj there was a huge seat of pant difference in more power than the crappy 0331 head motor. Link to comment Share on other sites More sharing options...
Kickin’Chicken Posted February 11, 2020 Author Share Posted February 11, 2020 I have a new project on this Rubicon and forgive me for tacking it on to this thread. The PO threw in a SS header. He bought it but never put it on. I’m thinking about either replacing the head with a 7120(?) and installing the new SS header or installing it on my existing head and enlarging the ports with little grinder bits. I’m also surprised that it only has 3 bolt holes for fastening it to the head. Do the factory exhaust manifolds only have 3 bolts? Link to comment Share on other sites More sharing options...
Pete M Posted February 11, 2020 Share Posted February 11, 2020 if I remember right, those tabs will be held down by a bolt that gets shared with the intake manifold. Link to comment Share on other sites More sharing options...
87Warrior Posted February 11, 2020 Share Posted February 11, 2020 Yup, Pete is right. Same mounting scheme as the MJ 4.0 :) Link to comment Share on other sites More sharing options...
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